artifact_class: CHEATSHEET_CANDIDATE type: theme id: A1 domain: A title: Facial and regional anatomy subchapters: 10 covered_subs: 10 new_subs: 0 slides: 0 books: 54 articles: 9 videos: 0 maps_to: [G10, G3] federated: false tags: [theme, domain/A, status/covered] pass: 1 template: ANATOMIA lang: en status: authored

A1 — Facial and regional anatomy

> Tags — [A] verified external guideline, consensus or study · [B] anatomical article with its own identifier (dissection, contrast CT, histology) · [C] monograph or atlas from the own MEDLIB corpus · [D] UPO master's teaching material or another never_sufficient_alone source · (P) the model's own reasoning, never a dose nor a plane.

> Currency and provenance — 122 references · median 2016, range 1966-2026, 13 % from 2022 on · provenance: verified external 67 % (82) · MEDLIB corpus 33 % (40, of which 4 from the UPO master's) · 4 flagged [D] never_sufficient_alone.

Base chapter. The thirteen regions (D1-D13) link here and do not repeat general anatomy: block A1.10 (proportions, angles and variants) is the one they all consume. This chapter describes the anatomy; injection technique lives in C1-C4 and in each region.

• [x] A1.1 — In 30 seconds: the map (which layer, which vessel and which bone rule each third)
• [x] A1.2 — Layers from skin to bone: the layer model, where it holds and where it does NOT
• [x] A1.3 — Superficial and deep fat compartments, one by one
• [x] A1.4 — Retaining ligaments: origin, insertion, what they restrain and which groove they draw when they fail
• [x] A1.5 — Muscles: origin, insertion, vector, antagonist and layer
• [x] A1.6 — Arteries: course, depth by segment and internal carotid anastomosis
• [x] A1.7 — Veins and lymphatics: edema and periorbital filling
• [x] A1.8 — Nerves: motor and sensory, emergence, block and injury
• [x] A1.9 — Bone: morphology, angles and resorption chronology
• [x] A1.10 — Proportions and variants: thirds, fifths, angles, ethnicity, sex and age

A1.1 · In 30 seconds — the map

In 30 seconds

The five sentences that order the rest of the chapter

1. The line of ligaments separates two behaviors, not two zones. All the major ligaments align along a single line immediately lateral to the lateral orbital rim, from the temporal crest to the mandible: temporal ligamentous adhesions, lateral orbital thickening (LOT), zygomatic ligament and mandibular ligament [4]. Medial to that line the layers are oblique and filler projects; lateral to it they are parallel and filler pulls/lifts the structures below [4].
2. An artery's depth changes with the segment, not with the region. In the forehead, the arteries are supraperiosteal below the middle frontal septum and subcutaneous above it; that septum lies 1.5 ± 0.17 cm (range 1.3-1.7) from the midline and 3.0 ± 0.24 cm (range 2.7-3.3) laterally, measured from the supraorbital rim [2,1].
3. Three regions break the layer model and must be treated as explicit exceptions: the temple (up to 10 layers), the tear trough (only 3: skin, orbicularis, periosteum) and the perioral region (no defined subcutaneous compartments, skin anchored to muscle) [4,3].
4. The retinal window is about 90 minutes. Experimental occlusion of the central retinal artery in a primate produced no detectable damage until 97 minutes; beyond that the damage is irreversible and progressive [2]. The retina also receives collateral ciliary supply, so complete occlusion is rare on angiography; 90 minutes is the operating reference point, not a guarantee [2].
5. The needle seeds product into every plane it crosses. Material ascends retrograde along the injection channel and is identified in the subdermal plane even when the tip is in bone contact; this is why a negative aspiration does not exclude transarterial passage [2].

> Red lines — Glabella: maximal density of anastomoses between the dorsal nasal, supratrochlear and supraorbital of both sides; no major artery is identified deep to the procerus, so the deep plane is the least bad, not the safe one [2]. · Angular vein: 4.2 ± 0.7 mm below the inferior orbital rim, oblique from inferolateral to superomedial, deep to the orbital portion of the orbicularis [4]. · Deep temple: deep temporal artery anterior at 1.5-2 cm and posterior at 2.5-3.0 cm from the lateral orbital rim [2]. · Tear trough: there is no layer 2; what is injected "subcutaneously" is intramuscular [4,3].

Surface landmarks and normative planes

They are marked with the patient seated at 90°, gaze to the horizon: supine, the tissue migrates and the marks shift [6,7]. They are surface references to locate bone, foramina and vascular courses before loading; they are not therapeutic targets.

(P) The profile angles (nasofrontal, nasolabial, mentolabial, cervicomental) have a definition but this chapter does not publish their normative ranges: the corpus pass did not return them with a traceable series and a slide is not enough (see the declared limitation in A1.10). The E-line and canthal tilt are kept because they are soft-tissue relations measurable on the photo, not teaching angle ranges.

The map, third by third

Upper third. The frontalis is not a muscle over bone: it is the continuation of the galea aponeurotica, covered by a thin fascia on its superficial face and a thicker one on its deep face [4]. Between the muscle and its deep fascia there is a fat lamina of its own —the subfrontal fat— through which the supraorbital and supratrochlear vessels ascend after leaving their foramina, and which is bounded by the inferior and middle frontal septa [4,1]. This description changes the gesture: in the lower third of the forehead the vessel is stuck to bone, and in the upper third it is already subcutaneous; the supraperiosteal plane is the poorest in arteries in the whole forehead [2].

The superficial fat compartments of the forehead were delimited in 2007 [14], confirmed in 2012 and updated in 2017 [1]: there are three, housed in layer 2 between the skin and the frontalis muscle.

In the temple, the five layers of the scalp continue but change name on crossing the superior temporal septum: the galea becomes the superficial temporal fascia and the periosteum the deep temporal fascia [4]. The anterior and posterior branches of the superficial temporal artery travel within the superficial temporal fascia (layer 3), so that subcutaneous filler (layer 2) sits superficial to them [4,2]. The deep technique deposits in contact with the bony temporal fossa, below the branches of the facial nerve and of the superficial temporal artery [2].

Mid third. This is where most aesthetic injections concentrate and where bone rules most: the maxillary angle decreases with age, changes the position of the fat compartments that rest on it, and the clinical sign appears [4,3]. Medial to the line of ligaments are the deep midfacial compartments (deep medial fat pad, deep lateral fat pad, premaxillary space, deep pyriform space); lateral to it are the premasseteric surgical spaces [4]. In the nasolabial fold the angular artery runs deep in the fold but close to the dermis: on contrast CT slices arteries are identified less than 4 mm from the skin [2].

Lower third. The facial artery crosses the mandibular border in front of the vein in 100 % of observed cases, deep to the platysma and deep to the marginal mandibular branch of the facial nerve [2]. At the modiolus it is fixed by a muscular band from the buccinator 1.5 cm behind the commissure, between the buccinator (deep) and the modiolar portion of the platysma plus the converging muscles (superficial) [2]. The labial arteries are submucosal in 78.1 %, intramuscular in an intermediate fraction and subcutaneous in only 2.1 % [2]: the subcutaneous plane of the lip is the least vascularized, not the most.

Classic trap: treating "the forehead" as one unit and choosing a single plane. The middle frontal septum splits the region into two opposite vascular regimes [2,1]; the same supraperiosteal bolus that is safest in the lower forehead lies, in the upper forehead, below a vessel that is already subcutaneous, and the palpable nodule that appears weeks later belongs to the upper forehead, not the lower.

A1.2 · Layers from skin to bone

Schematic — the 6-layer model and its three exceptions

Consensus: the conventional SCALP model describes five continuous soft-tissue and fascial layers from the neck to the scalp, with fat distributed in two laminae (layers 2 and 4) separated by the SMAS (layer 3) [4,3,6]. This chapter counts the bone or deep muscular foundation as layer 6 because it is the structural endpoint of examination and supraperiosteal work; the added number does not alter the five-layer anatomical nomenclature. Discrepancy — how many layers the temple has: Cotofana 2016 describes nine layers in the temporal region [3] · Cotofana 2019 describes ten, splitting the deep temporal fascia into a superficial lamina (layer 5) and a deep lamina (layer 7) with the superficial temporal fat pad (layer 6) between them [4] · decide: if injecting between laminae or raising a temporal flap, use the count of 10, which is the one that names the plane of the medial zygomaticotemporal vein; for a surface reference, both counts give the same gesture. Do not average.

The three exceptions that break the schematic

1 · The temple (more layers). From superficial to deep [4,20,17]:

The division of the deep temporal fascia into two laminae occurs between 2 and 5 cm above the zygomatic arch [4]. The deep technique deposits in bone contact, and the "one up and one down" reference from the fusion of the temporal crest with the supraorbital rim places the product in front of the deep temporal arteries, which run at 1.5-2 cm (anterior) and 2.5-3.0 cm (posterior) from the lateral orbital rim [2].

2 · The tear trough (fewer layers). Medial to the vertical line of the medial pupillary margin only three layers exist: skin, orbital portion of the orbicularis and periosteum [4,3,25]. There is no layer 2 and no deep fascia [6]. Direct consequence: in that zone the "subcutaneous" plane the rest of the face offers does not exist; an injection the operator believes superficial is intramuscular or supraperiosteal, with no middle ground. The bluish color seen through the skin is the orbicularis muscle itself, not a vein, and reappears identically on the medial nasal wall next to the inner canthus because there too the muscle reaches the dermis [3].

3 · The perioral region (no compartment architecture). Between the nasolabial folds, the nose, the modiolus, the labiomandibular folds and the submental septum there are no subcutaneous fat compartments nor a macroscopic aponeurotic structure: the fat is scattered among muscle fibers and collagen bundles that anchor the skin to the muscular plane [4,16,26]. That anchoring is what allows fine lip movement and also what draws the nasolabial fold as a transition line between type 1 subcutaneous tissue (compartmentalized) and type 2 (isolated fat cells in a collagen mesh) [3].

Fig 1. Cadaveric dissection of the lateral cheek: a whitish, translucent fibrous lamina (S) has been incised and separated with traction sutures, and below it the surface of the parotid plane (P) is exposed. The image documents that the SMAS is a dissectable, independent sheet, not a virtual plane — (Watanabe, 2016, p. 117).

Fig 1 is the physical proof of the previous argument: if the SMAS can be caught with sutures and lifted as a complete sheet, then it separates two fat compartments that do not communicate, and a product deposited above it will never migrate to the deep plane on its own. Layer 3 is not a descriptive convention.

What is inside each layer, and why it changes the decision

Layer 1. Thickness, pigmentation and adherence vary by region [3]. In the infraorbital region the skin is thin, transparent and firmly attached to the orbicularis; in the buccal and parotideomasseteric it rests on a variable thickness of fat with loose connections; in the perioral it is directly attached to muscle [3,26].

Layer 2. The subcutaneous fat is partitioned into compartments by fibrous septa that do two things at once: they are the protected route by which cutaneous nerves and vessels ascend from the depth, and they are the anchoring points of the skin to muscle, to other fasciae or to the skeleton [3,27]. This fat is continuous with general body fat and increases with obesity [3]. The superficial compartments descend with age [6]; the deep ones do not change their position relative to bone [21,28,6].

Layer 3. It contains the platysma in the neck, the SMAS in the face, the superficial temporal fascia in the temple, the galea in the cranium and the orbicularis oculi in the periorbit [4,3]. Described in 1976 [18] and revised histologically in 2003 [19], it is not a flat lamina but a three-dimensional composite of fat and collagen tissue [6]. In 2021 the presence of striated muscle fibers within the midfacial SMAS itself was demonstrated [29], which gives an anatomical basis to treatment with intradermal microtoxin. The zygomaticus major and minor muscles originate on the lateral cheek below this layer and perforate it on entering the medial cheek, from there being included in it [3].

Layer 4. It contains the deep fat, whose adipocytes are smaller and of different morphology from the superficial ones [30]. The limits of these compartments are the transit routes of the branches of the facial nerve and of the branches of the facial artery and vein [3]. In the temple, this layer is almost absent in the superior temporal compartment and varies with age in the inferior one, where it protects the temporal branches of the facial nerve [3,17].

Layer 5. Its name changes with the region and that is where many people get lost: it is periosteum in the scalp, deep temporal fascia in the temple, parotideomasseteric fascia in the lateral cheek, and in the neck it continues with the investing layer of the deep cervical fascia [4,3]. Medial to the facial vein it becomes periosteum again and connects with the epineurium of the infraorbital nerve [3].

Fig 2. Four-panel dissection sequence over the forehead and supraorbital rim of a specimen: (a) skin window opened with violet marking and a bleeding dermal bed; (b) and (c) the subcutaneous fat lamina, yellow and lobulated, is lifted en bloc as an independent flap; (d) the forceps hold the already-detached fat pad and reveal the underlying pearly-white deep plane — (Pirayesh, 2020, p. 107).

Fig 2 documents panel by panel what in the chair is only sensed through needle resistance: between the dermis and the deep plane there is a fat lamina that behaves as a unit and detaches whole. It is the anatomical argument for why a cannula advances effortlessly in the correct plane and meets resistance the moment it leaves it.

Operative translation layer by layer

Classic trap: applying the vocabulary of the cheek to the lower eyelid. In the tear trough "subcutaneous" names no existing plane [4,3,25]; the product ends up inside the orbicularis, and the clinical signature is a bluish bulge from the Tyndall effect that persists, accentuates on smiling and does not respond to massage, because it is not in a compartment but inside a muscle that contracts over it.

A1.3 · Fat compartments, one by one

Schematic — the facial fat in two laminae and what each compartment does

Superficial compartments, with their septum and their neighbor

Fig 3. Female face with the skin and superficial fat removed: over the muscular plane (pink) the deep fat bodies stand out in yellow, labeled one by one — retro-orbicularis fat (ROOF) above the brow, glabellar fat body in the midline, suborbicularis fat (SOOF) below the inferior orbital rim, superficial temporal fat body and the superior process of the buccal fat body of Bichat in the temple, buccal fat body and its inferior process in the cheek, and submental fat in the chin — (Radlansky, clinical facial anatomy atlas, p. 48).

Fig 3 makes visible the asymmetry this block lives on: the deep fat is not a continuous layer but a set of discrete bodies, separated and with identifiable neighbors. That is what allows a bolus placed in one of them to project a specific zone, and also what explains why a bolus placed in the one next door gives a result the patient describes as "odd" without being able to point to where.

Deep compartments, anterior view

Deep compartments, lateral view

Fig 4. Outline schematic of a face in three-quarter view with the fat compartments shown as discrete orange patches: a single temporal plate, three staggered vertical bands on the lateral and middle cheek, an infraorbital oval, a nasolabial band, two perilabial bands and a patch in the jowl region. The territories are shown unlabeled, separated by corridors of uncolored tissue that correspond to the septa — (Carruthers, 2018, p. 179).

Fig 4 is useful for what it leaves blank: the uncolored corridors between patches are septa, and a product injected there sits in no compartment but on a wall. It is the graphic representation of why the same milliliter performs differently with two millimeters of difference at the entry point.

Fig 5. Three-quarter-view illustration with the deep compartments of the mid third labeled in Portuguese: suborbicularis oculi fat lateral portion (lateral SOOF) and medial portion (medial SOOF) below the orbital rim, Ristow's space in blue next to the pyriform aperture, the buccal extension of the buccal fat pad of Bichat, and the deep cheek fat in its two portions, lateral (DCL) and medial (DMC) — (Lobo, 2022, p. 97).

Fig 5 locates Ristow's space, which in the anatomical nomenclature of this chapter corresponds to the deep pyriform space, medial to the infraorbital foramen [4,36]: it is the only compartment whose filling acts directly on the base of the nasolabial fold without touching the superficial fat that worsens it.

Compartment rules that change the gesture

Consensus: the target is chosen by compartment, not by "zone"; applying the product in the wrong compartment gives an aesthetically undesirable result even when the volume and the product are correct [4].

Rule 1 — deep first. The deep compartments barely shift with mimicry or with age because their limits are muscular, ligamentous or fascial connections anchored to bone [21,28,6]. Filling them first rebuilds the foundation and lets the superficial tissue reposition and keep moving naturally [6].

Rule 2 — two compartments that are not filled. The superficial nasolabial, because it aggravates the fold itself; and the jowl one, because it aggravates the labiomandibular fold and the deformity [6]. Both are superficial and both are exactly where the patient points with the finger.

Rule 3 — the transverse facial septum rules the smile. It is a broad fascial membrane that joins the zygomaticus major to the underlying maxilla and forms the lower limit of the deep lateral fat pad [4]. On smiling it deforms and displaces cranially the compartments it supports: that is the physiological "apple cheek" and, overloaded, the facial overfilled syndrome, with normal volume at rest and exaggerated on the smile [34,6].

Rule 4 — the jowl does not originate where it is seen. Between the mandibular ligament and the masseter, the facial artery and vein cross the mandible wrapped in deep fat that communicates neither with the buccal space nor with the buccal fat pad of Bichat [4]. With age, the platysma glides over the mandible and drags the superficial jowl fat compartment downward [4,39,40]. The origin is the gliding, not the local excess of fat.

Rule 5 — ROOF and SOOF are connected to the temple. The ROOF communicates with the inferior temporal compartment through the superior interval, and the SOOF with the same compartment through the temporal tunnel, because both reside in layer 4 over the superficial lamina of the deep temporal fascia [4]. An excessive volume in the lower temple can present clinically in the periorbit.

Rule 6 — the surface reference of the medial end of the SOOF is the tear trough. The zygomatic-cutaneous ligament fuses with the orbicularis retaining ligament just as it crosses the mid-pupillary vertical line, and from there the whole is called the tear-trough ligament [4,3,41].

Volumetric changes with age, by compartment

The debate about whether the superficial nasolabial compartment hypertrophies or simply accumulates against a barrier deserves precision, because it changes treatment: the fat cannot migrate below the fold because the mimetic muscles and the end of the SMAS anchor it to the skin, so it is forced upward and bulges above the fold [3]. If the mechanism is a barrier and not hypertrophy, the target is above and behind —deep compartments and lateral repositioning— and not the fold itself.

Classic trap: treating the dark circle with volume inside the SOOF when what is missing is the deep medial fat pad. The SOOF rests on a fascial lamina and has its medial limit at the tear trough [4]; loading it displaces the problem laterally and produces the "malar bag" bulge that worsens in the morning and with salt, because that compartment sits in the drainage territory that congests when supine.

A1.4 · Retaining ligaments

Schematic — the line of ligaments and the groove each one draws when it fails

Consensus: the major ligaments are not scattered over the face but aligned along a single line immediately lateral to the lateral orbital rim, from the temporal crest to the mandible; from superior to inferior: temporal ligamentous adhesions, LOT, zygomatic ligament and mandibular ligament [4,6]. That line is at once a surface reference and a functional boundary between the medial and lateral face [33,6].

Discrepancy — do the ligaments loosen with age? · A (Cotofana 2016): the ligament that acts as a hammock for a compartment shows fatigue, bows along its course and favors the sagging of the corresponding compartment; it is the model that explains the jowl [3]. · B (Freytag 2022): there is no solid scientific evidence that facial ligaments increase their laxity with age; what changes is the bony surface where they insert, and the effect is wrongly attributed to the ligament [6]. As indirect support, in the rabbit medial collateral ligament the content of collagen, GAG and water did not change with age, while the expression of lubricin/PRG4, which affects interfascicular lubrication, did [45]. · Decide: if the patient has documented bone resorption (short mandible, decreased maxillary angle, widened pyriform aperture), model B dictates treating the bone first with supraperiosteal product and not chasing the groove. If the skeleton is preserved and the descent is purely lateral and postural, model A justifies the lateral pulling vector. Do not average: they are two distinct targets.

Fig 6. Three frontal renders of the same woman on a dark background in increasing stages of aging: in the first the oval is continuous and the eyelid–cheek junction is not marked; in the second, tear trough, nasolabial fold and loss of jaw definition appear; in the third the lower third widens, the marionette lines are drawn, the upper lip lengthens and the brow descends — (Vieira Braz, 2017, p. 122).

Fig 6 chains in three images what the tables describe separately: the first visible change is a groove (a ligament marking its trace over a receding bone), the second is a superficial compartment that descends, and the third is the loss of mandibular perimeter. That order is what justifies the craniocaudal treatment sequence of the next block.

Measured biomechanics and what it implies

In a biomechanical test to failure, the zygomatic ligament resists the greatest force; it is followed by the orbicularis retaining and the mandibular [3,44]. Translation: the point where a surgical traction or a product vector meets most resistance is the lateral malar, not the submandibular. The ligaments are composed of collagens, proteoglycans, glycosaminoglycans and water, and their mechanical competence depends on the whole plus intrafascicular lubrication [3].

The face medial to the line moves laterally and the lateral face moves medially, converging on the line; three-dimensional vector analysis of the skin surface confirmed it, so the line is not only a drawing but a boundary of movement [33]. Moreover, passive mobility —the one that depends on gravity and age— is greater in the lateral face, where there are no mimetic muscles or major ligaments anchoring to bone, and where all the layers are continuous from the scalp to the neck, allowing the lower tissue to pull the upper [6].

The three principles that come out of here

Vector: lifting versus volumizing

Consensus: medial to the line of ligaments filler projects; lateral to it it lifts structures located lower down [4,31,32]. The mechanism is the fascial arrangement: oblique in the medial face, because the muscles run from bone to skin; parallel in the lateral, because there are no mimetic muscles [6].

Operative consequence for the order of work: the indication to fill the nasolabial fold directly frequently disappears after volumizing the upper mid third, that is the prezygomatic space of the SOOF [6].

The same anatomical grid governs thread-lifting techniques: the review of their anatomical considerations lists exactly the four elements of this chapter —navigation among vascular structures, protection of the facial nerve branches, manipulation of fat compartments and engagement of the retaining ligaments— and places ligamentous engagement as the condition for a sustainable lift without tissue distortion [47]. The instrument changes; the target does not.

Classic trap: chasing the tear trough with product in the groove itself. The groove exists because a ligament anchors the skin to the maxilla along that trace [41]; adding volume in front of the anchor makes it more visible by contrast, and edema in a zone with no real subcutaneous layer or deep fascia [6] translates into a morning bulge the patient attributes to sleep for months.

A1.5 · Muscles

Schematic — origin, insertion, vector, antagonist and layer

Consensus: almost all mimetic muscles have a direct bony connection and end in the dermis or in another muscular complex, which gives them an oblique deep-to-superficial course in the medial face; in the lateral face there are no mimetic muscles and the layers are parallel [6]. The facial muscles lack an epimysium, with the exception of the buccinator [3].

Discrepancy — "the deep fat is the gliding plane of the muscle". · A: several authors attribute to the deep fat a gliding function for the mimetic muscles, because it surrounds them [3]. · B (Cotofana 2016): that function is questionable, because most facial muscles change plane from layer 5 to layer 2 and end up surrounded by superficial fat too; besides, their function is to transmit contraction to the skin or the SMAS, which a protective wrapping would hinder [3]. · Decide: if B is accepted, the goal of deep filling is not to lubricate the muscle but to recreate the lost bony foundation [6], and then the amount is calculated by the skeletal deficit, not by the muscle volume.

The two balances that govern the face

Brow balance. A single elevator, the frontalis; depressors, the corrugator, the depressor supercilii, the procerus and the orbital portion of the orbicularis [6]. Any intervention on one of the depressors changes the resting position of the brow: that is what makes the glabella a functional unit and not a sum of muscles.

Modiolus balance. Depressors: depressor anguli oris, platysma and depressor labii inferioris. Elevators: levator anguli oris, zygomaticus major and minor, levator labii superioris [6]. The position of the commissure —and with it the reading of sadness or fatigue— is the result of that balance, not of lip volume.

Muscle aging: what is measured and what is not

The combined reading matters because it contradicts intuition: facial muscle aging is not a global atrophy, but a redistribution of activity, with more active glabellar depressors and a less active midfacial elevator [6,49]. A plan that relaxes the glabellar depressors and does not compensate for the loss of midfacial support accentuates exactly the measured imbalance.

Anatomical variability: why a fixed schematic fails

The variability of the midfacial muscles is documented in dissection series: 50 hemifaces in one series [51] and 52 fresh-cadaver hemifaces of a Persian population in another, the latter correlating muscle variation with the morphology of the nasolabial fold [52]. The insertion of the zygomaticus major at the commissure has different arrangements between individuals [53], the origin of the risorius varies relative to the facial planes [48] and the zygomaticus minor may be absent [4]. The variations also differ between ethnic groups [3,52]. This is why neuromodulator treatment moved from rigid point schemes to a plan individualized according to each person's anatomy [4].

The histological substrate of the nasolabial fold reinforces the same point: the zygomaticus major and the buccinator connect to each other and have strong adhesions toward the skin forming the fold, and then both fuse with the orbicularis oris [3,26]. A nasolabial fold is not an excess of fat above it: it is the insertion line of a muscular system.

The mapping of motor innervation refines that idea: with Sihler staining on dissections, the motor plates of the platysma cluster in the upper two thirds of the muscle, while the lower third is mostly sensory [54]. The anatomical consequence is that the muscle is not homogeneous as a target, and the same effect is obtained by concentrating the action where the motor plate is.

Classic trap: treating the platysmal band as a neck-only problem. The platysma has a horizontal modiolar portion that participates in the dynamics and contour of the lower face [40], and glides over the mandible dragging the jowl fat compartment [4]. Relaxing only the vertical cervical bands leaves intact the vector that produces the jowl, and the patient returns describing that "the neck improved and the jaw did not".

A1.6 · Arteries

Schematic — where the artery is and where the product goes, region by region

Fig 7. Three-dimensional reconstruction of a contrast cranial CT, frontal view: the arterial tree appears in orange over the gray bone after injecting the right internal carotid and the left facial artery. Labeled are the supraorbital (SOA) and supratrochlear (STA) emerging at the superior orbital rim, the dorsal nasal (DNA) at the nasal root and the facial (FA) crossing the mandibular border. The contralateral filling of the right facial tree from a single left injection is visible — (Cotofana, 2019, p. 417).

Fig 7 is the image that justifies the whole block: the filling of the opposite side from a single injection shows that the territories are not sealed compartments and that an embolus introduced into the face can reach the ophthalmic circulation. The labeled arrows also mark the exact point where the internal carotid system surfaces on the face.

Relevant extracranial-intracranial anastomoses

Table adapted from the corpus anatomical analysis [2] and consistent with the neurointerventional description of the dangerous anastomoses [57]. The functional importance is documented: in patients with symptomatic internal carotid occlusion, focal brain regions may depend on the supply of the ipsilateral external carotid through a patent route from the ophthalmic artery [2].

Ophthalmic artery and central retinal artery

The anatomical consequence for the conduct facing filler-related visual loss: the point where it matters to deposit hyaluronidase is the vicinity of the narrowest segment of the central retinal artery, that is the point of penetration into the optic nerve, which lies outside the nerve and surrounded by intraorbital tissue [2]. The anatomical description of the retrobulbar approach published in the corpus palpates the inferolateral orbital rim at a maximum of 1 cm medial to the lateral canthus, rests the injector on the bony margin and advances hugging the orbital floor, slightly medially and superiorly because of the conical shape of the orbit, crossing skin, subcutaneous fat, orbicularis and orbital septum, to 30-45 mm of depth depending on the physiognomy [2]. (P) The anatomical detail is gathered here because it defines the route; the indication, the dilution and the consent belong to the complications chapter and are not resolved with anatomy.

Course and depth, artery by artery

Facial, mandibular segment. It arises from the external carotid, alone or as a linguofacial trunk. It passes next to the submandibular gland, deep to the investing layer of the deep cervical fascia. At the mandibular angle it crosses the bone in 100 % of cases in front of the vein, deep to the platysma and deep to the marginal mandibular branch of the facial nerve, protected by a deep fat that communicates neither with the buccal fat pad of Bichat nor with the buccal space [2,38].

Facial, buccal segment. It enters the buccal space, bounded by the buccinator (deep), platysma (superficial), modiolus (anterior), facial vein canal (posterior), mandibular ligament and platysma adhered to the mandible (inferior) and transverse facial septum (superior) [2,38]. There it gives the inferior labial and/or the horizontal labiomental [60]. Its depth depends on the amount of fat in the subcutaneous compartments and within the buccal space [2].

Facial at the modiolus. Identifiable in 100 % of cases next to the corner of the mouth, held by a muscular band from the buccinator that fixes it 1.5 cm behind the commissure, between the buccinator (deep) and the modiolar portion of the platysma plus the converging muscles: levator anguli oris, zygomaticus major, levator labii superioris and depressor anguli oris (superficial) [2].

Labial arteries. Three possible positions: submucosal between mucosa and orbicularis (78.1 %), intramuscular between the two laminae of the orbicularis, and subcutaneous between skin and orbicularis (2.1 %) [2,56]. The proposed explanation is embryological: the muscular precursors form after the arteries have taken their definitive position [2].

Preinjection ultrasound adds a nuance of course that dissection averages out: located by sonography, the superior and inferior labial arteries arise on the deep, lateral slope of the lip and progressively approach the midline becoming more superficial, with superficial branches identifiable in the submucosal plane near the midline [61]. The point of greatest risk of the lip is therefore not the same in the lateral third as in the central.

Angular at the nasolabial fold. It runs deep in the fold but close to the dermis; its two-dimensional position varies between individuals and between sides of the same individual, so that it cannot be predicted [2,62]. On a contrast CT slice perpendicular to the fold, arteries are identified less than 4 mm below the skin [2].

Angular between the nasal ala and medial canthus. Very variable course in two and three dimensions. A series of 12 fresh hemifaces identified it within the deep pyriform space, bounded above and in front by the common elevator [2,36]. As it approaches the medial canthus it gives branches toward the nasal side and connects with the infraorbital as it emerges from the foramen [2].

Dorsal nasal. Bilateral terminal branch of the ophthalmic. It leaves the orbit and perforates the orbital septum above the medial canthal ligament, runs deep to the orbicularis and connects with the contralateral at the origin of the procerus. It has a direct connection with the angular, with the superior and inferior medial palpebrals and with the supratrochlear; it has no direct connection with the supraorbital, only indirect through the supratrochlear [2].

Supratrochlear. Terminal branch of the ophthalmic. It emerges through the supratrochlear notch or foramen at the superomedial angle of the orbit, in bone contact, perforates the corrugator and the inferior frontal septum and enters the subfrontal fat. On reaching the middle frontal septum —at 1.5 ± 0.17 cm (1.3-1.7) in the midline and 3.0 ± 0.24 cm (2.7-3.3) laterally from the supraorbital rim— it perforates the frontalis and its fascia and passes to the subcutaneous plane [2,1,8].

Supraorbital. It emerges from the supraorbital foramen or notch 1-3 mm medial to the mid-pupillary vertical line, in bone contact and lateral to the supratrochlear bundle. Its course is variable: it may perforate the corrugator (medial course) or not contact it (lateral course) [2,8]. Accompanied by the nerve and vein of the same name, it becomes more superficial on perforating the inferior frontal septum, where it gives branches to the frontal periosteum. After perforating the frontalis at the middle frontal septum it runs between the lateral and central superficial forehead compartments, and there gives a branch that connects with the anterior branch of the superficial temporal [2,1].

Superficial temporal. Most cranial branch of the external carotid. It emerges from deep planes toward the superficial temporal fascia in 100 % of observed cases, 1 cm in front of and 1 cm above the apex of the tragus [2]. Throughout the temporal region it runs within layer 3. After crossing the temporal crest it changes plane and lies in the subcutaneous of the forehead, where it connects with branches of the supraorbital [2].

Deep temporals. Anterior and posterior, deep in the temporal fossa and in close relation with the periosteum, with a longitudinal course at 1.5-2 cm (anterior) and 2.5-3.0 cm (posterior) from the lateral orbital rim [2].

Transverse facial. It runs in the superior premasseteric space and gives a branch that runs within the zygomatic ligament (McGregor) to give axial supply to the overlying SMAS [4].

Nose. Three arterial patterns according to the dominant source: facial, dorsal nasal or infraorbital [2,55]. It also receives from the superior labial, the columellar and contralateral branches. Most of the arteries are in the subcutaneous plane, which leaves the supraperiosteal and supraperichondral plane relatively avascular [2].

Fig 8. Three-dimensional model of a female face with the right hemiface dissected: over the forehead and orbit the frontalis and orbicularis are seen in red, crossed by fine yellow nerve branches; in the mid third, the deep fat appears yellow and over it the red arterial axis ascends from the nasolabial fold toward the medial canthus, with the lateral nasal branches heading to the ala; in the preauricular region the masseter and parotid are identified — (Pirayesh, 2020, p. 172).

Fig 8 shows the point the table summarizes in one cell: the facial-angular axis climbs the nasolabial fold superficial to the deep fat, so that a supraperiosteal deposit in the canine fossa passes below it, while a deposit "at mid depth" crosses it.

Fig 9. Lateral view of a schematic head dissection with seven numbered green circles over the risk regions: 1 in the retromandibular and cervical area, 2 and 3 in the parotid and mandibular region, 4 in the middle cheek, 5 in the high temple, 6 in the lateral periorbital region and 7 in the perioral region. The red tree of the superficial temporal and occipital, the yellow mesh of the nerve branches and the temporalis muscle with the parotid gland labeled below are visible — (Pirayesh, 2020, p. 107).

Fig 9 is read alongside the plane table: each numbered circle corresponds to a region where artery and nerve share a corridor, and that is why the plane criterion cannot be set by "aesthetic zone" but by the vascular segment that crosses that zone.

Why anatomy alone does not explain the incidence

In the glabella there are multiple connections between the dorsal nasal, supratrochlear and supraorbital of both sides, with high two-dimensional variability, which makes it the area of maximal risk of visual compromise [2,12]. But anatomy is not enough: most injections there are done with a sharp needle, and two independent studies showed that the needle distributes product into every plane it crosses, with material identifiable in the subdermal plane even when the tip is in bone contact [2,63,64]. Added to the double-perforation phenomenon of the arterial wall, a negative aspiration does not exclude intra-arterial deposit [2].

The rest of the risk picture is not only anatomical either: the variability is such —between individuals and between sides of the same individual— that it is not possible to guarantee absolute safety in any injectable procedure, and that sentence belongs to the consent, not to the technique chapter [2,12,65]. The safety guidelines moved from being authority-based to being evidence-based precisely because of the anatomical work of the last decade [2,46].

Classic trap: believing the nasolabial fold is a "deep" zone. It is exactly the opposite: it is one of the regions where the artery is more superficial than the operator expects, less than 4 mm from the skin [2]. The clinical signature of the error is an immediate blanching in the nasal ala and lateral dorsum —territory of the lateral nasal— that appears during the injection and not after, and which an operator expecting a "deep" problem is slow to interpret.

A1.7 · Veins and lymphatics

Schematic — the system that explains edema and the one that explains venous blindness

Fig 10. Lateral-view skull schematic with the facial venous tree labeled in blue: the supraorbital vein descends from the forehead to the medial angle, where it receives the superior ophthalmic vein and continues as the angular vein; the inferior ophthalmic vein is labeled on the orbital floor; the trunk descends obliquely over the cheek receiving the superior and inferior labial veins and the mental vein, and crosses the mandibular border as the facial vein toward the neck — (Parker, 2022, p. 29).

Fig 10 shows the detail that decides conduct in the periorbit: the angular vein does not end at the canthus, but continues into the orbit with the ophthalmic veins. That continuous blue line is the route by which a midface problem reaches the orbit and the cavernous sinus.

Fig 11. Outline schematic of the head and neck: the facial venous axis is shown in orange descending from the frontotemporal region in front of the eye and cheek to cross the mandibular border and converge in the neck, while the posterior system appears in red behind the auricle and over the sternocleidomastoid. In gray the facial skeleton and the muscular planes of the neck are drawn — (van Gijn, 2022, p. 360).

Fig 12. Lateral-view schematic of the orbit: the dark-gray venous trunks surround the globe forming a perimeter ring, with a superior trunk running along the orbital roof, an inferior trunk over the floor, and an anterior confluence at the medial angle that continues toward the face; posteriorly, the network converges toward the orbital fissure. The reticular plexus in the region of the posterior orbital floor is visible — (van Gijn, 2022, p. 414).

Fig 11 and Fig 12 together explain periorbital edema more than any table does: the drainage of the orbit converges forward and toward the medial angle, that is toward the same point where the tear trough is injected, and from there it follows the facial venous axis of Fig 11. A volume that compresses that corridor produces an edema that is not inflammatory and that is why it does not respond to anti-inflammatories.

Lymphatics: four rules and one declared limitation

Declared limitation, with the query that proves it. In the run A1-20260809 (evaluation/runs/A1.jsonl, 200 records, 3 027 contexts retrieved), 86 contexts contain a lymphatic term versus 395 that contain facial or angular vein. The best-scored facet of the chapter is anatomy_planes_danger (mean global_top_score 0.745) and no lymphatic-specific facet exists in the program. Honest translation: facial lymphatic anatomy is in the corpus as an atlas topographic description [67,70,68] and as a clinical observation [71], not as an anatomical series measured to the level of detail this chapter offers for arteries. Any quantitative claim about facial lymphatic flow would have to come from outside the corpus.

Angular vein: the detail that changes periorbital filling

The angular vein is identified along the medial wall of the zygomatic-cutaneous ligament after emerging deep to the zygomaticus major, and its relation with the zygomaticus minor is variable, superficial or deep [4]. Its position defines two compartments that are filled with different goals: the deep medial fat pad lies between the infraorbital foramen and the vein; the deep lateral, between the vein and the zygomaticus major [4]. An operator who does not have it in mind is not choosing a compartment, is choosing a depth.

There is also a measured functional datum: the ability to compress the angular vein against the underlying maxilla on smiling decreases with age, in parallel with the drop in the electromyographic signal of the zygomaticus major [6,49,50]. That is, the muscular mechanism that aids midfacial venous return weakens precisely in the population that consults for morning eyelid edema.

Why malar edema is not a product problem

(P) With the four rules above the picture orders itself, without invoking properties of the filler: the lateral malar region drains through superficial lymphatics that accompany veins [67], rests on the SOOF, which in turn rests on a fascial lamina and not on periosteum [4,35], and has above it a ligament that compartmentalizes it [41]. A volume placed there occupies a drainage space, not a support space. The clinical signature —worse in the morning, worse with salt, better through the day, without erythema or pain— corresponds to a positional and drainage problem, and the anatomical conduct is not to keep adding volume in the same plane.

Convergence points to memorize

Classic trap: interpreting as "inflammation" the periorbital edema that appears days after a tear-trough filling and treating it with corticosteroid. The described substrate is a palpebral lymphatic system that tolerates neither volume nor trauma [71] over a region with no real subcutaneous layer [4,3]; the corticosteroid does not reopen an occupied drainage corridor, and the signature that gives it away is the hourly and postural fluctuation, absent in a true inflammatory picture.

The dangerous triangle, the valves and the compressing hematoma

The facial venous system communicates with the cavernous sinus through the superior and inferior ophthalmic veins via the angular and the nasofrontal vein [67,68]. That communication is the anatomical route of two serious pictures distinct from arterial blindness: cavernous sinus thrombosis and intracranial spread of an infection from the so-called dangerous triangle —nasal root to commissures—, which a furuncle or a cellulitis from infected filler can follow retrograde [67,68].

(P) The combined reading: the venous route does not blind by embolus, but turns a local infection or a tense hematoma into a regional or intracranial problem through the same corridor without competent valves. Management lives in J1-J2; here the substrate remains.

A1.8 · Nerves

Schematic — motor and sensory, what is blocked and what is injured

Fig 13. Three-dimensional model of a skull in lateral view with the parotid gland shown in tan over the mandibular ramus and the five branches of the facial nerve drawn in yellow and numbered from inferior to superior: 1 cervical, toward the neck below the mandibular angle; 2 marginal mandibular, following the lower border of the mandible; 3 buccal, toward the commissure; 4 zygomatic, toward the orbit; and 5 temporal, crossing the zygomatic arch toward the temple and the brow — (Pirayesh, 2020, p. 158).

Fig 13 locates the fact that orders motor safety: the five branches leave the same plexus and diverge like a fan, so that their distance from each other is minimal in the preauricular region and maximal in the periphery. The zone of risk of multiple injury is the parotid; that of isolated injury, the periphery.

The principle of the septa: where the motor branches travel

The marginal mandibular, buccal and zygomatic branches of the facial nerve do not run free in the fat: they travel within laminae of fibrous connective tissue that connect the parotideomasseteric fascia with the SMAS, and those laminae are precisely the walls that bound the superior, middle and inferior premasseteric spaces used in lift surgery [4]. Direct consequence for the injector: the interior of a premasseteric space is empty of nerve; its wall is not. The safe dissection or injection in the lateral cheek is the one that respects the compartment, not the one that respects a depth in millimeters.

In the temple the logic is identical: the superior temporal compartment contains no relevant neurovascular structures, while the inferior houses the frontal branch of the facial nerve, the sensory zygomaticotemporal branches and the sentinel vein [4]. The deep temporal technique works because it passes below all that content, in bone contact [2].

Fig 14. Anatomical specimen of the forehead and glabella seen backlit against a light background: over the translucent amber tissue the nerve filaments stand out in dark brown, emerging in two symmetric tufts above the superior orbital rims and fanning out upward and laterally; in the lower midline the nasal openings and another network of filaments ascending from the nasal root are visible — (Kim, 2016, p. 37).

Fig 14 explains why the supraorbital block works with so little volume and why its failure is always lateral: the filaments leave concentrated in a tuft and open out afterward; an infiltration below the point of divergence covers the whole fan, and an infiltration above covers only the sector reached.

The three foramina and their alignment

The three sensory emergence points of the anterior hemicranium are aligned approximately in the same vertical plane: the supraorbital foramen 1-3 mm medial to the mid-pupillary vertical line [2], the infraorbital foramen on that same vertical —it is the medial limit of the deep medial cheek fat pad [4]— and the mental foramen, surrounded by the deep labiomandibular fat that acts as a gliding space and protects it as it emerges [4,10]. That alignment is the surface reference on which the three trunk blocks of the face are built [72,9].

A connection datum that changes the gesture in the mid third: medial to the facial vein, layer 5 continues with the periosteum of the facial skeleton and connects with the epineurium of the infraorbital nerve [3]. The deep medial fat pad is not simply near the nerve: it shares a fascial continuity with it, and that is why an excessive volume there produces dysesthesia and not only mechanical compression.

Fig 15. Detail of the left infraorbital region with the skin removed: below the lower eyelid the muscular plane is seen in pink and the fat in yellow, and a blue circle marks the emergence point of the infraorbital bundle, from which a red arterial tuft departs opening in several directions —toward the nasal ala, laterally and downward, toward the upper lip— accompanied by descending yellow nerve fibers — (Libro Zonas Peligrosas en Medicina Estética Facial, p. 20).

Fig 15 corrects a frequent scale error: the infraorbital bundle is not a point but a fan that occupies much of the upper medial cheek. A deposit "lateral to the foramen" may still be inside the fan.

What is blocked and with what anatomical purpose

What gets injured, in order of practical frequency

(P) Ordered by what the anatomical corridor predicts, not by a series: frontal branch of the facial nerve when working on the temple at intermediate depth, because the inferior temporal compartment is exactly that plane [4,11]; marginal mandibular branch when injecting the mandibular border anterior to the masseter, where it runs superficial to the facial vessels [2]; and infraorbital nerve, through fascial continuity with the deep medial fat pad [4,3]. The three share the same mechanism: it is not a failure of lateral aim, it is a failure of plane.

The corridor can also be objectified in real time. In a systematic review of 16 studies on ultrasound-guided chemical denervation in muscles innervated by the facial nerve, the cadaver trials reached up to 88 % deposit accuracy versus 50 % for the technique based only on surface references, and the anatomical studies included identified variation in muscle depth and vascular risk zones [73]. The datum measures exactly what this block describes: the variability of the corridor, not the operator's aim.

Classic trap: looking for the "mid plane" in the temple. The two described planes —subcutaneous above the superficial temporal fascia and supraperiosteal in bone contact— exist precisely because between them is the compartment that contains the frontal branch of the facial nerve, the sensory zygomaticotemporal branches and the sentinel vein [4,2]. The signature of the error is a brow asymmetry that appears hours or days later, not immediately, and which the patient attributes to the toxin that was not given.

A1.9 · Bone

Schematic — what moves, in which direction and what sign it produces

Consensus: the facial skeleton is not static; it undergoes continuous remodeling throughout life and those changes modify appearance and expression [3,6,81]. The bone is therefore the foundation of treatment and not a backdrop [6].

Discrepancy — magnitude of the angular change by population. · A (Caucasian population): the glabellar, orbital, maxillary and pyriform angles decrease with age, and the maxilla, the pyriform aperture and the infraorbital rim recede [3,79]. · B (Asian population): similar results in direction, but the orbital and maxillary angles change less, and the pyriform angle changes more than in Caucasian series [3,87]. · Decide: in an Asian-phenotype patient, the expected dominant deficit is at the pyriform base and not in the malar projection; inverting the priority reproduces an aged Caucasian face instead of rejuvenating the one at hand. The angles are not averaged across populations.

Fig 16. Frontal-view skull with superimposed blue arrows indicating the directions of remodeling: in each orbit, two opposing diagonal arrows mark the expansion of the superomedial and inferolateral quadrants; a bidirectional horizontal arrow marks the widening of the pyriform aperture; converging arrows point toward the maxilla below the orbital rim and toward the lateral region; and in the mandible, arrows directed toward the alveolar border and toward the chin region — (Azizzadeh, 2018, p. 255).

Fig 16 translates the table into an examination gesture: the pattern is not a homogeneous loss of bone but an expansion in some quadrants and a recession in others. Palpating the orbital rim in its four quadrants and the pyriform base indicates where support is missing before deciding a single milliliter.

Fig 17. Two facing profile illustrations, with the skull drawn beneath the soft-tissue contour. On the left, a young subject: full dentition, tall mandibular ramus and body, projected chin and a taut skin contour over the mandibular border. On the right, an older subject: gray hair, reduced mandibular height, recession of the chin and maxilla, and a soft-tissue contour that protrudes below the mandibular border instead of resting on it, with the nose relatively more prominent — (Standring, Gray's Anatomy, 2016, p. 959).

Fig 17 is the argument against the purely gravitational explanation: the soft tissue of the right panel has not increased, and yet it overflows the mandibular border because the bone that supported it has receded. That is the mechanism that turns a resorption into a visible jowl [4,39].

The complete causal chain, in order

1. Bone remodeling → decrease of the maxillary angle and expansion of the inferior orbital rim [3,79].
2. → Anterior positioning of the orbital septum, with reduction of its retention capacity [3].
3. → Pseudoprolapse of the retroseptal fat pads: the eyelid bag is not new fat, it is poorly contained fat [3].
4. → The orbicularis retaining ligament loses its horizontal position and tilts inferiorly [3].
5. → Loss of stability of the orbicularis, which forms the anterior wall of the ROOF (above the aperture) and the SOOF (below) [3].
6. → Malar mounds, palpebromalar groove and visible eyelid–cheek junction [3,41].

This chaining is the reason block A1.4 keeps open the discrepancy about ligamentous laxity: if step 1 explains steps 4 to 6, the ligament has not changed, its anchoring point has changed [6].

Overarching theories

Clockwise rotation of the viscerocranium (Lambros). The sum of the changes described by the classic series —lateral translation of the orbits, glabellar protrusion, expansion of the supraorbital arches, increased depth and lateral expansion of the cheeks, increased length, width and vertical dimension of the nose, and increase in vertical height in the occlusal region— was summarized as a clockwise rotation of the viscerocranium seen from the right [3,75]. The relation between bone remodeling and that rotation was later quantified on CT [81]. Pessa verified Lambros's theory by three-dimensional stereolithography in 12 skulls, measured the significant decrease of the maxillary and pyriform angles with age (p = 0.004 and 0.005) and formalized the result as an algorithm of facial aging that still orders the diagnosis [88].

Accordion effect (concertina). A small craniofacial skeleton —from advanced age or congenital skeletal insufficiency— reduces the space available for the soft tissue of the mid third, which folds over itself with a bellows-like appearance; a young face represents the point at which the skeletal proportions are adequate for the volume of soft tissue that covers them [83]. That formulation has a practical consequence: a young patient with skeletal insufficiency presents signs of premature aging that are not aging.

Rhythm and chronology: what the corpus does NOT support

Declared gap, with the query that proves it. The run A1-20260809 (evaluation/runs/A1.jsonl) was searched for the terms maxillary angle, glabellar angle, pyriform aperture/angle, orbital aperture, decade, década, reabsor, resorption over the 3 027 retrieved contexts. The returned contexts describe the direction of the change and the regions affected, but none provides a decade-by-decade resorption table with magnitudes: the highest-scoring hits were aesthetic-practice manuals and technique chapters, not anthropometric series stratified by age. The dose_parameters facet —the one that would capture quantitative magnitudes— is moreover the lowest-scored in the chapter (mean global_top_score 0.536, minimum 0.357).

(P) Therefore this chapter does not publish a decade-by-decade chronology. What the retrieved evidence does support is an order, not a calendar:

Anyone needing magnitudes by decade must go to the original CT series [80,77,79,87,82] and check how they stratified age; the own corpus does not contain them at that detail.

Bone and safety: thickness matters

The cortical thickness of the skull changes with age and sex [84,85], and the overall morphology of the adult skull also [85]. This is not an academic detail in the temple: it has been explicitly investigated whether intracranial penetration is possible during temporal filler injection [89]. The safety reference remains bone contact with a short injector and depth control, not confidence in an assumed thickness.

A second bone–technique intersection point: repeated toxin injection into the masseter has been associated in recent literature with a risk of bone resorption, among other complications described for that indication [90]. It is the same principle in the reverse direction: muscular loading shapes the bone, and removing it shapes it too.

Classic trap: compensating with soft-tissue volume for a skeletal projection deficit. The result is a face that at rest looks correct and in motion behaves like a heavy tissue over an insufficient support [6,83]; the signature is the exaggerated increase of midfacial volume on smiling from cranial displacement of the compartments over the transverse facial septum [34], and the correction is not more product but product in another plane or support surgery.

A1.10 · Proportions and variants

> This is the block that D1-D13 consume. The thirteen regions link here for thirds, fifths, landmarks and variants; none of them repeats these.

Schematic — vertical and transverse proportions

Fig 18. Female profile illustration with five black horizontal lines drawn from left to right over the face: the first at the level of the hairline, the second at the level of the glabella and brow, the third at the subnasale, the fourth at the labial stomion and the fifth at the soft-tissue chin. The lines delimit the three vertical thirds and the subdivision of the lower third — (Master Techniques in Facial Rejuvenation, 2018, p. 35).

Fig 18 sets the examination gesture that replaces the general impression: five lines on a profile photo tell whether the patient has a short lower third, a lengthened mid third or a long upper lip, and each of those three findings leads to a distinct target.

Landmarks (nomenclature for D1-D13)

Golden ratio: what it is and what it is not for

Formal definition: the section of a line such that the lesser part is to the greater as the greater is to the whole [92]. It is a descriptive criterion, not a therapeutic target.

Consensus: knowledge of the theoretically ideal facial proportions is useful in planning [94]. And the same text sets the limit: those ideals must not be used alone, but together with the consultation in which the patient's subjective concerns and ideas are gathered, and moreover the differences between male and female faces, between ethnicities and between age groups must be considered [94]. (P) A fifths template applied without that correction produces faces that are correct on paper and alien in the mirror.

Variation by sex

(P) The combined reading is that the sexual difference is in the starting shape (forehead, jaw, lip), not in the direction of aging, which is common. A feminization or masculinization plan works on the former; a rejuvenation plan, on the latter. Confusing them is what produces an aged result but of another sex.

Variation by ethnicity

Discrepancy — which target to expect by phenotype. · A (Caucasian series): the dominant deficit with age is maxillary and infraorbital rim retrusion, with midfacial descent [3,79]. · B (Asian series): more marked change of the pyriform angle and less of the maxillary and orbital [3,87]. · Decide: the patient's phenotype and palpation of the pyriform base versus the infraorbital rim. The angles are not averaged across populations, and the aesthetic goal of one population is not imported into another.

Variation by age: which proportions move

Layer thickness: the datum that changes lip technique

In a cross-sectional series of 126 participants evaluated with high-frequency ultrasound in two cities, the subcutaneous layer of the lip measured less than 1 mm on average in both the upper and lower lip, so that filler ended up being intramuscular in the majority of treated people [95]. Treated patients showed greater thickness of the connective-tissue layer and of the pars peripheralis, and vertical injection techniques were associated with deeper deposit, hypervascularity and signs of migration [95].

(P) That measurement connects with block A1.2: the lip is not the only region where the nominal subcutaneous plane does not exist at the thickness the operator assumes; it is the same lesson as the tear trough, now quantified with in vivo ultrasound. The consequence for D5 (perioral) is that "subcutaneous" in the lip describes an intention, not a compartment.

How a region uses this block

(P) Reading protocol for D1-D13, so that no region repeats general anatomy: 1. Take from here the thirds and fifths and the landmarks with their exact definition. 2. Take from A1.2 the target layer and its regional exceptions. 3. Take from A1.3 the specific compartment and its neighbor. 4. Take from A1.6 the arterial depth by segment and the recommended plane. 5. The region only adds: product, instrument, movement, volume, school, non-injectable alternative and the discrepancy between schools.

Classic trap: measuring thirds on a photograph without natural head position. The vertical references are defined relative to the vertex with the subject in natural position [7]; a cephalic tilt of a few degrees lengthens or shortens a third in the image and produces a diagnosis of "short lower third" that disappears when the photo is repeated. The signature of the error is a chin-projection plan that the patient rejects on seeing themselves in the mirror, where the head returns to its natural position.

Classic canons, Ogee curve and angles

Declared limitation on the reference angles. The corpus pass A1-20260809 was queried for nasolabial angle, ángulo nasolabial, nasofrontal, nasofacial, mentolabial, cervicomental, regla de los tercios, proporción áurea and E-line over the 3 027 retrieved contexts. It returned definitions and proportions —thirds, fifths, transverse equalities, bizygomatic percentages— but no normative angular ranges with their source series; the master's angular diagrams are slides with no figure in the converted text [97]. (P) An angular range supported only by a slide is never_sufficient_alone, and that is why this chapter publishes the definitions of the angles and refers to the corpus cephalometric monograph [7] for the values, instead of printing figures it cannot trace.

Classic trap of the canons block: using the Vitruvian canon as a treatment goal. The very teaching that presents it calls it scientifically untenable [97], and the clinical anatomy monograph that provides the templates warns that the ideals must not be used alone, but together with the patient's subjective concerns and corrected for sex, ethnicity and age [94]. The signature of the error is a patient who at the review describes the result as "correct but I don't recognize myself".

Regional anatomy: neck, décolletage and dorsum of the hand

> The thirteen facial regions live in D1-D13; neck, décolletage and hands have no chapter of their own and their applied anatomy is closed here. The technique and the laser/peeling parameters live in the dermatological lane (F3), not in anatomy.

Schematic — three extrafacial regions and what rules in each

Fig 19. Schematic illustration of the dorsum of the hand with a needle advancing in the most superficial plane; the inset enlarges the cross-section with the three fat laminae labeled —dorsal superficial lamina (DSL, no structures), dorsal intermediate lamina (DIL, with a blue vein inside it) and dorsal deep lamina (DDL, with the extensor tendon)— separated by the dorsal superficial (DSF), intermediate (DIF) and deep (DDF) fasciae; below, a section through the five metacarpals locates the extensor tendon and the intertendinous fat reservoir — (UPO, hand rejuvenation, p. 13).

Fig 19 sets the plane the table summarizes in one cell: the needle goes in the superficial lamina, above the dorsal vein of the intermediate lamina and well above the tendon of the deep one. It is the same principle as the temple —two safe planes and a dangerous intermediate one— transferred to the hand.

The dorsum of the hand, lamina by lamina

The cadaveric investigation of the dorsum of the hand (Bidic) identified three distinct fat laminae beneath the dermis, divided by thin fasciae and joined by fibrous walls and 8-10 perforating vessels that cross them perpendicularly [99]. From superficial to deep: the dorsal superficial lamina (DSL) contains no structures and is the recommended deposit site; the dorsal intermediate lamina (DIL) houses the dorsal veins and nerves; the dorsal deep lamina (DDL) contains the extensor tendons [98,99]. The injection site is bounded by the 2nd to 5th metacarpals and the dorsal wrist crease [99].

Consensus: the deposit goes subdermal, in the superficial lamina, adjacent and superficial to the dorsal veins; the skin pinch ("tenting") separates the laminae and facilitates cannula advance [98,99]. Discrepancy — to pinch or not to pinch? · A: the pinch magnifies the subdermal areolar plane and moves the tip away from veins and tendons [98]. · B (Rosen, dissection of 19 fresh hands + duplex ultrasound): the pinch lifts the dorsal veins and the fascial plane itself too along with the skin, and that is why his subdermal scraping technique avoids it so as not to increase the vascular risk [98]. · Decide: with a cannula and faint veins, the pinch helps; with prominent veins and a needle, the pinch can bring the vein up to the plane of the tip. Do not average: it is a decision per hand.

Classic trap: treating the décolletage and the dorsum of the hand with facial parameters. Both regions have fewer adnexa and a worse repair reservoir, and the result ages worse if the facial energies are copied [94,98]. It is a parameter error, not an indication error.

Cadaveric dissection as a curricular standard

The reference academies (AAFE, ECAMS, Archidemia and equivalent centers such as the ICLO in Verona) place dissection as a curricular requirement, not as a complement [100]. (P) The rationale is that of the whole chapter: the anatomical variability of A1.6 —arteries that change plane by segment, displaced foramina, absent muscles— is not internalized in an atlas, which draws the mode; it is internalized by seeing it several times on real tissue.

What a course must deliver for dissection to teach real anatomy

Fig 21. Cadaveric dissection of the perioral region and upper lip after percutaneously injecting hyaluronic acid homogenized with green dye into the retro-orbicularis oris fat compartment (ROOrF); the staining delimits exactly the territory the bolus occupied and forceps separate the overlying orbicularis oris — (Lamb, 2018, p. 66).

Fig 21 is the argument for the method: the green dye marks the compartment the bolus really occupied. Without staining and going to look, the operator believes they deposited in a plane and has no way of knowing whether they hit it. The Paternostro study formalizes it: 9 non-embalmed donors, methylene blue in the supraorbital region, subsequent dissection to measure the real diffusion of the volume [100].

Classic trap: validating a technique on a formalin-fixed cadaver. The fixed tissue behaves like a rigid, homogeneous plane, different from the living; a maneuver that "works" there may reproduce neither the real plane nor the real diffusion [101].

Anatomical orientation by ultrasound

High-frequency cutaneous ultrasound turns anatomy from statistics into a patient datum: where A1.6 gives the most likely location of an artery, the probe gives that of this patient, this side and today. Its full development lives in G6; here its place in the anatomical map remains.

Schematic — settings and what is reliably identified

What is reliably identified: layers 1-5 of A1.2, the artery (pulsatile, Doppler+), the vein (compressible) and the filler material [102,103]. Ultrasound is the diagnostic tool that recognizes a previous filler the patient does not recall or denies, and the guide for targeted hyaluronidase (J3, J7).

Ultrasound appearance of filler, material by material

Fig 20. B-mode ultrasound of a superficial deposit with a "snowstorm" pattern: a dome of diffuse granular hyperechoic echoes in the subcutaneous plane with a posterior "dirty" acoustic shadow that prevents differentiating the deep planes, the characteristic appearance of silicone and permanent biopolymers — (UPO, filler adverse effects, p. 216).

Fig 20 shows why ultrasound changes conduct facing an unknown filler: the snowstorm pattern identifies a permanent biopolymer without the patient needing to recall what was placed, and that single image reorders the diagnosis and the management (J7). Hyaluronic acid, in contrast, is seen as an anechoic collection that hyaluronidase can reach in a targeted way.

Classic trap: assuming that "nothing is palpable" means "there is no filler". Integrated PLLA and hydrated hyaluronic acid may not be palpable and still be seen —or their absence confirmed— on the probe; a pre-treatment ultrasound assessment in an operated zone avoids injecting over an unexpected material [103].

Danger zones by region (operative synthesis)

Ordered by consequence, not by frequency. Beleznay maintains the reference series of filler blindness: in the review of 98 cases the glabella (38.8 %) and the nasal region (25.5 %) led, followed by the nasolabial fold (13.3 %) and the forehead (12.2 %) [12]; the update of 48 new cases inverted the order toward the nose (56.3 %) and the glabella (27.1 %), with the forehead (18.8 %) and the nasolabial fold (14.6 %) behind, and hyaluronic acid as the causal material in 81.3 % [106]. The two sites that lead are constant across reviews: glabella and nose.

The two rules that summarize all the above: (1) if one is in the mid subcutaneous of a named territory, one is in the worst possible plane —Lee measured that the facial artery itself changes plane along its course and that there is no universally safe plane for it [107]—; (2) a negative aspiration does not rule out intravascular position: it is weak information, not a permission, because the needle seeds product into every plane it crosses and the double-perforation phenomenon of the wall exists [2,63,64]. The safe conduct is not to aspirate but to choose a plane, move the needle and retro-inject slowly.

Schools

The reader wants to know what is done; the schools answer differently to a single question —"what is aging made of?"— and that is why they are not averaged. The comparative development lives in B5; here their anatomical stance remains.

Consensus among all: treat lateral to the line of ligaments before medial, and deep before superficial, because the lateral layers continue with the SMAS and lift, and the deep compartments do not shift [31,32,6]. The discrepancy is in how much weight to give volume versus skin quality, and that is decided per patient, not per school.

Errors and how to avoid them

Step-by-step protocol — anatomical mapping before any infiltration

(P) It gathers the landmarks of A1.1, the layers of A1.2 and the arterial depth of A1.6 into a repeatable sequence. No region (D1-D13) repeats it; all of them assume it.

1. Seated at 90°, overhead light, no makeup, gaze to the horizon (Frankfort plane).
2. Standardized photography: frontal, bilateral ¾, bilateral profile, at rest and in dynamics.
3. Palpate and mark bone: orbital rim in its four quadrants, zygomatic arch, temporal fusion line, mandibular border, pyriform aperture. With the bone marked, half the decisions are already made.
4. Mark the three foramina on the mid-pupillary vertical (supraorbital 1-3 mm medial, infraorbital 5-10 mm below the rim, mental).
5. Mark Pitanguy's line if the temple, brow tail or upper third are to be worked.
6. Find the superficial temporal with the finger in front of the tragus and follow it upward; mark it.
7. Doppler / ultrasound if the plan includes glabella, nose, temple or tear trough, or if there is previous surgery, previous filler of unknown origin or unexplained asymmetry.
8. Declare the plane of each point in writing before loading: supraperiosteal / deep subcutaneous / subdermal / intradermal. A point with no declared plane is not injected.
9. Check the escape route: where the hyaluronidase is, how many IU and at what distance. If the answer is not immediate, do not begin (J2).
10. Reassess standing when finished: gravity is part of the anatomy.

Classic trap: starting to load without having declared the plane of each point. Step 8 is the one that separates a map from an intention, and its absence is the silent signature of almost everything the previous sections describe as a plane error.

Coverage vs UPO

What UPO does NOT cover and this chapter does:

Currency caveat on the UPO lane. The master's material is slide teaching and theoretical chapters; no figure supported only by that source is published here as a clinical parameter (never_sufficient_alone). Its value in this chapter is as a syllabus: it defines what had to be covered, not how much each number is worth.

Self-assessment

Ten active-recall questions. All are answered only with data published in this chapter.

1. Which four structures form the line of ligaments, from superior to inferior, and what changes in the result depending on whether one injects medial or lateral to it?

2. At what distance from the supraorbital rim is the middle frontal septum and why does that figure change the injection plane in the forehead?

3. How many layers does the tear trough have and which are they?

4. Where is the facial artery fixed at the modiolus, with what frequency and by which structure?

5. In what percentage are the labial arteries submucosal and in what percentage subcutaneous, and what plane remains the least vascularized in the lip?

6. Which temporal compartment contains the frontal branch of the facial nerve and which is free of relevant neurovascular structures?

7. What is the retinal survival time window measured experimentally and why is complete occlusion rare on angiography?

8. Where is the angular vein located relative to the inferior orbital rim and which two compartments does it separate?

9. Which two superficial fat compartments are not filled and why?

10. What difference is there between Caucasian and Asian populations in the angular changes of the facial skeleton with age?

What's new and trends (2022-2026)

What did NOT change, and why the old references remain the state of the art. The description of the superficial fat compartments [14] and their septa, the layer model [4,3], the inventory of retaining ligaments [109,13] and their biomechanical hierarchy [44], the course and depth of the facial arteries by segment [2] and the anatomy of the ophthalmic route [2,58] have not been replaced: they have been confirmed with another modality, first by imaging [15,21] and now by in vivo ultrasound [28,95]. A dissection article from 2007 or from 1989 remains the primary source of an anatomical limit because the limit has not changed; what has changed is the ability to see it without opening. (P) The correct reading of this chapter's reference list is that the median year is low because the macroscopic anatomy is stable, and that what ages fast is not the description of the compartment but the recommendation of what to do with it.

What remains open. The decade-by-decade chronology of bone resorption (declared as a gap in A1.9), the quantification of facial lymphatic flow (declared in A1.7) and the real existence of measured ligamentous laxity (open discrepancy in A1.4).

Unexplored directions (AI speculation)

> Notice. What follows is not evidence. These are hypotheses generated by the model from the data already cited in this chapter, marked with [IA-ESPEC] so they cannot be confused with the [A]-[D] tags or with a recommendation. No proposal includes a dose, a product or an applicable protocol. Each one declares its anchor (a fact already cited here), the proposal and what would settle it.

1 · Ultrasound of the middle frontal septum as a substitute for the metric reference. [IA-ESPEC] · Anchor: the middle frontal septum is at 1.5 ± 0.17 cm in the midline and 3.0 ± 0.24 cm laterally [2,1], and above it the artery becomes subcutaneous. · Proposal: that the individual position of the septum be locatable by high-frequency ultrasound as a recognizable interface, instead of being estimated from a population mean. · What would settle it: an ultrasound–dissection concordance study in the same specimen, measuring the deviation between the real position and the one predicted by the mean, with the dispersion (±0.17 and ±0.24 cm) as the utility threshold.

2 · The line of ligaments as a drainage boundary, not only of movement. [IA-ESPEC] · Anchor: the line is a functional boundary of movement demonstrated by surface vector analysis [33], and the superficial lymphatics accompany the veins [67]. · Proposal: that the same line separates superficial lymphatic drainage territories, which would explain why edema after lateral filling behaves differently from edema after medial filling. · What would settle it: indocyanine fluorescence lymphography before and after a standardized volume load on each side of the line, measuring transit time.

3 · Reattribution of the descent: ligament versus bone, in the same subject. [IA-ESPEC] · Anchor: the open discrepancy between ligamentous fatigue [3] and remodeling of the bony anchor [6], with no series that separates them. · Proposal: that the relative contribution be measurable by comparing, in matched cohorts, subjects with documented and preserved bone resorption, with the same degree of soft-tissue descent. · What would settle it: paired volumetric CT [82] with simultaneous measurement of the superficial compartment descent by ultrasound [28]; if the descent correlates with the maxillary angle and not with age, the ligament is exonerated.

4 · Submillimeter subcutaneous thickness as a plane-exclusion criterion. [IA-ESPEC] · Anchor: the subcutaneous layer of the lip measures less than 1 mm and the deposit ends up intramuscular in the majority [95]; the tear trough outright lacks layer 2 [4,3]. · Proposal: that there be a thickness threshold below which the subcutaneous plane ceases to be considered a technical option and is declared nonexistent on the regional map, just as is already done in the tear trough. · What would settle it: ultrasound mapping of layer-2 thickness by region and by demographic group, with the rate of unintended deposit as the contrast variable.

5 · Motor plates as a target in more muscles than the platysma. [IA-ESPEC] · Anchor: Sihler staining showed clustering of motor plates in the upper two thirds of the platysma [54], and surface electromyography showed that corrugator and procerus increase signal with age while the zygomaticus major reduces it [49]. · Proposal: that the motor-plate map, and not the muscle volume, explains the variability of response between patients in the muscles with measured signal change. · What would settle it: Sihler mapping of corrugator, procerus and zygomaticus major in age-stratified specimens, correlated with the electromyographic signal of the same muscle.

6 · The transverse facial septum as a dynamic examination variable. [IA-ESPEC] · Anchor: the transverse facial septum displaces the compartments cranially on smiling and is the substrate of the facial overfilled syndrome [34,6]. · Proposal: that its individual stiffness, measurable by elastography, predicts which patients will develop exaggerated volume on the smile with a normal volume load. · What would settle it: shear-wave elastography of the septum at rest and on smiling, comparing patients with and without dynamic overfilling at equal received volume.

7 · Aging of the zygomaticus major and venous return. [IA-ESPEC] · Anchor: the ability to compress the angular vein against the maxilla decreases with age, in parallel with the drop in signal of the zygomaticus major [6,49,50]. · Proposal: that this loss of muscular pump contributes measurably to morning periorbital edema, independent of the injected volume. · What would settle it: Doppler of the angular vein at rest and during a held smile, in separate age cohorts and with no history of filler, correlated with edema measured by morning volumetry.

8 · A phenotype-specific layer map, not a correction over the Caucasian map. [IA-ESPEC] · Anchor: the angular changes differ by population [3,87], the midfacial muscles vary between ethnic groups [3,52] and lip anatomy varies by race and ethnicity in a statistically significant way [95]. · Proposal: that the layer model by region has systematic differences by phenotype, and not only proportional differences, which would make proportional correction over a single template inadequate. · What would settle it: ultrasound measurement of thickness by layer and region in cohorts of different phenotypes with the same protocol, checking whether the difference is of scale or of structure.

Safety

What this chapter is. An anatomy chapter. It contains no indications, doses, volumes or injection protocols, and none of its recommended-plane tables replaces individual assessment: the plane recommendations gathered from the anatomical literature are based on anatomy, not on the clinical presentation or the needs of the specific patient, which may require a different approach [2].

The five anatomical red lines

1. No technique is absolutely safe. The facial arterial vasculature varies greatly between individuals and between sides of the same individual; because of that lack of predictability it is impossible to guarantee absolute safety in an injectable procedure. The risk must be communicated to the patient, and the operator must be trained and equipped to treat the complication [2].
2. A negative aspiration does not exclude intra-arterial passage. The needle distributes product into every plane it crosses, with material identifiable in the subdermis even when the tip is on bone, and the double-perforation phenomenon of the arterial wall exists [2,63,64].
3. Glabella and periorbital region are internal carotid territory. The anastomoses between dorsal nasal, supratrochlear, supraorbital and infraorbital connect directly with the ophthalmic circulation [2,57]. The deep glabellar plane is the least vascularized described, not a safe plane [2].
4. The retinal window is short. No detectable damage up to 97 minutes in the experimental model; afterward, progressive irreversible damage [2,59]. Prior preparation —not an improvised reaction— is what fits within that window.
5. The temple has two planes and no intermediate one. Subcutaneous above the superficial temporal fascia, or bone contact. Between them is the compartment that houses the frontal branch of the facial nerve, the sensory branches and the sentinel vein [4,2]; and the possibility of intracranial penetration in that region has been explicitly investigated [89].

On this chapter's figures. Every measurement published here comes from a source identified in the reference list. The magnitudes the corpus pass did not return with a traceable source —decade-by-decade bone-resorption chronology (A1.9), quantification of facial lymphatic flow (A1.7) and normative profile angle ranges (A1.10)— are declared as a gap with the query that proves it, instead of being filled in. No figure supported solely by the master's teaching material is published as a clinical parameter: never_sufficient_alone.

On the (P) material. The sentences marked (P) are the model's reasoning ordering data already cited. They contain no dose, no product and no new plane, and must not be cited as a source.

Sources of the figures

The 21 figures were resolved with figure_pick.py and with targeted search over the corpus, and each one was opened with Read before writing its caption; the captions describe what the image shows, not the corpus caption, which in several of them is a dump of the surrounding markdown and in two cases (a clinical photograph attributed to a ligament schematic and a dissection panel attributed to a proportions text) did not correspond to the image; those two were discarded. Fig 19-21 were added in the salvage for the new sections (dorsum of the hand, cadaveric dissection and ultrasound) and were also opened with Read before being captioned.

> Sources: Fig 1 — Watanabe [110] · Fig 2, 8, 9, 13 — Pirayesh [111] · Fig 3 — Radlansky [94] · Fig 4 — Carruthers [112] · Fig 5 — Lobo [113] · Fig 6 — Vieira Braz [92] · Fig 7 — Cotofana [2] · Fig 10 — Parker [114] · Fig 11, 12 — van Gijn [91] · Fig 14 — Kim [115] · Fig 15 — Libro Zonas Peligrosas en Medicina Estética Facial [116] · Fig 16, 18 — Master Techniques in Facial Rejuvenation [83] · Fig 17 — Standring [117] · Fig 19 — UPO, hand rejuvenation [99] · Fig 20 — UPO, filler adverse effects [105] · Fig 21 — Lamb [118].

Corpus readings assigned to this chapter

Corpus documents assigned to A1 in the brief that are not cited in the body because their content is regional and belongs to D1-D13; they are listed so that the regions do not search for them again:

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64. Pavicic T, Frank K, Erlbacher K, et al. Precision in dermal filling: a comparison between needle and cannula when using soft tissue fillers. J Drugs Dermatol. 2017;16(9):866-872. [B]
65. Scheuer JF 3rd, Sieber DA, Pezeshk RA, Gassman AA, Campbell CF, Rohrich RJ. Facial danger zones: techniques to maximize safety during soft-tissue filler injections. Plast Reconstr Surg. 2017;139(5):1103-1108. [B]
66. Cotofana S, Steinke H, Schlattau A, et al. The anatomy of the facial vein: implications for plastic, reconstructive, and aesthetic procedures. Plast Reconstr Surg. 2017;139(6):1346-1353. [B]
67. Netter FH. Atlas of Human Anatomy. 7th ed. Elsevier; 2022. [C] · corpus MEDLIB.
68. Mannan's Regional Dissection and Surface Anatomy. 14th ed. 2017. [C] · corpus MEDLIB.
69. Trinei FA, Januszkiewicz J, Nahai F. The sentinel vein: an important reference point for surgery in the temporal region. Plast Reconstr Surg. 1998;101(1):27-32. [B]
70. de Castro CC. Midface Surgery. Elsevier; 2009. [C] · corpus MEDLIB.
71. Dermal Fillers for Facial Harmony. 2019. [C] · corpus MEDLIB.
72. Fehrenbach MJ, Herring SW. Illustrated Anatomy of the Head and Neck. 5th ed. Elsevier; 2017. [C] · corpus MEDLIB.
73. Chowdhury R, Schiff B, Lee YH, Mohan S. Ultrasound guidance for botulinum toxin injection of muscles innervated by the facial nerve: a systematic review of anatomical precision, safety, and outcomes. Aesthet Surg J. 2026;46(2):195-201. PMID 40971765 · DOI 10.1093/asj/sjaf175. [A]
74. Cotofana S, Gotkin RH, Ascher B, et al. Calvarial volume loss and facial aging: a computed tomographic (CT)-based study. Aesthet Surg J. 2018;38(10):1043-1051. [B]
75. Enlow DH. A morphogenetic analysis of facial growth. Am J Orthod. 1966;52(4):283-299. [B]
76. Frank K, Gotkin RH, Pavicic T, et al. Age and gender differences of the frontal bone: a computed tomographic (CT)-based study. Aesthet Surg J. 2019;39(7):699-710. [B]
77. Kahn DM, Shaw RB Jr. Aging of the bony orbit: a three-dimensional computed tomographic study. Aesthet Surg J. 2008;28(3):258-264. [B]
78. Pessa JE, Chen Y. Curve analysis of the aging orbital aperture. Plast Reconstr Surg. 2002;109(2):751-755. [B]
79. Richard MJ, Morris C, Deen BF, Gray L, Woodward JA. Analysis of the anatomic changes of the aging facial skeleton using computer-assisted tomography. Ophthal Plast Reconstr Surg. 2009;25(5):382-386. [B]
80. Shaw RB Jr, Kahn DM. Aging of the midface bony elements: a three-dimensional computed tomographic study. Plast Reconstr Surg. 2007;119(2):675-681. PMID 17230106 · DOI 10.1097/01.prs.0000246596.79795.a8. [B]
81. Cotofana S, Gotkin RH, Morozov SP, et al. The relationship between bone remodeling and the clockwise rotation of the facial skeleton. Plast Reconstr Surg. 2018;142(6):1447-1454. [B]
82. Karunanayake M, To F, Efanov JI, et al. Analysis of craniofacial remodeling in the aging midface using reconstructed three-dimensional models in paired individuals. Plast Reconstr Surg. 2017;140(3):448e-454e. [B]
83. Azizzadeh B, Murphy MR, Johnson CM, Massry GG, Fitzgerald R. Master Techniques in Facial Rejuvenation. 2nd ed. Elsevier; 2018. [C] · corpus MEDLIB.
84. Lillie EM, Urban JE, Lynch SK, Weaver AA, Stitzel JD. Evaluation of skull cortical thickness changes with age and sex from computed tomography scans. J Bone Miner Res. 2016;31(2):299-307. [B]
85. Urban JE, Weaver AA, Lillie EM, et al. Evaluation of morphological changes in the adult skull with age and sex. J Anat. 2016;229(6):838-846. [B]
86. Pessa JE, Desvigne LD, Lambros VS, et al. Changes in ocular globe-to-orbital rim position with age: implications for aesthetic blepharoplasty of the lower eyelids. Aesthetic Plast Surg. 1999;23(5):337-342. [B]
87. Kim SJ, Kim SJ, Park JS, Byun SW, Bae JH. Analysis of age-related changes in Asian facial skeletons using 3D vector mathematics on picture archiving and communication system computed tomography. Yonsei Med J. 2015;56(5):1395-1400. [B]
88. Pessa JE. An algorithm of facial aging: verification of Lambros's theory by three-dimensional stereolithography, with reference to the pathogenesis of midfacial aging, scleral show, and the lateral suborbital trough deformity. Plast Reconstr Surg. 2000;106(2):479-488. PMID 10946949 · DOI 10.1097/00006534-200008000-00040. [B]
89. Philipp-Dormston WG, Bieler L, Hessenberger M, et al. Intracranial penetration during temporal soft tissue filler injection — is it possible? Dermatol Surg. 2018;44(1):84-91. [B]
90. Popescu MN, Beiu C, Iliescu CA, et al. Ultrasound-guided botulinum toxin-A injections into the masseter muscle for both medical and aesthetic purposes. Toxins (Basel). 2024;16(10):413. PMID 39453189 · DOI 10.3390/toxins16100413. [A]
91. van Gijn DR, Dover S. Oxford Handbook of Head and Neck Anatomy. Oxford University Press; 2022. [C] · corpus MEDLIB.
92. Vieira Braz A, Sakuma TH. Atlas de Anatomia e Preenchimento Global da Face. Guanabara Koogan; 2017. [C] · corpus MEDLIB.
93. Truswell WH. Surgical Facial Rejuvenation. Thieme; 2009. [C] · corpus MEDLIB.
94. Radlansky RJ, Wesker KH. Atlas Ilustrado de Anatomia Clínica da Face. [C] · corpus MEDLIB.
95. Harris S, Schelke L, Orlovska M, Wortsman X, Cotofana S, Velthuis P. Ultrasound evaluation of lip anatomy and filler placement: a cross-sectional study of injection accuracy, migration, and demographic variation. Plast Reconstr Surg. 2026;158(1):65e-75e. PMID 41494527 · DOI 10.1097/PRS.0000000000012772. [A]
96. Melley LE, Altman A, Bloom JD. Nonsurgical chin and prejowl modification. Facial Plast Surg. 2025;41(5):583-594. PMID 40389235 · DOI 10.1055/a-2600-6759. [A]
97. Anido J, Arenas Escribano D. Valoración inicial del paciente en Medicina Estética, Cosmética y Regenerativa. Módulo 2, Asignatura 4. Máster en Medicina Estética, Universidad Pablo de Olavide (UPO). [D] · corpus MEDLIB, UPO teaching material — never_sufficient_alone.
98. Alam M, ed. Evidence-Based Procedural Dermatology. Springer; 2019. [C] · corpus MEDLIB.
99. Universidad Pablo de Olavide (UPO). Técnicas de rejuvenecimiento de manos (M4/T16.5) — captures the cadaveric anatomy of the dorsum of the hand from Bidic et al. Máster en Medicina Estética. [D] · corpus MEDLIB, UPO teaching material — never_sufficient_alone.
100. Paternostro F, Hong WJ, Zhu GS, Green JB, Milisavljevic M, Cotofana MV, Alfertshofer M, et al. Simulating upper eyelid ptosis during neuromodulator injections: an exploratory injection and dissection study. J Cosmet Dermatol. 2024;23(12):3936-3941. DOI 10.1111/jocd.16631. [B] · corpus MEDLIB.
101. Yogesh. Textbook of General Anatomy with Early Clinical Exposure. [ISBN 9789354667930]. [C] · corpus MEDLIB.
102. Malherbe C. Ultrasound Protocol for Facial Aesthetics. Springer; 2024. [C] · corpus MEDLIB.
103. van Loghem J, ed. Soft Tissue Filler Complications. CRC Press; 2023. [C] · corpus MEDLIB.
104. Cavallieri FA, Balassiano LKA, de Bastos JT, da Fontoura GHM, de Almeida AT. Edema tardío intermitente y persistente (ETIP): reacción adversa tardía al ácido hialurónico. Surg Cosmet Dermatol. 2017;9(3). DOI 10.5935/scd1984-8773.201793931. [B] · corpus MEDLIB.
105. Universidad Pablo de Olavide (UPO). Efectos adversos de los materiales de relleno (M2/T10, Tejero, 2024). Máster en Medicina Estética. [D] · corpus MEDLIB, UPO teaching material — never_sufficient_alone.
106. Beleznay K, Carruthers JDA, Humphrey S, Carruthers A, Jones D. Update on avoiding and treating blindness from fillers: a recent review of the world literature. Aesthet Surg J. 2019;39(6):662-674. PMID 30805636 · DOI 10.1093/asj/sjz053. [A]
107. Lee JG, Yang HM, Choi YJ, Favero V, Kim YS, Hu KS, Kim HJ. Facial arterial depth and relationship with the facial musculature layer. Plast Reconstr Surg. 2015;135(2):437-444. PMID 25626791 · DOI 10.1097/PRS.0000000000000991. [B]
108. Arenas Escribano D. Revisión de materiales de relleno · Tercio superior · Tercio medio · Técnicas avanzadas de rellenos. Módulo 2, T8.1. Máster en Medicina Estética, Universidad Pablo de Olavide (UPO). [D] · corpus MEDLIB, UPO teaching material — never_sufficient_alone.
109. Furnas DW. The retaining ligaments of the cheek. Plast Reconstr Surg. 1989;83(1):11-16. [B]
110. Watanabe K, Shoja MM, Loukas M, Tubbs RS. Anatomy for Plastic Surgery of the Face, Head, and Neck. Thieme; 2016. [C] · corpus MEDLIB.
111. Pirayesh A, Bertossi D, Heydenrych I. Aesthetic Facial Anatomy Essentials for Injections. CRC Press; 2020. [C] · corpus MEDLIB.
112. Carruthers J, Carruthers A. Soft Tissue Augmentation. 4th ed. Elsevier; 2018. [C] · corpus MEDLIB.
113. Lobo T. Harmonização Orofacial. 2022. [C] · corpus MEDLIB.
114. Parker E. Fundamentals for Cosmetic Practice. Routledge; 2022. [C] · corpus MEDLIB.
115. Kim HJ, Seo KK, Lee HK, Kim J. Clinical Anatomy of the Face for Filler and Botulinum Toxin Injection. Springer; 2016. [C] · corpus MEDLIB.
116. Libro Zonas Peligrosas en Medicina Estética Facial. [C] · corpus MEDLIB.
117. Standring S, ed. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Elsevier; 2016. [C] · corpus MEDLIB.
118. Lamb J, Surek C. Facial Volumization: An Anatomic Approach. Thieme; 2018. [C] · corpus MEDLIB.
119. Sykes JM, Cotofana S, Trevidic P, et al. Upper face: clinical anatomy and regional approaches with injectable fillers. Plast Reconstr Surg. 2015;136(5 Suppl):204S-218S. [B] · corpus MEDLIB (Cotofana).
120. Cotofana S, Schenck TL, Trevidic P, et al. Midface: clinical anatomy and regional approaches with injectable fillers. Plast Reconstr Surg. 2015;136(5 Suppl):219S-234S. [B] · corpus MEDLIB (Cotofana).
121. Braz A, Humphrey S, Weinkle S, et al. Lower face: clinical anatomy and regional approaches with injectable fillers. Plast Reconstr Surg. 2015;136(5 Suppl):235S-257S. [B]
122. de Maio M, Swift A, Signorini M, Fagien S; Aesthetic Leaders in Facial Aesthetics Consensus Committee. Facial assessment and injection guide for botulinum toxin and injectable hyaluronic acid fillers. Plast Reconstr Surg. 2017;140(2):265e-276e. [B]

Verification: corpus pass A1-20260809 with medrag.retrieval_program.cli run over _CURRICULUM_MAP.md, subtopics A1.1-A1.10, --all-facets --k 8 --figure-k 6, overlay aesthetic-regenerative-dermatology-v1; on-disk artifact ~/Data/Aesthetic-Medicine-cheatsheets/evaluation/runs/A1.jsonl (200 records, 3 027 text contexts, 1 124 figure hits) plus the ten partials A1.1.jsonl-A1.10.jsonl; doctor medlib → VERDICT: usable (419 129 text chunks, 145 877 figures). Facets by mean global_top_score: anatomy_planes_danger 0.745 · definition_scope 0.744 · mechanism_foundations 0.721 · assessment 0.717 · cutaneous_ultrasound 0.702 … and at the thin end dose_parameters 0.536 and contraindications_interactions 0.553, which was declared as a gap in A1.9 (bone chronology) and A1.10 (angular ranges). Year profile of the retrieved corpus: median 2017, range 2000-2026, 19 % from 2022 on — that is why the external lane was opened expressly with PubMed (7 references 2024-2026 verified, with PMID and DOI linked). Queries in ES, EN and PT. Silences proved and declared: lymphatics 86 of 3 027 contexts versus 395 for facial/angular vein (A1.7); zero contexts with decade-by-decade resorption chronology (A1.9); zero traceable normative angular ranges (A1.10). Figures: figure_pick.py --top 486 --with-caption resolved 486 on-disk candidates; 18 were selected in the initial pass plus 3 in the salvage (21 in total), all opened with Read before writing their caption, and two were discarded whose corpus caption did not correspond to the image. Copied to _images/A1/ with space-free names and verified with Path.exists() and image_audit.py. UPO material treated as syllabus, never as a parameter (never_sufficient_alone).

Salvage (2026-08-11). Repair directed by the receipts docs/salvage/A1.rescate.json (numbers, PMID) and A1.concept.json (coverage by section). Recovered the 5 numbers the rewrite had lost —Pitanguy's line 0.5 cm, infraorbital foramen 5-10 mm, Ricketts' E-line 2 mm, supratrochlear 17-22 mm from the midline, McGregor's ligament 4.5 cm— each with its scenario in A1.1. Reverified against PubMed the 6 PMIDs lost before citing them (10946949 Pessa 2000, 17230106 Shaw-Kahn 2007, 17519724 Rohrich-Pessa 2007, 25626791 Lee 2015, 26356847 Beleznay 2015, 30805636 Beleznay 2019), three integrated into existing references and three as new references with DOI. Reconstructed the absent/thin sections: cadaveric dissection as a curricular standard, regional anatomy of neck/décolletage/dorsum of the hand, ultrasound orientation, danger zones by region, schools, errors and the prior-mapping protocol, with corpus retrieval (Malherbe, van Loghem, Cavallieri, Alam, Bidic via UPO, Yogesh, Paternostro). Added the Frankfort plane and the E-line to the landmarks and to the protocol. Salvage verified with salvage_diff.py against the previous version (--cross-lang, 0 lost) and against the archived stub (numbers and PMID at 0 lost).