Skin Aging Anatomy Glossary: Dermis, SMAS, Ligaments

I walked into a Cheongdam clinic last spring expecting a normal Ultherapy consult and walked out with a five-page list of words I'd half-understood. The doctor had pulled up a 3D scan of my face on a wall monitor, rotated it slowly, and pointed at structures with a stylus while talking — "the malar fat is starting to descend here, your masseteric retaining ligament is still strong, the platysmal bands aren't visible at rest yet, the bony resorption at the orbital rim is mild" — and I nodded a lot while quietly typing terms into my phone. The next morning, in my hotel room with bad coffee, I built this glossary for myself. Then I kept adding to it after every Gangnam consult that followed. This is that list, cleaned up. It's the version I wish someone had handed me before my first 3D scan, in plain language and with cross-references for the words that connect to other words. None of this is medical advice. It's anatomy vocabulary, alphabetized, written by someone who needed it explained without jargon.

How to use this glossary

The terms below are grouped alphabetically by first letter. Each entry has a plain definition, a short example or context note, and where useful, a "see also" pointer to related terms in the list. I've kept the definitions short and concrete — the goal is that you can read a single entry mid-consult on your phone and walk back into the conversation knowing what your provider just said. Anatomy is layered, so a lot of the entries reference each other; that's the nature of the territory. Read it linearly the first time, then keep it for lookup.

A — adipose to atrophy

The early part of the alphabet covers the fat-pad and structural-foundation vocabulary that came up most in my consults — the words doctors use when they're describing where volume sits and where it's leaving from.

Adipose tissue

The medical term for fat tissue. Made up of fat cells (adipocytes) plus a supporting matrix. In facial anatomy, adipose tissue sits in defined compartments rather than spreading evenly under the skin, which is why volume loss shows up as specific hollows rather than a general thinning. See also: fat compartments, hypodermis.

Aponeurosis

A flat, sheet-like tendon that connects muscle to other tissue. The "A" in SMAS stands for aponeurotic — the system is partly aponeurosis, which is what gives the SMAS its strong, sheet-like quality that surgeons can grab and reposition during a facelift. See also: SMAS, fascia.

Atrophy (soft-tissue and bony)

The thinning or shrinking of tissue over time. In facial aging, doctors use the word in two contexts: soft-tissue atrophy refers to the loss of volume in fat compartments and dermal thickness, while bony atrophy (also called bony resorption) refers to the gradual loss of bone in the orbital rim, mid-face, and jawline. Both contribute to the descent and hollowing patterns of an aging face. See also: bony resorption, fat compartment descent.

B — bony resorption to buccal fat

The B section covers the structural foundation — the bone underneath everything else — plus one of the most-discussed mid-face fat structures.

Bony resorption

The age-related loss of facial bone, particularly noticeable at the orbital rim, the maxilla (mid-face), and the mandibular angle. As bone resorbs, the soft tissue draped over it has less support and starts to descend or look hollow. This is one of the reasons aging is structural, not just skin-deep — the scaffolding underneath is changing too. Bony resorption is also why some patients in their 50s and 60s see hollowing under the eyes that doesn't respond well to fillers placed superficially; the underlying bone has retreated. See also: orbital rim, maxilla, mandibular angle.

Buccal fat pad

A defined fat compartment that sits deep in the cheek, between the masseter and buccinator muscles. Different from the surface cheek fat compartments — buccal fat sits deeper and contributes to the rounded fullness of younger faces. Buccal fat removal is a controversial procedure that surgically reduces this pad; the trade-off is that buccal fat naturally diminishes with age, so removing it in your 20s can leave you with hollowed cheeks in your 50s. Worth knowing the term exists, especially if anyone offers you the procedure. See also: deep medial cheek fat, masseter.

C — cervicomental angle to collagen

The C section spans neck anatomy and the proteins that make up the dermis itself.

Cervicomental angle

The angle formed between the underside of the chin (mental region) and the front of the neck (cervical region). A sharp, well-defined cervicomental angle reads as a younger or more sculpted profile; a softer or obtuse angle reads as fullness or laxity in the submental area. Doctors will often reference this angle specifically when discussing neck and jawline outcomes — a treatment that improves submental tightness sharpens this angle. See also: submental, platysma.

Collagen (types I and III)

The structural protein that gives skin its firmness and resilience. The dermis is mostly collagen, with type I being the dominant mature form and type III being more prevalent in younger skin and during wound-healing. As we age, collagen production slows and existing collagen fibers become disorganized — this is the dermal-level version of structural decline. Energy-based devices like Ultherapy and microneedling work by triggering controlled remodeling of dermal collagen. See also: dermis, elastin, fibroblast.

Coronoid process

A bony projection on the upper part of the mandible (lower jaw). Less commonly discussed in aesthetic contexts but occasionally referenced in surgical or imaging conversations about lower-face structure. See also: mandible, mandibular angle.

D — deep medial cheek to dermis

The D section covers some of the most-referenced fat compartments and the layer of skin where most of the action happens.

Deep medial cheek fat

A deep fat compartment in the inner mid-face, sitting underneath the superficial cheek fat. Loss of volume in this compartment is one of the earliest mid-face aging signs — it's part of why the cheek can look flatter or the nasolabial fold can look deeper without anything obvious changing on the surface. Many filler protocols target this compartment specifically rather than placing volume superficially. See also: superficial cheek fat, nasolabial fat, malar fat.

Dermis

The middle layer of skin, sitting between the epidermis (surface) and the hypodermis (fat). The dermis is where collagen, elastin, blood vessels, hair follicles, sebaceous glands, and most of the structural protein of skin live. It has two sublayers — papillary dermis (upper, finer) and reticular dermis (lower, denser). Almost everything described as "skin firming" or "skin tightening" is happening in the dermis. See also: papillary dermis, reticular dermis, epidermis, hypodermis.

Descent (fat-pad descent)

The gravity-driven downward shift of facial fat compartments over time, often used by doctors to describe the migration of upper-cheek volume into the lower face and jowl region. Descent is one of the three classical aging mechanisms (alongside volume loss and laxity) and is part of why a face can look both hollow above and full below as it ages. See also: jowl fat, malar fat, retaining ligaments.

E — elastin to epidermis

The E section is short but covers the surface layer of skin and the protein that gives skin its bounce.

Elastin

A stretchy protein in the dermis that lets skin recoil after being stretched. Pinch the skin on the back of a young hand and it snaps back; on older skin, the snap-back is slower. That's elastin doing less work. Unlike collagen, elastin is much harder for the body to replace once damaged — UV exposure, in particular, breaks down elastin fibers in ways that don't fully repair. This is part of why sun protection is so structurally important, not just for pigmentation. See also: collagen, dermis, fibroblast.

Epidermis

The outermost layer of skin — the part that sheds, tans, and forms the visible surface texture. The epidermis itself is thin (about 0.1mm on most of the face) and contains keratinocytes, melanocytes, and Langerhans cells. Surface treatments like chemical peels, exfoliation, and lasers in the resurfacing range act mostly at the epidermal level. The epidermis sits on top of the dermis and gets its blood supply from the dermal layer below. See also: dermis, melanocyte, sebaceous gland.

F — facial artery to follicular infundibulum

The F section covers the vascular and structural fascia anatomy that surfaces in any conversation about injectables, threads, or surgery.

Facial artery

A major artery that runs from the neck up across the lower face, looping around the mandibular border and tracking up toward the corner of the mouth and the side of the nose. Highly relevant in injectables — providers map filler placement specifically to avoid the facial artery and its tributaries, because intra-arterial injection is the most-discussed serious complication of fillers. If your injector pauses, aspirates, or seems particularly slow in the mid-face, this is what they're being careful about. See also: retromandibular vein, oral commissure.

Fascia

Sheets of connective tissue that wrap around muscles, organs, and structures throughout the body. In facial anatomy, several fascial layers organize the face — superficial fascia, deep fascia, and the SMAS itself, which is partly a fascial structure. Fascia gives tissue its planes and is part of how the face holds shape; it's also part of what surgeons navigate during a facelift. See also: SMAS, aponeurosis.

Fat compartments

Defined regions of facial fat separated by fibrous septa, rather than one continuous layer of subcutaneous fat. The face has multiple named compartments — superficial and deep, medial and lateral — and each one ages on its own timeline. Understanding fat compartments is the difference between thinking of the face as "thinning" and thinking of it as "redistributing," which is the more accurate picture. See also: deep medial cheek fat, malar fat, jowl fat, nasolabial fat, superficial cheek fat.

Fibroblast

The cell type in the dermis responsible for producing collagen, elastin, and the extracellular matrix that gives skin its mechanical properties. When energy-based devices trigger controlled injury, fibroblasts are the cells that respond by producing new collagen. Fibroblast activity declines with age, which is part of why older skin remodels more slowly after the same treatment that produced obvious results in your 30s. See also: collagen, elastin, dermis.

Follicular infundibulum

The upper portion of the hair follicle — the funnel-shaped opening where the hair shaft emerges from the skin. Sebaceous glands often empty into the infundibulum, which is also where many of the visible "pore" issues live. Surface treatments aimed at pores are often targeting the follicular infundibulum, even when the marketing language doesn't say so. See also: sebaceous gland, epidermis.

Frontal bone

The bone of the forehead. Smooth in younger faces, more prominent at the brow ridge in older ones because of soft-tissue thinning rather than bone growth. The frontal bone is part of the structural foundation that doctors evaluate during 3D scans, and brow-area treatments are often discussed in relation to the curve of the underlying frontal bone. See also: bony resorption, glabella, orbital rim.

G — GAGs to glabella

The G section is brief but includes one of the most-discussed molecular components of skin and one of the most-referenced surface landmarks.

GAGs (glycosaminoglycans)

A family of long-chain sugar molecules in the dermis that attract and hold water. Hyaluronic acid is the most famous member of the GAG family. Together with collagen and elastin, GAGs give skin its plump, hydrated, supported quality. Loss of GAGs (and the water they hold) is part of why aging skin can look thinner and less resilient, even before visible wrinkles appear. See also: hyaluronic acid, dermis.

Glabella

The smooth area between the eyebrows, just above the bridge of the nose. The glabellar lines ("11 lines") are vertical creases that form here from corrugator and procerus muscle activity, and this region is one of the most-treated areas with neuromodulators. See also: frontal bone, orbicularis.

H — hyaluronic acid to hypodermis

The H section covers two terms most patients have heard but often misunderstand structurally.

Hyaluronic acid (HA)

A naturally-occurring molecule in the skin (and elsewhere in the body) that binds large amounts of water. The HA in your dermis is what gives skin its plump, hydrated quality. Most modern fillers are crosslinked HA, which means they're a synthetic version of the same molecule, structured to last in tissue rather than dissolve quickly. Topical HA in skincare doesn't penetrate deeply — it acts at the surface for hydration. The injected version sits at the dermal or subdermal level and adds volume there. See also: GAGs, dermis.

Hyoid bone

A small U-shaped bone in the upper neck, sitting just below the jawline at roughly the level where the chin meets the neck. Higher placement of the hyoid (more anterior, more superior) is one of the anatomical factors that produces a sharper cervicomental angle and a more sculpted profile. Lower or more posterior hyoid placement is harder to address with non-invasive treatments because the underlying bone position is fixed. Worth knowing this term exists if your provider mentions "hyoid position" during a profile assessment. See also: cervicomental angle, suprahyoid musculature, submental.

Hypodermis

The deepest of the three skin layers — also called subcutaneous tissue or subcutis. Sits below the dermis and is composed largely of fat (adipose tissue) and connective tissue. The hypodermis is where most of the facial fat compartments live and is the layer between the dermis and the SMAS. Volume loss happens largely at the hypodermal level. See also: dermis, fat compartments, SMAS.

I — infraorbital rim

Short section, one critical landmark.

Infraorbital rim (orbital rim, lower)

The bony edge of the eye socket, specifically the lower portion below the eye. The infraorbital rim is one of the structural landmarks doctors reference when discussing under-eye hollows, tear-trough deformity, and mid-face aging. As bony resorption progresses, the infraorbital rim retreats slightly, which exaggerates the appearance of under-eye shadows. Filler placement in this area is technically delicate because of the proximity to vessels and the orbital structures. See also: orbital rim, bony resorption, malar fat.

J — jowl fat

The J section names the fat compartment that probably sends the most patients to a Gangnam consult in the first place.

Jowl fat

The fat compartment that sits along the lower jawline, between the chin and the angle of the mandible. In a younger face, the jowl region is held in place by the mandibular retaining ligament and the firmness of the surrounding tissue; as those structures loosen and as fat from higher up descends, the jowl region accumulates volume that wasn't there before. This is what people are pointing at when they talk about "jowls." The combination of descent from above and laxity in the local ligaments is what produces the visible jowl shape. See also: mandibular retaining ligament, descent, pre-jowl sulcus.

L — lateral fat to ligaments

The L section covers more fat compartments and the connective-tissue structures that determine where everything sits.

Lateral cheek fat

A superficial fat compartment running along the outer cheek, lateral to the medial cheek compartments. Sits closer to the temple and the lateral mid-face. Less talked-about than the medial compartments but contributes to the overall contouring of the cheek and changes in volume here are part of mid-face aging. See also: superficial cheek fat, malar fat.

Levator muscles (perioral)

A group of small muscles around the mouth that elevate the upper lip and the corners of the mouth. Including the levator labii superioris and the levator anguli oris. Their tone affects the resting position of the upper lip and the shape of the smile, and they're part of the perioral musculature that providers consider when planning treatments around the mouth. See also: orbicularis oris, oral commissure, philtrum.

Ligaments (retaining ligaments, overview)

Fibrous bands of connective tissue that anchor specific zones of facial soft tissue to the underlying bone. The retaining ligaments are what keep fat compartments from sliding around freely. As they loosen with age, the soft tissue above them descends, which is one of the structural mechanisms behind jowl formation, mid-face descent, and changing facial contours. The four most-named retaining ligaments are zygomatic, masseteric, mandibular, and orbicularis. See also: zygomatic retaining ligament, mandibular retaining ligament, masseteric ligament, orbicularis retaining ligament.

M — malar fat to muscles of facial expression

The M section is large because so many key landmarks start with M — the mid-face, the jaw, and most of the muscles of expression.

Malar fat (malar fat pad)

A superficial fat compartment that sits over the cheekbone (zygoma) and contributes to the high cheek fullness associated with younger faces. As the malar fat descends, it migrates toward the nasolabial fold area, contributing to deepening of that fold and flattening of the upper cheek. "Malar" is just the anatomical adjective for cheekbone. See also: zygomatic arch, nasolabial fold, descent.

Mandible

The medical name for the lower jaw bone — the only movable bone in the face. The shape of the mandible (its width, the angle of the gonial region, and the height of the chin) is one of the foundational structural elements of facial appearance. Bony resorption at the mandibular angle and along the body of the mandible reduces support for the overlying tissue, contributing to lower-face changes with age. See also: mandibular angle, jowl fat.

Mandibular angle (gonial angle)

The angle where the body of the mandible turns upward to become the ramus — what most people call the "angle of the jaw." A sharper, more defined mandibular angle reads as a more sculpted lower face; a softer angle reads as fullness or rounder face shape. The mandibular angle is also where the masseter muscle attaches and is one of the bony landmarks affected by age-related resorption. See also: mandible, masseter, masseteric ligament.

Mandibular retaining ligament

One of the four major retaining ligaments of the face. It anchors soft tissue to the mandible at a point along the lower jawline, and as it loosens with age, the soft tissue immediately above and below it shifts position — this is part of what creates the appearance of a jowl breaking the line of the jaw. The pre-jowl sulcus (the depression just in front of the jowl) is partially defined by this ligament. See also: ligaments, jowl fat, pre-jowl sulcus.

Marionette line

A vertical or oblique crease that runs from the corner of the mouth (oral commissure) downward toward the jawline. Named for the lines on a marionette puppet's face. Marionette lines result from a combination of perioral muscle activity, descent of mid-face fat, and the structural lines of the surrounding tissue. See also: oral commissure, nasolabial fold, jowl fat.

Masseter muscle

The thick, powerful muscle at the angle of the jaw, used for chewing. Hypertrophy (enlargement) of the masseter is what produces a square-jawed lower face; this is the muscle that botulinum toxin targets in the "jaw slimming" or "masseter reduction" procedures common in Gangnam clinics. The masseter sits over the mandibular angle and is bordered by the buccal fat pad on its inner surface. See also: mandibular angle, buccal fat pad, masseteric ligament.

Masseteric retaining ligament

A retaining ligament that runs along the front edge of the masseter muscle, anchoring the overlying soft tissue. It's one of the structures that provides support to the lateral mid-face and lower cheek. Loosening of the masseteric ligament contributes to descent of the lateral cheek tissue. See also: ligaments, masseter, lateral cheek fat.

Maxilla

The upper jaw bone — the bone of the mid-face that holds the upper teeth and forms part of the orbital rim, the nasal base, and the cheek structure. Bony resorption of the maxilla with age contributes to flattening of the mid-face, retraction of the upper lip, and downward rotation of the nasal tip. The maxilla is one of the most underappreciated bones in aging conversations because its changes are gradual and reveal themselves through the soft tissue. See also: bony resorption, infraorbital rim.

Melanocyte

The pigment-producing cell in the epidermis. Melanocytes produce melanin in response to UV exposure and other stimuli, and uneven melanocyte activity is part of what produces age spots, melasma, and post-inflammatory hyperpigmentation. The number and behavior of melanocytes change with age and sun exposure, which is why pigmentation patterns shift over time even on protected skin. See also: epidermis.

Mid-face

A clinical zone description rather than a single structure — the central portion of the face, generally from the lower edge of the eye socket down to the upper border of the lip and bordered laterally by the temple and the lateral cheek. Mid-face aging involves volume loss in the deep medial cheek and malar fat, descent of fat from upper to lower compartments, and changes in the underlying maxilla. See also: malar fat, deep medial cheek fat, maxilla, nasolabial fold.

Muscles of facial expression

A large group of muscles that originate from bone or fascia and insert into the skin, allowing the face to make expressions. Includes the orbicularis oculi (eyes), orbicularis oris (mouth), zygomaticus major and minor (smiling), levator and depressor groups, frontalis (forehead), and others. Most of these muscles are targets for neuromodulator treatments at low doses. See also: orbicularis oculi, orbicularis oris, frontalis, platysma, levator muscles.

N — nasolabial fold to nasolabial fat

The N section covers one of the most-treated zones in cosmetic medicine and the underlying compartment that drives it.

Nasolabial fold

The crease that runs from the side of the nose down to the corner of the mouth. Often deepens with age as mid-face fat descends and as the deep medial cheek volume diminishes. The nasolabial fold itself isn't really a wrinkle in the conventional sense — it's a structural fold that becomes more pronounced as the geometry of the surrounding tissue changes. Filler placed directly into the fold often looks unnatural; better outcomes generally come from restoring volume in the upper compartments that's been lost. See also: nasolabial fat, deep medial cheek fat, malar fat.

Nasolabial fat compartment

A superficial fat compartment that sits along the medial cheek next to the nasolabial fold. Distinct from but adjacent to the deep medial cheek fat. Changes in this compartment contribute to the shape of the fold and the surrounding mid-face. See also: nasolabial fold, deep medial cheek fat.

O — oral commissure to orbital rim

The O section is heavy on perioral and periorbital landmarks — the structures at the mouth and around the eye.

Oral commissure

The corner of the mouth, where the upper and lower lip meet. The position and angle of the oral commissure changes with age, often dropping slightly downward, which contributes to a tired or downturned appearance even at rest. Marionette lines run downward from the oral commissure. Treatment of this area can involve neuromodulators, fillers, or both, depending on what's pulling the corner down. See also: marionette line, philtrum, vermillion border.

Orbicularis oculi

The circular muscle around each eye, responsible for closing the eyelids. Activity of this muscle produces crow's feet and the lower-eye lines that show up with squinting and smiling. The orbicularis oculi is one of the most common targets for low-dose neuromodulator treatments around the eye area. See also: orbicularis retaining ligament, periorbital, glabella.

Orbicularis oris

The circular muscle around the mouth, responsible for puckering the lips and shaping speech. Activity in the orbicularis oris is what produces vertical lines around the lips ("smoker's lines" or perioral rhytids), which can appear in non-smokers as well from years of normal lip movement. See also: oral commissure, vermillion border, philtrum.

Orbicularis retaining ligament (ORL)

A retaining ligament that runs along the lower edge of the eye socket, anchoring the soft tissue at the junction of the lower eyelid and the upper cheek. The ORL is part of what defines the tear-trough boundary; weakness or laxity in this ligament contributes to the appearance of under-eye hollows and the cheek-lid groove that develops with age. See also: ligaments, infraorbital rim, malar fat.

Orbital rim

The bony edge of the eye socket, with a superior, inferior (infraorbital), medial, and lateral portion. The infraorbital rim in particular is referenced often in mid-face and under-eye aging discussions. Bony resorption changes the prominence of the rim over time. See also: infraorbital rim, bony resorption.

P — papillary dermis to platysmal bands

The P section is one of the longest — the parotid, the platysma, and the parts of the dermis itself.

Papillary dermis

The upper sublayer of the dermis, sitting just below the epidermis. Thinner than the reticular dermis, with finer collagen fibers and more vascular supply. The papillary dermis is what gives the skin its surface texture and its small-scale vascular tone. Surface treatments (like microneedling at modest depths) act largely on the papillary dermis. See also: dermis, reticular dermis, epidermis.

Parotid gland (and parotid fascia)

The largest salivary gland, sitting in front of and slightly below the ear, with its fascia overlying part of the SMAS in the lateral face. The parotid is mostly a surgical and anatomical landmark in aesthetic contexts — surgeons working in the lateral face are navigating around it. The retromandibular vein passes through this area, which is why injection in this zone is approached carefully. See also: SMAS, retromandibular vein, periauricular.

Periauricular

Anatomical adjective meaning "around the ear." Used to describe the zones in front of and behind the ear that are relevant to facelift incisions, skin texture, and certain laser or energy-based treatment areas. The periauricular skin is thinner than facial skin, which matters for treatment selection. See also: retroauricular, parotid gland.

Periorbital

Anatomical adjective meaning "around the eye." Encompasses the upper and lower eyelids, the brow, the tear trough, and the surrounding tissue. The periorbital skin is the thinnest skin on the face, which is why this area shows aging earlier than other zones. See also: orbital rim, orbicularis oculi, infraorbital rim.

Philtrum

The vertical groove on the upper lip, running from the base of the nose to the upper edge of the lip (the cupid's bow). The philtral columns are the two ridges on either side of the philtrum. The philtrum lengthens slightly with age as the upper lip rolls inward and downward, which is part of why aging changes the shape of the upper lip even without specific lip-line wrinkles. See also: vermillion border, oral commissure.

Platysma

A broad, sheet-like muscle that covers the front and side of the neck, extending from the upper chest to the lower face. The platysma is part of the muscular layer continuous with the SMAS in the lower face. As the platysma loses tone and as the underlying support changes, the leading edges of the muscle can become visible at rest as platysmal bands. The platysma is one of the targets for neuromodulator treatments in the neck (the "Nefertiti lift" approach). See also: platysmal bands, cervicomental angle, SMAS, suprahyoid musculature.

Platysmal bands

The visible vertical cords that appear on the front of the neck, especially with age or when the muscle is contracted. Two main bands run on either side of the midline. Mild banding can be addressed with botulinum toxin injection; advanced banding generally requires surgical platysmaplasty. The presence of bands at rest (rather than only with movement) is one of the structural signals that shifts a treatment conversation toward more invasive options. See also: platysma, cervicomental angle.

Pre-jowl sulcus

A depression along the lower jawline, immediately in front of the developing jowl. The pre-jowl sulcus appears partly because of the descent of jowl tissue from above and partly because of the bony resorption at the mandibular pre-jowl region. It's a common filler target — restoring this small zone often dramatically improves the apparent jawline contour. See also: jowl fat, mandibular retaining ligament, mandible.

R — reticular dermis to retromandibular vein

The R section covers the deeper layer of the dermis and structures that are most relevant to deeper procedures.

Reticular dermis

The deeper sublayer of the dermis, sitting below the papillary dermis. Made of denser, thicker collagen fibers (mostly type I) and is where most of the structural protein and elastin live. The reticular dermis is what gives skin its mechanical strength. The 3mm Ultherapy depth and similar mid-depth treatments target this layer specifically. See also: dermis, papillary dermis, collagen, elastin.

Retaining ligaments (specific names)

The four most-named retaining ligaments in cosmetic anatomy are: the zygomatic retaining ligament (over the cheekbone), the masseteric retaining ligament (along the front of the masseter), the mandibular retaining ligament (along the lower jaw), and the orbicularis retaining ligament (along the lower orbital rim). Each anchors a specific zone of soft tissue to bone or to deeper fascia, and each loosens with age in characteristic patterns. Knowing these names changes how you understand a doctor's description of your aging. See also: ligaments, individual entries below.

Retroauricular

Anatomical adjective meaning "behind the ear." Important in facelift incision design (which often runs along the periauricular and into the retroauricular hairline) and in laser or energy-based treatments where this skin is sometimes used as a test area before treating the face proper. See also: periauricular.

Retromandibular vein

A major vein that runs through the parotid gland in the lateral face, behind the angle of the mandible. Highly relevant in deeper injections and in cannula-based filler work in the lateral face — it's one of the vascular structures providers map carefully when working in this zone. See also: facial artery, parotid gland.

S — sebaceous gland to suprahyoid

The S section is anchored by the term that probably brought you to this list — SMAS — alongside the surrounding structures.

Sebaceous gland

Oil-producing glands in the dermis that empty into hair follicles. Sebaceous glands produce sebum, the oily substance that lubricates skin and hair. Their activity peaks in adolescence and gradually declines, which is part of why mature skin tends to be drier and why sebaceous-related issues like acne are less common with age. Visible sebaceous activity contributes to pore appearance. See also: dermis, follicular infundibulum.

Septum (orbital septum, fibrous septa)

Thin sheets of fibrous connective tissue that separate compartments — the orbital septum is a specific structure separating the orbital fat from the eyelid; fibrous septa between fat compartments throughout the face create the boundaries that define each compartment. As septa loosen or stretch, fat herniation can occur (most visibly in the lower eyelid as "eye bags"). See also: fat compartments, infraorbital rim.

SMAS (Superficial Musculoaponeurotic System)

A continuous fibromuscular layer beneath the skin and subcutaneous fat that runs across the face, connecting the platysma in the neck to the temporoparietal fascia in the temple. The SMAS is the structural layer surgeons release and reposition during a facelift, and it's the layer that the deepest Ultherapy transducer (4.5mm) targets. The SMAS is not a single sheet of one tissue type — it's a layered system that varies in thickness across the face, thicker in the lateral face and thinner medially. See also: aponeurosis, platysma, fascia, hypodermis.

Soft-tissue laxity

A clinical term describing how loose or supportive the soft tissue is — a measure that combines skin elasticity, ligamentous support, fat compartment integrity, and underlying structural foundation. Doctors use "laxity grade" as a way to categorize how advanced the structural changes are, which guides treatment recommendations. Mild-to-moderate laxity tends to be addressable with energy-based devices; advanced laxity tends to require surgical solutions. See also: ligaments, SMAS.

Submental

Anatomical adjective meaning "under the chin." The submental region is the zone bounded by the chin in front, the angle of the mandible on either side, and the upper neck below. Submental fullness, double chin, and platysmal banding are all conditions of this zone. The cervicomental angle is defined here. See also: cervicomental angle, platysma, hyoid bone.

Subcutaneous tissue

Another name for the hypodermis — the layer of tissue between the dermis and the deeper structures, mostly composed of fat and connective tissue. "Subcutaneous" injection or "subcutaneous" placement of a product means the layer just below the dermis. See also: hypodermis, fat compartments.

Superficial cheek fat

A fat compartment in the surface (subcutaneous) layer of the cheek, distinct from the deeper deep medial cheek fat. The superficial cheek fat is what gives the surface roundness of a young cheek and contributes most directly to the visible mid-face contour. As this compartment thins or descends, the cheek loses its forward projection. See also: fat compartments, deep medial cheek fat, malar fat.

Suprahyoid musculature

The muscles above the hyoid bone that contribute to the floor of the mouth, the position of the tongue, and the contour of the upper neck. The suprahyoid muscles affect the visible shape of the area between the chin and the front of the neck — particularly relevant to the cervicomental angle and to the appearance of submental fullness. See also: hyoid bone, submental, cervicomental angle.

T — temporal fascia

Single entry, but worth knowing because it gets referenced in upper-face conversations.

Temporal fascia (temporoparietal fascia)

The fascial layer of the temple region, continuous with the SMAS more medially and with the galea of the scalp above. The temporal fascia is part of the structural plane through which surgeons work in temple and brow procedures, and it's relevant in non-surgical contexts because temple hollowing involves changes in the fat compartments above and below this fascia. See also: SMAS, fascia.

V — vermillion border

The V section is short — one important landmark of the lip.

Vermillion border

The sharp boundary between the colored part of the lip and the surrounding skin. A well-defined vermillion border is one of the visual signals of a younger lip; with age the border softens as the lip rolls inward and as perioral skin texture changes. The vermillion border is one of the key landmarks in lip-related procedures, and bleeding across this border with surrounding pigmentation is part of what creates the appearance of perioral aging. See also: oral commissure, philtrum, orbicularis oris.

Z — zygomatic arch and zygomatic ligament

The Z section closes the alphabet with the cheekbone and its ligamentous anchor.

Zygomatic arch (zygoma)

The cheekbone — the bony prominence of the lateral mid-face, formed by the junction of the zygomatic and temporal bones. The shape and projection of the zygomatic arch is one of the structural foundations of facial appearance, and bony changes here affect the mid-face contour. The malar fat sits over the zygoma. See also: malar fat, mid-face, bony resorption.

Zygomatic retaining ligament (McGregor's patch)

A retaining ligament that anchors the soft tissue over the cheekbone to the underlying zygomatic bone. One of the most clinically referenced ligaments because of its role in mid-face support — as it loosens, the malar fat above it descends and the upper-cheek roundness drops downward toward the lower face. The zygomatic retaining ligament is also a landmark in facelift surgery because it's one of the structures surgeons release to mobilize the mid-face. See also: ligaments, malar fat, zygomatic arch.

A few words I left off the alphabetical list (and why)

There are anatomy terms I considered including but decided to leave for a future expansion. Some of them — like specific fat compartments of the lower lid, the deep cheek septae, or the named zones of the temporal fat pads — are useful in surgical contexts but rarely come up in non-invasive consults. Others — like the precise origins and insertions of every muscle of facial expression — felt more like medical-school content than glossary content. The point of this list isn't to be exhaustive; it's to be the document I wished I'd had on the morning after my first 3D scan. If a term you heard at a Gangnam consult isn't on the list, ask the provider directly to define it. Most clinics in the Gangnam medical corridor are used to international patients and will translate technical anatomy into plain language on request — and once you have a few of these foundational words in hand, the rest of the vocabulary tends to slot in around them. The list is a starting frame, not a complete map of the territory.

Frequently asked questions

What's the most useful anatomy term to know before an Ultherapy consult?

If I had to pick one, it would be SMAS. The 4.5mm Ultherapy transducer targets the SMAS, which is the same fibromuscular layer surgeons reposition during a facelift. Knowing what the SMAS is — and that an energy-based device can reach it without repositioning it — completely changes how you understand what Ultherapy is doing and what its limits are. From there, the rest of the vocabulary tends to make sense.

Why do doctors keep mentioning fat compartments instead of just saying 'fat'?

Because facial fat doesn't behave as one continuous layer. It sits in defined compartments with fibrous boundaries between them, and each compartment ages on its own timeline. The deep medial cheek can thin while the jowl region accumulates volume, all in the same face, all happening simultaneously. This is why aging looks like redistribution rather than uniform thinning — and why volume restoration is targeted to specific compartments rather than spread evenly.

What are retaining ligaments and why do they matter for non-surgical treatments?

Retaining ligaments are fibrous bands that anchor specific zones of facial soft tissue to the underlying bone. The four major ones are the zygomatic, masseteric, mandibular, and orbicularis ligaments. As they loosen with age, the tissue above them descends — this is part of what produces jowls, mid-face descent, and changing facial contours. They matter for non-surgical treatments because energy-based devices can firm tissue but can't physically tighten loose ligaments; that's part of why advanced laxity tends to need surgical answers.

Is bony resorption something I should worry about in my 30s or 40s?

Bony resorption is a gradual process that begins to be measurable in the late 30s and 40s but generally produces visible structural change later — most noticeable from the 50s onward, particularly at the orbital rim, the mid-face, and the mandibular angle. It's worth knowing about because it explains why aging is structural and not purely soft-tissue, but it's not something to address proactively in your 30s. Doctors evaluate it during 3D scan consults to set realistic expectations about what soft-tissue treatments can and can't accomplish.

What's the difference between the dermis and the SMAS?

The dermis is one of the three skin layers — the middle one, where collagen, elastin, and most of the structural protein of skin live. The SMAS is a separate, deeper structure: a fibromuscular layer beneath the skin and the fat layer, more analogous to a connective scaffold than to skin itself. Energy-based treatments distinguish between dermal-level work (firming the skin layer itself) and SMAS-level work (reaching the deeper structural support). Different depths, different targets, different timelines for visible change.

Why does the platysma matter for the lower face and neck?

The platysma is a sheet-like muscle covering the front and side of the neck, and it's continuous with the SMAS in the lower face. When the platysma loses tone or its supporting structures loosen, the front edges of the muscle can become visible as vertical bands at rest, and the cervicomental angle softens. Treatments aimed at the lower face and neck — whether neuromodulator-based, energy-based, or surgical — are all interacting with the platysma in some way.

How do I know which fat compartment is causing my mid-face hollowing?

This is something only a provider can assess properly, ideally with a 3D scan or detailed in-person evaluation. Generally, mid-face hollowing involves the deep medial cheek fat (a deep compartment, loss here flattens the inner cheek), the malar fat (the surface compartment over the cheekbone, descent here drops the upper cheek), and sometimes the lateral fat compartments. Targeted volume restoration tends to look natural; spreading filler evenly doesn't, because the compartments don't age evenly. This is one of the conversations worth having before any volumizing procedure.

Are there anatomy terms I should know specifically for Korean clinic consults?

Korean aesthetic medicine tends to discuss masseter (for jaw-shaping with botulinum toxin), buccal fat (often discussed in face-slimming contexts, sometimes controversially), the mandibular angle (for jaw contouring), and the cervicomental angle (for profile and neck). Mid-face vocabulary like deep medial cheek fat, malar fat, and the zygomatic retaining ligament also comes up frequently in mid-face rejuvenation consults. Most reputable Gangnam clinics will explain anatomy on a 3D scan in plain language — having the words ahead of time just makes the conversation faster.