Facial Layers and Fat Compartments: What Is Under the Needle
Deep and superficial are the words injectors use most and examine least. They only mean something if you can say which layer you are in and what lies directly above and below it.
This is a short guide to the anatomy behind those words: the five layers and where the model stops working, how facial fat is divided, what the ligaments hold, and how the face changes with age.
The five layers, and how they change by region
The face is usually described in five layers: skin; subcutaneous fat with its fibrous septa; the superficial musculo-aponeurotic system; deep fat; and periosteum or deep fascia. The arrangement varies between regions, especially where ligaments pass through it [1].
The third layer changes name and depth from region to region: galea in the scalp, temporoparietal fascia in the temple, SMAS in the cheek, orbicularis oculi around the eye, orbicularis oris in the lip and platysma in the neck. Below the muscle therefore means a different depth in each place.
The fourth layer contains glide planes. In the lower face, the premasseter space is lined by membrane, reinforced by retaining ligaments and has a floor of thin, dense connective tissue, with the branches of the facial nerve running beneath that floor rather than through the space [3]. This is why it is described as a safe, bloodless plane.
Fat is divided into compartments
Subcutaneous facial fat is divided into separate compartments rather than spread as one sheet. The study that established this concluded that the face does not age as a single mass, and that shifting between neighbouring compartments may contribute to sagging. The septa between compartments also confined injected dye in cadavers, which helps explain why a deposit often stops where it does [2].
What the ligaments hold
A true ligament connects bone to skin; where the attachment is to the parotid or masseteric fascia, the structure is usually called fascia [5]. The zygomatic ligaments anchor cheek skin to the lower border of the zygoma, and the mandibular ligaments tether skin to the front of the mandible [4]. Authors still describe the origin of the masseteric ligament differently [5]. Some researchers see certain ligaments as the points where the septa between fat compartments meet [2]; the review of ligament terminology treats these as different structures [5].
How the face changes with age
Studies in living people show redistribution rather than uniform loss. A computed tomography study that compared repeat scans of 262 patients found that the upper and middle fat compartments of the midface shrank with age while the lower compartment grew [8]. A smaller magnetic resonance series by the same investigators found all three compartments shrinking [13], so whether total volume falls is still disputed. A magnetic resonance study of 100 women found the superficial temporal fat larger in older age than in youth [9].
Fat also moves. An ultrasound study of 24 volunteers found that the superficial midfacial compartment moved upwards during smiling while the deep compartments barely moved [10].
The bone changes as well. Computed tomography of the orbit in 60 people found the orbital aperture widening with age and its rim receding [6]. A study of 107 Korean subjects found no significant change in the area of the orbital aperture with age [7], so the pattern often taught as universal may not apply to every population.
Where the five-layer model does not fit
The temple. The middle temporal vein runs between the superficial and deep layers of the deep temporal fascia, and in more than a quarter of cases it splits and reunites [11]. Going deep in the temple is a choice between several planes, one of which holds a large vein.
The lip. Under the skin and a thin subcutaneous layer lie orbicularis oris, the submucosa and the mucosa, with no deep fat compartment, so the five-layer model fits poorly. Depth still matters: the labial arteries usually run deep, behind orbicularis oris.
The nose. Apart from the lateral nasal veins, the main arteries, veins and lymphatics run above the musculo-aponeurotic layer, and the plane beneath it preserves the blood supply [12]. In the nose, the habit that superficial is safer is the wrong one.
What this means at the consultation
- Name the plane by region. Deep in the midface means on the bone, below the nerve branches, and the mobility study supports placing product for the deep compartments there [10]. Deep in the temple means choosing between fascial planes; deep in the lip means close to the labial arteries.
- Decide what you are treating. Redistribution and volume loss are different problems [8][9]. No study shows that filling a named compartment recreates a younger face.
- Use the planes the anatomy provides. A plane with a firm floor and few crossing structures, such as the premasseter space, is safer than steering around a remembered line. That space was described in open dissection, not tested with needles [3].
- Expect boundaries to stop product. When filler does not spread where you expected, a septum or ligament is the first explanation to consider.
- Check who was studied. Many of these studies included only one ancestry, sex or age group [6][7][9].
None of the studies above examined faces after repeated filler, which may alter the planes and boundaries they describe. Learning to feel these layers under the needle, in faces that have and have not been treated, is what supervised hands-on training is for.
Read next
- Mid-Face and Cheek Filler: Restoring Support Without Adding Weight
- Facial Arteries Vary: Why Landmarks Are Not Guarantees
- Non-Surgical Rhinoplasty: Why This Is the Least Forgiving Region on the Face