The Dynamic Nature of the Adult Skeleton
Many people believe that once adulthood is reached, the skeleton is a static structure. However, our bones are living tissues that are in a constant state of turnover, involving two primary processes: bone resorption, where old bone is broken down by cells called osteoclasts, and bone formation, where new bone is built by osteoblasts. While this process slows with age, it never truly stops. In the skull, this remodeling is particularly evident in the facial bones and less so in the cranial vault, or the part protecting the brain.
Why does the facial skeleton change?
The facial skeleton is more susceptible to age-related remodeling than the cranium. Several factors contribute to this dynamic reshaping:
- Hormonal shifts: Declining levels of hormones like estrogen in women and testosterone in men can affect bone density and turnover throughout the body, including the face.
- Biomechanical forces: The repetitive stress from chewing, muscle attachments, and even gravity influences bone structure. As we age, these forces, combined with changes in the overlying soft tissues, drive continuous remodeling.
- Tooth loss: Edentulism (tooth loss) significantly accelerates bone resorption in the maxilla (upper jaw) and mandible (lower jaw), further altering facial shape.
Specific Age-Related Changes to the Skull
Advanced 3D computed tomography (CT) scans have given researchers unprecedented insight into precisely how the skull changes over time. These changes are subtle and occur differently in specific regions.
The periorbital region
One of the most noticeable changes occurs around the eyes. With age, the eye sockets (orbits) tend to enlarge, particularly at the superomedial (inner, upper) and inferolateral (outer, lower) aspects of the orbital rim. This selective resorption of bone contributes to the appearance of hollow, sunken eyes and can cause the eyebrows to droop, creating a tired or sad appearance.
The midface and nose
- Maxilla: The midface, particularly the maxilla (the bone that forms the upper jaw and supports the nose and cheeks), experiences bone loss over time. This bone resorption leads to a loss of projection in the midface, which can contribute to the deepening of nasolabial folds (the lines from your nose to the corners of your mouth).
- Piriform Aperture: The piriform aperture, the bony opening for the nose, enlarges with age as the bone around it is resorbed. This can cause the nose to appear longer and the tip to droop, as it loses its foundational support.
The jaw and chin
- Mandible: The mandible (jawbone) also undergoes significant changes. Studies show that bone resorption occurs in the front of the mandible, especially in the prejowl area, while some bone is added to the back. This shifts the jaw's angle and can worsen the appearance of jowls as soft tissue loses its support structure.
- Chin: While the jawline changes, the chin can also become shorter and more pointed with age due to bone remodeling.
The cranial vault
While the facial skeleton is in constant flux, the cranial vault—the main protective casing for the brain—is much more stable in terms of overall shape. However, even this area experiences remodeling, specifically a thickening of the inner table of the frontal bone in some individuals, particularly older women. This thickening is a normal, benign finding but can reduce the intracranial volume slightly over time.
The Role of Gender in Skull Remodeling
Research shows that skull changes differ between men and women, both in timing and pattern. In women, many facial skeletal changes, such as in the orbital rims, begin earlier, often between young and middle age. In men, these changes tend to be more prominent later in life. Differences in hormone levels, bone density, and facial anatomy play a role in these gender-specific patterns.
Comparing an Aging Skull with a Younger Skull
| Feature | Young Adult Skull | Aging Adult Skull | Key Remodeling Process |
|---|---|---|---|
| Midface Projection | More prominent and projects forward | Recedes and flattens | Maxillary bone resorption and backward rotation |
| Orbital Rims | Defined, with smaller orbital apertures | Rims resorb, orbits enlarge | Selective resorption at superomedial and inferolateral areas |
| Jawline Angle | Often sharper and more defined (especially in men) | Becomes more obtuse (wider angle) | Bone resorption at the angle and prejowl areas |
| Nasal Aperture | Smaller and more contained | Enlarges over time | Resorption of the piriform aperture's lateral and inferior walls |
| Chin Projection | More pronounced and projects forward | Becomes shorter and more oblique | Anterior and inferior bone resorption |
| Forehead | Stable bone thickness | Can thicken on the internal surface | Deposition of new bone (inner table thickening) |
Conclusion: More Than Just Soft Tissue
Understanding that your skull continues to remodel is crucial for appreciating the aging process. The sagging skin and wrinkles we associate with getting older aren't just a result of gravity's pull on soft tissue; they are profoundly influenced by the changing skeletal foundation beneath. By addressing the underlying bone changes through interventions like fillers or implants, and by focusing on overall bone health with proper nutrition and exercise, it is possible to mitigate some of the visual effects of facial aging. As the scientific community learns more about these intricate processes, we gain a more complete understanding of how to support healthy aging for our entire body, including our bones. For additional information on broader bone health issues, consult authoritative sources like the National Institutes of Health.
