The Pterygoid Process vs. The Pterygoid Bone
In anatomy, it's important to clarify terminology. While some vertebrates have a separate pterygoid bone, in humans, the structure is known as the pterygoid process. These are two bony, wing-like projections extending from the sphenoid bone, a butterfly-shaped bone located at the base of the skull. The pterygoid processes are divided into medial and lateral plates, which are crucial attachment points for the muscles of mastication, or chewing. Understanding how these specific processes change with age provides insight into broader issues of senior health, from diet to jaw comfort.
Age-Related Remodeling of the Craniofacial Skeleton
The skull is not a static structure; it undergoes continuous remodeling throughout life. Studies using imaging, such as helical CT scanning, have revealed distinct patterns of change. In the sphenoid bone, aeration within the sinuses expands until approximately the third decade of life. After this period, a gradual reduction in aeration occurs, with the volume decreasing in later decades. Notably, the aeration in peripheral portions of the sphenoid, including the pterygoid processes, also recedes over time.
This remodeling is a complex process involving a tight coupling of bone resorption and formation, influenced by hormones and mechanical forces. In addition to the sphenoid, other facial bones like the maxilla and mandible experience significant, predictable resorption as people age. These skeletal changes have aesthetic implications, altering the facial profile and providing less support for soft tissues.
Impact on Masticatory Muscles
The pterygoid processes are essential for proper mastication, serving as the origin points for the medial and lateral pterygoid muscles. These muscles are responsible for key jaw movements, including side-to-side motion and protrusion. With age, the function and mass of these masticatory muscles can decline.
Some research suggests a heterogeneous effect, meaning different muscles are affected differently. For example, a study using MRI found that the lateral pterygoid muscle's cross-sectional area decreased substantially with age in women, while the change was less pronounced in men. Reduced muscle bulk can significantly affect chewing strength and effectiveness in older adults, who may need to adapt their diets to softer foods. The weakening of these muscles, coupled with changes in the underlying bone, creates a compounding effect on jaw function.
Pterygoid Structure and Sleep Apnea
Emerging research suggests a link between the morphology of the pterygoid process and obstructive sleep apnea (OSAS), a condition more prevalent in older adults. The pterygoid hamulus, a small hook-shaped projection off the medial pterygoid plate, and the distance between the two pterygoid processes (interpterygoid distance) have been specifically investigated.
Studies have shown an association between reduced interpterygoid distance and increased OSAS severity. Similarly, the length and thickness of the pterygoid hamulus have been inversely associated with the severity of sleep apnea. These findings suggest that age-related remodeling in this area, which can alter the structural dimensions of the upper airway, plays a role in the pathophysiology of sleep apnea. This connection highlights the critical importance of understanding these seemingly minor bony changes.
Comparison of Younger vs. Older Pterygoid Processes
| Feature | Younger Pterygoid Process | Older Pterygoid Process |
|---|---|---|
| Aeration | Often well-aerated as part of the expanding sphenoid sinus, typically reaching maximum volume in the 20s or 30s. | Reduced aeration and potential bony sclerosis, part of the sphenoid's recession phase after its third decade. |
| Remodeling | Stable or continuing gradual expansion in early adulthood after peak growth. | Marked by specific patterns of bone resorption, altering the process's shape and affecting its role as a structural anchor. |
| Muscle Attachment | Supports robust and strong masticatory muscles, facilitating effective chewing and jaw movement. | Associated with potential atrophy or decreased bulk of the pterygoid muscles, leading to reduced masticatory force and altered jaw mobility. |
| Hamulus & Distance | Structural dimensions are typically associated with less severe conditions, such as lower apnea-hypopnea index scores. | Altered hamulus length and reduced interpterygoid distance have been linked to more severe obstructive sleep apnea. |
Effects on Temporomandibular Joint (TMJ) Function
The pterygoid muscles, particularly the lateral pterygoid, are integral to the movement of the temporomandibular joint (TMJ). Dysfunction or atrophy of these muscles, as can occur with age, can directly contribute to temporomandibular disorders (TMD). Poor muscle coordination and weakness, coupled with shifts in the bony structures, can disrupt the positioning of the articular disc within the TMJ, leading to pain, clicking, and restricted jaw movement. The lateral pterygoid's role in jaw protrusion and side-to-side movement means that age-related changes can directly impede these critical functions. For further reading on the complex interplay of TMJ disorders, a resource like Physiopedia offers a detailed overview of the lateral pterygoid muscle's function and dysfunction.
Overall Health Implications
While the pterygoid process is a small component of the overall skeleton, its age-related changes have cascading effects on senior health. Impaired mastication can lead to nutritional deficiencies if food choices become restricted to softer items. The discomfort and limited mobility of TMD can reduce quality of life. Furthermore, the link to sleep apnea underscores the broader systemic implications, as OSAS is associated with cardiovascular issues and other health problems. Therefore, understanding how the pterygoid process changes with age is not merely an anatomical curiosity but a critical factor in managing healthy aging.
Conclusion
In summary, the pterygoid processes of the sphenoid bone do change with age through a complex and predictable process of bony remodeling and recession of aeration. These structural changes, in turn, contribute to the weakening and potential atrophy of the attached masticatory muscles. Functionally, this can manifest as reduced chewing ability, temporomandibular disorders, and a potential increase in the severity of obstructive sleep apnea. For healthcare professionals and seniors alike, recognizing these deep-seated skeletal shifts is crucial for developing effective strategies for maintaining oral health and overall well-being throughout the aging process.
