Chapter 34: Skull Anatomy

Skull Anatomy comprehensively details the skull, the complex bony framework of the head that protects the brain within the neurocranium (subdivided into the calvaria or cranial vault and the basicranium or cranial base) and supports the specialized sense organs, facial structures, and upper respiratory/digestive systems in the viscerocranium and mandible. The neurocranium is formed by parts of the frontal, parietal, temporal, occipital, ethmoid, and sphenoid bones. Many of the flat vault bones develop through intramembranous ossification and consist of an outer, thicker, resilient table and an inner, thinner, more brittle table, separated by the cancellous layer known as diploë. Movement is largely restricted to the synovial temporomandibular joint and the atlanto-occipital joint. Most cranial bones articulate via fibrous joints called sutures that facilitate growth; variations include simple butt-end, bevelled, and serrated morphologies. Premature fusion of these sutures is termed craniosynostosis, leading to deformities like scaphocephaly or plagiocephaly. Internal inspection divides the cranial base into the highest anterior cranial fossa (supporting the frontal lobes and featuring the perforated cribriform plate for olfactory nerves and the crista galli), the intermediate middle cranial fossa (supporting the temporal lobes, containing the sella turcica or pituitary fossa, and pierced by the foramen ovale and foramen spinosum), and the lowest posterior cranial fossa (containing the cerebellum, pons, and medulla oblongata, dominated by the foramen magnum). External views highlight key landmarks like the bregma and lambda (sites of the closed anterior and posterior fontanelles in infants), the pterion (a crucial H-shaped sutural junction overlying the middle meningeal artery), and the external occipital protuberance (inion). Structures enter and exit the base via several foramina, notably the large, often asymmetric jugular foramen (transmitting the internal jugular vein and cranial nerves IX, X, and XI) and the hypoglossal canal. Skull growth continues postnatally, influenced by cerebral development (vault) and the requirements of dentition and mastication (face). Growth of the cranial base involves the fusion of cartilaginous joints like the spheno-occipital synchondrosis, which typically closes between 13 and 18 years. In forensic and biological anthropology, the skull is crucial for identification, aiding in sex estimation (males typically exhibit greater robustness, larger mastoid processes, and more pronounced muscle attachment sites) and age estimation, which is most reliably accomplished by assessing dental maturation.