Structure and Functions of the Skull
- The skull is composed of four types of bone: cranial bones, facial bones, ear ossicles, and hyoid bone.
- The cranium and the mandible are the two most prominent parts of the skull.
- The skull houses the brain and various sensory structures such as the eyes, ears, nose, and mouth.
- The functions of the skull include protecting the brain, enabling stereoscopic vision, and facilitating sound localization.
- The human skull supports the structures of the face and forms a cavity for the brain.
- It consists of the neurocranium (braincase), sutures, and facial skeleton.
- The neurocranium surrounds and protects the brain, while the facial skeleton supports the face.
- The bones of the human skull include the occipital, temporal, parietal, sphenoid, ethmoid, frontal, vomer, nasal, maxilla, mandible, palatine, zygomatic, and lacrimal bones.
- The skull contains sinuses, which are air-filled cavities that lessen the weight of the skull, aid resonance to the voice, and warm and moisten the air drawn into the nasal cavity.
- It also has numerous foramina, including the foramen magnum, which allows the passage of the spinal cord, nerves, and blood vessels.
- The sinuses are lined with respiratory epithelium.
- The foramina are openings in the skull, and the largest one is the foramen magnum.
- The skull also contains other processes, such as the mastoid process and zygomatic processes.
- The skulls of other vertebrates have fenestrae, which are openings in the skull.
- Examples of fenestrae include the antorbital fenestra, mandibular fenestra, quadratojugal fenestra, subsquamosal fenestra, and temporal fenestra.
- In reptiles, amphibians, and birds, the jugal bone is equivalent to the zygomatic bone in mammals.
- The prefrontal bone separates the lacrimal and frontal bones in many tetrapod skulls.
- Fish skulls can be formed from cartilaginous elements or a combination of cartilage and dermal bone.
- Jawless fish have a trough-like basket of cartilaginous elements that partially enclose the brain.
- Cartilaginous fish, such as sharks and rays, have a single structure forming a case around the brain, with openings for the olfactory organs and cranial nerves.
- Ray-finned fish have a well-formed roof of the skull and modified elements, such as the premaxilla and symplectic bones, for jaw structure.
- The lower jaw in fish defines a chin and is separate from the cranium.
- Skulls of earliest tetrapods resemble those of lobe-finned fishes.
- Skull roof composed of plate-like bones including maxilla, frontals, parietals, and lacrimals.
- Endocranium corresponds to cartilaginous skull in sharks and rays.
- Temporal bone of humans is part of the skull roof series.
- Lower jaw composed of multiple bones, with dentary being homologous to mammalian mandible.
- Birds have a diapsid skull, similar to reptiles.
- Skull consists of frontal, parietal, premaxillary, nasal, and mandible bones.
- Living amphibians have reduced skulls with many bones absent or replaced by cartilage.
- Skull modifications occurred in mammals and birds to accommodate brain expansion.
- Fusion between bones is notable in birds, making identification difficult.
- Skull bones formed by both intramembranous and endochondral ossification.
- Skull roof bones are dermal bones formed by intramembranous ossification.
- Endocranium bones supporting the brain formed by endochondral ossification.
- Geometry of skull base and its fossae changes rapidly during development.
- Fontanelles separate skull bones at birth, gradually replaced by sutures.
- Craniosynostosis is the premature fusion of fibrous sutures in an infant skull.
- Fusion alters growth pattern of the skull, resulting in abnormal head shape and facial features.
- Craniosynostosis can lead to increased intracranial pressure and various impairments.
- Copper beaten skull is a condition where intracranial pressure disfigures the skull's internal surface.
- Skull injuries can be life-threatening, with raised intracranial pressure causing brain herniation.
- Skull protects the brain from damage due to its high resistance to deformation.
- Raised intracranial pressure can lead to brain herniation and significant damage.
- Subdural hematoma can cause raised intracranial pressure.
- Trepanning, a Neolithic skull operation, involved drilling a burr hole in the cranium.
- 3D-printed polymer implants have been used for skull replacements in medical procedures.
Skull in Society and Culture
- Adam was believed to have been buried on Mount Calvary.
- Some cultures practiced artificial cranial deformation, altering the shape of infants' skulls.
- Silk embroidery from the 17th century depicts skull motifs.
- Mount Calvary is associated with the burial of Adam.
- Cranial deformation involved using cords and wooden boards to reshape infants' skulls.
- Skull and teeth can provide information about a person's life history and origin.
- Osteologists use quantitative and qualitative traits to estimate the appearance of individuals based on their skulls.
- Traits like proportions of length, height, and width can reveal relationships between populations.
- Spitalfields in the UK and JÅmon shell mounds in Japan are sites where significant bone findings have been made.
- Anthropologists in the mid-nineteenth century distinguished between male and female skulls.
- James McGrigor Allan argued that female brains were similar to those of animals, supporting the idea of female inferiority.
- Cranial measurements were used to draw connections between women and black people.
- Male skulls tend to be larger and more robust than female skulls in adulthood.
- Studies show that women
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone, however two parts are more prominent: the cranium (pl.: craniums or crania) and the mandible. In humans, these two parts are the neurocranium (braincase) and the viscerocranium (facial skeleton) that includes the mandible as its largest bone. The skull forms the anterior-most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, and mouth. In humans, these sensory structures are part of the facial skeleton.
| Skull | |
|---|---|
 Volume rendering of a mouse skull | |
| Details | |
| System | Skeletal system |
| Identifiers | |
| MeSH | D012886 |
| FMA | 54964 |
| Anatomical terminology | |
Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals, such as horned ungulates (mammals with hooves), the skull also has a defensive function by providing the mount (on the frontal bone) for the horns.
The English word skull is probably derived from Old Norse skulle, while the Latin word cranium comes from the Greek root κρανίον (kranion). The human skull fully develops two years after birth. The junctions of the skull bones are joined by structures called sutures.
The skull is made up of a number of fused flat bones, and contains many foramina, fossae, processes, and several cavities or sinuses. In zoology, there are openings in the skull called fenestrae.
