The Skull

​The Skull has two major components: The calvarium (calvaria = skull) which is composed of 8 bones and 15 facial bones. The cranial bones surround the brain, housed in the cranial cavity, and provide a rigid protective covering for the brain. The cranial bones severely limit the expansion of the brain (even when expansion becomes necessary in response to disease). The cranial cavity is formed by the frontal, parietal, sphenoid, temporal and occipital bones. The floor of the human skull viewed from above is divided into three distinct compartments (fossae) on each side: anterior, middle and posterior. The cranial nerves emerge through symmetrically placed holes (foramina) in the base of the skull to innervate peripheral structures.
These are the major bones of the skull which can be seen clearly. 
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  • frontal bone: the frontal bone forms the forehead and inside (anterior fossa) of the base of the skull. (drilling to the interior is a sinus) 
  • parietal bones: there are two parietal bones which compose the roof and lateral portions of the posterior skull. 
  • temporal bone: the temporal bone, which compose the lateral portions of the skull around the ear is composed of 4 parts
    • squamous portion of the temporal bone; square-shaped, thin, flat
    • mastoid portion of the temporal bone; thin, flat
    • zygomatic process; posterior portion of cheek
    • petrous portion of the temporal bone; houses the inner ear
  • occipital bone: the occipital bone composes the posterior portion of the skull and includes the foramen magnum, the opening where the spinal cord attaches to the brain and articulates with the first cervical vertebrae (C1/Atlas) which holds up the skull​​
The floor of the skull is composed of bones that are deep

  • sphenoid bone: the sphenoid bone lies medio-laterally and is posterior to the frontal bone, it is the keystone of the floor of the skull. The sphenoid sinus forms the lateral wall of the orbit. It forms the sella turcica (Turkish saddle) which has four clinoid processes which surrounds the pituitary gland from anterior to posterior.
  • ethmoid bone: the ethmoid bone is located in the anterior midline of the skull and houses the cribriform plate, which has many small openings, to allow smell impulses to reach small nerve fibers which transmit sensation to the olfactory nerve.​​
Sutures (a seam-like, immovable junction between two bones) join the calvarium bones
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  • coronal suture: between the frontal and parietal bones
  • lambdoidal suture: (greek letter lambda) posterior aspect of the skull that joins the parietal lobe with the occipital lobe
  • occipito-mastoid/occipito-temporal suture: joins the occipital lobe with the mastoid bone or temporal bone
  • sagittal suture: separates the left and right parietal bones​​
Facial Bones
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  • nasal bones: inferior medial orbit
  • zygomatic bones: form the middle aspect of the cheek bone
    • ​zygomatic process of maxilla
    • zygomatic Bone
    • zygomatic process of the temporal bone
  • ​palatine bones: 2 bones that form the posterior portion of the hard palate (roof of the mouth)
  • inferior conchae: lateral nasal cavity
  • vomer: medial nasal cavity; commonly referred to as the septum
  • hyoid bone: u-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. It lies at the level of the base of the mandible anterior to the third cervical vertebra (C3). It functions to support the tongue above it and larynx below it and also transmits force of muscles to help open the jaw.