March 9, 2008

The Skull

Filed under: — Peter Laws @ 3:16 am

The skull is the bony framework of the head. It is comprised of the eight cranial and fourteen facial bones.

Cranial Bones

The cranial bones makeup the protective frame of bone around the brain.

The cranial bones are:

  • The frontal forms part of the cranial cavity as well as the forehead, the brow ridges and the nasal cavity.
  • The left and right parietal forms much of the superior and lateral portions of the cranium.
  • The left and right temporal form the lateral walls of the cranium as well as housing the external ear.
  • The occipital forms the posterior and inferior portions of the cranium. Many neck muscles attach here as this is the point of articulation with the neck.
  • The sphenoid forms part of the eye orbit and helps to form the floor of the cranium.
  • The ethmoid forms the medial portions of the orbits and the roof of the nasal cavity.

The joints between bones of the skull are immovable and called sutures. The parietal bones are joined by the sagittal suture. Where the parietal bones meet the frontal is referred to as the coronal suture. The parietals and the occipital meet at the lambdoidal suture. The suture between the parietals and the temporal bone is referred to as the squamous suture. These sites are the common location of fontanelles or “soft spots” on a baby’s head.

Facial Bones

The facial bones makeup the upper and lower jaw and other facial structures.

The facial bones are:

  • The mandible is the lower jawbone. It articulates with the temporal bones at the temporomandibular joints. This forms the only freely moveable joint in the head. It provides the chewing motion.
  • The left and right maxilla are the upper jaw bones. They form part of the nose, orbits, and roof of the mouth.
  • The left and right palatine form a portion of the nasal cavity and the posterior portion of the roof of the mouth.
  • The left and right zygomatic are the cheek bones. They form portions of the orbits as well.
  • The left and right nasal form the superior portion of the bridge of the nose.
  • The left and right lacrimal help to form the orbits.
  • The vomer forms part of the nasal septum (the divider between the nostrils).

The left and right inferior turbinate forms the lateral walls of the nose and increase the surface area of the nasal cavity.

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