Anatomy of the Skull

Superior View of the Skull

• Major bones visible: Parietal and Occipital.
• Parietal bones:
  • Joined to the occipital bone by the lambdoid suture.
  • Sagittal suture joins the two parietal bones.
• Sutural (Wormian) bones:
  • Extra small bones that may form along the lambdoid suture.
• External Occipital Protuberance:
  • Present on the posterior surface of the occipital bone.
  • Can be felt through the scalp at the base of the head.
  • Size varies from person to person.
  • Attachment site for the ligamentum nuchae.
• Ligamentum Nuchae:
  • Elastic ligament extending down the neck.
  • Helps keep the head erect by pulling on the occipital region of the skull.
• Nuchal Lines:
  • Small ridges extending laterally from the external occipital protuberance.
  • Points of attachment for several neck muscles.

Lateral View of the Skull

• Parietal bone and squamous part of the temporal bone form a major portion of the side of the head.
• Temporal Bone:
  • Named so because the hair of the temples is often the first to turn white, indicating the passage of time.
• Squamous Suture:
  • Joins the parietal and temporal bones.
• External Auditory Canal (External Acoustic Meatus):
  • Large hole in the temporal bone.
  • Transmits sound waves toward the eardrum (tympanic membrane).
  • The external ear (auricle) surrounds the canal.
• Mastoid Process:
  • Large inferior projection, posterior and inferior to the external auditory canal.
  • Can be seen and felt as a prominent lump just posterior to the ear.
  • Filled with mastoid air cells, which are connected to the middle ear.
  • Attachment site for important neck muscles involved in rotating the head.
• Superior and Inferior Temporal Lines:
  • Attachment points for the temporalis muscle.
  • Temporalis muscle: major muscle of mastication.
  • Arch across the lateral surface of the parietal bone.
• Sphenoid Bone:
  • The lateral surface of the greater wing is immediately anterior to the temporal bone.
  • A single bone that extends completely across the skull.
• Zygomatic Bone (Cheekbone):
  • Anterior to the sphenoid bone.
  • Easily seen and felt on the face.
• Zygomatic Arch:
  • Consists of joined processes from the temporal and zygomatic bones.
  • Forms a bridge across the side of the skull.

Jaws

• Composed of two maxillae (upper jaw) and one mandible (lower jaw).
• Maxilla:
  • Anterior and inferior to the zygomatic bone to which it is joined.
• Mandible:
  • Inferior to the maxilla and attaches posteriorly to the temporal bone.
  • Consists of two main portions: the body and the ramus.
• Mandible Body:
  • Extends both anteriorly and posteriorly.
• Ramus (branch):
  • Extends superiorly from the body toward the temporal bone.
  • Superior end has a mandibular condyle and a coronoid process.
• Mandibular Condyle:
  • Articulates with the mandibular fossa of the temporal bone.
• Coronoid Process:
  • Attachment point for the temporalis muscle (a chewing muscle).
• Alveolar Processes:
  • Of the maxillae contain the superior set of teeth.
  • Of the mandible contains the inferior teeth.

Anterior View of the Skull

• Major structures seen:
  • Frontal bone (forehead).
  • Zygomatic bones (cheekbones).
  • Maxillae.
  • Mandible.
• Orbits:
  • Cone-shaped fossae with apex directed posteriorly.
  • Eyes rotate within the fossae.
  • Provide protection for the eyes and attachment points for eye muscles.
• Orbit Contents:
  • Eyeball.
  • Blood vessels.
  • Nerves.
  • Adipose tissue.
• Nasolacrimal Duct:
  • Passes from the orbit into the nasal cavity through the nasolacrimal canal.
  • Carries tears from the eyes to the nasal cavity.
• Optic Nerve:
  • Passes from the eye through the optic canal at the posterior apex of the orbit and enters the cranial cavity.
• Superior and Inferior Fissures:
  • In the posterior region of the orbit.
  • Provide openings through which nerves and blood vessels communicate with structures in the orbit or pass to the face.