Anatomy

Lateral Skull

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CRANIAL BONES

  • Enclose and protect the brain

Frontal bone

  • Comprises the forehead and the superior portion of the eye orbit

Parietal bone

  • Comprises the superior portion of the lateral skull

Sphenoid bone

  • Only small portion visible in lateral view
  • Gives rise to pterygoid processes

Temporal bone

  • Forms inferior boundary of lateral skull
  • Squamous portion is area inferior to squamous suture
  • Tympanic portion surrounds the external auditory meatus
  • External auditory meatus is the external opening of the ear
  • Mastoid process is the large bony projection near the occipital bone
  • Styloid process is a long, pointy projection
  • Mandibular fossa is a depressed area of the temporal bone that articulates with the mandible to form the temporomandibular joint

Occipital bone

  • Comprises posterior and inferior portion of cranium

FACIAL BONES

  • Form the face and protect the entrances to the oral and nasal cavities.

Zygomatic

  • Contributes to the lateral eye orbits and cheeks

Nasal

  • Forms the bony component of the external nose

Maxilla

  • Contributes to the medial eye orbit, cheeks, and upper jaw
    *Anterior nasal spine is the projection of the maxillae that contributes to the inferior border of the opening of the nasal cavity.

Ethmoid

  • Contributes to medial eye orbit

Lacrimal

  • Contributes to medial eye orbit
  • Fossa for the lacrimal sac, through which tears pass from the eye to the nasal cavity. This connection explains why your nose runs when you cry.

Mandible

  • Bone of the lower jaw; it houses the lower teeth.
  • Condyle (aka, head) articulates with the mandibular fossa of the temporal bone posteriorly
  • Coronoid process provides an attachment site for temporalis, a powerful muscle of the jaw.
  • Mandibular notch lies between condyle and coronoid process
  • Ramus is the vertical portion
  • Body is anterior and lateral base
  • Angle lies between body and ramus, posteriorly
  • Mental protuberance, which forms the chin

FOUR MAJOR SUTURES:

  • Sutures are the immoveable joints between the skull bones.

Coronal suture

  • Lies between the frontal bone, anteriorly, and the parietal bones, posteriorly;

Sagittal suture

  • Lies between the right and left parietal bones;

Squamous suture

  • Lies between the temporal and parietal bones.

Lambdoid suture

  • Lies between the parietal and occipital bones.

Sutural bones (formerly called Wormian bones)

  • Small, irregularly shaped bones that form between the major skull bones.

Pterion

  • Where the temporal, sphenoid, parietal, and frontal bones meet
  • Overlies the middle meningeal artery; thus, injury to the pterion is a common cause of intracranial epidural hematoma.

Additional Features:

Paranasal sinuses

  • Spaces within the frontal, ethmoid, sphenoid, and maxilla; they are continuous with the nasal cavity (and are addressed in detail with the respiratory system).

Zygomatic arch

  • The zygomatic process, which is a projection of the temporal bone
  • The temporal process, which is a projection of the zygomatic bone

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