›

Lateral Skull - Essentials

Notes

Lateral Skull - Essentials

Sections




Cranial bones

The 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

The 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

Sutures

There are four major sutures. They are 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.

Additional Skull features

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.

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.