03/11 Notes: Bones

Anatomy of the Skull

Cribriform Plate

  • Located bilaterally within the ethmoid bone.

  • Contains foramina for olfactory nerve passage from the nasal cavity to cranial cavity.

Sphenoid Bone

  • Butterfly-shaped bone situated in the midline of the skull.

  • Consists of two sets of wings:

    • Lesser Wing: Smaller pair of wings.

    • Greater Wing: Larger pair of wings.

  • Optic Canal: Allows optic nerve (cranial nerve II) to enter the cranial cavity.

  • Sella Turcica: A saddle-like structure that protects the pituitary gland.

    • Important for the endocrine system as it houses the pituitary gland.

Canals and Foramina

  • Optic Canal: Passageway for the optic nerve.

  • Foramina associated with the Greater Wing of Sphenoid Bone:

    • Foramen Rotundum: Round-shaped foramen.

    • Foramen Ovale: Oval-shaped foramen.

    • Foramen Spinosum: Spiny-shaped foramen.

Temporal Bone

  • Carotid Canal: Canal that allows internal carotid artery to enter cranial cavity.

  • Petrous Portion: Raised ridge posteriorly within the temporal bone.

  • Jugular Foramen: Permits the jugular vein to exit the cranial cavity.

Foramen Magnum

  • Large opening at the base of the skull allowing the brainstem to transition to the spinal cord.

  • Important landmark:

    • Superior Structure: Brainstem.

    • Inferior Structure: Spinal cord.

  • Divided into three segments:

    • Midbrain: Superior segment of the brainstem.

    • Pons: Middle segment of the brainstem.

    • Medulla Oblongata: Inferior segment.

Hypoglossal Canal

  • Located bilaterally near the foramen magnum.

  • Allows passage of hypoglossal nerve.

Hard Palate

  • Bony roof of the mouth; composed of two bones:

    • Maxillary Bone: Forms the anterior portion (palatine process).

    • Palatine Bone: Forms the posterior portion (horizontal plate).

Ethmoid Bone

  • Features: crista galli, cribriform plates, and perpendicular plate.

  • Nasal Conchae: Superior and middle conchae belong to the ethmoid bone.

Review of Bone Features

  • Maxillary Bone: Contains infraorbital foramen.

  • Temporal Bone: Zygomatic process, external acoustic meatus, styloid process, mastoid process, and mandibular fossa.

  • Occipital Bone: Include external occipital protuberance, superior and inferior nuchal lines, and occipital condyles.

  • Sphenoid Bone: Features the lesser wing, greater wing, optic canal, sella turcica, and pterygoid plates.

  • Structures to Remember:

    • Optic Canal: For optic nerve.

    • Jugular Foramen: For jugular vein.

    • Foramen Magnum: For brainstem and spinal cord.

    • Hypoglossal Canal: For hypoglossal nerve.

Final Notes

  • Be equipped with specific structures for potential examination questions regarding the skull anatomy.