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Skull - Inferior View
Features of the inferior skull
Helpful Definitions:
- Foramina are holes that allow neurovascular structures to pass through the bone.
- Processes serve as muscle attachment sites.
Maxilla:
- Palatine process
- Portion of the maxilla that extends posteriorly, towards the palatine.
- Incisive foramen
- A small opening for neurovascular structures; its name reflects its location posterior to the incisors (the front teeth).
- The nasopalatine nerve and sphenopalatine artery (and vein) pass through the incisive foramen to serve the palate and associated structures.
- Alveolar margin (aka, ridge)
- The border of the maxilla where the upper teeth reside.
Sphenoid:
- Pterygoid process
- Gives rise to the medial and lateral pterygoid plates, which are extensions where muscles of mastication (aka, chewing) attach.
- Foramen ovale
- Petrosal nerve, mandibular nerve, and accessory meningeal artery.
- Foramen spinosum
- Middle meningeal artery and meningeal branch of the mandibular nerve.
Temporal bone:
- Mandibular fossa
- Shallow depression where the mandible (the bone of the lower jaw) articulates with the cranium.
- External auditory meatus
- External opening of the ear.
- Styloid process
- A pointy projection for attachment of muscles.
- Mastoid process
- Larger, roughened cone-shaped projection for muscle attachment (sternocleidomastoid).
- Opening of the carotid canal
- Internal carotid artery enters the cranium to supply the brain via this opening.
- Stylomastoid foramen
- Lies between the styloid and mastoid processes.
- CN VII (facial nerve).
Occipital bone:
- Foramen magnum
- A large hole where the spinal cord enters the cranium to become the brainstem.
- The brainstem, vertebral arteries, and CN XI (accessory nerve) pass through the foramen magnum.
- Occipital condyles
- Lie on either side of the foramen magnum; these rounded surfaces articulate with the vertebral column.
- Hypoglossal canal
- A small opening near the foramen magnum and the occipital condyles.
- CN XII (hypoglossal nerve)
- External occipital crest
- Extends from the posterior edge of the foramen magnum, and terminates at the external occipital protuberance
- External occipital protuberance
- A roughened elevation; it serves as a muscle attachment site and is usually larger in adult males.
- Inferior and superior nuchal lines
- Extend horizontally from the crest; they serve as muscle attachment sites.
- Foramen lacerum
- Lies between the occipital, sphenoid, and temporal bones; it is irregularly shaped.
- Greater petrosal nerve; it is a branch of the facial nerve (CN VII).
- CNs IX (glossopharyngeal nerve), X (vagus), and XI (accessory), and the jugular vein