Osteology of the Skull

Comprehensive vocabulary flashcards covering the bones, sutures, ossification processes, and clinical relevance of the cranial and facial skeleton.

Skull

A bony structure comprised of $22$ bones that supports the face and forms a protective cavity for the brain.

Intramembranous Ossification

Also referred to as desmal ossification, the process where mesenchymal cells differentiate into osteoblasts to directly deposit bone, forming the flat bones of the skull.

Neurocranium

The division of the skull that encloses and protects the brain, meninges, and cerebral vasculature; it is subdivided into the cranial roof and cranial base.

Calvarium

Also known as the cranial roof, it is comprised of the frontal, occipital, and two parietal bones.

Cranial Base

The part of the cranium comprised of the frontal, sphenoid, ethmoid, occipital, parietal, and temporal bones which articulate with the atlas ($1^{st}$ cervical vertebra), facial bones, and mandible.

Viscerocranium

The facial skeleton consisting of $14$ bones that supports the soft tissues of the face and houses the orbits, nasal and oral cavities, and sinuses.

Sutures

Unique fibrous joints in the skull that are immovable and typically fuse completely around the age of $20$.

Coronal Suture

The fibrous joint that fuses the frontal bone with the two parietal bones.

Sagittal Suture

The fibrous joint that fuses both parietal bones to each other.

Lambdoidal Suture

The fibrous joint that fuses the occipital bone to the two parietal bones.

Fontanelles

Membranous gaps between incompletely fused suture joints in neonates; the two major types are frontal and occipital.

Occipital Bone

The bone forming the back and base of the cranium, containing the foramen magnum and articulating with the first vertebra of the spinal column.

Foramen Magnum

The large opening in the occipital bone through which the spinal cord passes as it enters the vertebral column.

Basilar Skull Fracture

A fracture of the base of the skull typically resulting from trauma to the occiput.

Basion-dens Line

The distance between the basion and the top of the dens as seen on a radiograph, used to diagnose dissociation injuries.

Temporal Bones

Bones situated at the base and sides of the skull consisting of squamous, mastoid, petrous, and tympanic regions.

Zygomatic Process (Temporal)

A projection from the lower squamous region of the temporal bone that articulates with the zygomatic bone to form the zygomatic arch.

Styloid Process

A downward projection from the interior of the temporal bone that provides attachment for muscles associated with the tongue.

Parietal Bones

Two large bones that make up part of the roof and sides of the human skull, articulating at the sagittal suture.

Sphenoid Bone

A butterfly-shaped bone situated in the middle of the skull towards the front, consisting of a body, greater wings, lesser wings, and pterygoid processes.

Battle Sign

A clinical sign associated with fractures of the sphenoid bone following injury to the orbit and base of the skull.

Ethmoid Bone

A lightweight, spongy bone located at the roof of the nose that separates the nasal cavity from the brain.

Cribriform Plate

A part of the ethmoid bone crossed by the olfactory nerve ($1^{st}$ cranial nerve) to reach the nasal cavity.

Frontal Bone

The bone forming the forehead, consisting of squamous, orbital, and nasal parts, and housing the frontal sinuses.

Zygomatic Bone

The bone forming the cheek skeleton and the lateral rim and wall of the orbit; it provides attachment for the masseter muscle.

Maxilla Bone

The bone forming the upper jaw, housing the upper teeth and the maxillary paranasal sinus, and comprising the majority of the hard palate.

Le Fort Classification

A system ranging from $1$ to $3$ used to classify fractures affecting the maxillary bones.

Alveolar Process

The part of the maxilla or mandible that supports the teeth; it is resorbed in the event of tooth loss.

Nasal Bones

Two small, rectangle-shaped bones that form the bridge of the nose and support the nasal septum.

Inferior Nasal Conchae

Scroll-shaped bones (turbinates) within the nasal cavity that help filter and moisten inspired air.

Mandible

The largest and strongest bone of the face, also known as the jaw bone, and the only mobile bone of the facial skeleton.

Meckel's Cartilage

The cartilage around which the intramembranous ossification of the mandible occurs.

Coronoid Process

The anterior most superior extension of the mandibular ramus that provides attachment for the temporalis muscle.

Condylar Process

The posterior extension of the mandibular ramus that forms a condyle to join with the temporal bone at the temporomandibular joint (TMJ).

Lacrimal Bone

Small, fragile, rectangular bones situated in the antero-medial part of the orbit.

Palatine Bone

L-shaped bones that form part of the nasal cavity and the posterior portion of the hard palate.

Vomer Bone

An unpaired, plough-shaped bone that forms the posterior inferior portion of the nasal septum.