Axial Skeleton: Skull, Vertebral Column, and Thoracic Cage Anatomy

A comprehensive vocabulary review deck covering the bones, landmarks, sutures, sinuses, vertebrae, and thoracic cage structures of the human axial skeleton.

Anterior cranial fossa

The anterior-most and shallowest depression of the internal cranial base that accommodates and supports the frontal lobes of the brain.

Middle cranial fossa

The intermediate depression of the cranial base located posterior and inferior to the anterior cranial fossa, accommodating the temporal lobes of the brain.

Posterior cranial fossa

The deepest and posterior-most depression of the internal cranial base that supports the cerebellum, pons, and medulla oblongata.

Cranial fossae

The three distinct depressions (anterior, middle, and posterior cranial fossae) forming the tiered floor of the cranial base to accommodate different regions of the brain.

Coronal suture

The transverse joint across the superior cranium uniting the anterior frontal bone with the paired parietal bones.

Sagittal suture

The superior midline fibrous joint extending anterior-to-posterior between the two parietal bones.

Lambdoid suture

The inverted-V shaped suture located posteriorly that articulates the parietal bones with the occipital bone.

Squamous suture

The arched suture on each lateral skull wall connecting the temporal bone to the adjacent parietal bone.

Sphenoid bone

A complex, central, bat-shaped cranial bone that articulates with nearly all other cranial bones and features a central body, greater wings, and lesser wings.

Hypophyseal fossa of sella turcica

A prominent central saddle-like depression in the body of the sphenoid bone that houses and protects the pituitary gland.

Optic canal

An aperture located at the base of the lesser wing of the sphenoid bone through which the optic nerve and ophthalmic artery enter the orbit.

Superior orbital fissure

A long, oblique slit between the greater and lesser wings of the sphenoid bone that transmits nerves controlling eye movements.

Pterygoid process

A paired inferiorly directed bony extension of the sphenoid bone providing attachment for muscles of chewing.

Ethmoid bone

A delicate, sponge-like bone situated in the anterior cranial floor and superior nasal area between the orbits.

Crista galli

A superior vertical midline ridge of the ethmoid bone projecting into the anterior cranial fossa that anchors the anterior end of the falx cerebri.

Perpendicular plate of ethmoid bone

A thin vertical plate descending along the midline of the ethmoid to form the superior part of the bony nasal septum.

Paranasal sinuses

Air-filled, mucosa-lined cavities situated in the frontal, ethmoid, sphenoid, and maxillary bones that connect to the nasal cavity.

Hyoid bone

A U-shaped bone located in the anterior neck that does not articulate directly with any other bone, consisting of a body, greater horns, and lesser horns.

Vomer

A slender, plow-shaped midline facial bone that forms the posteroinferior component of the bony nasal septum.

Inferior nasal concha

An independent, scroll-like facial bone projecting horizontally from the lateral wall of the nasal cavity.

Maxilla

A paired facial bone forming the upper jaw, midface, floor of the orbit, and anterior hard palate.

Infraorbital foramen

An opening in the maxilla situated just inferior to the orbital margin that permits passage of the infraorbital nerve and vessels.

Alveolar process

The inferior border of the maxilla or superior border of the mandible containing the sockets (alveoli) for the teeth.

Mandible

The largest, strongest, and only movable bone of the adult skull, comprising a horizontal body and two vertical rami.

Condylar process

The posterior superior projection of the mandibular ramus that articulates with the mandibular fossa of the temporal bone to form the temporomandibular joint.

Coronoid process of mandible

The anterior, pointed projection atop the mandibular ramus serving as the insertion point for the temporalis muscle.

Mental foramen

An aperture on the anterolateral body of the mandible transmitting blood vessels and nerves to the chin and lower lip.

Mandibular foramen

An opening on the medial surface of each mandibular ramus through which the inferior alveolar nerve passes into the mandibular canal.

Lateral wall of nasal cavity

The complex anatomical boundary formed by the ethmoid bone, palatine bone, maxilla, and inferior nasal concha, containing the superior, middle, and inferior meatuses.

Vertebral column curvatures

The four natural curves of the adult spine: concave cervical ($7$ vertebrae, $C_1 - C_7$), convex thoracic ($12$ vertebrae, $T_1 - T_{12}$), concave lumbar ($5$ vertebrae, $L_1 - L_5$), and convex sacral curvature ($5$ fused sacral vertebrae).

Typical vertebra

A standard vertebral unit consisting anteriorly of a weight-bearing body (centrum) and posteriorly of a vertebral arch enclosing the vertebral foramen.

Vertebral foramen

The large opening formed between the vertebral body and the vertebral arch that accommodates and protects the spinal cord.

Herniated intervertebral disc

A spinal condition in which the soft inner nucleus pulposus protrudes through a tear in the outer anulus fibrosus, frequently impinging on nearby spinal nerves.

Anulus fibrosus

The tough, outer ring of concentric fibrocartilage laminations enclosing the nucleus pulposus of an intervertebral disc.

Nucleus pulposus

The gel-like, high-water-content central core of an intervertebral disc that functions as a shock absorber.

Atlas ($C_1$)

The first cervical vertebra, which lacks a body and spinous process and articulates directly with the occipital condyles to support the skull.

Axis ($C_2$)

The second cervical vertebra, distinguished by the tooth-like dens (odontoid process) projecting superiorly into the atlas to permit head rotation.

Dens of axis

The prominent vertical pivot projection of the second cervical vertebra held securely against the anterior arch of the atlas by the transverse ligament.

Vertebra prominens ($C_7$)

The seventh cervical vertebra, characterized by a long, prominent, non-bifid spinous process that can be readily palpated at the base of the neck.

Cervical vertebrae

The seven superior vertebrae ($C_1 - C_7$) distinguished by transverse foramina in their transverse processes and often bifid spinous processes.

Thoracic vertebrae

The twelve vertebrae ($T_1 - T_{12}$) distinguished by presence of costal facets on their bodies and transverse processes that articulate with the ribs.

Rib articulation with thoracic vertebra

The dual synovial attachment where the rib head articulates with the costal facets on the vertebral body and the rib tubercle articulates with the transverse costal facet.

Lumbar vertebrae

The five robust vertebrae ($L_1 - L_5$) characterized by massive, kidney-shaped bodies and thick, blunt spinous processes suited for weight bearing.

Sacrum and coccyx

The inferior terminal components of the vertebral column consisting of five fused sacral vertebrae articulated with four fused coccygeal vertebrae.

Median sacral crest

A bumpy vertical ridge running along the posterior midline of the sacrum formed by the fused spinous processes of the sacral vertebrae.

Sacral canal

The continuation of the vertebral canal through the interior of the sacrum that ends inferiorly at the sacral hiatus.

Sternum

The anterior midline flat bone of the thorax consisting of three fused portions: the manubrium, body, and xiphoid process.

Manubrium

The broad superior segment of the sternum articulating with the clavicles and the first pair of costal cartilages.

Xiphoid process

The small, cartilaginous or ossified inferior terminal point of the sternum that serves as an attachment site for abdominal muscles.

Thoracic cage

The protective framework formed by the thoracic vertebrae posteriorly, the ribs laterally, and the sternum and costal cartilages anteriorly.

True ribs

Rib pairs $1$ through $7$ that connect directly to the sternum through their own individual costal cartilages.

False ribs

Rib pairs $8$ through $12$ that do not attach directly to the sternum, including those that attach to the cartilage of the rib above and floating ribs.

Floating ribs

Rib pairs $11$ and $12$ that lack any anterior connection to the sternum or costal cartilage.