Axial Skeleton - Anatomy and Terminology

Comprehensive flashcards covering bone markings, cranial and facial bones, sutures, musculature of mastication and the neck, vertebral structures and curves, and thoracic cage anatomy from the Axial Skeleton lecture.

Condyle

A large, smooth, rounded oval articulating structure on a bone.

Facet

A small, flat, shallow articulating surface on a bone.

Trochlea

A smooth, grooved, pulley-like articulating process.

Alveolus

A deep pit or socket in the maxillae or mandible for tooth attachment.

Fossa

A flattened or shallow depression on a bone.

Sulcus

A narrow groove along the surface of a bone.

Crest

A narrow, prominent, ridgelike projection for tendon and ligament attachment.

Ramus

An angular extension of a bone relative to the rest of the structure.

Trochanter

A massive, rough projection found exclusively on the femur.

Meatus

A canal-like passageway through a bone.

Cranial Bones

The $8$ bones that enclose and protect the brain, consisting of the unpaired ethmoid, frontal, occipital, and sphenoid bones, and the paired parietal and temporal bones.

Facial Bones

The $14$ bones that form the face without making direct contact with the brain, consisting of the unpaired vomer and mandible, and the paired maxillae, nasal, lacrimal, zygomatic, palatine, and inferior nasal conchae.

Calvaria

The skullcap that forms the roof of the cranium.

Coronal Suture

The immovable joint located at the junction between the frontal bone and the parietal bones.

Lambdoid Suture

The immovable joint located at the junction between the occipital bone and the parietal bones.

Sagittal Suture

The immovable joint along the midline junction between the left and right parietal bones.

Squamous Suture

The immovable joint found at the junction between the temporal bone and the parietal bone.

Pterion

The H-shaped sutural junction on the lateral aspect of the skull where the frontal, parietal, temporal, and sphenoid (greater wing) bones meet.

Fontanelles

Membranous regions of an infant skull (anterior, posterior, anterolateral, and posterolateral) that allow flexibility during birth and later develop into cranial sutures.

Temporomandibular Joint (TMJ)

The only mobile joint of the skull; a diarthrotic synovial hinge joint formed between the mandibular fossa and articular tubercle of the temporal bone and the head of the condylar process of the mandible.

Masseter

A mastication muscle that originates on the zygomatic arch, inserts onto the ramus and angle of the mandible, and acts to elevate and protract the mandible.

Temporalis

A mastication muscle originating on the superior and inferior temporal lines and inserting on the coronoid process of the mandible, responsible for elevating and retracting the mandible.

Medial Pterygoid

A muscle of mastication originating from the lateral pterygoid plate of the sphenoid (as well as maxilla and palatine) and inserting on the medial surface of the mandibular ramus; acts to elevate, protract, and move the mandible side-to-side.

Lateral Pterygoid

A muscle of mastication originating from the lateral pterygoid plate and greater wing of the sphenoid and inserting on the pterygoid fovea of the condylar neck; acts to protract, depress, and move the mandible side-to-side.

Hyoid Bone

A U-shaped bone in the anterior neck between the mandible and larynx that does not articulate with any other bone; consists of a body, greater cornu, and lesser cornu.

Suprahyoid Muscles

A group of muscles associated with the floor of the mouth (including mylohyoid, geniohyoid, stylohyoid, and digastric) that elevate the hyoid bone during swallowing and speaking.

Infrahyoid Muscles

Strap muscles of the anterior neck (omohyoid, sternohyoid, thyrohyoid, and sternothyroid) that depress the hyoid bone and larynx.

Sternocleidomastoid

An anterolateral neck muscle originating on the manubrium and sternal end of the clavicle and inserting on the mastoid process; unilaterally produces lateral flexion and contralateral rotation of the head, and bilaterally flexes the neck.

Scalene Muscles

Cervical muscles (anterior, middle, and posterior) that flex the neck when the 1st rib is fixed, and elevate the 1st and 2nd ribs during forced inhalation when the neck is fixed.

Quadratus Lumborum

A posterior abdominal wall muscle originating on the iliac crest and inserting on the 12th rib and lumbar transverse processes; bilaterally extends and unilaterally laterally flexes the vertebral column.

Primary Spinal Curvatures

Accommodation curves present during fetal development, consisting of the thoracic and sacral curvatures.

Secondary Spinal Curvatures

Compensation curves that appear at $3\text{–}4$ months of age as an infant begins holding up the head and walking, consisting of the cervical and lumbar curvatures.

Hyperkyphosis

An exaggerated posterior curvature of the thoracic region of the vertebral column, commonly referred to as hunchback.

Hyperlordosis

An exaggerated anterior curvature of the lumbar region of the vertebral column, commonly referred to as swayback.

Scoliosis

An abnormal lateral, side-to-side curvature of the vertebral column.

Zygapophysial Joints

Synovial plane facet joints formed between the superior and inferior articular processes of adjacent vertebrae.

Atlas (C1)

The first cervical vertebra, which lacks a vertebral body and spinous process and features superior articular facets that articulate with the occipital condyles.

Axis (C2)

The second cervical vertebra, distinguished by a superior tooth-like projection called the dens (odontoid process) that articulates with the atlas.

Vertebra Prominens (C7)

The seventh cervical vertebra, characterized by a long, prominent, non-bifid spinous process that serves as an anatomical landmark.

Anulus Fibrosus

The outer ring of fibrocartilage that forms the external perimeter of an intervertebral disc.

Nucleus Pulposus

The inner gelatinous core composed of water and fibers within an intervertebral disc.

Herniated Disc

A condition in which the inner nucleus pulposus protrudes through a tear or weakness in the anulus fibrosus, most commonly occurring in the lumbar region.

Nuchal Ligament

A strong midline fibrous ligament extending from the external occipital protuberance to the $C_7$ vertebra, continuing inferiorly as the supraspinous ligament.

True Ribs

Ribs $1\text{–}7$ (vertebrosternal ribs) that articulate directly with the sternum via individual costal cartilages.

False Ribs

Ribs $8\text{–}12$, whose costal cartilages do not connect directly to the sternum; includes vertebrochondral ribs ($8\text{–}10$) and vertebral/floating ribs ($11\text{–}12$).

Floating Ribs

Ribs $11$ and $12$ (vertebral ribs), which have no anterior attachment to the sternum or costal cartilage.

Manubrium

The trapezoidal, superior part of the sternum articulating with the clavicles and first pair of costal cartilages, containing the suprasternal (jugular) notch.