Human Anatomy: Axial and Appendicular Skeleton

Vocabulary flashcards covering the axial and appendicular skeleton, including bone tissue types, major bones, bone landmarks, and clinical anatomy.

Axial Skeleton

The central axis of the human body consisting of $80$ bones, including the skull, hyoid bone, vertebral column, and thoracic cage, whose primary function is protecting the brain, spinal cord, heart, and lungs.

Appendicular Skeleton

The section of the skeleton consisting of $126$ bones (or $130$ including foot sesamoids) that comprises the upper and lower limbs along with the pectoral and pelvic girdles.

Bone Classifications

The five categories used to classify human bones based on shape and structure: long, short, flat, irregular, and sesamoid.

Compact Bone

The dense, load-bearing outer layer of bone tissue made up of densely packed hydroxyapatite organized into osteons.

Spongy Bone

The internal lattice-like bone tissue composed of trabeculae that manages mechanical stress from multiple directions.

Red Bone Marrow

The tissue located within bone cavities that serves as the site of red blood cell (RBC) production.

Yellow Bone Marrow

The tissue located within bone cavities that is filled primarily with adipose tissue.

Osteon

The basic structural unit of compact bone tissue, consisting of a central canal surrounded by concentric lamellae, lacunae containing osteocytes, and canaliculi.

Epiphyseal Plate

The hyaline cartilage region situated between the diaphysis and epiphysis where active longitudinal bone growth occurs before converting into the epiphyseal line.

Hyaline Cartilage

The most abundant cartilage type in the skeleton, providing flexible support and covering articulating joint surfaces.

Fibrocartilage

A stiff, tough cartilage type that absorbs mechanical force, found in intervertebral discs and the knee meniscus.

Elastic Cartilage

The least abundant and most flexible cartilage type, found in the external ear and epiglottis.

Frontal Bone

The cranial bone forming the forehead, superior orbital rims, and anterior cranial floor, containing supraorbital foramina or notches for nerves and vessels.

Parietal Bones

A pair of cranial bones that form the posterior roof and posterolateral walls of the skull.

Temporal Bones

A pair of cranial bones forming lateral skull walls; featuring the zygomatic arch, mastoid process, styloid process, and external acoustic meatus.

Sphenoid Bone

An irregular keystone cranial bone of the cranial floor containing the sella turcica, a saddle-like depression that holds the pituitary gland.

Ethmoid Bone

A cranial bone located at the medial orbit, nasal roof, and superior nasal septum, containing superior and middle conchae that stir inspired air.

Occipital Bone

The cranial bone forming the posterior cranial floor, featuring the foramen magnum for spinal cord transmission and occipital condyles that rock on C1.

Maxillae

A pair of facial bones forming the central face, holding the upper teeth, forming most of the hard palate, and featuring infra-orbital foramina.

Mandible

The lower jawbone; the only movable skull bone, which holds the lower teeth and features mental and mandibular foramina.

Zygomatic Bones

A pair of facial cheekbones whose temporal processes join the temporal bone to complete the zygomatic arch.

Lacrimal Bones

Tiny facial bones situated in the anteromedial orbit, containing a lacrimal fossa that drains tears from the eye into the nasal cavity.

Hyoid Bone

A U-shaped bone at C3 that floats in the neck without articulating with any other bone, suspended from temporal styloid processes by ligaments.

Paranasal Sinuses

Mucus-lined air cavities situated within the frontal, sphenoid, ethmoid, and maxillary bones that lighten the facial structure and shape voice resonance.

C1 (Atlas)

The first cervical vertebra, lacking a body, whose superior articular facets articulate with occipital condyles to allow nodding 'yes'.

C2 (Axis)

The second cervical vertebra, featuring a vertical projection called the dens (odontoid process) around which the atlas rotates to allow shaking 'no'.

C7 (Vertebra Prominens)

The seventh cervical vertebra, characterized by a prominent non-bifid spinous process forming a palpable bump at the base of the neck.

Thoracic Vertebrae

The $12$ vertebrae ($T1-T12$) characterized by heart-shaped bodies, costal facets for rib articulation, and downward spinous processes resembling a giraffe head in lateral view.

Lumbar Vertebrae

The $5$ vertebrae ($L1-L5$) carrying upper body weight, characterized by massive bodies, small triangular foramina, and hatchet-shaped spinous processes resembling a moose head in lateral view.

Sacrum

A bone formed by the fusion of $5$ sacral vertebrae ($S1-S5$) that articulates with L5, the coccyx, and the os coxae, featuring four pairs of sacral foramina.

Coccyx

The tailbone formed by $3-5$ (or $4-5$) fused vertebrae that curves anteriorly and anchors pelvic-floor muscles.

Scoliosis

An abnormal lateral curvature of the spinal column.

Kyphosis

An exaggerated thoracic curvature of the spine.

Lordosis

An exaggerated lumbar curvature of the spine.

Sternum

The anterior chest bone composed of three fused parts: manubrium, sternal body, and xiphoid process.

True Ribs

Rib pairs $1-7$, which attach directly to the sternum via their own individual costal cartilages.

False Ribs

Rib pairs $8-10$, whose costal cartilages attach indirectly to the sternum by fusing with the cartilage of rib $7$.

Floating Ribs

Rib pairs $11-12$, which have no anterior costal cartilage connection to the sternum.

Clavicle

An S-shaped pectoral girdle bone with a thick triangular sternal end and a flat acromial end; it is the only upper-limb bone articulating directly with the axial skeleton.

Scapula

A flat triangular bone over the posterior ribs that features a spine dividing supraspinous and infraspinous fossae, an acromion, a coracoid process, and a shallow glenoid cavity.

Humerus

The single bone of the arm, featuring a proximal head, anatomical and surgical necks, greater/lesser tubercles, deltoid tuberosity, capitulum, trochlea, olecranon fossa, and epicondyles.

Ulna

The medial bone of the forearm that drives elbow joint motion via its proximal olecranon process and C-shaped trochlear notch, ending distally in a head and styloid process.

Radius

The lateral bone of the forearm that rotates around the ulna to drive hand orientation, featuring a disc-shaped head, radial tuberosity, and distal radial styloid process.

Carpals

The $8$ wrist bones arranged in two rows: proximal (scaphoid, lunate, triquetrum, pisiform) and distal (trapezium, trapezoid, capitate, hamate).

Carrying Angle

The angle of approximately $10-15^\bullet$ of valgus formed at the extended elbow that allows the forearms to clear the hips when arms hang naturally.

Os Coxae

The hip bone formed by the embryonic fusion of three bones: the ilium, ischium, and pubis.

Acetabulum

The lateral deep cup-like socket on the os coxae formed by the ilium, ischium, and pubis that receives the head of the femur to form the hip joint.

Obturator Foramen

The large opening in the os coxae enclosed by the ischium and pubic rami.

Ilium

The superior, largest region of the os coxae featuring the iliac crest, iliac fossa, auricular surface, and four prominent spines (ASIS, AIIS, PSIS, PIIS).

Ischium

The posteroinferior part of the os coxae that includes the ischial body, ischial spine, lesser sciatic notch, and the ischial tuberosity that supports weight when sitting.

Pubis

The anteroinferior region of the os coxae consisting of a pubic body, superior and inferior pubic rami, and pubic crest that meets the opposite side at the pubic symphysis.

Femur

The largest and heaviest bone in the body, featuring a head with fovea capitis, neck angled medially at ~$125^\bullet$, greater/lesser trochanters, linea aspera, and distal condyles.

Patella

A triangular sesamoid bone embedded within the quadriceps tendon that protects the knee joint and improves quadriceps leverage.

Q Angle

The angle measured between lines drawn from ASIS to mid-patella and tibial tuberosity to mid-patella, measuring ~$8-10^\bullet$ in males and ~$10-15^\bullet$ in females.

Tibia

The medial, weight-bearing bone of the lower leg featuring proximal condyles, tibial tuberosity, anterior margin (shin), and medial malleolus.

Fibula

The lateral, non-weight-bearing bone of the lower leg that serves primarily as a muscle attachment site, featuring a proximal head and distal lateral malleolus.

Tarsals

The $7$ bones of the ankle and midfoot: talus, calcaneus, navicular, cuboid, and three cuneiforms (medial, intermediate, lateral).

Fontanels

Membranous 'soft spots' between cranial bones in a newborn skull that allow bone compression during passage through the birth canal and rapid brain expansion in infancy.