Skeletal System and Joint Classifications

Comprehensive vocabulary flashcards covering skeletal anatomy, cranial and facial bones, vertebrae, thoracic cage, limbs, and joint classifications.

Joint (Articulation)

The location or junction where two or more bones come together; its two primary roles are to allow movement and hold the skeleton together.

"Arthro-"

The Latin root word referring to a joint.

Fibrous Joint

An anatomical joint classification where bones are separated by fibrous connective tissue high in collagen; it is firm and immovable.

Cartilaginous Joint

An anatomical joint classification where bones are separated by cartilage, providing limited flexibility.

Synovial Joint

An anatomical joint classification where the space between bones is filled with synovial fluid, making it freely moving.

Synarthrosis

A physiological joint classification referring to an immovable joint (such as cranial sutures).

Amphiarthrosis

A physiological joint classification referring to a slightly movable joint (such as intervertebral disks or the pubic symphysis).

Diarthrosis

A physiological joint classification referring to a freely moving joint.

Hinge Joint

The most common type of synovial joint; allows 1 type of movement by only bending (flexing) and straightening (extending) (e.g., knee, phalanges, temporomandibular joint).

Pivot Joint

A synovial joint that allows only $180^{\circ}$ rotation as one bone rotates around another (e.g., atlas-axis, radius-humerus).

Saddle Joint

A synovial joint that allows 2 types of movement: bending/straightening and moving side-to-side (e.g., metacarpal of thumb to trapezium).

Plane Joint

A synovial joint where bones slide against each other like blocks gliding; common in short bones such as carpals and tarsals.

Ball & Socket Joint

The most movable type of synovial joint, allowing many different types of movements (e.g., femur-pelvis, humerus-scapula).

Condyloid Joint

A modified ball and socket joint that allows 2 types of movement: flexion/extension and slightly shifting side-to-side (e.g., knuckles, wrist joint).

Flexion

Movement that decreases the angle between 2 bones.

Extension

Movement that increases the angle between 2 bones.

Hyperextension

Extending a joint beyond a straight line.

Dorsiflexion

Movement where the toes or foot point upwards.

Plantarflexion

Movement where the toes or foot point downwards.

Abduction

Pulling limbs away from the midline of the body.

Adduction

Pushing limbs towards the midline of the body.

Circumduction

Circular motion characteristic of a ball and socket joint.

Supination

Rotation of the forearm that turns the palm up.

Pronation

Rotation of the forearm that turns the palm down.

Eversion

Elevating the lateral soles of the feet (big toe side down).

Inversion

Elevating the medial soles of the feet (pinkie toe side down).

Protraction

Movement that involves sticking out a body part.

Retraction

Movement that involves pulling a body part back in.

Elevation

Movement that raises a body part up.

Depression

Movement that lowers a body part.

Long Bones

Bones characterized by a long diaphysis and 2 epiphyses whose job is to support weight and enable movement (e.g., femur, metacarpals).

Short Bones

Bones whose job is to provide stability to weight-bearing joints (e.g., carpals, tarsals).

Flat Bones

Bones that protect internal organs and provide broad surfaces for muscle attachment (e.g., frontal bone, ribs, sternum, pelvis).

Irregular Bones

Bones with complex shapes adapted for specialized functions (e.g., vertebrae, sacrum, zygomatic bone, hyoid bone).

Sesamoid Bones

Short bones buried within tendons whose job is to protect tendons running over joints from stress and wear (e.g., patella).

Thoracic Cage

The chest skeleton consisting of the sternum, ribs, and thoracic vertebrae; protects the heart, lungs, kidneys, and blood vessels.

Sternum

The breastbone, formed by three fused sections: the manubrium (top), body (middle), and xiphoid process (pointy bottom).

True Ribs

Rib pairs 1–7; they attach directly to the sternum anteriorly via individual pieces of costal cartilage.

False Ribs

Rib pairs 8–12; they either attach to the sternum via shared costal cartilage (pairs 8–10) or do not attach at all.

Floating Ribs

Rib pairs 11–12; false ribs that have no anterior attachment to the sternum.

Clavicle

The collarbone; connects the sternum to the shoulder girdle and is the most commonly broken bone in the human body.

Vertebral Column

The backbone or spine, composed of 26 irregular bones in an adult, featuring 4 natural curves to distribute pressure.

Atlas (C1)

The first cervical vertebra; supports the head, articulates with the occipital condyles, and allows you to nod "yes."

Axis (C2)

The second cervical vertebra; features a knoblike dens upon which the atlas pivots, allowing you to shake your head "no."

Cervical Vertebrae

The 7 smallest vertebrae located in the neck.

Thoracic Vertebrae

The 12 medium-sized vertebrae that attach posteriorly to the ribs.

Lumbar Vertebrae

The 5 largest vertebrae found in the lower back.

Sacrum

Bone attached to the hip bones; originally consists of 5 separate bones that fuse into one by age 30.

Coccyx

The tailbone; originally consists of 4 separate bones that fuse into one by age 30.

Intervertebral Disks

Cushions made of fibrocartilage that separate individual vertebrae.

Kyphosis

An abnormal spine curvature marked by an extreme thoracic curve ("hunchback").

Lordosis

An abnormal spine curvature marked by an extreme lumbar curve.

Scoliosis

An abnormal spine condition characterized by a sideways curvature of the entire spine.

Cranial Bones

The 8 bones that surround and protect the brain and provide attachment points for head and neck muscles.

Frontal Bone

A single cranial bone forming the forehead and anterior wall of the cranium; contains the supraorbital margin of the orbit.

Parietal Bones

A pair of cranial bones forming the superior and lateral walls of the cranium.

Temporal Bones

A pair of cranial bones on the inferior and lateral cranium; features include the zygomatic process, mastoid process, and temporomandibular joint.

Occipital Bone

A single cranial bone forming the posterior and inferior wall of the cranium; contains the foramen magnum and occipital condyles.

Sphenoid Bone

A single, butterfly-shaped cranial bone deep in the cranium; acts as the keystone bone by joining with almost every other skull bone.

Ethmoid Bone

A single cranial bone located deep in the cranium behind the orbits; forms part of the nasal cavity, nasal septum, and orbits.

Facial Bones

The 14 bones that form facial structure, provide openings for air and food, and serve as attachment points for facial expression muscles.

Maxillae

Paired bones of the upper jaw that touch all other facial bones except the mandible; form the anterior portion of the hard palate.

Mandible

The lower jawbone; the largest, strongest, and only freely movable bone of the adult skull.

Zygomatic Bones

Paired cheekbones forming the lateral walls of the orbits and part of the zygomatic arches.

Nasal Bones

A pair of facial bones that form the bridge of the nose.

Lacrimal Bones

The smallest facial bones, located in the anterior interior corner of each orbit; contain the lacrimal fossa for tear drainage.

Palatine Bones

Paired facial bones that form the posterior one-third of the hard palate.

Vomer Bone

A single triangle-shaped facial bone that forms the posterior and inferior portion of the nasal septum with the ethmoid.

Inferior Nasal Conchae

A pair of curved facial bones projecting from the lateral walls of the nasal cavity.

Alveoli

The sockets located in the maxillae and mandible where the teeth are anchored.

Humerus

The longest and strongest bone of the upper extremity; articulates with the scapula, radius, and ulna.

Radius

The lateral forearm bone located on the thumb side; rotates to turn the palm up or down and forms the main part of the wrist joint.

Ulna

The medial forearm bone located on the pinkie side; forms the main part of the elbow joint and features the olecranon process (elbow bump).

Carpals

A set of 8 short bones making up the wrist (trapezium, trapezoid, capitate, hamate, scaphoid, lunate, triquetrum, pisiform).

Metacarpals

The 5 bones of the palm of the hand whose heads form the visible knuckles.

Femur

The thigh bone; the longest and strongest bone of the entire body, fitting into the acetabulum of the pelvis.

Acetabulum

The deep cup-like socket in the coxal (hip) bone where the head of the femur articulates.

Patella

The kneecap; a sesamoid bone embedded in the quadriceps femoris tendon that protects the knee joint from wear and tear.

Tibia

The medial shin bone; the primary weight-bearing bone of the lower leg and the second largest bone in the human body.

Fibula

The lateral, non-weight bearing bone of the lower leg that aids in balance and stability.

Tarsals

A set of 7 short bones composing the ankle (calcaneus, talus, navicular, cuboid, lateral cuneiform, medial cuneiform, intermediate cuneiform).

Metatarsals

A set of 5 bones that form the sole/instep of the foot and articulate with the proximal phalanges.

Phalanges

The skeletal segments of the fingers and toes (14 per hand and 14 per foot, arranged into proximal, intermediate, and distal, with thumbs and big toes having only 2).