Unit #2 Skeletal System Study Guide

Vocabulary flashcards covering skeletal divisions, major bones, bone matrix, cells, joints, growth, fracture healing, and skeletal evolution from the Unit #2 Skeletal System study guide.

Axial skeleton

The division of the skeletal system comprising bones along the central axis of the body—such as the vertebrae, ribs, and sternum—which primarily functions to protect internal organs and support the body.

Appendicular skeleton

The division of the skeletal system consisting of the bones of the limbs and girdles—including the humerus, radius, ulna, femur, tibia, fibula, patella, ilia, clavicle, and phalanges—which primarily facilitates locomotion and movement.

Vertebrae

The series of bones forming the spinal column in the axial skeleton that support trunk posture and protect the spinal cord.

Sternum

An axial skeleton bone situated along the midline of the anterior chest that anchors the anterior ends of the ribs.

Ribs

The curved bones of the axial skeleton forming the thoracic cage to enclose and protect vital thoracic organs.

Humerus

The long bone of the upper arm located in the appendicular skeleton.

Radius

The lateral bone of the forearm within the appendicular skeleton that articulates with the wrist on the thumb side.

Ulna

The medial bone of the forearm within the appendicular skeleton that parallels the radius.

Femur

The thigh bone within the appendicular skeleton, which is the longest and strongest bone of the human body.

Tibia

The larger, weight-bearing inner bone of the lower leg within the appendicular skeleton.

Fibula

The slender outer bone of the lower leg within the appendicular skeleton that runs parallel to the tibia.

Patella

A sesamoid bone located at the anterior knee joint within the quadriceps tendon that protects the knee and improves muscular leverage.

Ilia (pelvic bones)

The large, flaring upper bones of the pelvic girdle belonging to the appendicular skeleton.

Clavicle

The collarbone; an appendicular skeleton bone connecting the arm to the trunk and serving as a strut for the shoulder.

Phalanges

The bones that compose the fingers and toes within the appendicular skeleton.

Mesenchymal stem cells

Multipotent stem cells in bone that contribute to the skeletal system by differentiating into specialized cells such as osteoblasts and chondrocytes.

Bone matrix

The intercellular composite structure of bone tissue, primarily consisting of inorganic calcium salts embedded in organic collagen fibers.

Calcium salts

The mineral component of the bone matrix that provides bone with hardness, rigidity, and resistance to compression.

Collagen

The fibrous protein component of the bone matrix that contributes flexibility and tensile strength to bone tissue.

Joints

Articulations or junctions where two or more bones meet, categorized by their structure and degree of mobility.

Growth plates

Specialized cartilaginous bands in growing long bones that enable lengthening, reflect an individual's pattern of growth, and assist in determining the age of human remains.

Ligaments

Bands of tough, fibrous connective tissue that connect bones to other bones across joints to provide stability.

Knee joint

A specialized, complex hinge joint composed primarily of three bones (femur, tibia, and patella) and stabilized by four ligaments, menisci, and a sesamoid bone.

Menisci

Crescent-shaped fibrocartilaginous pads in the knee joint that absorb shock, disperse load, and enhance articular stability between the femur and tibia.

PCL and ACL

The posterior cruciate ligament and anterior cruciate ligament; specialized crossing ligaments located within the knee joint capsule that maintain anterior-posterior joint stability.

Sesamoid bone

A bone embedded directly within a tendon, specifically exemplified by the patella in the human knee joint.

Osteocytes

Mature bone cells embedded in the bone matrix that monitor mechanical strain and coordinate the bone remodeling process.

Osteoclasts

Large, multinucleated cells responsible for the resorption and breakdown of bone matrix during remodeling and fracture repair.

Osteoblasts

Bone-forming cells that synthesize and deposit new bone matrix during skeletal growth, remodeling, and fracture healing.

Bone remodeling cycle

The continuous physiological cycle of bone turnover driven by the coordinated activity of osteocytes, osteoclasts (resorption), and osteoblasts (deposition).

Fracture repair process

The four-stage healing sequence (hematoma formation, fibrocartilaginous callus formation, bony callus formation, and bone remodeling) that restores structural integrity to broken bone.

Nicholas St. Fleur's Argument

The thesis in 'The future looks bleak for bones' that human bone density has progressively declined from hunter-gatherers through agricultural societies to modern post-industrial societies due to decreasing physical activity.