skeletal system - dc anatomy & physiology

Bones

Organs that are complex living structures made up of cells, protein fibers, and minerals.

Compact bone

Dense bone that looks smooth and homogenous, found in the shaft of long bones and surrounds spongy bone at the ends.

Spongy bone

Bone composed of small pieces with open spaces, found in the ends of long bones and fills short and flat bones.

Osteocytes

Mature bone cells found in tiny cavities within the bone matrix called lacunae.

Diaphysis

The shaft of a long bone, composed of compact bone.

Epiphysis

The end of a long bone, composed mostly of spongy bone.

Articular cartilages

Cartilages that cover the epiphyses of long bones for smooth movement at joints.

Red marrow

Found in the cavities of spongy bone and epiphyses of long bones, site of hematopoiesis (blood cell formation).

Axial skeleton

Bones that form the longitudinal axis of the body, including the vertebral column, bony thorax, and skull.

Vertebral column

Composed of vertebrae, including 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, sacrum, and coccyx.

Bony thorax

Consists of ribs and sternum, protecting the organs of the thoracic cavity.

Skull

Formed by the cranium and facial bones, joined by immovable joints except for the mandible (jawbone).

Hyoid bone

A bone that does not directly articulate with another bone, providing attachment for muscles involved in floor of mouth, tongue, larynx, and apiglottis movement.

Appendicular skeleton

Includes the limbs and girdles that attach the limbs to the axial skeleton.

Pectoral girdle

Consists of clavicle (collar bone) and scapula (shoulder blade), connecting the upper limbs to the axial skeleton.

Pelvic girdle

Composed of coxal bones (ilium, ischium, and pubis), connecting the lower limbs to the axial skeleton.

Humerus

Upper arm bone.

Ulna

Lower arm bone on the pinkie side of the wrist.

Radius

Lower arm bone on the thumb side of the wrist.

Femur

Thigh bone, the largest bone in the body.

Patella

Knee cap.

Tibia

Large bone in the lower leg, also known as the shin bone.

Fibula

Smaller bone in the lower leg, forms the lateral ankle.

Long bones

Bones that are longer than they are wide, such as the femur and humerus.

Short bones

Bones that are roughly cube-shaped, such as the carpals and tarsals.

Flat bones

Bones that are thin, flat, and usually curved, such as the sternum and scapula.

Irregular bones

Bones that do not fit into other categories due to their complex shapes, such as the vertebrae and facial bones.

Sesamoid bones

Small, round bones that develop within tendons, such as the patella (knee cap).

Joints

Also known as articulations, where two bones meet and allow mobility.

Fibrous joints

Joints with no movement, such as the sutures in the skull.

Cartilaginous joints

Joints with slight movement, such as the pubic symphysis and intervertebral discs.

Synovial joints

Joints with the most movement, separated by a cavity filled with synovial fluid, such as the ball and socket joints in the shoulder and hip.

Support

The skeletal system provides an internal framework that supports and anchors soft organs.

Protection

Some bones protect soft body organs.

Movement

Skeletal muscles attach to bones and use them as levers to move body parts.

Storage

Bones store minerals (calcium and phosphorus) and fat (in yellow marrow), and red marrow is the site of hematopoiesis (blood cell formation).

Ossification

The formation of bone from cartilage, occurring throughout development and growth.

Bone remodeling

The breaking down and reforming of bone that occurs throughout life to maintain proportion, strength, and healthy calcium levels.

Osteoporosis

Weakening of the bone that occurs with aging, leading to increased risk of fractures, especially in women over age 50.

Arthritis

Inflammation of the joints.

Rickets

A condition caused by a lack of vitamin D, calcium, or phosphorus, resulting in soft bones, typically seen in children.

Herniated disc

Protrusion of discs of cartilage between the vertebrae, causing pain, numbness, or weakness in the limbs.

Scoliosis

Abnormal curvature of the spine, which can be congenital or result from disease or trauma.