Skeletal System: Bone Structure and Function

Vocabulary practice cards covering bone anatomy, cell types, matrix composition, and growth regions based on Chapter 07A Skeletal System.

Compact bone

Also called dense or cortical bone, it makes up $80\%$ of bone mass and is located on the external surface of bones.

Spongy bone

Also called cancellous or trabecular bone, it makes up $20\%$ of bone mass, appears porous, and is located internal to compact bone.

Hyaline cartilage

A semirigid connective tissue that attaches ribs to the sternum, covers ends of some bones, and serves as a model for bone formation.

Fibrocartilage

A weight-bearing cartilage that withstands compression; located in intervertebral discs, pubic symphysis, and menisci of the knee.

Ligaments

Structures composed of dense regular connective tissue that connect bone to bone.

Tendons

Structures composed of dense regular connective tissue that connect muscle to bone.

Hematopoiesis

The process of blood cell production that occurs in red bone marrow.

Long bones

Bones that are greater in length than width, such as the femur and humerus.

Short bones

Bones where the length is nearly equal to the width, such as carpals and tarsals.

Flat bones

Bones with flat, thin surfaces that may be slightly curved, such as cranial bones.

Irregular bones

Bones with elaborate or complex shapes, such as vertebrae.

Diaphysis

The elongated, usually cylindrical shaft of a long bone that provides leverage and weight support.

Medullary (marrow) cavity

The hollow cylindrical space within the diaphysis containing red bone marrow in children and yellow marrow in adults.

Epiphysis

The knobby region at each end of a long bone; includes the proximal epiphysis (closest to trunk) and distal epiphysis (farthest from trunk).

Articular cartilage

A thin layer of hyaline cartilage covering joint surfaces to reduce friction and absorb shock.

Metaphysis

The region in a long bone where the bone widens and transfers weight between the diaphysis and epiphysis.

Epiphyseal plate

A thin layer of hyaline cartilage within the metaphysis of a growing bone that provides for lengthwise bone growth.

Epiphyseal line

The remnant of the epiphyseal plate found in adult bones.

Periosteum

A tough sheath covering the outer surface of bone except where articular cartilage is present; composed of an outer fibrous layer and an inner cellular layer.

Endosteum

A thin layer of connective tissue containing osteoprogenitor cells and osteoblasts that covers all internal surfaces of bone within the medullary cavity.

Diploë

The specific name for spongy bone located within the flat bone of the skull.

Nutrient foramen

A small opening or hole in the bone where an artery enters and a vein exits to provide blood supply.

Red bone marrow (myeloid tissue)

Hematopoietic tissue containing reticular CT and developing blood cells; found in spongy bone and adult axial skeletons.

Yellow bone marrow

A fatty substance resulting from the degeneration of red bone marrow as children mature; can convert back to red marrow during severe anemia.

Osteoprogenitor cells

Stem cells derived from mesenchyme that undergo division to produce osteoblasts; located in the periosteum and endosteum.

Osteoblasts

Cells that synthesize and secrete osteoid; they eventually become entrapped in the matrix and differentiate into osteocytes.

Osteocytes

Mature bone cells that maintain the bone matrix and detect mechanical stress to trigger new bone formation.

Osteoclasts

Large, multinuclear, phagocytic cells derived from fused bone marrow cells that are involved in bone resorption.

Osteoid

The initial semisolid organic form of bone matrix produced by osteoblasts, containing collagen protein and ground substance.

Hydroxyapatite

Natural salt crystals formed by calcium phosphate and calcium hydroxide that deposit around collagen fibers to harden the bone matrix.

Bone resorption

The process where bone matrix is destroyed by osteoclasts releasing proteolytic enzymes and hydrochloric acid; happens when blood calcium levels are low.

Osteitis Deformans

A condition characterized by excessive bone resorption followed by excessive deposition of poorly formed bone, most commonly affecting the pelvis, skull, and vertebrae.