Bone Structures

Long Bone

Cylinder-shape, longer than wide

Short Bone

cube shaped, equal in length, shape, and thickness

Flat bone

thin and curved

Sesamoid Bone

small and round, embedded in tendons

Irregular Bone

complex shape.

Function of Long Bone

Leverage

Function of Short Bone

Provide stability, support, allows for limited motion

Function of Flat bone

Points of muscle attachments, protect internal organs

Function of Sesamoid Bone

Protect tendons from compressive forces

Function of irregular bone

protect internal organs

Examples of Long Bone

Femur, tibia, fibula, metatarsals, humerus, radius, ulna, metacarpals, phalanges

Examples of short bone

carpals, tarsals

Examples of flat bone

sternum, ribs, scapulae, cranial bones

Examples of sesamoid bones

patellae (kneecaps)

Example of irregular bones

vertebrae, facial bones

Endochondral ossification

bone replaces hyaline cartilage

Bone remodeling

the process by which old or damaged bone is resorbed and replaced

Bone modeling

the process by which the diaphysis and medullary cavity increase in diameter

Osteogenic cells

mitotic bone cells that differentiate and develop into osteoblasts

Osteoclasts

cells that are responsible for bone resorption

Osteoblasts

Responsible for forming new bone (does not undergo mitosis)

osteocyte

cells in mature bone that maintain mineral concentration of matrix (sit within lacunae and does not undergo mitosis)

Calcitonin

Inhibits osteoclast activity and stimulates calcium uptake by bones

Parathyroid hormone (PTH)

Stimulates osteoclast proliferation and resorption of bone by osteoclasts; promotes reabsorption of calcium by kidney tubules; indirectly increases calcium absorption by small intestine

Parathyroid and Thyroid Glands

detect abnormal calcium levels and release hormone effectors regulate Calcium blood levels

trabeculae

a lattice like network of matrix

Epiphyseal Plate

region of growth

Reserve Zone (Epiphyseal Plate)

region with chondrocytes that don’t participate in bone growth; attaches epiphyseal plate to epiphysis

Proliferative Zone (Epiphyseal Plate)

mitotic chondrocytes that replace dead ones near the diaphysis

Zone of maturation and hypertrophy (Epiphyseal Plate)

zone with older and larger chondrocytes

Zone of calcified matrix (Epiphyseal Plate)

chondrocytes are dead due to matrix calcification; osteoblasts and capillaries move in.