2.3 Bone formation & growth

Appositional growth

Process by which bones increase in diameter or thickness through the deposition of new bone tissue beneath the periosteum

Atrophy

Loss of mass and function

Bone remodeling

Ongoing lifelong process where mature bone tissue is removed by osteoclasts and new bone tissue is formed by osteoblasts

Bony callus

Rigid structure composed of spongy bone tissue that replaces the fibrocartilage callus during the middle stage of fracture healing

Calcitonin

Hormone secreted by the thyroid gland that lowers blood calcium levels by inhibiting osteoclasts and stimulating osteoblasts to deposit calcium into bone matrix

Closed (simple) fracture

Bone break where fractured bone fragments do not tear or penetrate through the surrounding skin

Epiphyseal plate

Layer of hyaline cartilage in the metaphysis of a long bone where lengthwise growth occurs; commonly called the growth plate

External callus

Collar of hyaline cartilage and bone that forms around the outside of a fracture

Fibrocartilage callus

Temporary splint composed of collagen fibers and cartilage that forms between the broken ends of a bone during the early stages of fracture repair

Fracture

Partial or complete break in a bone resulting from mechanical stress or trauma

Fracture hematoma

Blood clot that forms at the site of a broken bone

Hematoma

Localized mass of clotted blood that forms at the site of a bone fracture due to ruptured blood vessels

Hypercalcemia

Condition characterized by abnormally high levels of calcium

Hypocalcemia

Condition characterized by abnormally low levels of calcium

Internal callus

Fibrocartilaginous matrix in the endosteal region between the two ends of a broken bone

Open (compound) fracture

Severe bone break where at least one end of the fractured bone tears through the surrounding skin, increasing infection risk

Ossification (osteogenesis)

Bone formation

Ossification center

Cluster of osteoblasts found in the early stages of intramembranous ossification

Osteoblast

Cell responsible for forming new bone (bone matrix)

Osteoclasts

Large, multinucleate cells that resorb (break down) bone tissue to release minerals into the blood and assist in bone remodeling

Osteoid

Uncalcified bone matrix secreted by osteoblasts

Osteoporosis

Disease characterized by a decrease in bone mass; occurs when the rate of bone resorption exceeds the rate of bone formation

Parathyroid glands

Four small endocrine glands located on the posterior surface of the thyroid that monitor blood parameters and release PTH when blood calcium levels are low

Parathyroid hormone (PTH)

Hormone secreted by the parathyroid glands that increases blood calcium levels by stimulating osteoclasts to break down bone matrix and release calcium into the blood

Remodeling

Process by which osteoclasts resorb old or damaged bone while osteoblasts form new bone to replace it

Thyroid gland

Endocrine gland located in the neck that monitors blood parameters and releases calcitonin when blood calcium levels are too high