Skeletal System 7: Bone Structure, Growth, and Repair

Vocabulary terms covering bone histology, growth mechanisms, hormonal regulation of calcium, types of bone fractures, and the stages of bone repair based on lecture notes.

Epiphyseal line

The remnant of the epiphyseal plate that forms in the late teens to adult humerus once growth is complete.

Zone of resting cartilage

Zone 1 of growth in bone length, characterized as the layer closest to the epiphysis.

Zone of proliferating cartilage

Zone 2 of growth in bone length.

Zone of hypertrophic cartilage

Zone 3 of growth in bone length.

Zone of calcified cartilage

Zone 4 of growth in bone length.

Zone of ossification

Zone 5 of growth in bone length, located closest to the diaphysis.

Appositional growth

The process of growth in bone width where bone is deposited by osteoblasts and resorbed by osteoclasts.

Bone remodeling

A continual process of bone deposition and resorption that occurs at periosteal and endosteal surfaces.

Growth Hormone

Hormone that stimulates cartilage growth at the epiphyseal plate in conjunction with somatomedin.

Thyroid Hormone

Hormone that influences the basal metabolic rate ($\text{BMR}$) of osteoblasts.

Glucocorticoids

Hormones that at high levels promote bone loss and impair growth at the epiphyseal plate.

Serotonin

A hormone that in high levels blocks osteoprogenitor cells from becoming osteoblasts.

Calcitriol

Active form of Vitamin D converted in the kidney that increases absorption of calcium from the small intestine.

Parathyroid hormone (PTH)

Hormone secreted by the parathyroid glands in response to low blood calcium levels.

Calcitonin

Hormone released from the thyroid gland in response to high blood calcium levels that inhibits osteoclast activity and stimulates calcium loss in urine.

Osteopenia

Insufficient ossification and decreased calcification associated with aging where osteoblast activity decreases while osteoclast activity remains the same.

Osteoporosis

A condition characterized by porous bones and reduced bone mass sufficient to compromise normal function.

Avulsion fracture

A complete severing of a body part, typically a toe or finger.

Colles fracture

A fracture of the distal end of the lateral forearm bone (radius) that produces a "dinner fork" deformity.

Comminuted fracture

A fracture where the bone is splintered into several small pieces between the main parts.

Compound (open) fracture

A fracture where the broken ends of the bone protrude through the skin.

Greenstick fracture

A partial fracture where one side of the bone breaks and the other side is bent.

Pott fracture

A fracture occurring at the distal ends of the tibia and fibula.

Stress fracture

Thin fractures due to repeated, stressful impact such as running, which may require a bone scan to identify.

Hematoma

A localized mass of blood released from blood vessels but confined within an organ or space.

Callus

A mass of tissue that forms at a fracture site and connects the broken ends of the bone.

Internal callus

Tissue that forms between the ends of broken bone and in the medullary cavity during bone repair.

External callus

A collar around the ends of bone fragments that stabilizes the two pieces during bone repair.