Osseous Tissue & Bone Structure

Vocabulary flashcards covering bone structure, functions of the skeletal system, bone cell types, matrix composition, ossification pathways, calcium regulation, fracture types, and healing stages.

Diaphysis

The shaft portion of a long bone.

Epiphysis

The expanded end section of a long bone.

Periosteum

The tissue layer covering the outer surface of a bone, composed of an inner cellular/osteogenic layer for bone formation or breakdown and an outer fibrous layer of dense irregular connective tissue.

Endosteum

The cellular lining present on the inner marrow cavity surface of a bone.

Epiphyseal Plate

A region of hyaline cartilage present in growing bone until adulthood that appears as a black line on an X-ray.

Articular Cartilage

Hyaline cartilage that covers the outer surface of the epiphysis where a bone forms a joint with another bone.

Diploë

The layer of spongy bone situated between two layers of compact bone in flat bone structures.

Osteon

The basic structural unit of compact bone, composed of concentric lamellae surrounding a central canal.

Ground Substance (Bone Matrix)

The inorganic component of bone matrix consisting of calcium phosphate and calcium carbonate that provides compression strength.

Collagen Fibers (Bone Matrix)

Organic matrix fibers that provide flexible strength, preventing bone tissue from becoming brittle.

Osteoprogenitor Cells

Mesenchymal stem cells located in the endosteum and periosteum that differentiate into osteoblasts.

Osteoblasts

Cells that synthesize and secrete new organic bone matrix called osteoid.

Osteoid

The organic bone matrix produced by osteoblasts before it undergoes calcification.

Osteocytes

Mature bone cells that reside within spaces called lacunae and maintain bone tissue.

Osteoclasts

Large cells derived from white blood cells (monocytes) that resorb and break down bone tissue.

Trabeculae

An open, branching meshwork of matrix in spongy bone that lacks blood vessels inside itself and contains red marrow in surrounding spaces.

Central Canal (Haversian Canal)

A central passageway within an osteon running parallel to the bone surface, housing blood vessels and nerves.

Osteogenesis

The biological process of bone formation.

Ossification

The process of replacing preexisting tissues with functional bone tissue.

Calcification

The process of depositing calcium salts within tissue.

Intramembranous Ossification

The form of ossification starting directly from mesenchymal or fibrous connective tissue, forming flat bones like the mandible, clavicle, and skull.

Endochondral Ossification

The process of bone development in which preexisting hyaline cartilage models are converted into bone tissue.

Epiphyseal Line

The remnant structure left when longitudinal bone growth finishes and the epiphyseal plate ossifies.

Parathyroid Hormone (PTH)

A hormone produced by parathyroid glands that elevates blood calcium ion levels by stimulating osteoclast activity.

Calcitonin

A hormone secreted by C cells of the thyroid gland that reduces blood calcium ion levels by inhibiting osteoclasts.

Closed Fracture (Simple Fracture)

A bone fracture where the skin remains intact over the break.

Open Fracture (Compound Fracture)

A fracture where the broken bone ends breach the surface of the skin.

Colles Fracture

A break in the distal portion of the radius that typically occurs when extending an arm to cushion a fall.

Greenstick Fracture

An incomplete break in which one side of the shaft fractures while the other side bends, common in children.

Fracture Hematoma

A localized mass of blood clot formed at a fracture site immediately following blood vessel rupture.

Soft Callus (Fibrocartilaginous Callus)

A temporary tissue bridge of fibrocartilage and collagen fibers formed by fibroblasts and osteoblasts during fracture repair stage two.

Bony Callus

A rigid hard callus of spongy bone trabeculae that replaces the soft callus during the third stage of fracture healing.

Osteopenia

The age-related thinning and loss of bone mass that typically begins between ages $30$ and $40$.

Osteoporosis

A severe degree of bone mass reduction that compromises structural and physiological function.