Bone Growth and Development Lecture 5

Vocabulary practice flashcards covering key terms and concepts related to bone histology, growth, intramembranous and endochondral ossification, appositional growth, fractures, and bone repair mechanisms.

Osteogenic cell

A mesenchymal stem cell that divides and differentiates into bone-forming osteoblasts.

Osteoblast

A bone cell that forms bone matrix by secreting organic components called osteoid.

Osteocyte

A mature bone cell housed within a lacuna that maintains existing bone tissue.

Osteoclast

A cell that resorb bone tissue, breaking down bone matrix and releasing calcium into the bloodstream.

Osteoid

The unmineralized organic component of bone matrix secreted by osteoblasts before calcium salts crystallize within it.

Ossification center

The precise location in tissue where mesenchymal cells differentiate into osteoblasts and bone matrix mineralization begins.

Spicules

Small struts of developing bone that branch outward from an ossification center and interconnect to trap blood vessels, forming spongy bone trabeculae.

Intramembranous Ossification

Also called dermal ossification; the formation of bone directly from mesenchymal stem cells within a connective tissue membrane, starting around the 8th week of embryonic development.

Endochondral Ossification

The process of bone development where bone tissue replaces a pre-existing hyaline cartilage model, beginning by the 9th week of embryonic development.

Bone Collar

A thin layer of compact bone produced by osteoblasts around the shaft of a hyaline cartilage model during early endochondral ossification.

Primary Ossification Center

The central region in the shaft (diaphysis) of a cartilaginous model where blood vessels enter and osteoblasts first begin replacing calcified cartilage with spongy bone.

Secondary Ossification Center

Regions that develop around birth in the epiphyses of long bones as capillaries and osteoblasts migrate into the cartilage ends.

Epiphyseal Plate

A band of hyaline cartilage located within the metaphysis that separates the epiphysis from the diaphysis, allowing long bones to grow in length.

Epiphyseal Closure

The event at maturity when epiphyseal cartilage enlargement slows, osteoblast activity replaces the remaining cartilage, and growth in length ceases.

Concentric Lamellae

Concentric rings of collagen fibers and osteocytes surrounding the central canal inside an osteon.

Interstitial Lamellae

Layers of bone matrix that fill the physical spaces located between osteons.

Circumferential Lamellae

Layers of bone matrix found at the outermost and innermost surfaces of long bone shafts.

Appositional Bone Growth

Growth in bone diameter where osteoblasts beneath the periosteum deposit new bone on the outer surface while osteoclasts resorb bone along the endosteal surface.

Compound Fracture

An open fracture where the broken ends of the bone protrude through the skin, introducing a risk for bacterial infection known as osteomyelitis.

Greenstick Fracture

An incomplete fracture in which one side of the bone shaft breaks while the other side bends, commonly occurring in children whose bones are not fully ossified.

Comminuted Fracture

A fracture in which the bone shatters into a multitude of bony fragments.

Transverse Fracture

A bone break occurring directly across the long axis of the bone shaft.

Spiral Fracture

A fracture caused by twisting stresses that spread along the length of a bone.

Fracture Hematoma

A large blood clot that forms at a fracture site over a period of several hours due to extensive hemorrhaging from broken blood vessels.

Internal Callus

A network of spongy bone formed during fracture repair that unites the inner edges of the broken bone within the medullary cavity.

External Callus

A collar of cartilage and spongy bone that forms around the outside of a fracture site to stabilize the broken outer edges.