CH6 BONE PT2 - Ossification and Bone Development -

Vocabulary flashcards covering ossification, bone growth, calcium homeostasis, and fracture repair based on lecture notes.

Ossification (osteogenesis)

The process of bone formation, occurring in embryonic development, fracture repair, and lifelong remodeling; includes endochondral and intramembranous pathways.

Endochondral ossification

Bone forms by replacing a hyaline cartilage model; primary ossification center develops in the diaphysis, followed by secondary centers in the epiphyses.

Intramembranous ossification

Bone forms directly from mesenchyme or dense fibrous connective tissue, forming flat bones like those of the skull, mandible, and clavicle.

Mesenchyme

Embryonic connective tissue that differentiates into bone, cartilage, and other tissues.

Hyaline cartilage

Glassy cartilage that forms the initial bone model in endochondral ossification.

Osteoprogenitor cell

Bone stem cell derived from mesenchyme that differentiates into an osteoblast.

Osteoblast

Bone-forming cell that secretes osteoid, which mineralizes into bone; can mature into an osteocyte.

Osteoid

Organic bone matrix secreted by osteoblasts that becomes mineralized.

Calcification

Deposition of calcium salts into osteoid or cartilage matrix, hardening the tissue.

Primary ossification center

First area of bone formation within a cartilage model, typically in the diaphysis during endochondral ossification.

Secondary ossification center

Later sites of bone formation in the epiphyses during endochondral ossification.

Diaphysis

The shaft of a long bone; site of the primary ossification center and medullary cavity formation.

Epiphysis

The ends of a long bone; contain secondary ossification centers.

Metaphysis

Region between the diaphysis and epiphysis; contains the epiphyseal plate (growth plate) in children.

Epiphyseal plate

Hylaine cartilage growth plate that enables bone lengthening; becomes the epiphyseal line after growth stops.

Epiphyseal line

Ridge formed when the epiphyseal plate closes; indicates cessation of growth in length.

Articular cartilage

Hylaine cartilage covering joint surfaces to reduce friction and absorb impact.

Fontanelle

Soft spots on a fetal skull where fibrous connective tissue persists, allowing birth-time molding; can be spelled fontanelle or fontanel.

Suture

Fibrous connective tissue joints between skull bones in newborns, allowing for skull flexibility during birth.

Periosteum

Outer fibrous layer and inner osteogenic layer surrounding bone; a key site for growth in width (appositional) and repair.

Interstitial growth

Cartilage growth from within via chondrocyte division, contributing to length; characteristic of cartilage, not direct bone growth.

Appositional growth

Growth by adding new layers on a surface; in bone, increases diameter via periosteum; in cartilage, adds layers on the surface.

Perichondrium

Dense connective tissue surrounding cartilage; when ossification begins, it becomes the periosteum.

Bony collar

Bone collar formed around a cartilage model by osteoblasts during endochondral ossification.

Fracture hematoma

Blood clot formed at a fracture site that stops bleeding and provides a scaffold for healing.

Fibrocartilage callus (soft callus)

Initial cartilage-like bridge that stabilizes fracture ends before hard bone forms.

Spongy bone (trabecular bone)

First-formed, porous bone that bridges fracture ends and is later remodeled into compact bone.

Remodeling (bone remodeling)

Replacement of immature bone with mature bone; reshapes and reconstitutes medullary cavity; coordinated by osteoblasts and osteoclasts.

Parathyroid hormone (PTH)

Hormone from the parathyroids that increases blood calcium by stimulating osteoclast-mediated bone resorption.

Calcitonin

Thyroid hormone that inhibits osteoclasts, promoting calcium deposition in bone and lowering blood calcium.

Osteoclasts

Bone-resorbing cells that dissolve mineralized bone to release calcium into the blood.

Osteoblasts

Bone-forming cells that secrete osteoid and become osteocytes as bone matures.

Osteocytes

Mature bone cells derived from osteoblasts that reside in lacunae and maintain bone tissue.

Calcium homeostasis

Regulation of blood calcium levels via PTH and calcitonin; bone acts as a calcium reservoir through remodeling.

Carpal bone ossification as age indicator

Radiographic progression of carpal bone ossification helps estimate age and growth stage.