BIO 215 Chapter 6: Bone Tissue and Skeletal System

Vocabulary practice flashcards covering functions of the skeletal system, bone histology, endochondral ossification, epiphyseal growth zones, remodeling and hormonal regulation, bone pathologies, fracture classifications, and the stages of bone repair from BIO 215 Chapter 6.

Support

A skeletal system function that serves as a structural framework for the body, supporting soft tissues and providing attachment points for tendons of most skeletal muscles.

Protection

A skeletal system function that shields many internal organs from injury.

Movement

A skeletal function where bones and muscles work together to produce motion; muscles attach to bones and pull on them upon contracting.

Mineral Homeostasis

A bone tissue function where several minerals, mainly calcium and phosphorus, are stored in bone tissue and released on demand into the blood to maintain critical mineral balances and distribution.

Blood Cell Production

A primary bone tissue function that takes place within red bone marrow.

Triglyceride Storage

A bone tissue function localized in yellow bone marrow.

Osteogenic (Osteoprogenitor) Cells

Unspecialized stem cells derived from mesenchyme; they are the only bone cells that undergo cell division, producing daughter cells that develop into osteoblasts, and are found in the periosteum, endosperm, and canals with blood vessels.

Osteoblasts

Bone-building cells that synthesize and secrete collagen fibers and other organic compounds to build the bone matrix, ultimately becoming trapped as osteocytes; they do not undergo cell division.

Osteocytes

Mature bone cells that do not undergo cell division and function to maintain cellular metabolism, including exchanging nutrients and wastes within the blood.

Endochondral Ossification

The process forming most bones (except cranial bones and clavicles) through five stages: bone collar formation around a cartilage model diaphysis, central cartilage calcification and cavitation, periosteal bud invasion forming spongy bone, diaphysis elongation and medullary cavity formation, and epiphyseal ossification.

Resting (Quiescent) Zone

The relatively inactive region of cartilage located on the epiphyseal side of the epiphyseal plate.

Proliferation (Growth) Zone

The area of cartilage on the diaphysis side of the epiphyseal plate undergoing rapid cell division; new cells push the epiphysis away from the diaphysis, causing bone lengthening.

Hypertrophic Zone

The growth zone containing older chondrocytes closer to the diaphysis where cartilage lacunae enlarge and erode, forming interconnecting spaces.

Calcification Zone

The zone where the surrounding cartilage matrix calcifies, causing chondrocytes to die and deteriorate.

Bone Remodeling

The coordinated ongoing process of bone deposition by osteoblasts and stress-sensing osteocytes paired with bone resorption carried out by osteoclasts.

Parathyroid Hormone

A hormone released when blood calcium levels are too low that stimulates osteoclastic bone resorption to release calcium into the bloodstream and raise blood calcium levels.

Calcitonin

A hormone released when blood calcium levels are too high that lowers blood calcium by stimulating bone building by osteoblasts and osteocytes.

Bone Deposit

The addition of bone that occurs when a bone is injured or added strength is needed, requiring a diet rich in proteins.

Bone Resorption

The breakdown of bone by osteoclasts wherein lysosomal enzymes digest the organic matrix and hydrochloric acid converts calcium salts into soluble form.

Osteomalacia

A condition in which bones are poorly mineralized; osteoid is produced but calcium salts are inadequately deposited, causing soft, weak bones and pain upon bearing weight.

Rickets

Osteomalacia in children caused by vitamin D deficiency or insufficient dietary calcium, resulting in bowed legs and bone deformities from enlarged, abnormally long bone ends.

Osteoporosis

A group of diseases where bone resorption exceeds bone deposit, causing bone mass to decline while the composition of the matrix remains normal.

Paget's Disease

A condition of excessive and haphazard bone deposit and resorption that produces fast, poorly formed bone; typically affects the spine, pelvis, femur, and skull, rarely occurs before age 40, has an unknown (possibly viral) cause, and is treated with calcitonin and bisphosphonates.

Nondisplaced Fracture

A fracture classification based on bone position where the broken bone ends retain their normal position.

Displaced Fracture

A fracture classification based on position where the bone ends are out of normal alignment.

Complete Fracture

A fracture classification based on completeness in which the bone is broken entirely through.

Incomplete Fracture

A fracture classification based on completeness where the bone is not broken all the way through.

Linear Fracture

A fracture classification based on orientation where the break runs parallel to the long axis of the bone.

Transverse Fracture

A fracture classification based on orientation where the break runs perpendicular to the long axis of the bone.

Open (Compound) Fracture

A fracture where the broken bone ends penetrate through the skin.

Closed (Simple) Fracture

A fracture where the broken bone ends do not penetrate through the skin.

Hematoma Formation

The initial stage of bone repair where torn blood vessels hemorrhage to form a swollen, painful, and inflamed mass of clotted blood.

Fibrocartilaginous Callus Formation

The second repair stage wherein capillaries grow into the hematoma, fibroblasts secrete collagen fibers to span the break, and fibroblasts, cartilage, and osteogenic cells initiate bone reconstruction.

Bony Callus Formation

The third repair stage where new trabeculae appear within one week to convert the callus into a hard spongy bone callus, continuing for about 2 months until firm union is achieved.

Bone Remodeling (Repair Phase)

The final stage of bone repair where excess material on the diaphysis exterior and in the medullary cavity is removed and compact bone is laid down to reconstruct the shaft walls.

Comminuted Fracture

A fracture type where the bone fragments into three or more pieces; especially common in the elderly whose bones are more brittle.

Compression Fracture

A fracture type in which the bone is crushed; common in porous bones subjected to extreme trauma, such as in a fall.

Spiral Fracture

A common sports fracture resulting from excessive twisting forces applied to the bone, producing a ragged break.

Epiphyseal Fracture

A fracture where the epiphysis separates from the diaphysis along the epiphyseal plate, typically occurring where cartilage cells are dying and matrix calcification is taking place.

Depressed Fracture

A fracture type typical of skull fractures where the broken bone portion is pressed inward.

Greenstick Fracture

An incomplete break common in children where one side of the bone shaft breaks while the other side merely bends.