Chapter 6: Bone Tissue and the Skeletal System

Osteoprogenitor

Stem cells that develop into osteoblasts.

Osteoblasts

Cells that build new bone.

Osteocytes

Mature bone cells that maintain bone tissue.

Osteoclasts

Large, multinucleated cells that break down old bone.

Extracellular Matrix (ECM)

The substance in which tissue cells are embedded, consisting of protein and polysaccharides.

Bone formation

Process where osteoblasts produce osteoid, leading to mineralization.

Bone dissolution

Process where osteoclasts break down bone, releasing calcium and phosphorus into the blood.

Compact bone

Dense and strong bone; outer layer that resists bending.

Spongy bone

Porous and lightweight bone that contains trabeculae and bone marrow.

Epiphysis

Ends of a long bone.

Diaphysis

Long shaft or middle of a long bone.

Metaphysis

Area between epiphysis and diaphysis.

Epiphyseal plate

Cartilage growth plate responsible for lengthwise bone growth.

Periosteum

Covers the outside of bone and helps with growth and repair.

Endosteum

Lines the inside of bone and assists with growth and remodeling.

Red marrow

Produces blood cells and is found in spongy bone.

Yellow marrow

Stores fat and is more common in adult long bones.

Ossification

The process of forming bone from either connective tissue or cartilage.

Intramembranous ossification

Process where bone develops directly from mesenchymal tissue.

Endochondral ossification

Process where bone replaces a cartilage model.

Longitudinal growth

Increases the length of a long bone at the epiphyseal plate.

Appositional growth

Increases the width of a bone by adding new bone to the outer surface.

Osteon

Basic structural unit of compact bone.

Trabeculae

Thin bony plates or beams that form spongy bone.

Lacunae

Small spaces in bone that contain osteocytes.

Canaliculi

Tiny channels in bone that connect lacunae.

Bone remodeling

The process of removing old bone and replacing it with new bone.

Achondroplasia

A common cause of disproportionate short-limbed dwarfism affecting cartilage growth.

Axial skeleton

The part of the skeleton consisting of 80 bones including the skull, vertebral column, and thoracic cage.

Appendicular skeleton

The part of the skeleton consisting of 126 bones including the upper and lower limbs.

Vitamin D

Nutrient that helps absorb calcium.

Vitamin C

Nutrient that helps make collagen.

Calcium

Mineral that strengthens bones.

Phosphorus

Mineral that is important for bone strength.

Compact vs. Spongy Bone

Compact bone is dense; spongy bone is porous.

Osteoblast pathway

Osteoprogenitor -> STEM CELL -> Osteoblast -> BUILDS BONE -> Osteocyte.

Bone growth stopping

When the epiphyseal plate closes, longitudinal growth ends.