Bone Structure and Function

diaphysis

long cylindrical, main portion of the bone

Made up of compact bone

Provides structural strength and support

epiphysis

the proximal and distal ends of the bone

Made up of spongy bone

Forms joints for smooth movement

metaphysis

region between the diaphysis and the epiphyses

In growing bone, each metaphysis contains an epiphyseal (growth) plate: a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length

Crucial for bone growth and strength

periosteum

connective tissue that surrounds the bone where there is no articular cartilage

Enables the bone to grow in thickness

Consists of an outer layer of dense irregular connective tissue and an inner cellular layer of bone cells

red bone marrow

forms blood cells (hemopoietic)

red bone marrow in children

found in the medullary cavity of long bones and most spongy bones of the body

red bone marrow in adults

found in selected bones of the axial skeleton and epiphysis of humerus and femur

yellow bone marrow

Consists of adipose cells that store triglycerides (energy reserve)

Product of red bone marrow degeneration

yellow bone marrow in children

central of the medullary cavity of some long bones

yellow bone marrow in adults

fills the medullary cavity of most long bones

osteogenic cells

unspecialized stem cells

• only bone cells to undergo cell division (develop into osteoblasts)

osteoblasts

bone-building cells

• synthesize and secrete collagen fibers needed to build the extracellular matrix of bone tissue

osteocytes

mature bone cells

• Maintain its daily metabolism

osteoclasts

huge phagocytic cells that breakdown the bone extracellular matrix

• Resorption: breakdown of the bone matrix that is part of normal development, maintenance and repair of bone

compact bone

Makes up most of diaphysis of long bones

Provides protection and support and resists stresses of weight and movement

osteon:

• haversian canal

• lamellae

• lacunae

• canaliculi

• perforating/volkamnn’s canals

osteon

repeating functional units in compact bone

haversian (central) canal

runs longitudinally through bone in center of osteon; contain blood vessels and nerves

lamellae

concentric rings that surround the central canal; are made of calcified extracellular matrix/collagen fibers

canaliculi

channels radiating from the lacunae that contain processes of the osteocytes

perforating or Volkmann’s canal

canals containing blood vessels, lymphatic vessels and nerves from the periosteum

spongy bone

Does not contain osteons

Contains Trabeculae

Makes up the interior of short, flat bones and most of the epiphyses of long bones

Mostly yellow bone marrow

compact bone

Contains osteons

Does not contain trabeculae

Makes up most of the diaphysis of long bones