Skeletal System - 6.2 BONE HISTOLOGY

All types of connective tissue

1. Cartilage

2. Tendons

3. Ligaments

4. Bones

Mature bone matrix

Is normally about 35% organic and 65% inorganic material.

The organic material

consists primarily of collagen and proteoglycans.

The inorganic material

consists primarily of a calcium phosphate crystal called hydroxyapatite.

Hydroxyapatite

A calcium phosphate crystals

The collagen and mineral components

are responsible for the major functional characteristics of bone.

Brittle bone disease

Osteogenesis imperfecta

Osteogenesis imperfecta

which means imperfect bone formation.

Brittle bone disease (osteogenesis imperfecta)

A rare disorder caused by any one of a number of faulty genes that results in either too little collagen formation, or poor quality collagen.

3 types of bone cells

1. Osteoblasts

2. Osteocytes

3. Osteoclasts

Osteoblasts

Are bone building cells.

Osteoblasts

These cells have an extensive endoplasmic reticulum and numerous ribosomes.

Osteoblasts

Produce collagen and proteoglycans.

The hydroxyapatite

Acts as a templates that stimulate further hydroxyapatite formation and mineralization of the matrix.

The formation of new bone by osteoblasts is called

Ossification or Osteogenesis.

Ossification

Can occur multiple times during life: as a fetus, when growing larger, and any time in life when a fracture is repaired.

Ossification

Occur appositional growth on the surface of previously existing material, either bone or cartilage.

Osteoblasts

Become osteocytes once the osteoblasts have secreted sufficient bone matrix.

Osteocytes

Account for 90-95% of bone cells and are very long-lived, with a life span of up to 25 years.

Lacunae

Osteocytes cell bodies are housed within the bone matrix in spaces.

Canaliculi

Osteocytes cell extensions are housed in narrow, long spaces.

Osteoclasts

Are bone-destroying cells. These cells break down bone.

Bone Reabsorption

Breakdown of bone.

Bone Reabsorption

This breakdown is important for mobilizing crucial CA2+ and phosphate ions for use in many metabolic processes.

Osteoclasts

Are massive, multinucleated cells and develop from the red bone marrow cells that also differentiate into specialized white blood cells.

Mature osteoclasts

Carry out bone reabsorption through multistep process.

Ruffled border

Is a specialized reabsorption-specific area of the membrane.

Lamellar bone

A mature bone.

Lamellae

It is organized into thin, concentric sheets or layers.

Spongy bone

Which appears porous, has less bone matrix and more space than compact bone.

Compact bone

Has more bone matrix and less space than spongy bone.

Trabeculae

Spongy bone consists of interconnecting rods or plates of bones.

Compact bone or cortical bone

Is the solid, outer layer surrounding each bone.

Osteon or haversian system

The functional unit of compact bone

Osteon

Is composed of concentric rings of matrix, which surround a central tunnel and contain osteocytes.

Central Canal

The bull's eye of the target as osteon resembles a circular target.

Central Canals

Are lined with endosteum and contain blood vessels, nerves, and loose connective tissue.