Biology 6.2 - Bone Histology

made by me September 22nd, 2026

Collagen

Is flexible but can withstand compression or pulling

Proteoglycan

water-trapping proteins which the matrix ground substance is made of as well as making cartilage resilient and smooth

Bone matrix is what % of organic material?

35%

Bone matrix is what % of inorganic material?

65%

What is the inorganic material of the bone matrix made up of?

Hydroxyapatite

Hydroxyapatite is?

A calcium phosphate crystal

Bones major functional characteristics are?

Collagen and mineral components

What happens if the mineral in a bone is reduced, with collagen taking over?

The bone becomes overly flexible

What happens if collagen in a bone is reduced, with minerals taking over?

The bone becomes very brittle

Brittle Bones Disease

A rare disorder that results in either bad quality collagen or not enough collage formation

What are the three types of bones cells?

1. Osteoblasts, 2. Osteocytes, 3. Osteoclasts

What are the bone building cells?

Osteoblasts, they produce collagen and proteoglycans

When new bone is formed by Osteoblats, what is it called?

Ossification

Osteoblasts form?

Hydroxyapatite

Osteocytes are?

Mature bone cells

When matured, Osteoblasts become?

Osteocytes

What % of bone cells do Osteocytes make up?

90-95%

What are Osteocyte cell bodies inside of? (housed in)

Lacunae

Lacunae are?

The spaces inside the bone matrix

What are Osteocyte cell extensions inside of? (housed in)

Long and narrow spaces called Canaliculi

Osteoclasts are?

Cells that break down and “destroy” bone

The breakdown of bone is called what?

Bone reabsorption

When bone is broken down where does the Ca2+ (calcium) go back to?

Into the blood

Ruffled Border

Is created by Osteoclasts and is a specific re-absorption part of the membrane

What is mature bone called in specific?

Lamellar Bone

Lamellar bone is organized into what?

Layers called Lamella

Spongy Bone

Has more space and less bone matrix, looks porous

What does spongy bone have?

Innterconnecting rods of bone called trabeculae

Compact bone

Outside layer of bones, is dense and has more matrix. Less porous

What is osteon?

The functional unit of compact bones

What is the “bull’s-eye” of the Osteon called?

Centeral Canal