Bone Tissue Physiology

Question 1

Features of long bones

Answer 1

Diaphysis (shaft) compact dense bone and medullary cavity

Epiphysis (ends) - trabecular spongy bone

Articular cartilage

Question 2

What makes up bone tissue (Oseous tissue)

Answer 2

Ground substance - two thirds of bone matrix, minerals

Protein - one third of matrix, mostly protein type one collagen fibres

Bone cells - only 2% osteoblasts build and clasts (crushers) cytes (cells)

Question 3

What are osteoblasts, osteoclasts and osteocytes

Answer 3

Blasts - immature bone cell that secrets matrix proteins

Cytes- mature bone cells that maintains the bone matrix

Osteoclasts - multinucleate cells that secrete acids and enzymes to dissolve bone matrix

Question 4

Microscopic structure of compact bone

Answer 4

Osteons - basic functions units of compact bone

Central canal - tunnel for blood vessel, through middle of osteon

Lamellae - concentric layers of matrix

Lacunae - contain osteocytes

Question 5

Microscopic features of trabecular (sponges) bone

Answer 5

No osteons

Trabecular - arches, rods, plates of bone, branching network- strong in all directions

Red marrow - between trabecular, form red blood cells, provide nutrients to osteocytes

Yellow marrow - found in the medullary cavity, stores fat

Question 6

Bone structure and loading patterns

Answer 6

Osteon - structure of compact bone provides strength in long axis

Trabecular - bone provides strength in multiple directions

Trabeculae alight according to habitual loading patterns

Question 7

Periosteum

Answer 7

Membrane outside the bone

Outer fibrous layer - collagen fibres continuous with bone, ligaments, tendons and joint capsule

Also contains lymphatic vessels and nerves

Question 8

Endosteum

Answer 8

Membrane lining the bone

Incomplete cellular layer

Lines medullary cavity, central cavity and trabeculae

Question 9

What is ossification and the different types

Answer 9

The formation of or conversion into bone

Intramembranous (inside)
- flat bone formation

Endochronial (inner cartilage)
- formation from cartilage model

Appositional
- growth in width

Question 10

Explain intramembranous ossification

Answer 10

Mesenchymal cells differentiate into osteoblasts
Forms spicules of bone
Trabecular bone formed
Remodelled into compact bone

Question 11

Explain endochronal ossification

Answer 11

1. Chondrocytes within calcifying matrix expand then die
2. Osteoblasts cover shaft in a thin layer of bone
3. Blood vessels and osteoblasts penetrate to form a primary ossification centre
4. This enlarges
5. Secondary ossification centres formed at epiphyses

Question 12

Explain bone remodelling and homeostasis

Answer 12

• continuous breakdown and reforming, reabsorption by osteoclasts, build by blasts
• adaptation to loading, osteocytes detect force in the bone
• calcium homeostasis, hormones control storage and release

Question 13

Explain fracture repair

Answer 13

1. Bleeding and formation of clots
2. Formation of external callus made of cartilage and internal callus made of bone
3. Internal swelling eventually remodelled