BL Bone

Question 1

What are the two sections of the skeleton?
What are each section comprised of?

Answer 1

Axial - skull
- vertebrate
- ribs/thoracic cage
Appendicular - upper limbs
- shoulder girdle
- lower limbs
- pelvic girdle

Question 2

Why is bone a living tissue?

Answer 2

Contains blood vessles
Made out of various cells, proteins, mineral etc.
Can repair and remodel

Question 3

Functions of bone

Answer 3

• mechanical: protection, framework + levers in movement
• synthetic: haemopoiesis
• metabolic: mineral storage, fat storage (yellow bone marrow) + acid base homeostasis

Question 4

Outline the two types of bone

Answer 4

Cancellous bone - forms a network of bony columns calls trabeculae, spaces filled by bone marrow

Compact bone - forms the external surface of bone

Question 5

what are the two types of ossification?

Answer 5

Endochondral ossificaion
Intra-membranous ossification

Question 6

Outline endochondral ossification

Answer 6

Formation of long bones from cartilage template

• Continued lengthening at epiphyseal plates
• appositional growth - growth at the edges

Question 7

Outline intra-membranous ossification

Answer 7

Formation of bone from clusters of mesenchymal stem cells in the centre of the bone > flat bones

Interstitial growth - growth in the middle

Question 8

What are epiphyseal plates?

Answer 8

Part of the long bone where bone growth occurs

Question 9

What do mesenchymal stem cells develop into?

Answer 9

Connective tissue
Blood vessels
Lymphatic tissues
Bones

Question 10

What type of growth occurs in endochondral ossification?

Answer 10

Appositional growth - growth at edges

Question 11

What type of growth occurs at intra-membranous ossification?

Answer 11

Interstitial growth - growth in the middle

Question 12

How do flat bones develop?

Answer 12

Directly from mesenchymal tissue
By intra-membranous ossification

Question 13

How do long bones develop?

Answer 13

Require cartilage template to develop
By endochondral ossification

Question 14

Outline bone remodelling

Answer 14

Reabsorption:
- osteoclasts breakdown old bone
- uses acid to dissolve minerals

Formation:
1- osteoblasts lay down osteoid (collagen 1), enzymes and ground substance
2- osteoblasts change osteoid pH&raquo_space; deposition of hydroxyapatite
3- mineralisation occurs
4- osteoid turns into bone tissue
5- osteoblasts become trapped within bone lamellae&raquo_space; becomes osteocytes

Question 15

Outline the process of bone formation

Answer 15

1- osteoblasts lay down osteoid (collagen 1), enzymes and ground substance
2- osteoblasts change osteoid pH&raquo_space; deposition of hydroxyapatite
3- mineralisation occurs
4- osteoid turns into bone tissue
5- osteoblasts become trapped within bone lamellae&raquo_space; becomes osteocytes

Question 16

What is the cement line?

Answer 16

Where osteoid meet existing bone

Question 17

Outline the conversion of cancellous bone to cortical bone

Answer 17

1- MSC convert into osteoblasts that line recently formed trabeculae
2- osteoid laid down
3- mineralisation occurs
4- 1-3 repeat
5- central MSC convert into blood vessels, lymph vessels + nerves

Question 18

Similarities and differences between cancellous and cortical bone

Answer 18

Similarities:
- consist of concentrically arranged lamellae with osteoblasts between structures + osteocytes in lacunae

Differences:
- compact bones have osteons, Haversian canals + Volkman canals
- compact bone is a ‘solid continuous mass’
- spongy bone is a ’3D network of regular trabeculae’

Question 19

What do osteoblasts use to create bone matrix?

Answer 19

Extracellular components:
Collagen
Enzymes
Ground substance
Calcium
Phosphorus

Question 20

What are responsible for bone reabsorption?

Answer 20

Osteoclasts - secrete collagenase + acids to break down bone matrix

Question 21

What is periosteum?

Answer 21

Tough fibrous vascular connective tissue layer attached to external surface of bone

Question 22

What are the two steps in bone remodelling?

Answer 22

1- cutting cone - osteoclasts make a wide tunnel in the bone
2- closing cone - osteoblasts make a smaller tunnel of cortical bone

Question 23

What factors effect bone stability?

Answer 23

• activity of osteocytes, osteoblasts + osteoclasts
• nutrition: vitamin D3, C, K + B12

Question 24

How does the vitamin D3 affect bone stability?

Answer 24

Produces calcitriol - needed for calcium absorption

Question 25

How does vitamin C affect bone stability

Answer 25

Synthesis of collagen
Osteoid - collagen I

Question 26

How does do vitamin K and B12 affect bone stability?

Answer 26

Synthesis of bone proteins

Question 27

How many bones are there in the body?
How is it spread between the two skeletons?

Answer 27

206
Axial - 80
Appendicular - 126

Question 28

How are bones involved in acid base homeostasis?

Answer 28

Absorbs or releases alkaline salts to help regulate blood pH

Question 29

Compare the structure of immature and mature bones

Answer 29

• immature: osteocytes in random arrangements
• mature: oestocytes arranged in concentric lamellae of osteons

Question 30

Haversian canal vs Volkman canal

Answer 30

• Haversian canals run through osteons
• Volkmann’s canal connect Haversian canals