Bone and Joint Physiology

Question 1

List the 5 functions of bone

Answer 1

1. Supports the body
2. Facilitates movement
3. Produces RBCs (haematopoeisis)
4. Regulates calcium
5. Protects organs

Question 2

What conditions result from low Vitamin D

Answer 2

1. Rickets

2. Osteomalacia

Question 3

Where is Vitamin D converted to its active form

Answer 3

1. Liver

2. Kidney

Question 4

Where is parathyroid hormone produced

Answer 4

Chief cells of the parathyroid

Question 5

What is the effect of PTH on bone

Answer 5

Causes bone resorption by osteoclasts

Question 6

Where is Calcitonin produced

Answer 6

Parafollicular C-cells of the Thyroid

Question 7

How does growth hormone cause bone growth

Answer 7

1. GH stimulates the production of IGF-1 in the liver

2. IGF-1 stimulates bone growth

Question 8

Why is magnesium essential for bone health

Answer 8

Important in hydroxyapatite crystallisation

Question 9

What process increases bone length

Answer 9

Endochondral ossification

Question 10

What process increases bone width

Answer 10

Subperiosteal appositional ossification

Question 11

How is the bone matrix divided

Answer 11

1. Organic (35%)

2. Inorganic (65%)

Question 12

What is the main component of the inorganic matrix

Answer 12

Calcium hydroxyapatite (contains 99% of the body’s calcium and 85% of body phosphorus)

Question 13

What is the main component of the organic matrix

Answer 13

Bone proteins - namely Type 1 collagen

Question 14

What are the two ways in which osteoblasts lay down collagen

Answer 14

1. Random weave (woven bone)

2. Orderly layers (lamellar bone)

Question 15

From where are osteoprogenitor cells derived

Answer 15

Pluripotential mesenchymal stem cells

Question 16

Where are osteoblasts derived

Answer 16

Osteoprogenitor cells

Question 17

Where are osteocytes derived

Answer 17

Osteoblasts

Question 18

Where are osteoclasts derived

Answer 18

Haematopoietic progenitor cells

Question 19

Where are osteoclasts located

Answer 19

Sites of active bone resorption in pits called Howship’s lacunae

Question 20

What is woven bone and where is it found

Answer 20

Immature bone - seen in the fetal skeleton, growth plates and callus

Question 21

What is cortical bone

Answer 21

• Rigid with no marrow

- Well-defined haversian canals lying parallel to the long axis

Question 22

What is cancellous bone

Answer 22

• Lies inside the cortical layer
• Contains marrow in spaces between trabeculae
• No blood vessels

Question 23

What connects periosteum to the underlying bone

Answer 23

Sharpey’s fibres

Question 24

What are the two layers of periosteum

Answer 24

1. Cambrial (inner)

2. Fibrous (outer)

Question 25

What are the 3 functions of periosteum

Answer 25

1. Anchor - site of tendon/ligament attachment 2. Source of Osteoprogenitor cells 3. Nutrition

Question 26

What are the two ways in which a bone may ossify during development

Answer 26

1. Directly - intermembranous - e.g. clavicle | 2. Endochondral ossification of a hyaline cartilage template - e.g. long bones

Question 27

How may a long bone be divided

Answer 27

1. Diaphysis (shaft) - tube of cortical bone 2. Metaphysis - conical area of cancellous bone facilitating load transfer from the articular surface to the diaphysis 3. Physis - growth plate 4. Epiphysis - articular surface and consists of zone of cancellous bone

Question 28

Where are the primary and secondary ossification centres of long bones

Answer 28

1. Primary = diaphysis | 2. Secondary = epiphysis

Question 29

What are the 4 zones of the physis (growth plate)

Answer 29

1. Resting zone 2. Proliferative zone 3. Hypertrophic zone 4. Zone of provisional calcification

Question 30

Which zone of the growth plate are the chondrocytes dividing

Answer 30

Proliferative zone

Question 31

Between which zones of the growth plate do fractures typically occur

Answer 31

Between hypertrophic and calcific zones

Question 32

Define Wolff's law

Answer 32

Trabeculae are formed in response to the loads placed on the bone

Question 33

What percentage of cardiac output is distributed to the bone

Answer 33

5-10%

Question 34

Which artery typically supplies the bone marrow and trabecular bone

Answer 34

Nutrient artery

Question 35

Describe the circulus vasculosus

Answer 35

Arterial plexus surrounding the epiphysis derived from regional arterial branches

Question 36

Describe the venous drainage of bones

Answer 36

Venous flow is from the cortical capillaries draining into sinusoids and then to the emissary venous system

Question 37

What are the 3 classes of joint based on function

Answer 37

1. Immovable (synarthroses) e.g. skull suture 2. Slightly movable (amphiarthrosis) e.g. manubriosternal 3. Freely movable (diarthroses)

Question 38

What are the 3 classes of joint based on structure

Answer 38

1. Fibrous 2. Cartilaginous 3. Synovial

Question 39

What is a fibrous joint

Answer 39

- Lacks a joint cavity | - Fibrous tissue unites bone

Question 40

What are the 3 types of fibrous joint

Answer 40

- Sutures - Syndesmosis - Gomphosis

Question 41

What is an example of a gomphosis joint

Answer 41

Roots of teeth in alveolar socket

Question 42

What are the two types of cartilaginous joint

Answer 42

1. Primary (synchondrosis) - where bone and hyaline cartilage meet e.g. between rib and costal cartilage 2. Secondary (symphysis) - where hyaline covered articular surface of two bones are united by fibrous tissue e.g, intervertebral joints

Question 43

What type of collagen is found Hyaline cartilage

Answer 43

Mainly Type 2