Basic Science of the MSK system

Question 1

Functions of Bone? (4)

Answer 1

Protection
Mechanical Support
Calcium homeostasis
Haematopoiesis

Question 2

Two main types of bone? (microscopic classification) (2)

Answer 2

Woven - immature or pathological bone.

Lamellar - secondary made from remodelling woven.

Question 3

Where do you find woven bone? (3)

Answer 3

Healing #’s
Children <4
Metaphyses

Question 4

Features of woven bone? (4)

Answer 4

Random collagen array - not yet stress orientated
Rapid turnover
Has more osteocytes
High rate of turnover

Question 5

Two types of Lamellar (mature) bone? (2) and where you find them? (2)

Answer 5

Cortical - adult long bones

Cancellous/trabecular - meta/epiphyses and centre of cuboid bones (foot and wrist)

Question 6

What type of forces is cortical bone resistant to? (2)

Answer 6

Torsional strength - resists twisting

Flexural (bending) strength

Question 7

Functional unit of cortical bone? (1) and describe it’s structure (4)

Answer 7

Osteon

Outer border defined by cement lines
Vascular canals
Interstitial lamellae
Lamellae surround a central Haversian canal

Question 8

What makes cortical bone strong? (1)

Answer 8

Lamellae - fibrils of collagen aligned at varying angles to provide strength in multiple planes.

Fibrils are made up of type 1 collagen and hydroxyapatite crystals

Question 9

Cancellous bone properties (2)

Answer 9

Lower young’s modulus and so more elastic

High vascularity - high turnover - heals faster

Question 10

Layers of periosteum (2)

Answer 10

Fibrous

Cambium - deep and more important layer

Question 11

Cell types in bone (4)

Answer 11

Osteoclasts
Osteoclasts
Osteocytes
Osteoprogenitor

Question 12

Blood supply to bone (3)

Answer 12

Nutrient system (high pressure)
Metaphyseal/epipyseal (periarticular vascular complex)
Periosteal system (low pressure)

Question 13

Which homeostatic mechanism compensates for a decrease in Ca2+? (1)

Answer 13

Increase in PTH –> bone resorption + vit D activation + calcium resorption

Question 14

Which hormone activates with an increase in Ca2+? (1)

Answer 14

Calcitonin

Question 15

3 features of cartilage (3)

Answer 15

Aneural
Avascular
Alymphatic

Question 16

Structure of articular cartilage

Answer 16

3 zones;

1. Superficial
2. Transitional
3. Radial

Question 17

Go over the sliding filament theory of muscle contraction (5)

Answer 17

1. ATP binding causes the myosin head to detach from the actin filament
2. ATP hydrolysis causing cocking back of the myosin head
3. Release of the inorganic phosphate causes reattachment of the myosin head
4. Release of ADP leads to the power stroke; pulls the actin towards the centre of the sarcomere.

First proposed in 1954 by Huxley and Hanson, who studied muscle filaments using microscopy.