Tissue healing

Question 1

What is haemostasis?

Answer 1

Protective response to the rupture of blood vessels – preventing excess blood loss and a precursor to tissue repair

Limiting excessive bleeding during injury
Three main stages – vascular spasm, formation of the platelet plug and coagulation

Question 2

What are the three main stages of haemostasis?

Answer 2

vascular spasm
formation of the platelet plug
coagulation

Question 3

Whats the first stage of haemostasis?

Answer 3

Vascular spasm

Question 4

Explain vascular spasm

Answer 4

• vasoconstriction
• contraction of smooth muscle,
• limit blood loss.
• Vascular spasm essentially ‘buys time’ for the next two steps to occur.

Question 5

Whats the second stage of haemostasis?

Answer 5

formation of platelet plug

Question 6

explain the process of formation of platelet plug

Answer 6

1. Platelets aggregate (stick together) to form a temporary plug that seals the break in the vascular wall.
2. ‘activated’ platelets become stickier help adhesion to the site of injury, and this is facilitated by differing chemical messengers.
3. more platelets aggregate, more chemicals are released that stimulate more platelets to migrate to the area and aggregate.
4. Thus, this is an example of a positive homeostatic feedback system.

Question 7

Whats the third stage of haemostasis?

Answer 7

coagulation

Question 8

Whats the process of coasgulation?

Answer 8

• Infiltrating and reinforcing the platelet plug with fibrin threads acting as glue to aggregate platelets together – forms fibrin mesh – seals large breaks in blood vessel
• clot traps bloods formed elements so only plasma forming serum of yellow liquid

Question 9

What are fibrin threads?

Answer 9

• From dissolved blood proteins
• Made in process involving many blood clotting factors known as procoagulants
• active in coagulation stage of haemostasis

Question 10

Why is vitamin K important in coagulation?

Answer 10

• Co-factor for blood clotting
• Develops clotting factors in enzymatic cascade

Question 11

State the stages of soft tissue healing

Answer 11

1. haemostasis - inflammatory phase
2. proliferation and migratory phase
3. maturation and remodelling phase

Question 12

How can histamine add haemostasis?

Answer 12

triggers vasodilation and permeability of the blood vessels
- this increases microbes and foregin particles being cleared as phagocytotic cells have more acess to the site of injury

Question 13

Explain the proliferation and migratory phase of soft tissue healing

Answer 13

1. • 2/3 days
2. epithelial cells migrate across basal surface of scab connecting borders
3. fibroblasts migrate along fibrin threads and secrete collagen strengthening clot and blood vessels begin to grow back
4. granulation tissue - tissue under scab
5. fibroblasts trigger endothelial cells surrounding wound to proliferate under scab
6. collagen fibres deposited by fibroblasts in random arrangements
7. blood vessels continue to grow

Question 14

What is the maturation and remodelling phase of soft tissue healing?

Answer 14

– 3 weeks – 6 months
- scab slough off
- collagen more organised
- fewer fibroblasts
- blood vessels restored to normal
- deep wound leads to scarring (fibrosis)

Question 15

State the 4 stages of bone healing

Answer 15

1. haematoma
2. soft callous
3. hard callous
4. remodelling

Question 16

explain first stage of bone healing

Answer 16

haematoma
- collection of clotted blood forming at each end of bons surrounding the soft tissue

Question 17

explain the second stage of bone healing

Answer 17

soft callous
- acute inflammation and accumulation
- macrophages phagocytose the haematoma and small fragments of bone without blood supply (5 days)
- fibroblast migrate, granulation tissue and new capillaries develop

Question 18

explain the third stage of bone healing

Answer 18

hard callous
- new bone forms
- osteoblasts secrete spongy bone uniting broken ends (protect outer layer of bone and cartilage deposits called callus)
- callus develops and matures and is replaced by new bone

Question 19

explain the 4th and final stage of bone healing

Answer 19

remodelling
- reshaping gradually reopens medullary cannel through the callus
- callus tissue replaced with mature compact bone
- stronger and thicker than original so second fracture more likely to occur at a different site