Session 4 Lecture Notes

Question 1

What are the 3 processes involved in wound healing?

Answer 1

1. Haemostasis
2. Inflammation
3. Regeneration and repair

Question 2

What is regeneration of a wound?

Answer 2

Healing without any evidence there was an injury

Question 3

What is the difference between an abrasion and an ulcer?

Answer 3

Abrasion = lose the top layers of skin (epidermis and part of dermis)
Ulceration = injury that led into the submucosa (past epidermis, dermis and mucosa)

Question 4

In regeneration which cells replicate?

Answer 4

Stem cells

Question 5

Where are stem cells found in the following places:
epdermis
intestinal mucosa
liver?

Answer 5

epidermis = in the basal layer (adjacent to basement membrane)
intestinal mucosa = in the bottom of the crypts
liver = between the hepatocytes and bile ducts

Question 6

What are unipotent stem cells?

Answer 6

Stem cells that can only produce 1 type of differentiated cell
eg epithelial cells

Question 7

What are multipotent stem cells?

Answer 7

Stem cells that can produce several types of differentiated cells e.g. haemopoeitic stem cells in the bone marrow

Question 8

What are totipotent stem cells?

Answer 8

Embryonic stem cells i.e. can differentiate into any cell

Question 9

What the 3 types of tissue and which can regenerate?

Answer 9

1. Labile tissue = contain short lived cells that are replaced by stem cells eg epithelium
2. Stable = low level of replication but if necessary can proliferate eg bone
3. Permanent tissue = can’t undergo mitosis and only few stem cells available eg neural tissue

Question 10

Define fibrous repair

Answer 10

Healing with formation of fibrous connective tissue ie a scar

Question 11

In necrosis of labile or stable tissue when would fibrous repair and scar formation take place?

Answer 11

Only if collagen framework is destroyed or if there is ongoing chronic inflammation

Question 12

How many days after an injury would you remove stickers? What phase of healing is this?

Answer 12

After 7-10 days

Early scar is forming

Question 13

What 3 things do granulation tissue contain?

Answer 13

Developing capillaries
Fibroblasts and myofibroblasts
Chronic inflammatory cells

Question 14

What cells are responsible for wound contraction?

Answer 14

Myofibroblasts

They produce contractile proteins

Question 15

Why do scars turn white and stretch?

Answer 15

White because you can’t regenerate melanocytes

Stretch because myofibroblasts can’t lay down elastin

Question 16

How do you get scurvy?

Answer 16

Vitamin C deficiency

Resulting in inadequate vit C dependent hydroxylation of procollagen alpha chains

Question 17

Why in scurvy do old scars reopen and bleed?

Answer 17

Collagen turnover is taking place for 2 years in a scar

If you have scurvy = deficiency in collagen formation so scar can break open

Question 18

What is alport syndrome?

Answer 18

X linked disease = patients usually male

Type 4 collagen is abnormal (which makes up basement membrane )

Question 19

What genes produce growth factors?

Answer 19

Protooncogenes

They signal for cell to divide and so are important in wound healing

Question 20

Which cells produce growth factors?

Answer 20

Platelets
Macrophages
Endothelial cells

Question 21

What is contact inhibition?

Answer 21

Cells don’t like being on their own so will continue to divide until they are touching other cells
Important in wound healing

Question 22

What is healing by primary intention?

Answer 22

Common for incised, non-infected and sutured wounds

Death of small number of epithelial and CT cells

Question 23

What is healing by secondary intention?

Answer 23

Infected wounds with tissue loss
Open wound can be filled by abundant granulation tissue
It heals in same way as primary intention but takes longer and leaves a significant scar

Question 24

What are 2 complications of fibrous repair?

Answer 24

1. Formation of adhesions - fibrous tissue that forms between tissues and organs following surgery (scar tissue that connects tissues not normally connected
2. Loss of function - specialised cells replaced with non-specialised cells or scar tissue