Session 4 Lecture Notes Flashcards
What are the 3 processes involved in wound healing?
- Haemostasis
- Inflammation
- Regeneration and repair
What is regeneration of a wound?
Healing without any evidence there was an injury
What is the difference between an abrasion and an ulcer?
Abrasion = lose the top layers of skin (epidermis and part of dermis) Ulceration = injury that led into the submucosa (past epidermis, dermis and mucosa)
In regeneration which cells replicate?
Stem cells
Where are stem cells found in the following places:
epdermis
intestinal mucosa
liver?
epidermis = in the basal layer (adjacent to basement membrane)
intestinal mucosa = in the bottom of the crypts
liver = between the hepatocytes and bile ducts
What are unipotent stem cells?
Stem cells that can only produce 1 type of differentiated cell
eg epithelial cells
What are multipotent stem cells?
Stem cells that can produce several types of differentiated cells e.g. haemopoeitic stem cells in the bone marrow
What are totipotent stem cells?
Embryonic stem cells i.e. can differentiate into any cell
What the 3 types of tissue and which can regenerate?
- Labile tissue = contain short lived cells that are replaced by stem cells eg epithelium
- Stable = low level of replication but if necessary can proliferate eg bone
- Permanent tissue = can’t undergo mitosis and only few stem cells available eg neural tissue
Define fibrous repair
Healing with formation of fibrous connective tissue ie a scar
In necrosis of labile or stable tissue when would fibrous repair and scar formation take place?
Only if collagen framework is destroyed or if there is ongoing chronic inflammation
How many days after an injury would you remove stickers? What phase of healing is this?
After 7-10 days
Early scar is forming
What 3 things do granulation tissue contain?
Developing capillaries
Fibroblasts and myofibroblasts
Chronic inflammatory cells
What cells are responsible for wound contraction?
Myofibroblasts
They produce contractile proteins
Why do scars turn white and stretch?
White because you can’t regenerate melanocytes
Stretch because myofibroblasts can’t lay down elastin
How do you get scurvy?
Vitamin C deficiency
Resulting in inadequate vit C dependent hydroxylation of procollagen alpha chains
Why in scurvy do old scars reopen and bleed?
Collagen turnover is taking place for 2 years in a scar
If you have scurvy = deficiency in collagen formation so scar can break open
What is alport syndrome?
X linked disease = patients usually male
Type 4 collagen is abnormal (which makes up basement membrane )
What genes produce growth factors?
Protooncogenes
They signal for cell to divide and so are important in wound healing
Which cells produce growth factors?
Platelets
Macrophages
Endothelial cells
What is contact inhibition?
Cells don’t like being on their own so will continue to divide until they are touching other cells
Important in wound healing
What is healing by primary intention?
Common for incised, non-infected and sutured wounds
Death of small number of epithelial and CT cells
What is healing by secondary intention?
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
What are 2 complications of fibrous repair?
- Formation of adhesions - fibrous tissue that forms between tissues and organs following surgery (scar tissue that connects tissues not normally connected
- Loss of function - specialised cells replaced with non-specialised cells or scar tissue
