2.5 Wound healing Flashcards
What are the two general mechanisms of healing?
Regeneration or repair
What, generally, is regeneration? What is it dependent on?
Replacing damaged tissue with the native tissue
Dependent on the regenerative capacity of the tissue
What are labile tissues? Examples?
Tissues that continuously cycle to regenerate tissue
Small/ large bowel
Skin
Bone marrow
Where are the stem cells in the small and large bowel?
Crypts
Where are the stem cells in the skin?
Stratum basale of epidermis
What are the stem cells in the bone marrow?
Hematopoietic stem cells
What is the CD marker for hematopoietic stem cells?
CD34
What are the stem cells of the lung?
Type II pneumocytes
What are stable tissues?
Tissues that are quiescent, but can reenter cell cycle PRN
What are some examples of stable tissues?
Hepatocytes–compensatory hyperplasia
What are the three permanent tissues in the body?
Myocardium
Skeletal muscle
Neurons
When does repair occur, as opposed to regeneration?
If a tissues lacks regenerative capacity, or if the regenerative stem cells are lost
What material is initially deposited in tissues that lack regenerative capacity? What are the three major components of this?
Granulation tissue:
- Fibroblasts
- Capillaries
- Myofibroblasts
What type of collagen is laid down by fibroblasts with granulation tissue? What is this later replaced with?
Collagen type III initially, followed by type I after collagenases remove type III
What is the role of myofibroblasts in wound repair?
Contract wound edges
What are the enzymes that remove type III collagen in scar to allow for type I collagen to be depositied? What is the cofactor that is needed for these to work?
Collagenases
Zn is the cofactor
What type of signalling is used in regeneration and repair?
Paracrine signalling via growth factors
What is the role of TGF-alpha in the tissue repair process? (2)
Epithelial and fibroblast growth factor
What is the role of TGF-beta in the tissue repair process? (2)
Fibroblast growth factor and inhibits inflammation
What is the role of PDGF in the tissue repair process? (3)
Endothelium repair, smooth muscle repair, and fibroblast growth factor
What is the role of FGF in the tissue repair process? (2)
Angiogenesis and skeletal development
What is the role of VEGF in the tissue repair process?
Angiogenesis
What is primary intention wound healing?
Wound edges are brought together with minimal scar formation
What is healing by secondary intention?
Edges are not approximated–granulation tissue fills the defect
What causes wound to reduce in size?
Myofibroblasts
What is the most common cause of delayed wound healing?
Infection
What vitamin deficiency can cause delayed wound healing? Minerals?
- Vit C
- Cu
- Zn
What is procollagen?
Alpha chains of Gly-X-Y wrapped around each other, prior to crosslinking
What is the usual primary structure of collagen?
{Gly-X-Y | X=proline, Y=lysine}
What is the role of vitamin C in the formation of collagen?
Hydroxylation of proline / K
What is the role of Cu in collagen formation?
Lysl oxidase, an enzyme responsible for cross linking collagen chain, requires Cu as a cofactor
What, generally, is dehiscence?
Rupture of wound, commonly seen after abdominal surgery
What is a hypertrophic scar? What type of collagen is this made of?
Excess production of scar tissue that is localized to the wound
Type I collagen
What is a Keloid? What type of collagen is this comprised of?
Excess production of scar tissue that is out of proportion to the wound
Excessive type III collagen
