Wound Healing, cell death

Question 1

Types of cells

Answer 1

1. Permanent cells
2. Stable cells
   In G0 phase
   Divide when required
   Mesenchymal cells, PCT, DCT, liver
3. Labile cells
   G1 phase
   Continuously dividing

Question 2

Wound healing types

Answer 2

1. 1° intention:
 Clean, uninfected
 With apposed margins
 No tissue loss
 Eg., surgical incision
2. 2° intention:
 Wound is infected, lacerated
 With tissue loss
 Wound contraction is mediated by myofibroblasts

Question 3

Phases of wound healing

Answer 3

1. Hemostasis: seconds to hours
2. Inflammatory phase:
   Hours to days
3. Proliferative phase: days to weeks
4. Remodelling: weeks to months

Question 4

Features of wound healing wrt time frame

Upto 3 days

Answer 4

0. 0 hour:
 incision filled with blood clot
1. Within 1 day:
 Neutrophils infiltrate the clot
2. Within 2 days:
 Below scab, continuous thin layer of epithelium is formed
3. Day 3:
 Neutrophils replaced by macrophages, early granulation tissue
 Collagen evident at margins of incision

Question 5

Features of wound healing wrt time

From 3 days to 3rd month

Answer 5

Day 5:
 Abundant granulation tissue
 Maximum neovascularisation
 Collagen fibres bridge the incision
2nd week:
 Fibroblast proliferation
 Maximum collagen accumulation
3rd week: scar formation
3rd month:
 70-80% tensile strength regained

Question 6

Factors affecting wound healing

Answer 6

1. Local blood supply
2. Deficiency of vitamin C, Zn, Se
3. Immunosuppression with prolonged healing process (DM, steroid therapy)
4. Foreign body
5. Movement
6. Infection
7. Mechanical factors like pressure, torsion
8. Type of injury

Question 7

Types of collagen

Answer 7

1. Type 1:
 Most abundant with high tensile strength
 Bones, tendons and skin
2. Type 2:
 Cartilage, vitreous humour
3. Type 3:
 Granulation tissue, keloid 
4. Type 4:
 Basement membrane

Question 8

Components of basement membrane

Answer 8

Laminin (most abundant)
Proteoglycan
Type 4 collagen
Fibronectin

Question 9

Enzymes involved in apoptosis

Answer 9

1. Caspases:
 Cysteine proteases which cleave near aspartic acid residues
 Two types:
• initiator (8,9,10)
• executioner (3,6,7)
2. Endonucleases:

Question 10

Endonucleases wrt to apoptosis

Answer 10

Produces internucleosomal cleavage of DNA, producing 180-200 bp fragments
On PAGE (poly acrylamide gel electrophoresis) step ladder pattern is formed

Question 11

BAX and BAK increases permeability of cell membrane via

Answer 11

Formation of BAX-BAK channel between inner and outer mitochondrial membrane

Question 12

How is apoptosome formed

Answer 12

Leaked cytochrome C binds to APAF-1 (apoptosis activating factor-1) to form apoptosome

Question 13

Inhibitor of extrinsic pathway of apoptosis

Inhibitor of intrinsic mechanism of apoptosis

Answer 13

FLIP
Inactivates procaspase 8

IAP
Inactivates procaspase 9

Question 14

Macrophage induced elimination of apoptotic bodies

Phosphatidyl some flip

Answer 14

In an apoptotic cell, the phosphatidyl serine and phosphatidyl ethanolamine (which are usually found in the inner membrane) move to outer membrane which stimulates macrophages

Question 15

Annexin V

Answer 15

Marker for apoptosis

Identified and bind to phosphatidyl serine on the outer surface