Regeneration And Repair

Question 1

Which tissue types can regenerate?

Answer 1

Labile cells can- continuously cycling. Stable cells can- left cell cycle but can re-enter. Permanent cells can’t- left cell cycle, can’t re-enter.

Question 2

How does a scar form?

Answer 2

1. Bleeding and Haemostasis- prevention of blood loss (seconds-minutes). 2. Inflammation- acute then chronic, digestion of blood clot (mins to days). 3. Proliferation- of capillaries, fibroblasts, myofibroblasts, extracellular matrix -> granulation tissue (days-weeks).
2. Remodelling- maturation of scar: reduced cell population, increased collagen, myofibroblasts contract -> fibrous scar.

Question 3

Functions of granulation tissue.

Answer 3

Fills the gap, capillaries supply oxygen and nutrients, contracts and closes the defect.

Question 4

What cells are involved in fibrous repair?

Answer 4

Neutrophil and macrophage: phagocytosis and release of mediators. Lymphocyte: eliminate pathogens, co-ordinate other cells. Endothelial cell -> proliferation ->angiogenesis.

Question 5

What are growth factors?

Answer 5

Polypeptides that act on cell surface, causes cell to enter cell cycle and proliferate.

Question 6

Describe primary intention.

Answer 6

Incised wound + apposed edges, minimal clot and granulation tissue, epidermis regenerates and dermis undergoes fibrous repair.

Question 7

Describe secondary intention.

Answer 7

Significant tissue loss + unapposed edges, abundant clot, inflammation and granulation tissue; considerable wound contraction required; dermis requires significant repair, epidermis regenerates from edges.

Question 8

What are the stages of fracture healing.

Answer 8

1. Haematoma surround the injury- granulation tissue. 2. Soft callus- fibrous tissue and cartilage. 3. Hard callus- woven bone gradually organised into lamellar bone. 4. Remodelling- lamellar bone remodeled to original outline of bone.

Question 9

Local factors influencing wound healing.

Answer 9

Size, location, blood supply, local infection, foreign bodies.

Question 10

Systemic factors influencing wound healing.

Answer 10

Age, obesity, anaemia, diabetes, drugs, vitamin deficiencies, malnutrition.

Question 11

What are complications of fibrous repair?

Answer 11

Insufficient fibrosis- would dehiscence. Excessive fibrosis- keloid scar. Adhesions- fibrous bands, can cause obstruction of tubes. Loss of function- replacement of specialised tissue by fibrous tissue. Disruption of architecture. Excessive scar contraction.