Healing and repair

Question 1

What are the two main factors in tissue repair?

Answer 1

Parenchymal cell regeneration

Repair by connective tissue (fibrosis)

Question 2

What are the two methods of healing?

Answer 2

Resolution where tissues reform themselves

Repair invloves healing the tissue by scarring

Question 3

Describe parenchymal cell regeneration?

Answer 3

Stem cells in the epidermis and stable cells e.g. fibroblasts can replicate.
Permanent cells cannot replicate e.g. cardiac cells and are replaced by scar tissue
Cell regeneration depends on factors that stimulate parenchymal cell division

Question 4

What is required for the cells to restore to normal?

Answer 4

An intact basement membrane and a relatively intact ECM

Question 5

Describe repair by connective tissue e.g. fibrosis?

Answer 5

Occurs when the injury is severe or persistent
First requires neutrophil migration to liquefy injured tissue and then macrophage transmigration to remove debris
THen requires formation of granulation tissue
Type III collagen is produced and then dense scar tissue is produced by the granulation tissue containing the type III collagen
Remodelling occurs to increase the tensile strength of the scar and then matrix metalloprotinases replace the type III collagen with type I that is stronger

Question 6

What is primary intention of wound healing?

Answer 6

The wound edges are reapproximated and the wound will heal cleanly. This can occur naturally through wound contraction or through suturing.

Question 7

What is wound healing by secondary intention?

Answer 7

This involves a more intense inflammatory reaction than in primary intention. Results in increased granulation tissue and contraction leading to more scarring

Question 8

What is wound healing by tertiary intention?

Answer 8

contaminated wound that is treated with debridement of topical or systemic antibiotics

Question 9

What are the main factors that impair healing?

Answer 9

persistent infection e.g. staph aureus most common if MRSA usually use vancomyocin
Diabetes mellitus
Nutritional deficiencies
Glucocorticoids - interfere with collagen formation and used topically to treat keloid scars
Keloid or hypertrophic scars

Question 10

How does regeneration occur in the liver?

Answer 10

With mild injury the hepatocytes regenerate

In more severe injury the portal triads are lost in the regenerative nodules