Healing and repair

Question 1

Define healing and give the 3 processes

Answer 1

Healing is the process by the body replaces destroyed or dead tissue by living tissue

The process may take place in a number of ways :

1.Resolution
Complete restoration to normal both structurally and functionally

2.Regeneration
The proliferation of parenchyma cells with some loss of normal architecture

3.Organization
Lost/damaged tissue replaced by granulation and fibrous repair

For the resolution to take place the framework of the tissue must have been preserved.

Regeneration and organization occur together ,if the framework is lost, normal architecture may not be restored

Question 2

Discuss the 3 types of different cell capacities

Answer 2

1. labile cells
   * Cells that are constantly multiplying to replace damaged cells eg skin cells ,epithelial cells that line hallow organs eg stomach ,bone marrow haemopiotic cells
2. stable cells
   * Cells that have the capacity to regenerate but normal cells must be left behind after insult for generation to take place .
   * They normal divide slow but they can rapidly divide in response to a stimuli to restore the tissue of origin eg liver ,kidney , pancreases, smooth muscles and fibroblasts
3. Permanent cells :
   * cells that do not have the capacity to under go mitosis eg neuron ,heart and skeletal muscles .Damage to these tissue result in healing by replacement by fibrous scar tissue

Question 3

What are stem cells

Answer 3

• Cells that are lost through injury ,are usually replaced from the stem cell pool present in labile and stable tissue
• When stem cells undergo division ,one of the daughter cells will undergo differentiation according to the needs of tissue ,while the other retain the stem cells characteristics
• Stems cells are usually the minority and are located in discrete places
• The ability of a stem cell to regenerate is dependent on the integrity of the stem cell population eg stable and labile tissue have a high stem cell activity .

Stem cells are sensitive to radiation which can cause mutation in the stem cell daughter cell ,resulting in neoplastic transformation

Question 4

Repair by healing ,scar formation and fibrosis

Answer 4

*If repair cannot be accomplished by regeneration alone ,it occurs by replacement of the injured cells with connective tissue leading to formation of a scar or by combination of regeneration ad some residual cells and scar formation

when does scarring ?

• scaring may occur if the injured tissue is severely damaged or chromic ,resulting in damage of the parenchyma cells and epithelial cells as well as the connective tissue framework or if dividing cells are damaged
• In contrast to regeneration , which restores the tissue components ,scar formation is a response that patches rather than restore tissue

*define scrar
Healing of a wound but it also refers to the replacement of parenchyma by collagen

Question 5

Granulation tissue

Answer 5

• Repair begins early in inflammation
• If resolution has not occurred ,fibroblast and vascular endothelial cells begin to proliferate to form granulation tissue
• Skin beneath the skin wound
• its histological appearance is characterized by proliferation of the fibroblasts and new vessels

*Amount of granulation tissue depends on the size of the tissue defects

Question 6

List the 3 components of a granular tissue

Answer 6

1. Mucin-rich ground substance
2. Endothelial cells / capillaries
3. fibroblats

Question 7

tissue

Answer 7

• As collagen is laid down and fibrosis proceeds ,many of the blood vessels will thrombose and degenerate
• Maturation and reorganization of the connective tissue produces a pale and avascualr fibrous scare

Question 8

Healing of cutaneous wounds

Answer 8

*This process involves both regeneration of epithelial cells and formation of connective tissue scar

Question 9

Healing first by intention

Answer 9

when the injury involves the epithelial layer ,the principle mechanism of repair is epithelial tissue regeneration

Question 10

Healing by second intention

Answer 10

*Healing of skin wounds and wounds has separated edges
*Inflammation is intense
+development of granulation tissue
+Accumulation of ECM and the process is slower
*results in formation of a large scar and wound contraction by action of myofibroblats occurs

Question 11

How does secondary healing differ from primary healing

Answer 11

• In 2dary healing
• wounds cause a large tissue deficits and the fibrin clot is larger
• Inflammation is intense
• Larger amounts of granular tissue
• dermal appendage is permanently lost

Question 12

Factors affecting wound healing

Answer 12

1. Local
   * infection
   * foreign body
   * hypoxia
   * too much movement
   * irradaiation
   * corticosteriods
   * size of wound
2. Systemic
   * age
   * inadequate nutrition
   * diabetes mellitus
   * corticosteroids

Question 13

Complications of wound healing

Answer 13

1.infections
2.Overgrowth of granulation tissue preventing re-epithelialisation (“proud flesh”).
Cicatrisation (excessive contraction of a scar)
Skin deformity
Obstruction of a hollow organ e.g. – oesophagus
Contraction of scarred heart valves leading to stenosis.
Keloid formation
Excess production of mature collagen forming a lump in the scar.
Pain
As a result of a neuroma formed by proliferating nerve fibres caught up in the wound.
Weakness
Due to decreased tensile strength of fibrous scar tissue e.g. incisional hernia
Malignant transformation
Chronic scarred ulcers e.g. Chronic leg ulcers.