MoD Session 4- Healing And Repair

Question 0

What can’t damage be in order for regeneration to occur?

Answer 0

Extensive

Question 1

What is regeneration/resolution?

Answer 1

The growth of cells and tissues to replace dead/damaged tissue.

Question 2

What are stem cells?

Answer 2

Cells with a prolonged proliferative activity that show asymmetric replication.

Question 3

What is asymmetric replication?

Answer 3

Where one daughter cell remains a stem cell, whilst the other differentiates into a mature, non-dividing cell.

Question 4

Define unipotent

Answer 4

Where a cell can give rise to only one type of adult cell.

Question 5

Define multipotent.

Answer 5

Where a cell can give rise to multiple types of cell.

Question 6

Define totipotent.

Answer 6

When a cell can give rise to any type of cell.

Question 7

Give an example of a unipotent cell.

Answer 7

Epithelia

Question 8

Give an example of a totipotent cell.

Answer 8

Embryonic stem cells

Question 9

What are labile tissues? Give an example.

Answer 9

They are continuously dividing tissues that contain short lived cells that are continuously being replaced by rapid proliferation of stem cells.
Epithelia.

Question 10

What are permanent tissues?

Give an example.

Answer 10

They are non-dividing tissues that contain cells that have already left the cell cycle. There may be some stem cells present, but they can’t generate an effective proliferative response.
Neurones, cardiac myocytes

Question 11

What are stable tissues?

Give an example.

Answer 11

They are tissues that normally have a low level of replication, but the mature and stem cells present can be induced to more rapidly proliferate, if necessary.
Osteoblasts, fibroblasts, hepatocytes.

Question 12

What is fibrous repair and when does it occur? (3)

Answer 12

It is replacement of functional tissue with fibrous tissue because normal regeneration can’t occur.
It occurs when: the collagen framework is destroyed, there is chronic inflammation, there is necrosis of parenchymal cells.

Question 13

What is the five step process of fibrous repair?

Answer 13

1. Phagocytosis-of necrotic debris
2. Angiogenesis-formation of small capillaries due to endothelial cell proliferation
3. Granulation tissue formation- fibro and myofibroblasts synthesis collagen
4. Fibrous scar formation- granulation tissue becomes less vascular.
5. Maturation- fibrils contract

Question 14

Give examples of local and systemic factors that affect healing and repair.

Answer 14

Local- size, location and type of wound; blood and nerve supply; infection; necrotic tissue; mechanical stress
Systemic- age; hypoxia, hypovalaemia; obesity, diabetes; genetic disorders; malnutrition; drugs; vitamin deficiencies.

Question 15

How do cells communicate to produce a fibroproliferative response? (3)

Answer 15

• local mediators
• hormones
• cell-cell/cell-stroma contact

Question 16

What are the three forms of communication?

Answer 16

• autocrine- when cells respond to a signal that they have produced.
• paracrine- when adjacent cells respond to a signal produced by a cell.
• endocrine- when hormones are secreted into the blood stream.

Question 17

What are growth factors? What do they do?

Answer 17

Polypeptides coded for by proto oncogenes that act on specific cell surface receptors.
They stimulate cell proliferation or inhibition.

Question 18

What can growth factors effect besides proliferation/ inhibition of cells? (6)

Answer 18

• locomotion
• contractility
• angiogenesis
• activation
• viability
• differentiation

Question 19

What is the idea of contact inhibition?

Answer 19

That normal cells, when isolated from others, replicate until they have other cells touching them.
Cells adhere to each other using the adhesion molecule cadherin; and to ECM by integrin.
A loss of cell contact therefore promotes proliferation.

Question 20

When does healing by primary intention occur?

Answer 20

When the wound is incisional, closed, sutured and not infected.
I.e clean wounds with opposed edges.

Question 21

Which method of healing heals with more scarring?

Answer 21

Secondary intention

Question 22

Describe the 6 stages of primary intention healing.

Answer 22

• haemostasis- severed arteries contract and the space fills with clotted blood, so a scab forms and the wound is sealed off from the environment.
• inflammation - neutrophils appear
• cell migration- macrophages appear, activate and secrete cytokines, which attract fibroblasts and endothelial cells. Deposits of basement membrane are laid by the epithelial cells.
• regeneration- macrophages replace neutrophils and granulation tissue forms. Epithelial cells proliferate, causing the scab to come off. Collagen has been produced and angiogenesis continues.
• scarring- collagen produced by fibroblasts forms a scar.
• scar maturation- blood vessels disappear and the scar becomes white.

Question 23

When does healing by secondary intention occur?

Answer 23

In excisional, open, unopposed wounds, with tissue loss/infection.

Question 24

How is secondary intention different to primary intention healing? (3)

Answer 24

There is more scarring
Thinner epidermis
Takes longer

Question 25

How does cardiac tissue heal?

Answer 25

Limited regeneration and scar tissue follows an MI, which can compromise function.

Question 26

How does liver heal?

Answer 26

It regenerates. If part of liver is removed, the lobes will enlarge in order to restore the liver to its original mass.

Question 27

How do peripheral nerves heal?

Answer 27

Axons of severed nerve degenerates, but their stumps sprout and elongate. They are guided back to the tissue they innervated by Schwann cells.

Question 28

Why doesn’t cartilage heal well? (3)

Answer 28

It lacks blood, lymph and nervous supply.

Question 29

How does the CNS repair?

Answer 29

Because it is a permanent tissue, it repairs by neural tissue being replaced by glial cells.