Healing and repair

Question 1

What are the major types of cell injury?

Answer 1

Trauma
Thermal injury (hot/cold)
Poisons
Drugs
Infectious organisms
Ischaemia and reperfusion
Plasma membrane failure
DNA damage
Loss of GFs
Ionising radiation

Question 2

What are caustic agents?

Answer 2

Cause rapid local cell death due to their extreme alkalinity or acidity, as well as having corrosive effects.

Question 3

Blockage of cellular respiration?

Answer 3

Cyanide binds to cytochrome oxidase and interrupts oxygen utilisation. Cells with high metabolic requirements are most at risk.

Question 4

Ricin and protein synthesis?

Answer 4

Toxin from the castor oil plant - acts at ribosomal level by inhibiting protein synthesis.

Question 5

What are free radicals?

Answer 5

Atoms or groups of atoms with an unpaired electron. Highly reactive and form chemical bonds.

Question 5

Examples of mechanisms that damage cellular membranes?

Answer 5

Complement-mediated cytolysis
Perforin-mediated cytolysis
Specific blockage of ion channels
Failure of membrane ion pumps
Free radical attack

Question 5

What is responsible for the black appearance of tissues in gangrene?

Answer 5

Deposition of iron sulphide from degraded haemoglobin.

Question 6

What cell populations can be replaced if lost?

Answer 6

Labile and stable cell populations.

Question 7

Healing

Answer 7

Restitution with no, or minimal, residual defect. I.e.: superficial skin abrasion.

Question 8

Repair

Answer 8

There is tissue loss - healing by second intention.

Question 9

Classification of cells based on their renewal:

Answer 9

Labile cells: good capacity to regenerate. (surface epithelium)

Stable cell populations: divide very SLOWLY (hepatocytes)

Permanent: no effective regeneration (nerve cells)

Question 10

Stem cells

Answer 10

Undergo mitotic division - one daughter cells progresses along the differentiation pathways.

Stem cells are extremely vulnerable to radiation.

Question 11

Complete restitution

Answer 11

Loss of part of a labile cell population can be completely restored. Skin abrasion.

Cells proliferate and spread out as a sheet to cover the site: confluent layer is formed it stops CONTACT INHIBITION.

Indistinguishable from normal= healing.

Question 12

Organisation

Answer 12

Repair of specialised tissues by the formation of a fibrous scar.
Occurs by the production of granulation tissue and removal of dead tissue by phagocytosis.

Granulation tissue contract and accumulates collagen to form a scar.

I.e.: pneumonia, infarct.

Question 13

Granulation tissue (aka the combination of myofibroblasts and capillary loops)

Answer 13

A repair phenomenon.
Loops of capillaries supported by myofibroblasts.
Inflammatory cells may be present.
Actively contract to reduce wound size= may result in stricture later.

Question 14

What is a proud flesh?

Answer 14

Excessive granulation tissue protruding from a surface.

Question 15

Incised wound - healing by first intention

Answer 15

Little damage on either side of the cut. Bringing the sides together accurately= healing proceeds with minimum delay.

Question 16

Tissue loss - healing by second intention

Answer 16

Loss of tissue - margins are not apposed.

Phagocytosis to remove debris.
Granulation tissue to fill in defect and repair specialised tissue lost
Epithelial regeneration to cover the surface.

Question 17

Bone healing

Answer 17

Haematoma organised and dead bone removed.
Callus formed - then replaced by trabecular bone.
Finally, bone remodelling.

Question 18

Fracture healing is delayed if…

Answer 18

Bone ends are immobile, infected, very badly misaligned or avascular.

Question 19

Liver

Answer 19

Hepatocytes loss may be followed by complete restitution, but architecture may not.

Question 20

What are the modifying influences to healing?

Answer 20

Age
Vitamin C deficiency - collagen synt
Malnutrition impairs healing
Excess steroids
Advanced malignancy
Local ischaemia
Denervation increases tissue vulnerability.

Question 21

Apoptosis

Answer 21

Active process involving single-cell death.

Occurs in normal and abnormal situations.

The cell membrane is intact and no inflammatory response is elicited.

Question 22

Necrosis

Answer 22

Response to injury, almost always pathological.

Involves a group of cells. Cell membrane integrity is lost and an inflammatory and repair response is common.

Question 23

Coagulative necrosis

Answer 23

Cells are dead but tissue architecture is often preserved in the early stages - tissue softens, heals by fibrosis and scarring.

Question 24

Colliquative necrosis

Answer 24

In the brain - tissue liquifies and heals by cyst formation.

Question 25

Granuloma

Answer 25

Aggregate of epithelioid hystiocytes in some chronic inflammatory disorders.

Question 26

Granulation tissue

Answer 26

Important component of healing= made up of small blood vessels in a connective tissue matrix with myofibroblasts.

Question 27

Stenosis

Answer 27

Narrowing of an orifice, aperture or valve.

Question 28

Stricture

Answer 28

Narrowed tube.

Question 29

First intention healing

Answer 29

No significant tissue loss - edges are close.

Question 30

Second intention healing

Answer 30

Significant loss of tissue - defect is filled by granulation tissue.

Question 31

X-rays

Answer 31

Produced by machines and production can be controlled.

Question 32

Gamma rays

Answer 32

Produced by radioactive decay - protection only by barrier.