W4- Healing And Repair

Question 1

What is the fate of a stem cell?

Answer 1

Either remains as a stem cell to maintain the stem cell pool or differentiates into a specialised cell type

Question 2

What is a uni potent cell? Give an example

Answer 2

Can only produce one type of differentiated cell e.g epithelia

Question 3

What is a multipotent cell? Given an example

Answer 3

Can produce several types of differentiated cells e.g haematopoietic

Question 4

What is a totipotent cell? Give an example

Answer 4

Can produce any type of cell e.g embryonic stem cells

Question 5

What is a labile cell? Give an example.

Answer 5

A cell that continuously divides e.g epidermis

Question 6

What is a stable cell? Give an example

Answer 6

A cell that is mostly in G0 but if stimulated it can enter the cell cycle and undergo mitosis. E.g hepatocytes

Question 7

What is a non-dividing permanent cell? Give an example

Answer 7

A cell that will never enter the cell cycle and divide by mitosis (permanently in G0) e.g a neuron, cardiac myocyte

Question 8

What two factors control regeneration?

Answer 8

Growth factors, contact between BM and adjacent cells

Question 9

What is the role of contact of BM’s in the prevention of cancer?

Answer 9

Contact inhibition- contact inhibits the proliferation of intact tissues. If lost, proliferation may occur and lead to cancer

Question 10

What are the 3 key components of fibrous repair?

Answer 10

Cell migration, blood vessels, ECM production and remodelling

Question 11

Which cells produce the ECM and proteins e.g collagen?

Answer 11

Fibroblasts

Question 12

Why is the development of a blood supply to a wound vital?

Answer 12

To provide access for inflammatory cells and fibroblasts and to bring oxygen and nutrients.

Question 13

What factors initiate angiogenesis?

Answer 13

Pronation enrich factors e.g VEGF

Question 14

Where do new blood vessels come from?

Answer 14

Pre-existing blood vessels sprout new ones

Question 15

What are the 5 key steps of angiogenesis?

Answer 15

Endothelial proteolysis of BM, migration of endothelia via chemotaxis, endothelial proliferation, endothelial maturation and tubular remodelling, recruitment of periendothelial cells

Question 16

What are the 5 key functions of the ECM?

Answer 16

Support and anchor cells, separate tissue compartments, sequestration GF’s, allow communication between cells, facilitate cell migration.

Question 17

Define the term regeneration

Answer 17

The replacement of dead or damaged cells by functional, differentiated cells derived from stem cells

Question 18

How many types of collagen are there?

Answer 18

28

Question 19

What is the basic structure of a collagen unit composed of?

Answer 19

Triple helices of alpha polypeptide chains

Question 20

Which three types of collagen are fibrillar collagen?

Answer 20

Types I-III

Question 21

Which types of collagen are amorphous collagen?

Answer 21

TypesIV-VI

Question 22

Where are collagen alpha chain synthesised and what is the enzyme modification that occurs?

Answer 22

Synthesised in ER.

Vitamin C dependent hydroxylation

Question 23

What happens to collagen synthesis if you have scurvy?

Answer 23

Inadequate Vit C hydroxylation of alpha chains leads to defective helix formation, lack of strength, particularly blood vessels, may heamorhhage

Question 24

What is the collagen defect in Ehlers-Danlos syndrome?

Answer 24

Defective conversion of pro collagen to tropocollagen- stretchy skin

Question 25

What are the 3 stages of fibrous repair?

Answer 25

1)Inflammatory cell infiltration and blood clot formation. 2) clot replacement by granulation tissue. 3) maturation- collagen matures, contracts, remodels- left with fibrous scar

Question 26

What are the main features of healing by primary intention?

Answer 26

Incised wound, apposed edges, minimal clot and granulation tissue, epidermis regenerates and dermis undergoes fibrous repair, sutures out at around 10 days

Question 27

What are the key features of healing by secondary intention? E.g ulcer, abscess, any large wound

Answer 27

Unopposed wound edges, large clot dries to form scab, epidermis regenerates from BASE up, much MORE granulation tissue

Question 28

When comparing primary and secondary intention healing, what are the differences in contraction, scar and healing?

Answer 28

Secondary intention produces more contraction to reduce volume of defect, larger scar, takes longer

Question 29

Briefly outline the process of fracture repair.

Answer 29

Haematoma forms, cellular debris cleared and necrotic tissue, capillaries develop, soft callus goes to hard callus when replaced with woven bone, remodelled to lamellar bone then remodelled for strength

Question 30

List the local factors that effect wound healing

Answer 30

Type, size, location of wound. Lack of movement, apposition. Blood supply. Infection. Foreign material. Radiation damage

Question 31

List the general factors effecting wound healing

Answer 31

Age. Drugs e,g anti inflam. General (protein) and specific dietary deficiencies (Vit C). General state of health and CV status

Question 32

What are the effects of insufficient and excess fibrosis in repair?

Answer 32

Insufficient: Wound ulceration, hernia, dishiscence (rupture)- in obese, old, malnourished, steroid users.

Excess: cosmetic scarring, keloid, cirrhosis, lung fibrosis (coal workers)

Question 33

What are the two features that make a scar keloid?

Answer 33

Excessive collagen production leading to raided scar (hypertrophy) and spills outside wound edges

Question 34

What problems may occur if excessive contraction occurs during wound healing?

Answer 34

Obstruction of tubes and channels (strictures) e.g oesophageal. Limitation of joint movement (contractures)- excess fibrosis

Question 35

What is granulation tissue made up of? What is its function in wound closing?

Answer 35

CT, tiny blood vessels, fibroblasts, fibrin, collagen, elastin- closes wound from BASE up