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Flashcards in Responses To Cell And Tissue Injury Deck (49):
1

What is necrosis?

Necrosis is the death of tissues following bioenergetic failure and loss of plasma membrane integrity

2

What does necrosis do?

+ Pathological process

+ Often invokes an inflammatory response and repair

+ Often affects solid mass of tissue

3

What types of necrosis are there?

+ Coagulative
+ Colliquative
+ Caseous
+ Gangrene
+ Fibrinoid
+ Fat

4

What are features of coagulative necrosis?

+ The most common type

+ Involves coagulation of cellular proteins

+ Initially firm but later soft

+ Microscopically
-appearances develop over time
- ghost outlines of cells
- inflammatory response

5

What are features of colliquative necrosis?

+ In the brain

+ Liquefaction with formation of cystic spaces occurs

+ Proteolysis dominates over coagulation

6

What is caseous necrosis?

+ Characteristic of tuberculosis

+ There is pale yellow semi-solid material

7

What are features of gangrenous necrosis?

+ Necrosis with putrefaction
- wet and dry forms
- gas gangrene due to C perfringens

+ Follows vascular occlusion or certain infections

+ Black

8

What are features of fibrinoid necrosis?

+ Microscopic feature in arterioles

+ Most commonly associated with 'malignant' hypertension

+ Histological phenomenon

9

What are features of fat necrosis?

+ May occur following direct trauma and cause a mass,

+ May follow pancreatitis visible as multiple white spots (enzymatic lysis)

+ Related to death of fat cells

10

When does necrosis occur?

Necrosis occurs when a cell is damaged by an external force such e.g toxins, trauma, infection or ischaemia

11

What is apoptosis/PCD

The death of cells which occurs as a normal and controlled part of an organism's growth or development.

12

How does apoptosis differ from necrosis?

Necrosis is the premature death of living cells and tissues caused by factors external to the cell/tissue.

Apoptosis is programmed and a healthy, natural process:
+ removes a cell discreetly
+ takes our individual cells rather that groups of tissue
+ minimal fuss
+ preserves function as best as possible

13

What's the difference between apoptosis and Programmed Cell Death (PCD)?

Apoptosis is morphological; PCD is intent

14

Name some examples of apoptosis/PCD

+ Embryology: lumen of tubes
+ Growth signal response: menstrual cycle
+ Inflammation: resolution, death of neutrophils
+ Immune defence: T and Killer cell responses
+ Tumour prevention: prevent mutation
+ Autoimmune disease: self destruct
+ HIV/AIDS - HIV and activated T cell death

15

What are the types of abnormal apoptosis?

+ Reduced apoptosis

+ Increased apoptosis

16

Give examples of reduced apoptosis

+ Neoplasia

+ Autoimmune disease

+ Viral infection

17

Give examples of increased apoptosis

+ Neurodegenerative disorders

+ HIV infection of T lymphocytes

18

Apoptosis vs Necrosis: Induction

Apoptosis: physiological or pathological

Necrosis: pathological

19

Apoptosis vs Necrosis: Extent

Apoptosis: single cells

Necrosis: cell groups

20

Apoptosis vs Necrosis: Biochemical Events

Apoptosis: energy-dependent fragmentation of DNA

Necrosis: abnormal ion homeostasis

21

Apoptosis vs Necrosis: Cell Membrane Integrity

Apoptosis: maintained

Necrosis: lost

22

Apoptosis vs Necrosis: Morphology

Apoptosis: cell shrinkage and fragmentation

Necrosis: cell swelling and lysis

23

Apoptosis vs Necrosis: Inflammatory Response

Apoptosis: none

Necrosis: usual

24

Apoptosis vs Necrosis: Fate of dead cells

Apoptosis: phagocytosed by neighbouring cells

Necrosis: phagocytosed by inflammatory cells

25

What is pyroptosis?

+ Highly inflammatory form of programmed cell death

+ Occurs most frequently upon infection with intercellular pathogens

+ Likely to form part of the
antimicrobial response

+ Part apoptosis but then necrosis

+ Associated with Salmonella infection

26

What happens to cells after injury?

+ Death

+ Healing

+ Repair

27

What is healing?

The restitution with no/minimal residual defect

E.g superficial skin abrasion, incised wound healing by first intention

28

What is the difference between hearing and repair?

+ Healing is complete resolution

+ Repair is necessary when there is tissue loss: healing by second intention (second best option)

29

What three types of cell populations are there?

+ Labile

+ Stable

+ Permanent

30

What are features and examples of labile cells?

+ continuous regeneration

+ short lifespan

+ Skin, blood, gut

31

What are features and examples of stable cells?

+ Few divisions

+ Spend most of the time in the quiescent G0 phase of the cell cycle

+ Only multiply/repair when needed/ injured

+ Liver, Kidney, endocrine glands

32

What are features and examples of permanent cells?

+ Cannot regenerate once injured

+ Brain/neurones, skeletal muscle

33

What is organisation?

+ Repair of specialised tissue by formation of a scar

34

What does organisation involve?

+ Formation of granulation tissue

+ Removal of dead tissues by phagocytosis

+ Wound contraction and scarring

35

Describe the process of healing by first intention (wound with opposed edges)

1. Limited cell death
2. Basement membrane disrupted
3. Incisional space fills with blood
4. Scab forms
5. Neutrophils move towards the clot
6. Epidermis thinkers at its cut edges
7. Epidermal cells migrate among cut margins if the dermis
8. Epithelial cells fuse in midline beneath surface scan
9. Day 3 neutrophils largely replaced by macrophages
10. Day 5 granulation tissue invades incision space
11. Collagen fibres bridge the incision
12. Epidermis recovers to normal thickness

35

What happens during the second week of healing by first intention? (Wound with opposed edges)

+ Proliferation of fibroblasts

+ Collage accumulation

+ Leucocytes infiltrate, oedema reduced

+ Vascularity virtually disappeared

35

What happens by the end of the first month of healing by first intention? (Wound with opposed edges)

+ Scar consists of cellular connective tissue

+ Tensile strength now increases

36

Describe healing by second intention (wounds with separated edges) compared to first intention

+ Extensive cell loss
+ Common denominator is large tissue defect that must be filled
+ Large defects
- more fibrin
- more necrotic tissue
- inflammatory reaction more intense
+ Much larger amounts of granulation tissue
+ Wound contraction plays an important role in reducing size of defect

37

What most clearly differentiated healing by first intention and healing by second intention?

Wound contraction

38

What are the stages of bone healing?

+ Repair

+ Remodelling

+ Resolution

39

What are the steps involved in liver healing/repair?

+ Necrosis

+ Regeneration

+ Fibrous scarring

+ Architectural disruption

40

What is the wound strength process?

+ Sutures removed end of week 1
+ Strength 10% of unwounded skin
+ Strength increases rapidly over the following 4 weeks
+ Rate of increase slows
+ By third month strength at 70-80%
+ Full strength may not be recovered

41

What are the systemic factors that influence wound healing?

AGE: delayed healing in old and very young

NUTRITION: affects proteins and collagen synthesis

METABOLIC STATUS: healing delayed in diabetics

CIRCULATORY STATUS: adequate blood supply essential

HORMONES: glucocorticoids are anti-inflammatory but impair collagen synthesis

42

What are the local factors that influence wound healing?

INFECTION: most important cause of healing delay

MECHANICAL FACTORS: early movement of wounds delays healing

FOREIGN BODIES: e.g sutures or glass

SIZE/LOCATION/TYPE OF WOUND: wounds heal better in richly vascularised areas

43

What are some types of abnormal wound repair?

+ Deficient scar formation
- dehiscence
- ulceration

+ Excessive formation of repair components
- keloid scar

+ Formation of contractures
- exaggerated contraction
- deformity if the wound and surrounding tissues

44

What are the effects of scarring?

+ Functionally imperfect

+ Provides permanent patch

+ Allows surrounding tissue to continue to function

45

What sort of problems might scarring cause?

+ Cosmetic

+ Functional
- site e.g stricture
- size e.g healed myocardial infarct

46

Define keloid scars.

Excessive fibroblast proliferation and collagen production.

47

What processes are involved in sublethal injury?

+ Hydropic change/ oncosis
+ Fatty change/ steatosis
+ Reversible

Over longer time:
+ Autophagy
+ Atrophy