Week 2 - Tissue Injury And Repair

Question 1

What can happen when cell adaptation occurs?

Answer 1

• increased demand/stimulation –> hypertrophy, hyperplasia
• decreased nutrients/stimulation –> atrophy
• chronic irritation –> metaplasia

Question 2

What type of stimuli stimulates cellular injury?

Answer 2

Acute and transient

E.g. Hypoxia, chemical injury, microbial infection (reversible or irreversible injury)

Question 3

Name some causes of cellular injury

Answer 3

Hypoxia, physical agents, chemical agents, infectious agents, immunologic reactions, genetic derangements, nutritional imbalances

Question 4

What are the mechanisms of cellular injury?

Answer 4

• ATP depletion
• mitochondrial damage
• increased intracellular Ca2+
• oxidative stress
• membrane damage
• DNA and protein damage

Question 5

What is tissue regeneration?

Answer 5

-complete reconstitution

• tissues with high proliferative capacity
• requires viable stem cells and intact connective tissue scaffolding

Question 6

What is tissue repair?

Answer 6

• combination or regeneration and scar formation
• relative contribution of 2 processes depends on capacity to regenerate, extent of injury, and extent of scarring/fibrosis

Question 7

What is the fibro-proliferative response?

Answer 7

• deposition of collagen and ECM components (scar)

- “patches” tissue

Question 8

What does persistent damage of cells lead to?

Answer 8

Chronic inflammation then fibrosis (scar tissue formation)

Question 9

What is the sequence of healing?

Answer 9

• inflammation
• angiogenesis/neovascularisation
• migration and proliferation of parenchymal cells and fibroblasts
• scar formation
• connective tissue remodelling

Question 10

What are the local factors that effect wound healing?

Answer 10

• size
• location (how well vascularised)
• type (infection/necrotic/traumatic)
• infections, mechanical forces, foreign bodies delay healing

Question 11

What are the systemic factors that effect wound healing?

Answer 11

• nutritional status
• metabolic status (e.g. Diabetes mellitus)
• circulatory/vascular status
• hormones (e.g. Glucocorticoids)

Question 12

What are some complications of repair?

Answer 12

• deficient scar formation (wound dehiscence)
• excessive repair (excessive granulation tissue (proud flesh), excessive collagen accumulation - hypertrophic scar, keloid)
• formation of contracture e.g. Due to burn injury

Question 13

What is tissue injury?

Answer 13

• excessive physiologic stresses or adverse pathological stimuli –> leading to adaptation, reversible injury, irreversible injury + cell death