Stages of Tissue Injury & Repair

Question 1

What is inflammation?

Answer 1

The body’s protective response to an irritant or injury that prepares for healing.

Question 2

What are the five signs of inflammation?

Answer 2

calor
tumor
rubor
dolor
functio laesa

Question 3

What are the three phases of tissue repair?

Answer 3

acute inflammation
repair
remodeling

Question 4

What is the time frame of acute inflammation and what is its purpose?

Answer 4

Up to 2-3 days

defend against infection, dispose of dead tissue, immobilize injury, compartmentalize damage

Question 5

What are the neurologic events of acute inflammation?

Answer 5

Initial transitory and reflexive vasoconstriction (30s) with gradual vasodilation and onset of bleeding.

Question 6

What are the hemodynamic events of acute inflammation?

Answer 6

Vasoconstriction via norepinephrine and serotonin
Vasodilation via histamine and prostaglandins
Hemostasis (slowing of blood flow) via clotting
Neutrophilic migration
Permeability changes in very small vessels allow plasma to leak, causing edema and allowing tissue repair to start

Question 7

What are the cellular events of acute inflammation?

Answer 7

Mast cells in the tissue release histamine, which increases vasodilation and permeability, and heparin, an anticoagulant.
Basophils secrete anticoagulants and neutrophils phagocytose bacteria
Monocytes arrive after 5 hours and clean up

Question 8

What are the chemical events of acute inflammation?

Answer 8

Over 180 chemicals released from damaged cells, leukocytes, and platelets
serotonin: vasoconstrictor
heparin: temporary anti-coag
histamine: vasodilator, increases permeability
bradykinins: increase permeability and pain
prostaglandins

Question 9

What is the time frame of the repair phase?

Answer 9

Starts at 24hr and lasts up to 6 weeks

Question 10

What are the physiological events of the repair phase?

Answer 10

Formation of granulation tissue
Fibroplasia
Scar formation and contraction

Question 11

What is granulation tissue?

Answer 11

Highly vascular gel-like matrix of collagen, hyaluronic acid, and fibronectin.
Framework for scar

Question 12

Describe fibroplasia.

Answer 12

Begins within hours of injury.
Fibroblasts secrete collagen and GAG. Type III collagen is deposited randomly, eventually replaced with tougher Type I.
Myofibroblasts migrate to wound and secrete scar tissue.

Question 13

Describe wound contraction.

Answer 13

Beings once scar is laid down by myofibroblasts, about 4 days after injury, and can last 6-12 months.
After 6 weeks, wound size reduced 5-10%

Question 14

What is the purpose of the remodeling phase?

Answer 14

Reorganize the collagen laid down in repair phase to increase resilience of damaged tissue.

Question 15

What happens during the remodeling phase?

Answer 15

Collagen fibers (originally laid down at random) are reoriented into alignment with the tensile forces acting on the muscle.

Question 16

What are intrinsic factors that delay healing? (7)

Answer 16

age
chronic disease
blood supply
nutrition
neuropathy
nature of tissue
degree of damage

Question 17

What are extrinsic factors that delay healing? (5)

Answer 17

degree of immobilization
immune suppression
infection
irradiation
psychophysiologic stress

Question 18

What are iatrogenic factors that delay healing? (2)

Answer 18

medications

ischemia

Question 19

What healing potentials characterize the various soft tissues?

Answer 19

cartilage: limited b/c avascular
ligaments: slow healing due to low blood supply
skeletal muscle: same as other vascular tissues, forms collagen scar
nerve: peripheral-fair, depending on degree of damage
central-poor