Body Response To Tissue Damage: Healing And Repair

Question 0

Wound healing 2

Answer 0

Day 2
Late inflammation
Macrophages begin to infiltrate incisional space and demolish fibrin
Surface continuity is re-established in a thin surface layer

Question 1

Stages of wound healing 1)

Answer 1

Neutrophils appear at the margins of the incision
Acute inflammatory response-> platelets-> Chemokines
Swelling pain and redness
Exudate neutralises damage and initiates organisation
Epithelial cells undergo mitosis and migrate across wound

Initial vasoconstriction the vasodilation via prostaglandins, thrombin
Fibrin initiates coagulation

Question 2

Wound healing 3

Answer 2

Day 3
Granulation tissue begins to invade tissue space
Fibroblasts lay down collagen
Surface continuity is reinforced by thickening of epithelial layer

Question 3

Wound healing 4

Answer 3

Day 5
Incisional space filled with vascular granulation tissue
Collagen is deposited
Surface epithelial becomes normal thickness
Acute inflammatory response is reduced

Question 4

Wound healing 5

Answer 4

Day 7
Wound has 10% of tensile strength
Remove sutures

Question 5

Wound healing 6

Answer 5

Day 10
Further fibroblast proliferation and collagen deposition
Adds strength to the wound

Question 6

Wound healing 7

Answer 6

Day 15
Collagen deposition follows the lines of tissue stress
Granulation tissue looses some vascularity

Question 7

Wound healing 8

Answer 7

Wound has 50% of tensile strength

Question 8

Wound healing 9

Answer 8

3 months
Wound achieves 80% of tensile strength
Only marginally more vascular than normal skin-> removed in coming months to become white
Remodelling occurs

Question 9

Five key events in wound healing

Answer 9

Angiogenesis-> local vessels form-> basic fibroblast growth factor
Mitogenesis-> divide to form fibroblasts and myoblasts-> platelet derived and basic fibroblast growth factor
Chemotaxis and motility-> migration-> platelet derived and basic growth factor
Fibrogensis-> secrete collagen-> transforming growth factor, IL-1, tumour necrosis factor
Remodelling-> collagen degrading enzymes produced

Question 10

Adverse effects of acute inflammation

Answer 10

May cause the symptoms
-> meningitis, croup/diphtheria, pericarditis, pleurisy, peritonitis
Pleurisy-> painful because exudate is fibrinous
Meningitis-> Purulent exudate fills space in the pia-> raised intracranial pressure-> microthrombosis in small vessels

Question 11

Adverse effects of chronic inflammation/scars

Answer 11

Chronic inflammation always heals by a scar
Scars are functionless
Strong but not-> elastic, contractile, secretory, absorptive or pretty

Question 12

Factors leading to inadequate healing

Answer 12

Continuing infection
Foreign or uncleared necrotic material 
Ischaemia
Diabetes
Denervation
Steroid therapy
Previous irradiation

Question 13

Healing of brain necrosis or infarction

Answer 13

Brain parenchyma doesn’t contain fibroblasts-> can’t make collagen
Instead undergoes liquification
Phagocytosis-> following cell death removal of damaged cells by phagocytotic resident microglial cells, supplemented by monocytes from the blood
Gliosis-> astrocytes become activated-> proliferate to fulfil metabolic roles in protecting neurones
Damaged areas replaced by astrocyte proliferation-> glial scar

Question 14

Bone healing

Answer 14

Collagenous scar isn’t strong enough

Bone needs to be replaced by bone

Question 15

Stage of bone healing 1

Answer 15

Due to tearing of blood vessels a blood clot forms in the defect
Contains necrotic bone and marrow
Haematoma extends in to soft tissue around the bone
Phagocytosis of debris

Question 16

Bone healing 2

Answer 16

Haematoma undergoes organisation (like exudate)
Associated with migration of neutrophils and macrophages
Followed by in growth of capillaries and fibroblasts-> fibrovascular granulation tissue
Osteoprogenitor cells develop from mesenchymal precursors

Question 17

Bone healing 3

Answer 17

Osteoprogenitor cells produce osteoblasts-> deposit large quantitiesd of osteoid collagen in a haphazard way-> calcifies to woven bone
External callous bridges the fracture outside the bone, may include cartilage
Internal callous bridges the fracture in the medullary cavity
Direct ossification between fracture ends occurs

Question 18

Bone healing 4

Answer 18

Woven bone is mechanically weak
Remodelling occurs one the two bone ends are bridged by a bonŷ callus-> takes months
Osteoclastic erosion and organised osteoclastic osteoid synthesis-> lamellar bone

Question 19

Bone healing 5

Answer 19

With time remodelling creates new lamellar trabecular bone
Orientated in direction determined by stress
Cortical irregularity, minor marrow space and muscle scar left