Healing and repair - 2

Dr H.M.D.Moratuwagama

Dept of Pathology

Complications of cutaneous wound healing

1)Deficient scar formationWound dehiscence / ulceration

2.Incisional Hernia

I

3.a)Hypertrophic scar

3.b)Keloid

•What is the difference between a hypertrophic scar and a keloid?

Hypertrophic scar is raised, erythematous, and remains within the boundaries of the original trauma or wound. A keloid, on the other hand, extends beyond the confines of the wound and is more nodular. 

3.c)Exuberant granulation

4)Excessive contraction Formation of contractures

5.Implantation cyst

6.Marjolin's ulcer

Complications of cutaneous wound healing

1)Deficient scar formation• Wound dehiscence / ulceration2) Incisional hernia3)Formation of excessive amount of repair componenta)Hypertrophic scarb)Keloid formationc)Exuberant granulation 4)Excessive contraction Formation of contractures5) Implantation cyst6) Rarely – neoplasia may develop Squamous cell carcinoma following burns

Healing in specialized tissue

1.Bone2.GIT3.Nervous system4.Liver5.Kidney6.Muscle

Healing in specialized tissue

Fracture healing

1)Procallous formation

2)Osseous callous formation

3) Remodeling

Fracture healing cont.

1) Procalus formation• Haematoma forms at the site of fracture• Fibrin clot forms the framework• Local inflammatory response- PMN ,

macrophages• In growth of granulation tissue• Callus formed of woven bone forms ( fusiform shape)

Fracture healing cont.

2)Osseous callus formation• On the procallus lamellar bone forms• Woven bone cleared by osteoclasts

3) Remodeling• Osteoclasts clear the excess bone• Osteoblasts lay down bone• External callus - Cleared away• Intemediate callus - Compact bone forms ( cortex)• Internal callus - Bone marrow forms

Complications of fracture healing

1) Fibrous union• Usually when immobilization is not done• False joints may also form (Pseudoarthrosis)

2)Non –union• In the presence of soft tissue between the

fracture ends

3)Delayed union

Gastrointestinal tract

• Depends on the depth of injury

1)Mucosal erosions

• Viable epithelium proliferate and fill the defect

2)Mucosal ulceration• Defect covered by blood

• Macrophage remove debris

• Granulation tissue form• Mucosa spread from the margin to the base of

the ulcer

• Muscle replaced by scar tissue• May lead to stenosis and obstruction

Nervous system

Central nervous system• Nerve cells of the CNS , spinal cord and ganglia

are permanent cells• Only glial cells proliferate – Gliosis

Peripheral nerves - Wallerian degeneration• With transection of nerve fibres the axon and the

myelin sheath undergo degeneration upto the closest proximal node of Ranvier

• Disintegrated fibres are phagocytosed• Regeneration occurs with sprouting of axons

and proliferation of schwann cells from the proximal ends

Nervous system cont.

LIVER

• Hepatocytes have a high regenerative capacity

• Injury leads to complete restitution of the tissue

• However if connective tissue network is severely damaged fibrosis occur

The eagle Ethon eating each day a part of the liver of Prometheus

Kidney

• Tubular cell damage with intact BM

• Tubular epithelial cells regenerate

• Glomerular damage scaring

MuscleCardiac muscle• Permanent cells• Replaced by scar tissueSmooth muscle• Limited regenerative capacity• With larger injury scar tissue formSkeletal muscle• Intact muscle sheath Properly oriented muscle formDamaged muscle sheath Fibrous scar

The healing of an injured skeletal muscle usually follows a constant pattern

1.Destruction phase-the rupture and ensuing necrosis of the myofibres, formation of a haematoma between the ruptured muscle stumps, and

inflammatory cell reaction.

2.Repair phase - phagocytosis of the necrotised tissue, regeneration of the myofibres, and concomitant production of a connective tissue scar, as well

as capillary in growth into the injured area.

3.Remodelling phase-regenerated myofibres mature, the scar tissue contracts and is re-organised, and the functional capacity of the muscle

recovers.

Summary

• The process by which healing occurs in a tissue is dependant on several factors

– Type of cell , extent of injury etc• Depending on the type of wounds, healing

process follows two pathways - Healing by primary intension - Healing by second intension• There are systemic and local factors that may

delay wound healing• Healing in other specialized tissue also depends

on the type of tissue and the extent of injury