L5: The Process of Healing in Health and Disease

What is the difference between repair and regeneration in healing?

Repair is the replacement of lost tissue by granulation tissue, forming scar tissue. Regeneration is the replacement of lost tissue by similar type tissue, involving the proliferation of surrounding undamaged specialized tissue.

What is tissue repair?

Tissue repair involves the restoration of tissue architecture and function after an injury, often through regeneration or replacement with scar tissue.

What are labile cells and provide an example?

Labile cells continue to multiply throughout life; examples include epidermis and hemopoietic bone marrow.

What characterizes stable cells and give an example?

Stable cells normally cease multiplication when growth ceases but retain mitotic ability; examples include liver and pancreas.

What are permanent cells?

Permanent cells lose their capacity to proliferate in infancy, examples include nerve cells and cardiac muscles.

What role do growth factors play in healing?

Growth factors influence angiogenesis, chemotaxis, mitogenesis, and collagen synthesis, examples include fibroblast growth factors and vascular endothelial growth factors.

What happens in primary intention healing?

Healing occurs with clean wounds or incisions with minimal space, involving clotted blood and scab formation, acute inflammation, and granulation tissue formation.

What is the difference between primary and secondary intention wound healing?

Primary intention involves minimal tissue loss with quicker healing, while secondary intention involves greater tissue loss, more inflammation, and a larger scar.

What is granulation tissue?

Granulation tissue is formed by the migration and proliferation of fibroblasts and endothelial cells, which eventually matures into scar tissue.

What is the role of cell-cell and cell-matrix interactions in healing?

These interactions are crucial for the formation of a monolayer of cells and for ceasing proliferation after the injury is healed.

How does extracellular matrix synthesis affect wound strength?

Wound strength is related to the proliferation of fibroblasts and the synthesis of collagen and other extracellular elements.

What are the 3 important mechanisms in healing?

Growth factors, cell-cell and cell-matrix interaction and extracellular matrix synthesis and collagenisation

What is the role of myofibroblasts in wound healing?

Myofibroblasts are involved in wound contraction, particularly in secondary intention healing, helping to close the wound edges.

List complications that can arise during the healing process.

Infection can delay healing, and wound dehiscence can occur, leading to reopening of the wound.

What is a keloid, and why does it form?

A keloid is raised scar tissue caused by excessive collagen deposition during remodeling, often due to genetic predisposition or prolonged inflammation

What local factors can adversely affect wound healing?

Infection, foreign bodies, poor blood supply, excessive movement, and poor apposition of wound margins can all negatively impact healing.

How does bone fracture healing begin?

It begins with hematoma formation at the fracture site, followed by traumatic inflammation and demolition of necrotic bone fragments by macrophages and osteoclasts.

What role do osteoblasts and chondroblasts play in bone repair?

Osteoblasts form woven bone to bridge fracture ends, while chondroblasts produce cartilage if movement occurs; this cartilage later calcifies and is replaced by lamellar bone.

What happens during the remodeling stage of bone healing?

Osteoclasts resorb excess callus, while osteoblasts deposit lamellar bone, gradually restoring the bone’s original shape and strength.

How does skeletal muscle regeneration differ from cardiac muscle?

Skeletal muscle regenerates via satellite cells, whereas cardiac muscle lacks regenerative capacity and heals through scar tissue.

What are the roles of macrophages and astrocytes in CNS injury repair?

Macrophages clear debris and facilitate healing, while astrocytes form glial scar tissue, blocking regeneration.

Define Wallerian degeneration in the context of PNS injury.

Wallerian degeneration is the disintegration of the axon and myelin sheath distal to a nerve injury, allowing for potential regeneration if the cell body survives.

What is the typical healing capacity of cardiac muscle?

Cardiac muscle has no regenerative capacity; repair occurs through scar formation, not tissue regeneration.

Explain the concept of traumatic neuroma.

A traumatic neuroma is a painful mass formed when regenerating axonal sprouts grow randomly instead of reconnecting properly after nerve injury.

What are the general factors leading to poor wound healing?

Poor nutrition, excessive glucochorticosteroid production or administration and systemic disease.