Wound healing

What is a wound?

Break in the epithelial integrity of the skin which may affect deeper layers even to bone.

What are the types of wounds?

- Superficial

- Partial thickness

- Full thickness

Describe superficial wounds.

- Damage to the epithelium

- Heals rapidly through regeneration of epithelial cells.

Describe partial thickness wounds.

- Involves dermal layer

- Vascular damage

Describe full thickness wounds.

- Involves subcutaneous fat and deeper.

- Longest time to heal as new connective tissue is required.

- Contraction during healing.

What are the stages of wound healing?

- Haemostasis,

- Inflammatory (early, late)

- Proliferative

- Remodeling

Describe the haemostasis stage of wound healing.

- Blood flows into the wound, and injured vessels contract to reduce bleeding.

- Coagulation cascade activates, forming a clot.

- Platelets release growth factors, such as IGF, which attract and activate neutrophils and fibroblasts.

- Platelets also release serotonin, which increases vascular permeability.

What are the phases of the inflammatory stage of wound helaing?

- Early inflammatory phase

- Late inflammatory phase

Describe the early inflammatory phase.

- Activation of complement systems.

- Infiltration of neutrophils

- Phagocytosis of bacteria and foreign particles occurs.

- Dying cells are cleared by macrophages or extrusion to wound surface.

What are blood monocytes and what do they do?

- A type of cell in the blood essential for tissue repair.

- Secretes cytokines and growth factors which recruit fibroblasts and keratinocytes to repair damage.

- Also secrete collagenases to degrade damaged tissue.

Describe the late inflammatory phase.

- Blood monocytes arrive and become macrophages.

- Lymphocytes enter wound and are involved in remodelling.

Describe the proliferative stage of wound healing.

- Fibroblasts migrate to the wound, producing a new ECM and repair proteins like collagen.

- Neoangiogenesis organizes the vascular network.

- Granulation tissue forms, producing collagen, fibronectin, and GAGs.

- New epidermal cells migrate to form a delicate wound covering.

Describe the remodelling stage of wound healing.

- Collagen become more organised and increase in strength.

- Fibroblasts and macrophages apoptose.

- Angiogenesis stops and blood flow is reduced to the area

When are chronic wounds formed?

- When normal process of healing is disrupted at one of the stages, usually inflammatory or proliferative.

- Caused by disturbances in growth factors, cytokines or proteases.

What local factors affect wound healing?

- Pressure

- Mechanical injury

- Infection

- Oedema

- Necrosis

- Lack of oxygen

What systemic factors affect wound healing?

- Old age

- Obesity

- Chronic diseases e.g., diabetes

- Smoking

- immunosuppression

What causes chronic wounds?

- Neuropathy

- Peripheral oedema

- Pressure

- Ischemia

What are clinical features of chronic wounds?

- Presence of necrotic and unhealthy tissue

- Excess exudate and slough

- Lack of adequate blood supply

- Absence of healthy granulation tissue