Pathology Lecture 4: Wound Healing

The body's replacement of destroyed tissue with living tissue.

A breach or defect in living tissue caused by injury, accompanied by inflammation.

Tissue repair where lost tissue is replaced with similar tissue.

Tissue repair where lost tissue is replaced by scar tissue.

Cells in the surface epithelium (skin, gut, etc.) with high replication rate.

Cells that can regenerate after injury, such as smooth muscle, fibroblasts.

Cells that cannot divide after a certain point in development.

These cells cannot be replaced if lost because they lack the ability to divide (proliferate). Examples include neurons, striated muscle cells, and lens cells.

The goals of healing include restoring the skin's surface and the strength of underlying tissues.

A complex process with seven stages: inflammation, regeneration, cell proliferation, ECM synthesis, remodeling, collagenization, and contraction.

Small proteins that stimulate cell division and proliferation, crucial for the healing process.

Growth factors involved in wound healing can originate from platelets, serum, macrophages, or lymphocytes.

The process of replacing lost tissue with identical cells.

The success of regeneration depends on the cells' ability to divide, the damage to the supporting framework, and the type and severity of the injury.

A process that shrinks the wound by 70-80%, significantly speeding up healing by reducing the amount of tissue to be replaced.

Involves a coordinated series of events orchestrated by growth factors, leading to cell regeneration, migration, and the creation of new tissue.

Dense, cellular connective tissue with intact skin covering, lacking inflammation, and absent dermal/epidermal appendages. It takes months to regain full strength.

Wounds with significant tissue loss, large defects, and wide margins heal by second intention. This includes areas with significant necrosis, ulceration, and infection.

New connective tissue formed during wound healing, containing microscopic blood vessels and myofibroblasts. It grows from the wound base, fills the gap, and helps contract the wound.

The pulling together of wound edges by myofibroblasts in granulation tissue, reducing the wound size and promoting closure.

Factors at the wound site that influence healing speed and efficiency, including type, size, location, vascular supply, and infection.

The nature of the injury (e.g., clean cut, blunt trauma) affects healing speed. Clean wounds heal quicker than those with more damage and irregular edges.

Larger wounds take longer to heal than smaller ones, requiring more time for cell regeneration and tissue filling.

Wounds in highly vascularized areas (like the face) heal faster than those in poorly vascularized areas (like the foot).

Inadequate blood supply slows down wound healing, as cells need oxygen and nutrients from blood.

Microorganisms entering the wound can cause infection, delaying healing and increasing complications.

Macrophages, replacing neutrophils after 48-96 hours, clear debris and fibrin, promoting angiogenesis (new blood vessel formation) and ECM deposition (building the extracellular matrix) during tissue repair.

During the second week of healing, inflammation lessens, collagen accumulates, and vascular channels regress. This leads to the formation of a pale, avascular scar, composed of fibroblasts, dense collagen, and ECM components.

Wound contraction, prominent in large surface wounds, helps close the wound by decreasing the gap between dermal edges and reducing surface area. It's crucial for healing by secondary union.

Unlike skin wounds, fractures are repaired not with fibrous scar tissue but with specialized bone-forming tissue, restoring the bone nearly to its original state.

Woven, immature bone is characterized by irregular collagen fiber arrangement, less abundant osteomucin, and lower calcium content.

A separation of the layers of an abdominal wound, often occurring after surgery.

A protrusion of abdominal contents through a weakened abdominal wall, usually caused by poor wound healing after surgery.

Wound healing failure due to inadequate blood supply or persistent trauma.

A wound that fails to heal due to lack of sensation, often seen in patients with neuropathy.

An excessive buildup of scar tissue that remains localized to the wound area.

An excessive buildup of scar tissue that extends beyond the wound area.

A limitation of joint movement due to excessive scar tissue, often seen in burns.

The first stage of wound healing, where a blood clot forms at the wound surface to stop bleeding and act as a scaffold for cell migration.

The second stage of wound healing, where fibroblasts and blood vessels form granulation tissue to fill the wound.

The final stage of wound healing, where cells multiply and collagen is deposited to strengthen the wound.