General Pathology: Inflammation and Repair

Study Notes

Inflammation is the body's response to tissue injury and infection, involving vascular circulation and activation of inflammatory cells to eliminate pathogens and damaged cells.
The typical sequence of inflammatory events is encapsulated in the "5 R's":
- Recognition: Identification of the triggering stimulus through receptors that detect microbial products and damage signals, leading to mediator production.
- Recruitment: Leucocyte and plasma protein migration from circulation to affected tissues.
- Removal: Elimination of the initiating stimulus primarily by phagocytic cells.
- Regulation: Modulation of the inflammatory response to prevent excessive damage.
- Repair: Restoration of tissue integrity and function post-inflammation.

Inflammation can occur due to various stimuli including infections, tissue injury, toxins, and autoimmune responses.

The classic signs include redness, heat, swelling, pain, and loss of function, resulting from increased blood flow and vascular permeability.

Acute inflammation involves mainly neutrophils, while chronic inflammation includes macrophages and lymphocytes.
Different cells have specific roles in the inflammatory response and tissue repair.

Mediators include:
- Vasoactive amines: Such as histamine, contributing to vascular changes.
- Arachidonic acid metabolites: Including prostaglandins and leukotrienes.
- Cytokines and chemokines: Signaling proteins that regulate inflammation.
- Complement system: Enhancing phagocytosis and inducing inflammation.

Inflammation can produce both beneficial effects (e.g., fighting infection) and harmful effects (e.g., tissue damage).
Can have localized impacts and systemic effects, influencing overall health.

Key patterns include:
- Serous inflammation: Watery exudate, common in mild injuries.
- Fibrinous inflammation: Thick, fibrin-rich exudate indicating more severe injury.
- Suppurative inflammation: Formation of pus, typically from bacterial infection.
- Ulcers: Localized tissue loss, often associated with severe inflammation.

Possible outcomes include:
- Complete resolution: Restoration of normal tissue structure and function.
- Scarring/Fibrosis: Replacement of normal tissue with scar tissue, potentially leading to loss of function.
- Progression to chronic inflammation: Continuous inflammatory response with persistent injury.

Acute inflammation is characterized by rapid onset and short duration, while chronic inflammation persists over a longer period, often resulting from unresolved acute inflammation.
Granulomatous inflammation is a specific form of chronic inflammation marked by the formation of granulomas.

Tissue repair can occur through regeneration (complete restoration of tissue) or scarring (incomplete restoration).
Factors influencing repair include local conditions like blood supply, infection presence, and systemic factors such as age and nutritional status.

Issues may arise, leading to:
- Deficient scar formation: Weak or inadequate scars.
- Excessive scarring: Hypertrophic scars or keloids.
- Contractures: Tightening of skin or tissues affecting function.

Acute phase response includes fever, increased acute-phase proteins, and leukocytosis.
Severe cases may lead to septic shock, a life-threatening condition.