Inflammation: reaction of vascularized living tissue to local injury, irritants or agents.

• associated with the repair process

• protective response

Tissue Injury

Reversible: mild or moderate injury (leads to inflammation or degeneration)

Irreversible: severe injury (leads to necrosis)

Types of Inflammatory Response

• Acute inflammation

• Chronic inflammation

Two Major Components of Inflammation

1. Vascular reaction

2. Cellular response

Benefits of Inflammation

1. Contain and isolate injury

2. Destroy invading microorganisms and inactive toxins

3. Prepare tissue for healing and repair

Causes of Inflammation

Physical agents:

• excessive heat or cold

• irradiation

Tissue necrosis:

• ischemia

• trauma

• toxins

Foreign bodies:

• splinters

• dirt

• suture

• prosthetic device

• urate crystals (gout)

• cholesterol esters

Chemical agents:

• concentrated acids and alkalis

Infection: (most common cause)

• bacteria and their toxins

• fungi

• parasites

Immunological:

• due to: antigen - antibody reactions

Mediators of Defense

• phagocytic leukocytes

• antibodies

• complement proteins

Typical Inflammatory reaction

1. recognition of injurious agent

2. recruitment of leukocytes and plasma proteins

3. removal of the agent

4. regulation of the response

5. repair

Major participants

1. blood vessels

2. leukocytes

Harmful Consequences of Inflammation

Local tissue damage and its associated signs and symptoms are self-limited and resolve as the inflammation diminishes, leaving little or no permanent damage.

Inflammation becomes the cause of the diseases when it:

• is misdirected (autoimmune diseases)

• occurs against normally harmless environmental substances (e.g. allergies)

• inadequately controlled

Cardinal Signs of Inflammation

1. Hotness

   • due to: increased blood flow

2. Redness:

   • due to: vasodilation and increased blood flow

3. Swelling:

   • due to: exudate

4. Pain:

   • due to: irritation of nerve endings by metabolites

5. Loss of function:

   • due to: pain and tissue damage