Chronic Inflammation and Pain Signaling Quiz

Inflammation and Tissue Repair

• Inflammation is the body's response to infection or tissue damage
• The goal is to eliminate the offending agent (e.g., microorganism)
• Inflammation also leads to tissue repair
• Mediators include phagocytic leukocytes, antibodies, and complement proteins
• Inflammation is a positive response, a crucial process for eliminating threats to the body
• Failure of inflammation can negatively impact the body

Inflammation: Sequential Events

• Recognition: The body detects noxious stimuli
• This is the initiating stimulus

Causes of Inflammation

• Infection: Different microorganisms trigger varied inflammatory responses, the resulting damage varies based on many factors.
• Tissue necrosis: cell death triggers inflammation, regardless of the cause
• Foreign bodies: elicit inflammation by causing tissue damage
• Immune reactions: Hypersensitivity reactions where the immune system damages its own tissues

Acute Inflammation

• Immediate response to injurious stimuli, blood vessels dilate
• Increased permeability of vessels allows plasma proteins and leukocytes to move into the injured area
• Leukocytes migrate to the injured site to eliminate the offending agent
• Diapedesis: The movement of leukocytes between cells

Acute Inflammation: Leukocyte Recruitment

• Increased vascular permeability allows fluid to leak into the injured area
• Increased blood flow causes swelling and redness (erythema)
• Slowed blood flow (stasis) causes leukocytes to adhere to the vessel walls (margination)

Acute Inflammation: Leukocyte Adhesion

• Selectins mediate initial rolling of leukocytes
• Integrins slow rolling, aid firm adhesion

Acute Inflammation: Chemotaxis

• Chemoattractants signal the migration of leukocytes to the site of injury
• Chemoattractants can be exogenous (external) or endogenous (internal)

Acute Inflammation: Phagocytosis

• Recognition and attachment of the particle (e.g., microorganism) to the leukocyte
• Engulfment of the particle into the leukocyte (phagocytosis)
• Killing and degradation of the particle within the leukocyte

Morphological Patterns: Serous Inflammation

• Exudation of a fluid poor in cells into spaces or body cavities (e.g., pleural, peritoneal)
• Fluid is called an effusion if within body cavities

Morphological Patterns: Fibrinous Inflammation

• Large vascular leaks, or a large stimulus triggers the formation of a fibrinous material that coagulates
• Found in lining of body cavities (e.g., meninges)

Morphological Patterns: Purulent Inflammation

• Exudate contains neutrophils and dead cells (pus)
• Pus formation often associated with bacterial infection that causes liquefactive necrosis (e.g., Streptococcus)
• Abscess: a localized collection of pus, often in body cavities

Morphological Patterns: Ulcers

• Local defects or excavations of tissue surfaces
• Often involves chronic inflammation and may be caused by infection, ischemia, or other issues

Chronic Inflammation

• Prolonged response, tissue injury and attempts to repair coexist
• May follow acute injury or begin as slow-progressing issues
• Often due to persistent infection/toxin exposure
• Involves macrophages, lymphocytes, and other cells
• Chronic inflammation leads to tissue damage, scarring (fibrosis), and potential development of diseases

Chronic Inflammation: Macrophages

• Central in chronic inflammation
• Secrete cytokines and growth factors to activate other cells and mediate inflammatory responses

Tissue Repair

• Restoration of tissue architecture and function
• Regeneration: Complete restoration of the structure
• Scar formation: Connective tissue deposition if regeneration is impossible
• Healing proceeds in stages, with inflammation often a precursor

Chronic Inflammation: Causes

• Persistent infections (e.g., Mycobacteria)
• Hypersensitivity diseases (e.g., rheumatoid arthritis)

Wound Healing Mechanisms: Acute and Chronic Injuries

• Repairing tissues has two pathways: regeneration and scarring
• Inflammation precedes the healing process
• Regeneration replaces damaged tissue with identical tissue
• Scarring replaces damaged tissue with fibrous tissue