PATH2220 Study Guide - Final Guide: Basophil, Acne Vulgaris, Histopathology
Inflammation
What is Inflammation?
• Response of living tissue to injury
• Goal of inflammatory reaction
o Bring leukocytes and plasma proteins to site of infection or tissue
damage
o Eliminating causative agent
o Initiating healing
• Generally beneficial → essential for survival
• If severe of if unable to eradicate causative agent, or if inappropriately
directly inflammatory reaction may cause damage
• Types of inflammation
o Chronic
▪ Slow onset
▪ Monocytes/macrophages/lymphocytes
▪ Severe to progressive tissue injury
o Acute
▪ Fast onset
▪ Mainly neutrophils
▪ Mild tissue injury
• Cardinal signs of inflammation
o Rubor (redness) → increased blood flow
o Calor (heat) → increased blood flow
o Tumour (swelling) → leakage of cells/fluid into tissue
o Dolor (pain) → increased nerve sensitivity due to chemical
mediators
o Function laesa (loss of function)
• Causes of inflammation
o Infective agents → bacteria, viruses, parasites
o Foreign bodies → dirt, splinters, suture material
o Immune reactions → allergic, hypersensitivity, autoimmune
o Tissue necrosis → multiple causes
o Physical agents → trauma, heat, cold, irritation
o Chemical agents → drugs, toxins
The Inflammatory Process:
• Offending agent is recognized by host cells and molecules which then
produce chemical mediators
• Leukocytes and plasma proteins are recruited from the circulation to the
site where the offending agent is located
• Leukocytes and proteins are activated to destroy and eliminate the
offending substance
• Reaction is controlled and terminated
• Damaged tissue is repaired
find more resources at oneclass.com
find more resources at oneclass.com
The Inflammatory Response:
• Vascular changes
o Maximize movement of proteins and leukocytes from circulation to
site of injury
o Vasodilation → change in caliber of vessels
o Change in blood flow → increased at first, later slows
o Change in permeability → leakage of fluid and protein
• Cellular events
o Recruit leukocytes to site of injury/infection and allow them to
effect a response
o Leukocyte migration through endothelium → emigration
o Migration of leukocyte to site of injury → chemotaxis
o Recognition/removal of offending agent by phagocytosis
o Other leykocutic response → initiation of repair process
Vascular Changes:
• Vasodilators
o Action of mediators on vascular smooth muscle and initial
constriction
o Arterioles dilate followed by capillary bed expansion
o Increased blood flow → redness and heat
• Increased permeability
o Outpouring of protein-rich fluid into extravascular tissue →
exudate
o Swelling → edema
o Cellular emigration occurs last
o Changes to permeability can occur in 2 ways
▪ Retraction of endothelial cells
• Mediators cause endothelial cell contraction
• Gaps appear between endothelial cells
▪ Endothelial injury
• Direct damage caused by burns, microbial toxins
o End result is the same
▪ Fluid and proteins escape
▪ Small molecules first, fibrinogen last
▪ Increased osmotic pressure of tissue → swelling
• Chemical mediators of the vascular response
Mediator
Principle Source
Actions
Histamine
Mast cells, platelets,
basophils
Vasodilation, increase
permeability, endothelial
activation
Seretonin
Platelets
Vasodilation, increase
permeability
Prostaglandins
Mast cells, leukocytes
Dilation (+ pain, fever)
Platelet-activating factor
Leukocytes, mast cells
Vasodilation, increase
permeability
Cytokines TNF, IL-1
Macrophages, mast cells
Endothelial activation (+
pain, fever)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
What is inflammation: response of living tissue to injury, goal of inflammatory reaction, bring leukocytes and plasma proteins to site of infection or tissue damage, eliminating causative agent, initiating healing, generally beneficial essential for survival. Vascular changes: vasodilators, action of mediators on vascular smooth muscle and initial constriction, arterioles dilate followed by capillary bed expansion, increased blood flow redness and heat. Increased osmotic pressure of tissue swelling: chemical mediators of the vascular response. In response to cytokines, endothelial cells upregulate expression of adhesion molecules selectins: selectins bind to surface carbohydrates on leukocytes, firm adhesion. Healing and repair: healing, resolution, repair, occurs when resolution is impossible, maturation of granulation tissue to form scar tissue. Involves formation of granulation tissue organization: organisation, growth of new capillaries and fibroblasts into damaged tissue, new capillaries and fibroblasts granulation tissue, matures to form fibrous tissue, process involved in repair of tissue.
