Acute Inflammation Flashcards
What are the main differences between Acute and Chronic Inflammation?
Acute Inflammation:
- Rapid Onset
- Short Duration (hours-few days)
- Neutrophils and macrophages
- Exudation of fluid/plasma proteins
Chronic Inflammation:
- May follow Acute Inflammation
- Longer Duration
- Lymphocytes, plasma cells, macrophages
- Fibrosis, Tissue destruction and reparative processes
What are the Cardinal Signals of Acute Inflammation
- Rubor (Redness)
- Tumor (Swelling)
- Calor (Warmth)
- Dolor (Pain)
- Functio Laesa (Loss of function)
Causes of Acute Inflammation
- Infections
- Physical Agents (Mechanical, Heat, Cold, Ionising Radiation)
- Chemical Agents
- Ischaemia
- Immunological Reaction
Tissue changes in Acute Inflammation
- Hyperaemia
- Exudation of fluid and plasma protein
- Emigration of leukocytes
What happens during hyperaemia
- Lewis Triple Response
a. Initial Vasodilation (white line)
b. Arteriole Dilation (red line/Flush)
c. Capillary Dilation and Vascular Congestion (surrounding redness/Flare)
d. Oedema (weal) - Dilation of Arterioles and Capillaries - reflex action + chemical mediators eg. histamine
- Increased permeability of blood vessel wall - contraction/direct damage of endothelial cells, transport of fluids and proteins through endothelial cells (transcytosis)
What happens during exudation of fluid and plasma proteins
- Vascular Dilation and increased permeability + osmotic pressure + Protein exudation (Fibrinogen forming fibrin network and immunoglobulins)
- Oedema (swelling of inflammed tissue)
- Increased lymphatic outflow (Lymphangitis/Lymph node reaction)
what leukocytes are emigrated during emigration of leukocytes (WBCs)
- Mononuclear cells - Lymphocytes, Monocytes, Macrophages, Histocytes
- Polymorphonuclear leukocytes/Granulocytes - Eosinophils, Neutrophils, Basophils
What happens during emigration of leukocytes (WBCs)
- Margination, rolling and adhesions of leukocytes (Decrease in speed of bloodflow + Expression of adhesion molecules of leukocytes and endothelial cells eg. selectins, intergrins)
- Transmigration across endothelium
- Movement towards chemotactic molecules (Fibrin meshwork, complement component, C5a)
- Phagocytosis (remove offending agents)
- Secretion of chemical mediators (cytokines)
Leukocytic actions
- Phagocytosis
- Killing and degradation of ingested material (with ROS and degradative enzymes such as elastase) - Extracellular ROS may damage normal tissue :(
- Production of growth factor (for tissue repair)
Chemical mediators of inflammation
Plasma derived:
- Complement (chemotactic, opsonisation, direct damage)
- Kinins (Increase vascular permeability, vasodilation, pain)
- Clotting factors (inflammation and blood clotting promote each other)
Cell-derived:
- Macrophages, Leukocytes, Endothelium, Mast Cells
- Histamin, Serotonin, Nitric Oxide
- Arachidonic Acid Metabolites (Prostaglandins and Leukotrienes)
- Cytokines/ Chemokines eg. Tissue necrosis factor, Interleukin-1
Termination of acute inflammatory response
- Rapid degradation of chemical mediators
- Short half-lives of neutrophils
- Activation of anti-inflammatory mechanisms (eg. IL-10)
Possible Sequelae (consequences) of Acute Inflammation
- Complete resolution :) - little/no necrosis
- Healing by scarring (tissues that do not regenerate) - substantial necrosis, abundant fibrin exudation
- Suppuration/Abscess formation - Profuse neutrophils infiltration. necrotic tissue undergoes softening and liquefaction by proteolytic enzymes (eg. Meningitis)
- Chronic Inflammation
What is the Sequelae of Acute Inflammation dependent on
- Amount of Tissue Damaged
2. Whether the causative agent remains
What is an abscess
Collection of pus lined by pyogenic membrane
Patterns of acute inflammation
- Fibrinopurulent exudate (thick yellowish)
- Purulent exudate/pus (liquid yellowish) - a lot of neutrophils and dead tissue
- Serous exudate (watery) - burns
- Haemorrhagic exudate (bloody) - blood vessels
- Ulcer (local defect of tissue)