Untitled Quiz

• Inflammation is a defensive process initiated by the body in response to local tissue damage.
• It involves the reaction of blood vessels, plasma components, blood cells, and connective tissue.
• A key feature is the reaction of blood vessels, causing fluid and leukocyte accumulation in extravascular tissues.

Purposes of Inflammation

• It is a protective response
• Inflammation dilutes, localizes, and destroys the injurious agent.
• Inflammation limits tissue injury.
• Inflammation restores tissue towards normality.

Etiology of Inflammation

• Physical agents like excessive heat or cold, mechanical trauma, UV, or ionizing radiation can cause inflammation.
• Chemical agents, both inorganic and organic, can induce inflammation.
• Microbiological agents, including bacteria, fungi, and viruses, are etiological factors.
• Immune reactions, such as hypersensitivity, can lead to inflammation.
• Tissue necrosis from any cause can trigger inflammation.

Acute Inflammation

• It is a rapid, local response of living tissue to injury.
• It lasts for minutes to a few days.
• It involves the extravascular accumulation of protein-rich fluid and leukocytes, especially neutrophils, resulting in an exudative lesion.
• It is a stereotype, meaning that various agents share the same basic features.

Chronic Inflammation

• It persists for weeks to months.
• It involves the extravascular accumulation of lymphocytes and macrophages.
• Characterized by simultaneous tissue destruction and attempts at healing via proliferation, resulting in a proliferative lesion.
• It is not a stereotype.

Clinical Features of Acute Inflammation

• There are 5 cardinal signs
• Rubor: Reddening
• Tumor: Swelling
• Calor: Warmth
• Dolor: Pain
• Functio laesa: Loss of function

Components of Inflammation

• Physiology: Release of soluble mediators, vasodilation, increased blood flow, extravasation of fluid, cellular influx (chemotaxis), elevated cellular metabolism
• Symptoms of inflammation:
  • Calor (heat)
  • Rubor (redness)
  • Tumor (swelling)
  • Dolor (pain)

Pathogenesis of Inflammation

• Phases in acute inflammatory reaction include:
  • Damage (alteration) due to etiologic factors, accompanied by the release of inflammation mediators.
  • Exudation of vascular and cellular events
  • Proliferation and differentiation of cells

Components of Inflammation

• Connective tissue cells: mast cells, macrophages, fibroblasts
• Connective tissue matrix: elastic fibers, collagen fibers, proteoglycans
• Vessels: Neutrophil, lymphocyte, basophil, eosinophil, platelets, monocyte
• Soluble proteins

Vascular Responses

• Vasodilation with increased blood flow
• Increased vascular permeability (proteins and cells)
• Leukocyte transmigration and chemotaxis

Cellular Responses, Neutrophil recruitment

• Margination

• Pavementing

• Transmigration

• Chemotaxis

• Hemodynamic changes, Adhesion molecules (Selectins, Integrans, ICAM-1, VCAM-1)

• Bacterial products, Complement components (C5a), AA metabolites (leukotriene B4), Platelet Activating Factor (PAF)

• Margination of leukocytes, endothelial adhesion, and leukocyte emigration

• PECAM = platelet/endothelial cell adhesion molecule

• ICAM = intercellular adhesion molecule

Types of Exudative Inflammation

• Acute inflammation is accompanied by exudate formation.

• Exudate: an inflammatory extravascular fluid with high protein concentration, cellular debris, and specific gravity above 1.020 which indicates alteration in the normal permeability in small blood vessels in the area of injury.

• Transudate: fluid with low protein content and specific gravity of less than 1.012, formed as an ultrafiltrate of blood plasma due to hydrostatic imbalance across the endothelium and the permeability of the endothelium is normal

• Types of exudative inflammation, depending upon the composition of exudates, are divided into:

• Serous inflammation

• Catarrhal inflammation (depends on localization)

• Fibrinous (pseudomembranous) inflammation

• Purulent inflammation

• Hemorrhagic inflammation

• Mixed inflammation

Serous Inflammation

• Acute inflammation characterized by copious fluid exudation with minimal emigration of leukocytes and escape of red cells.
• The location is in serous membranes (pleura, pericardium, peritoneum, joints), the parenchyma of organs (serous hepatitis, nephritis, myocarditis).
• Blister formation as reaction of skin at burn and herpes virus infection is a typical example.

Catarrhal Inflammation

• Acute inflammation of a mucous membrane in the respiratory and gastrointestinal tracts accompanied by glandular secretion
• Etiology: Bacterial, viral, physical and chemical tissue injury
• Morphology: The mucosa and submucosa appear reddened and swollen with slight lymphocytic infiltration
• Part of the surface epithelium may die, and epithelial tissue may be sloughed off
• The mucous exudate may contain epithelial cells
• Examples: Acute rhinitis, Acute catarrhal bronchitis, Enteritis

Fibrinous Inflammation

• Acute inflammation with exudation of fibrinogen-containing serum, occurring in serous membranes (fibrinous pleuritis, fibrinous pericarditis, fibrinous peritonitis) and the parenchyma of inner organs (lobar pneumonia in the gray hepatization stage). Etiology includes bacteria, chemical and toxic tissue injury, excretion of toxic metabolites (uremic toxins)
• Examples: fibrinous inflammation of the pharynx or larynx, bacillary dysentery of colon.

Fibrinous Inflammation types

• There are two forms differentiated based on the relation of fibrin exudation and necrosis:
• First type: Fibrinous croupous form, acute inflammation with wide area of fibrinous exudate forms an easily removable pseudomembrane, which is limited to the mucosal epithelium, where inflammatory necrosis only involves part of the mucosa, with the submucosa remaining largely intact
• Second type: Fibrinous diphtheritic type, acute inflammation which extends into the submucosa with a fibrinous exudate forms of an adhesive pseudomembrane that can only be forcibly removed (diphtheric pseudomembrane). In this the inflammatory exudate extends to the submucosa, causing erosion of the submucosal vessels and resulting in the escape of fibrinous exudate over a wide area.
• Examples of fibrinous croupous form inflammation include amebic dysentery and croupous pneumonia
• Antibiotic enterocolitis and diphtheric inflammation on mucous membrane of the uterus, vagina, stomach, and intestine (at dysentery) are examples of Fibrinous inflammation

Purulent Inflammation

• Inflammation with exudates consisting primarily of neutrophils and cellular debris (detritus).

• Etiology: pyogenic pathogens such as Staphylococci, Streptococci. Examples of this type of inflammation are purulent meningitis caused by meningococci, staphylococci, and purulent pneumonia.

• Three types of acute purulent inflammation:

  • Abscess is accumulation of pus in a confined space
  • Phlegmon is the diffuse purulent inflammation.
  • Empyema is accumulation of pus in body cavity

• Pathogenesis: an empyema usually occurs where a suppurative inflammation of an organ breaks through into an adjacent cavity.

• Pulmonary abscesses occur after pulmonary infarction or lobar pneumonia, cerebral abscesses occur following open cranial and cerebral trauma, and kidney abscesses may spread from purulent pyelonephritis.

• Liver abscesses may spread from a suppurative inflammation in the region drained by the portal vein, such as amebic dysentery where they may also spread from suppurative cholangitis

• Septicopyemic abscesses occur focally in the subpleural lung, as medullary strip lesions in the kidney, as punctate subendocardial lesions in the heart, and as punctate subcapsular lesions in the liver. Examples include Muscular phlegmon, Mediastinal phlegmon and Phlegmon of the walls of hollow organs (such as phlegmonous cholecystitis, appendicitis).

• Pericardial, peritoneal, and pleural empyema, Gallbladder and appendiceal empyema, Pyosalpinx (pus in the uterine tube), Hypopyon (pus in the anterior chamber of the eye) are examples of Empyema.

Hemorrhagic Inflammation

• Acute inflammation involving microvascular injury with massive diapedesis, producing an exudate with a high erythrocyte
• The inflamed area is usually necrotic and filled with blood.
• Etiologic factors include bacterial exotoxins and endotoxins and viral cytopathic effect on the endothelium
• Observed at influenza, pneumonic plague and anthrax

Mixed Inflammation

• It is a mixture of secretion and exudate, and may consist of a mixture of mucus and pus
• The inflammation is initially catarrhal and becomes mucopurulent
• Catarrhal bronchitis seen in mild influenza is often complicated by bacterial infections, with similar effects

Outcomes of Acute Inflammation

• Causative agent is removed with no tissue loss, resulting in resolution.
• Tissue damage due to suppuration results in tissue loss that progresses into:
  • Organization of Fibrinous exudate
  • Repair/Regeneration
• If Casualive agent persist, the result is chronic inflammation all lead to fibrosis

Healing

• Tissue injuries associated with inflammation are followed by some form of healing
• Removal of inflammatory and necrotic cellular debris must precede any such healing
• Resolution restores the tissue to its normal state when tissue loss after injury is absent
• Regeneration replaces the lost tissue or part with identical tissue
• Organization (repair by scar formation) is the replacement of injured tissue by scar (connective) tissue

Negative Sides of Inflammation

• Inflammatory reactions underlie life-threatening hypersensitivity reactions to insect bites, drugs, and toxins as well as some common chronic diseases like rheumatoid arthritis, atherosclerosis, and lung fibrosis
• Repair by fibrosis may lead to disfiguring scars or fibrous bands that cause intestinal obstruction or limit the mobility of joints
• Several chronic infectious diseases are associated with development of malignancies. For example, schistosomiasis of the urinary bladder leads to squamous cell carcinoma of that organ and Ulcerative colitis is at higher risk for adenocarcinoma in this organ