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Questions and Answers
What is the primary characteristic of granulomatous inflammation?
What type of granuloma is primarily formed in response to inert foreign materials?
Which of the following correctly describes the composition of a granuloma?
What triggers immune granuloma formation?
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What central feature is often found in granulomas?
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What condition results from the hyperplasia of lymphoid follicles?
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Which of the following is NOT a characteristic of chronic inflammation compared to acute inflammation?
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What is a characteristic feature of fibrinous inflammation?
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What is the primary role of activated macrophages during chronic inflammation?
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Which type of acute inflammation is primarily associated with viral infections of the respiratory tract?
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How is lymphangitis commonly diagnosed?
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What contributes to the formation of pus during acute inflammation?
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Which mechanism allows monocytes to migrate into the extravascular space during inflammation?
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Which outcome is associated with abscess formation?
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Which of the following is a common effect seen in both lymphadenitis and lymphangitis?
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How do lymphatics contribute to the process of inflammation?
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What defines the pathological changes in reactive lymphadenitis?
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What defines pseudomembranous inflammation?
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Which of the following components is typically involved in the healing process during chronic inflammation?
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Which type of inflammation is characterized by an excessive accumulation of protein-poor fluid?
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What is the likely outcome when acute ulceration occurs?
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Study Notes
Acute Inflammation
- The effects of acute inflammation depend on the nature and severity of the injury.
- Factors affecting the effects of acute inflammation include the type of tissue affected and the causative agent.
- It can lead to complete resolution, scarring and fibrosis, abscess formation, progression to chronic inflammation.
Complete Resolution
- Complete resolution occurs when the inflammatory process is successfully resolved without any residual damage.
Scarring and Fibrosis
- Occurs when extensive tissue destruction and damage take place.
- Fibrosis is characterized by the deposition of collagen fibers, leading to scar formation.
Abscess Formation
- A localized collection of pus, usually following extensive tissue damage, particularly that caused by pyogenic bacteria like staphylococcus aureus.
- Pus is a thick yellow viscous fluid resulting from the liquefaction of tissue due to the action of lysosomal enzymes.
- Pus contains dead and dying neutrophils, necrotic tissue debris, microorganisms, and the fluid component of acute inflammation.
Progression to Chronic Inflammation
- Persistent inflammatory stimuli or inadequate resolution of acute inflammation can lead to chronic inflammation.
Morphological Features in Acute Inflammation
- Depending on the type and severity of the injury and the type of tissue affected, we can have the following types of acute inflammation.
Mild Acute (Catarrhal) Inflammation
- Characteristic of mild infection of the mucous membrane, as seen in viral upper respiratory tract infections.
- Manifestations include hotness, redness, and swelling.
- Often results in complete resolution.
Serous Inflammation
- Characterized by excessive accumulation of protein-poor fluid, often leading to blister formation.
- Commonly seen in burns and viral infections of the skin.
Fibrinous Inflammation
- Characteristic of more severe injury, where greater vascular permeability leads to the exudation of large amounts of fibrinogen.
- Potential outcomes include complete resolution or organization, where fibrin deposition is followed by the ingrowth of new capillaries and fibroblasts, leading to fibrosis.
- Commonly occurs in inflammation of serosal membranes and joints.
Suppurative (Purulent) Inflammation
- Marked by the accumulation of large amounts of pus, often resulting in abscess formation.
- Frequently associated with certain bacterial infections.
Acute Ulceration
- Occurs when severe infection affects the surface epithelium, causing loss of part of the epithelium.
Pseudomembranous Inflammation
- Characterized by necrotizing infection of the surface epithelium of the colon caused by certain bacteria like clostridium difficile.
Role of Lymphatics in Inflammation
- Lymphatics play a crucial role in the inflammatory response, helping drain edema fluid, leukocytes, and cell debris from the extravascular space.
- In severe inflammatory reactions, especially to microbes, lymphatics can transport the offending agent.
- Lymphatics themselves can become inflamed (lymphangitis), as can the draining lymph nodes (lymphadenitis).
- Inflamed lymph nodes often enlarge due to hyperplasia of the lymphoid follicles, a condition known as reactive or inflammatory lymphadenitis.
- Red streaks near a skin wound, following the course of lymphatic channels, are indicative of lymphangitis and may be accompanied by painful enlargement of draining lymph nodes, suggesting lymphadenitis.
Chronic Inflammation
- Defined as inflammation of prolonged duration, characterized by active inflammation, tissue destruction, and simultaneous attempts at repair.
- Can result from persistent infection, prolonged exposure to toxins, autoimmune reactions, or other unknown causes.
Chronic Inflammation Arises in Three Ways
- Persistence of the inciting agent
- Immune-mediated inflammation
- Failure to completely resolve acute inflammation
Components of Chronic Inflammation
- Characterized by the recruitment of mononuclear cells, specifically macrophages and lymphocytes, due to the production of chemotactic factors.
- Tissue destruction is caused by the persistent stimulus or the inflammatory cells themselves.
- Attempts at healing involve connective tissue replacement of damaged tissue, accompanied by angiogenesis (new blood vessel formation) and fibrosis.
Role of Macrophages
- Monocytes emigrate into the extravascular space, guided by specific adhesion molecules and chemotactic factors.
- They differentiate into larger macrophages, which are then activated by cytokines like interferon.
- Activated macrophages release various active products (chemical mediators) that contribute to tissue injury (e.g., enzymes and reactive oxygen species) and fibrosis (e.g., fibroblast growth factors).
Gross Morphological Features of Chronic Inflammation
- Infiltration of mononuclear cells, mainly macrophages, lymphocytes, and plasma cells.
- Tissue destruction, often accompanied by fibrosis.
- Granuloma formation (aggregates of macrophages) in specific conditions.
- Angiogenesis (formation of new blood vessels)
- Fibrosis (excessive collagen deposition).
Granulomatous Inflammation
- A distinctive pattern of chronic inflammation characterized by the formation of granulomas.
- Granulomas are aggregates of modified macrophages with a characteristic epithelial-like appearance, called epithelioid histiocytes.
- The central part of a granuloma may exhibit necrosis.
Importance of Granulomatous Inflammation
- Important to recognize in various pathological conditions.
- Associated with certain infections, such as tuberculosis.
- A reaction to poorly digestible materials, including inorganic metals, irritant lipids, and foreign materials.
- May be indicative of unknown immune disorders, like sarcoidosis.
Granuloma
- Consists of a microscopic aggregation of epithelioid macrophages surrounded by a collar of lymphocytes and externally bounded by fibroblasts.
- Several epithelioid macrophages often fuse together to form large multinucleated cells, called giant cells.
Types of Granuloma
- Foreign body granuloma: Formed in response to relatively inert foreign bodies that are poorly digestible and cannot be phagocytosed by a single macrophage, leading to the formation of giant cells. Examples include suture material.
- Immune granuloma: Formed in response to the presence of insoluble particles that induce a T-cell mediated immune response, such as in tuberculosis.
System Effects of Inflammation
- Fever
- Leukocytosis (Increased white blood cell count)
- Increased production of acute-phase proteins by the liver.
- Sepsis (Systemic inflammation) and septic shock.
Summary of Key Points in Chronic Inflammation
- Chronic inflammation is characterized by a persistent inflammatory response, tissue destruction, and repair attempts.
- Granuloma formation is a common feature in chronic inflammation, particularly in response to certain infections or foreign materials.
- Understanding the various types of chronic inflammation and their morphological features is crucial for diagnosing and managing inflammatory conditions.
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Description
This quiz covers the key concepts of acute inflammation, including its effects, resolution, scarring, and abscess formation. Understand the factors that influence the severity and outcomes of inflammation and identify the biological processes involved. Test your knowledge on the interactions occurring during tissue injury.
