Inflammation: Causes, Types, and Responses PDF

**INFLAMMATION** **Definition:** Response of living tissues to an injury in the form of vascular and cellular reactions in order to eliminate or limit the spread of injurious agent, remove necrotic cells and prepares the affected tissue for repair. [**Roles of Inflammation**:] 1 - Isolation and e...

**INFLAMMATION** **Definition:** Response of living tissues to an injury in the form of vascular and cellular reactions in order to eliminate or limit the spread of injurious agent, remove necrotic cells and prepares the affected tissue for repair. [**Roles of Inflammation**:] 1 - Isolation and elimination of the injury. 2 - Destruction of invading organisms and inactivation of toxins. 3 - Achieving **healing** and **repair.** [**Causes of inflammation:** ] **1- Infective agents:** Bacteria, viruses and their toxins, fungi, parasites. 2- **Immunological agents**: Cell-mediated and humoral reactions. 3**- Physical agents**: Heat, cold, radiation, mechanical trauma. 4- **Chemical agents**: Organic and inorganic poisons. 5- **Inert materials**: foreign bodies. **[Types of inflammation:]** Depending upon the defense capacity of the host and duration of inflammatory response, inflammation is classified into **acute** and **chronic**. **(A) [Acute inflammation]**[:] Characterized by short duration (lasting less than 2 weeks) and represents the early body reaction, resolves quickly and is usually followed by healing. **Fulminant acute inflammation**: Severe acute inflammatory response begins and lasts in few hours e.g. Bee stings. **(B) [Chronic inflammation:]** Persists for longer duration and occurs either after repeated episodes of acute inflammation or begins as chronic from the start. **Chronic active inflammation**: Type of chronic inflammation during the course of which there are acute exacerbations of activity. **Subacute inflammation**: Transition state between acute and chronic inflammation. According to [**location** of the lesion] within the organ. Inflammation may be **focal, multifocal, locally extensive or diffuse:** **[Nomenclature of inflammation:]** **The Greek, Latin or English name of** **the organ + suffix "itis" as:** \- Gastritis: inflammation of the stomach. \- Orchitis: inflammation of the testis. \- Glossitis: inflammation of the tongue. \- Hepatitis: inflammation of the liver. \- Appendicitis: inflammation of appendix. **[Exceptions:]** \- Pneumonia = inflammation of the lung. \- Pleurisy = inflammation of the pleura. **ACUTE INFLAMMATON** Definition: Immediate response of living tissue to an injury. Its aim is to deliver leukocytes and mediators to the site of injury by the blood stream. ACUTE INFLAMMATORY REACTION Acute inflammatory response of the host to an injury is a process that involvs a series of overlapping vascular and cellular events. Intimately linked to these events is tissue destruction and release of chemical mediators. [The acute inflammatory reaction includes local and systemic reactions.] **[I- LOCAL REACTIONS:]** **(1) LOCAL TISSUE DESTRUCTION**: [ ] \- Maximum at the site of the irritant and depends on its severity. \- Necrosis usually occurs at the site of the irritant while adjacent tissues undergo degenerative changes. \- Both necrotic and degenerated tissue release chemical mediators that initiate and maintain the inflammatory reaction. **(2) VASCULAR RESPONCE:** **(a) Transient vasoconstriction**: Due to direct stimulation of the vascular wall of arterioles. It is inconstant finding and depends on the extent of injury. **(b) Vasodilatation**: \- Involves mainly the arterioles, but to a lesser extent, affects venules and capillaries. \- Occurs due to local axon reflex and release of vasodilator substances as histamine. \- The arteriolar blood flow is increased (**hyperemia**) in the inflamed area which becomes red and hot. Progressive vasodilatation, elevates the local hydrostatic pressure. **(c)** **Slowing of blood stream**: due to: \- Vasodilatation. \- Opening of new capillary buds. \- Increased vascular permeability. \- Increased blood viscosity due to formation of fluid exudate. \- Swelling and roughness of vascular endothelium