Acute Inflammation

1. AcuteInflammation Dr. Nisreen Abu Shahin Consultant of Pathology Assistant professor of Pathology Pathology Department, Faculty of Medicine University of Jordan

2. Inflammation Is a protective response to remove both the cause of cell injury (e.g. microbes) and to remove necrotic cells and tissues arising as consequence of cell injury. Inflammation is grouped in two basic forms : 1. Acute inflammation 2. Chronic inflammation

3. Acute Inflammation Is the immediate and rapid response to injury which is of short duration (minutes/days), characterized by fluid and plasma protein exudation, and by leukocytic infiltration, predominantly neutrophils - examples of acute inflammation: sore throat burns insect bite.

4. The Acute inflammatory response has 2 main functions: 1.Eliminating causative agent 2. Removal of necrotic cells

5. Causes of Acute Inflammation 1. Microbial Infections - One of the commonest cause of inflammation is microbial infection by producing specific exotoxins(chemicals), or endotoxins (associated with their cell walls). 2. Hypersensitivity reactions A hypersensitivity reaction occurs when an altered state of immunological responsiveness causes an inappropriate or excessive immune reaction which damages the tissues. Example: asthma

6. 3. Physical agents Physical trauma Radiation Burns Excessive cooling Acids, alkalies and oxidizing agents 4.Tissue necrosis Death of tissues from lack of oxygen or nutrients resulting from inadequate blood flow (e.g. infraction) is a potent inflammatory stimulus.

7. Effects of Inflammation The local effects are usually beneficial, however the destruction of normal tissue on the other hand may be harmful.

8. Beneficial effects: Both the fluid and cellular exudates may have useful effects, these beneficial effects are as the following: 1- Dilution of toxins: Dilution of toxins, such as those produced by bacteria, are carried away by the lymphatics. 2- Entry of antibodies & drugs Increased vascular permeability allows antibodies to enter the extra vascular space.

9. 3- Fibrin formation Fibrin formation may prevent the movement of micro-organisms trapping them. 4- Delivery of nutrients and oxygen. Delivery of nutrients and oxygen essential for the cell. 5- Stimulation of immune response. The drainage of this fluid exudate into the Lymphatics allows antigens to reach the local lymph nodes where they may stimulate the immune response.

10. Harmful effects The release of lysosomal enzymes by inflammatory cells may also have harmful effects: 1- Digestion of normal tissues. Enzymes such as collagenases and proteases may digest normal tissues, resulting in their destruction. 2- Swelling - The swelling of acutely inflamed tissues may be harmful: for example the swelling of the epiglottis in acute epiglottitis in children due to Haemophilus Influenzae infection may obstruct the airway, resulting in death. - Inflammatory swelling is especially serious when it occurs in an enclosed space such as the cranial cavity, when intracranial pressure is raised to the point where blood flow into the brain is impaired, resulting in ischemia damage (e.g. acute meningitis).

11. Clinical Aspects of Acute Inflammation The five signs of acute inflammation are: 1- Redness (rubor). - An acutely inflamed tissue appears red e.g. skin affected by sunburn - It is due to dilatation of small blood vessels within the inflamed area. 2- Heat (calor) -Increase in temperature is seen only in peripheral parts of the body, such as the skin - It is due to increased blood flow (hyperaemia) through the region, resulting in vascular dilatation and the delivery of warm blood to the area. - Systemic fever, which results from some of the chemical mediators of inflammation, also contributes to the local temperature.

12. 3- Swelling (tumor) Swelling results from edema (the accumulation of fluid in the extra vascular space as part of the fluid leakage) - And to a much lesser extent, from the physical mass of the inflammatory cells migrating into the area. 4- Pain (dolor) - For the patient, pain is one of the best known features of acute inflammation. - It can be due to : 1. distortion of tissues due to inflammatory edema 2. some of the chemical mediators of acute inflammation, including the prostaglandins and serotonin 5- Loss of function: - Loss of function, is a well-known consequence of inflammation ,movement of an inflamed area is consciously inhibited by pain.

13. Acute inflammation has 2 major components 1. Vascular change a.vasodilation (Changes in vessel caliber and , consequently increase blood flow ) b.increased vascular permeability ( transudate & exudate formation) 2. Cellular events cellular recruitment & activation

14. The components of acute and chronic inflammatory responses and their principal functions

15. Vascular Reactions in Acute Inflammation • 1-Vasodilationis induced by chemical mediators such as histamine (described later), and is the cause of erythema and stasis of blood flow. • 2- Increased vascular permeabilityis induced by histamine, kinins and other mediators that produce gaps between endothelial cells, by direct or leukocyte-induced endothelial injury, and by increased passage of fluids through the endothelium • increased vascular permeability allows plasma proteins and leukocytes to enter sites of infection or tissue damage; fluid leak through blood vessels results in edema

16. Mechanisms of increased vascular permiability • 1- endothelial cell contraction: most common • 2- endothelial injury • 3- leukocyte-mediated endothelial injury • 4- increased transcytosis of proteins (occurs via channels formed by fusion of intracellular vesicles) • 5- leakage from new blood vessles

17. The major local manifestations of acute inflammation, compared to normal

18. Formation of transudates and exudates