UNIVERSITY COLLEGE OF HUMANITIES Technical Lab Analysis Department. Lectures of Histopathology. INFLAMMATION NOVEMBER –

At the end of this lecture the student must be able to 1- define histopathology 2- know the uses of histopathology 3- define some pathologic terms related especially to inflammation 4- define inflammation 5- understand the components and sequence of inflammatory process

6- know the cardinal features of inflammation 7- understand why some times the inflammation is acute and other times is chronic 8-can compare between the acute and chronic inflammation 9- know the process of repair

Necrosis = the morphological changes indicative of cell death caused by progressive enzymatic degradation; it may affect groups of cells or part of a structure or an organ.

Tissue repair = restoration of tissue architecture and function after an injury.

Trigger factors = any messenger that acts on blood vessels, inflammatory cells or other cells to contribute to an inflammatory response.

Inflammatory mediators = Molecules that are released by immune and other cells during times when harmful agents or Trigger factors (exogenous or endogenous ) invade our body.

Interstitial space = pertaining to or situated between parts or in the interspaces of a tissue.

Edema = denotes an excess of fluid in the interstitial tissue ; it can be either an exudate or a transudate. Exudate = is fluid, such as pus or clear fluid, that leaks out of blood vessels into nearby tissues. The fluid is made of cells, proteins, and solid materials. Pus= a purulent exudate, is an inflammatory exudate rich in leukocytes (mostly neutrophils), the debris of dead cells and, in many cases, microbes.

Transudate = a fluid substance that has passed through a membrane or has been extruded from a tissue; in contrast to an exudate, it is of high fluidity and has a low content of protein, cells, or solid materials derived from cells.

OVERVIEW OF INFLAMMATION AND TISSUE REPAIR: Inflammation is a protective response involving host cells, blood vessels, and proteins and other mediators that is intended to eliminate the initial cause of cell and tissue injury, as well as the necrotic cells and tissues resulting from the original insult ( invader), and to initiate the process of repair ( healing ).

Although inflammation helps clear infections and other noxious stimuli and initiates repair, the inflammatory reaction and the subsequent repair process can themselves cause considerable harm if the injury is sever,and / or persistent

Etiology(causes) The causes of inflammation are many and varied: 1-Exogenous causes: Physical agents – Mechanic agents: trauma,fractures, foreign bodies, sand, etc. – Thermal agents: burns, freezing Chemical agents: toxic gases, acids, bases Biological agents: bacteria, viruses, parasites 2-Endogenous causes: Circulation disorders: thrombosis, infarction, hemorrhage Enzymes activation – e.g. acute pancreatitis abnormal or forgein cells deposit

THE COMPONENET & SEQUENCE OF THE INFLAMMATORY REACTION: 1- The inflammatory mediators 2- Vascular and metabolic reaction : 3- Cellular reactions 4- Repair or healing process.

1 - The inflammatory mediators: Inflammation is induced by chemical mediators that are produced by host cells in response to injurious stimuli. A- When the cells injured they release the cell membranes phospholipids. B- macrophages, dendritic cells, mast cells, and other cell types also secret inflammatory mediators C- injured endothelial cells and aggregated platelets at the site of injury

2- Vascular and metabolic reaction : consist of A- vasodilation and increase in the flow of blood at the site of inflammation and this will deliver more oxygen, nutrients, proteins, and more inflammatory cells and chemicals necessary for protection and repair process. B - increase in the permeability of vessels. C- Proliferation of blood vessels (angiogenesis) is prominent during repair and in chronic inflammation,

3-Cellular reaction As mentioned earlier, a critical function of inflammation is to deliver leukocytes to the site of injury and to activate the leukocytes to A- eliminate the offending agents and necrotic tissue : B -Leukocytes also produce growth factors that aid in repair.

NOTE -- The components of the inflammatory reaction that destroy and eliminate microbes and dead tissues are also capable of injuring normal tissues.

Types of inflammation : ACUTE /CHRONIC # Acute inflammation is rapid in onset and of short duration # Chronic inflammation may be more insidious, is of longer duration (days to years), and is typified by influx of lymphocytes and macrophages with associated vascular proliferation and fibrosis (scarring). however, these two basic forms of inflammation may coexist.

Cardinal signs of inflammation : 1- heat and 2-redness ( vasodilation and more blood in the area of inflammation ),3- swelling ( extravasation of protein rich fluid into extracellular spaces at the site of inflammation. 4-pain ( some inflammatory chemical act on nerve ending at the site of inflammation making them more sensitive to pain), and 5- loss of function if the inflammation is sever, prolonged and healed with scaring.