Question

Human Physiology

Describe in detail the steps that lead to inflammation, beginning with the introduction of pathogens into a wound, and ending with the formation of a clot. Include in your description the types of cytokines released and the various leukocytes involved.

Answer 1

Inflammation is the immune system's response to harmful stimuli, such as pathogens, damaged cells, toxic compounds, and acts by removing injurious stimuli and initiating the healing process.

As soon as injury occurs, small blood vessels adjacent to the injury dilate (vasodilatation) and blood flow to the area increases. The endothelial cells initially swell, then contract to increase the space between them, thereby increasing the permeability of the vascular barrier.  Vasodilation occurs through release of mediators from cells. These mediators include histamine, prostacyclin and nitric oxide . Vasodilation occurs first at the arteriole level, progressing to the capillary level, and brings about a net increase in the amount of blood present, causing the redness and heat of inflammation.

Exudation of fluid leads to a net loss of fluid from the vascular space into the interstitial space, resulting in oedema, The formation of odema or increased tissue fluid acts as a medium for which inflammatory proteins (such as complement and immunoglobulins) can migrate through. It may also help to remove pathogens and cell debris in the area through lymphatic drainage

Cellular phase The predominant cell in this phase is neutrophil, they are attracted to the site of injury by the presence of chemotaxins such as interleukin,Activated macrophages in the tissue release cytokines such as IL-1 and TNFα, which in turn leads to production of chemokines that bind to proteoglycans forming gradient in the inflamed tissue and along the endothelial wall. chemokines are involved in initiating pain, as well as in the persistence of pain.  Once in the region, neutrophils recognise the foreign body and begin phagocytosis, the process whereby the pathogen is engulfed and contained with a phagosome.The phagosome than is destroyed

Following the process of acute inflammation, several process could take place depending upon the severity. Resolution: complete return to normal tissue following acute inflammation. Fibrosis takes place when the tissue destruction in acute inflammation is extensive so that there is no tissue regeneration. But when tissue loss is superficial, it is restored by regeneration.