KEGS Biology Blog


Thursday 10th January Section 3
January 10, 2013, 11:33 am
Filed under: Uncategorized

Primary defences and phagocytosis

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Primary Defences:
-Skin
-Mucus membranes found in the reproductive tract, respiratory system and the ears
-Cilia found in the trachea
Keratinocytes found in the bottom layer of the skin gradually rise to the epidermis layer and is known as keratin. The keratin found here is flaky and acts as a physical barrier to disease.

Trachea:
-Ciliated epithelial cell
-Goblet cell: Produces mucus to trap pathogens/dust and pollen. The cilia wafts mucus up the throat where the mucus is either coughed up or swallowed into the stomach. HCl in the stomach denatures the pathogen enzymes.

When pathogens get into the body and damage cells, the damaged cells release stress chemicals to stimulate B-cells and T-cells.

Phagocytes (Non-specific):
-Neutrophils: travel in blood and squeeze into tissue fluid. It is multinucleated to give it a flat shape which allows it to squeeze into the fluid.
-Macrophoges: travel in blood as monocytes where they mature in the lymph nodes.

Antigens on a pathogen are known as non-self. Once a phagocyte detects a non-self antigen, it engulfs the pathogen using its cytoskeleton which enables cells to move. The phagocyte forms an outer circle around the pathogen known as the phagosome. Lysosomes found in the phagocyte contains the enzyme lysin which fuses with the phagosome and destroys the pathogen. Once this happens, the phagocyte then attaches antigens on its surface so that the body detects it as a foreign body and destroys the phagocyte. This is known as an antigen presenting cell, and it warns the body’s defence system of the presence of pathogens.

The chemical histamine is released by the antigen presenting cell. This makes the capillaries leaky so that phagocytes and red blood cells can arrive quickly to the affected area.

Comment by candicetam




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