lymphatic system merit task for unit 11 BTEC

Topics: Immune system, White blood cell, B cell Pages: 1 (433 words) Published: February 10, 2015
Merit task- lymphatic system

A detailed explanation as to how the lymphatic system protects the body showing use of at least 4 different types of information.

It protects the body by the lymph nodes. They are hundreds of small lymph nodes clustered along the lymphatic vessels. They are bean shaped and less than 2.5cm long. Each is surrounded by a fibrous capsule. Strands of connective tissue from the capsule extend inwards and divide the node into compartments. Many reticulate fibres support the internal structures and the lymphocytes. Lymph nodes contain many B lymphocytes which many be dividing to produce plasma cells. They also contain T lymphocytes that are in transit as these cells circulate between the blood, lymph nodes and the lymphatic vessels.

As lymphatic fluid flows through these nodes, macrophages engulf bacteria, cancer cells and other particles such as bits of debris from dead cells. This cleanses the lymph fluid before it enters the blood. The lymphocytes which began life in the bone marrow but have migrated to lymph nodes and other lymph organs, can mount an immune response against any pathogens in the lymphatic fluid.

Macrophages, B lymphocytes and T lymphocytes defend us from infection. The macrophages are attracted to invading pathogens by chemicals. They ingest the pathogen and break it down into smaller pieces. They then put pieces of the pathogens outer membrane that contains the pathogens antigens onto its surface membrane. It is now called an antigen presenting cell. Each antigen has a specific shape. Somewhere in the lymphatic system there is one T lymphocyte that has receptors that fit this antigen. The macrophage searches for this T lymphocyte. When it is found, the T lymphocyte docks with the antigen on the surface of the macrophage. This stimulates the T lymphocyte to multiply and produce helper T cells and killer T cells. Helper T cells stimulate B cells to divide. Killer T cells destroy cells that are infected...


References: Books
BTEC national applied student book unit 11
AS biology Glenn and Susan Toole
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