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The Immune and the lymphatic system, Immune system, Lymphatic system -…
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Immune system
Structure
Immunity is best understood as human body's line of defence against foreign agents such as bacteria and viruses also called pathogens.
First line of defence:
Mechanical barriers, for example, intact skin and mucous membrane.
Chemical barriers, for example, saliva, tears.
Reflexes, for example, coughing, sneezing, and vomiting.
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Third line of defence
- Lymphocytes- T cells and B cells that fight foreign agents.
Immunity can be either natural or active. Natural immunity is an individual’s ability to ward off pathogens and is influenced by the person’s state of health, their nutritional status and their emotional response to stress.
Active immunity occurs as the body builds up a resistance to pathogens that have been introduced through exposure or by immunisation.
Function
The immune system is a complex system of cells and responses that recognises something as foreign and acts to remove it. For example micro-organisms, foreign tissue, body cells such as in cancer.
Lymphatic system
Structure
Lymphatic capillaries, Lymphatic vessels, Lymphatic nodes, Lymphatic tissue, Lymphatic ducts.
Lymph nodes are found in the axilla (under the arm), in the neck and in the groin. Lymphatic tissue is found in the spleen, the tonsils and the thymus. It is in the lymphatic tissue the lymphocytes are formed.
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Function
The lymphatic system is closely connected to the circulatory system. It consists of an additional set of vessels through which some of the tissue passes before reaching the large veins and entering the blood.
