The lymphatic system is a network of tissues and organs that primarily consists of lymph vessels, lymph nodes and lymph.The tonsils, adenoids, spleen and thymus are all part of the lymphatic system. There are 600 to 700 lymph nodes in the human body that filter the lymph before it returns to the circulatory system. When bacteria are recognized in the lymph fluid, the lymph nodes make more infection-fighting white blood cells, which can cause swelling. The lymph flows in only one direction — upward toward the neck — within its own system. It flows into the venous blood stream through the subclavian veins, which are located on either sides of the neck near the collarbones. Plasma leaves the cells once it has delivered its nutrients and removed debris. Most of this fluid returns to the venous circulation through the venules and continues as venous blood. The remainder becomes lymph.
Lymph leaves the tissue and enters the lymphatic system through specialized lymphatic capillaries.
The main functions of the lymphatic system are:
- To collect and transport tissue fluids from the inter-cellular spaces in all the tissues of the body, back to the veins in the blood system.
- To returning plasma proteins to the bloodstream
- To transport digested fats from the villi in the small intestine to the bloodstream via the lacteals and lymph vessels.
- To manufactured new lymphocytes and antibodies in the lymph nodes to assist the body to build up an effective immunity to infectious diseases;
- To filter out micro-organisms (such as bacteria) and foreign substances such as toxins, etc.
- To transports large molecular compounds such as enzymes and hormones from their manufactured sites to the bloodstream.
You can click on the link below for some practice questions:
1.
Lymphatic system
2.
Phagocytic cells
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