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The Lymphatic System explained in details


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The lymphatic system runs though the body and is made up of organs and lymphatic tissue, this includes organs like the spleen and thymus and also lymphatic tissue like lymphatic capillaries, vessels and nodes. These components help achieve the functions of the lymphatic system which are the draining of interstitial fluid, transportation of lipids and fighting infection (immune response).  

At the extremities of the lymphatic system are the lymphatic capillaries. They are blind end tubes and are bigger than blood capillaries , they also have a unique one-way structure that allows interstitial fluids in but not out [1] they are very permeable. Lymphatic capillaries are not everywhere in the body, for example they are not found in nervous tissue, the brain or spinal cord, but can be found in vascular tissue. 


Their roll is to absorb interstitial fluid that has built up in the tissue, in the process they also pick up broken cells, bacteria and viruses . Attached to the capillaries are anchoring filaments which extend out from the capillary attaching lymphatic endothelial cells to the surrounding tissue. So if there is an accumulation of fluid in an area, the resulting swelling will cause the anchoring filament to be pulled, opening up the cells of the lymphatic capillaries wider to enable them to absorb the excess fluid more rapidly. 

The capillaries then form lymphatic vessels , the lymphatic’s  are larger than the capillaries and open out into lymphatic nodes. The fluid, lymph (a usually clear fluid containing electrolytes, proteins and lymphocytes) is helped along by skeletal muscle contractions and also by respiratory movements, the lymphatic’s have a one way valve to prevent backflow.

 The lymph will always pass through at least one lymph node.  There are approximately 600 lymph nodes in the body and are bean-shaped. They are between 1 -25mm long and are found usually in groups. They are named according to where they are, what they surround or the organ they receive lymph from.




There are main groups of nodes such as axillary nodes, inguinal nodes and cervical nodes.  The nodes are surrounded by an external capsule made of collagen.  Projecting in from the external capsule are trabecula also called septa.

 The trabeculae divide the node, provide support and also allow blood vessels a route into the interior node. On one side is a depression called hilus, this is also where blood vessels leave and enter and also where efferent lymphatic vessels
emerge


 The lymph node is like a filtration system. Lymph enters the node by the afferent lymphatic’s, into the cortical sinuses and then into the medullary sinuses. The sinuses are lined with macrophages which destroy substances like damaged cells, unwanted protein and bacteria by ingesting. This process is called phagocytosi. Lymphocytes then destroy other substances by immune response through the production of antibodies

Lymphocytes will also become detached and leave the node in the lymph entering the blood stream where they can then deal with infection in the tissues.  The lymph, once it has been cleaned then leaves the node via the efferent lymphatics. The efferent lymphatics at this point then join to form lymph trunks which then empty into two main ducts, the thoracic duct and the right lymph duct. 

The lymph from specific areas is drained into one or the other, so lymph from left side of the head, neck and thorax, left arm, whole of the abdomen, both legs and ileum all drain into the thoracic duct  this is the main duct and is about 38-45cm long and begin as a dilation called cistern chyli That leaves the right side of head, neck and thorax and also the right arm to drain into the right lymph duct  which as about 1.2cm long. From here the lymph finally enters the blood stream via the subclavian veins.  
As well as the lymph system there are several other components that make up the complete lymphatic system. These include the thymus, red bone marrow found in flat bones and epiphyses of long bones in adults, the splee and lymphatic nodules (tonsils and peyer’s patch)

The spleen is a dark red highly vascular organ about 12 cm long and is similar in construction to a lymph node having a capsule, hilum and trabeculae. the spleen is the largest single mass of lymphatic tissue in the body. It is filled with white and red pulp. The white pulp is lymphoid tissue and the red is filled with blood and cords of phagocytic cells. The function of the spleen in the case of the lymph system is to destroy bacteria, worn out red blood cells and platelates by phagocytosis which is completed in the white pulp.

The thymus is a gland and is made up of lymphoid tissue, which is larger in children than adults as the lymphoid tissue is replaced by connective tissue and fatSpecial lymphocytes are produced here which attack and destroy antigens.

Red bone marrow creates B cells which are mature, immunocompetent  and T cells which migrate to the thymus where they become mature.

Lymphatic nodules are masses of lymphatic tissue, they can be small and solitary or they can become a group in specific areas of the body like the tonsils
The Lymphatic System explained in details The Lymphatic System explained in details Reviewed by gafacom on June 03, 2019 Rating: 5

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