Friday, 10 July 2015

All About .... The Lymphatic System!

As I mentioned last week, today I want to cover the Lymphatic system.  This system helps to maintain a suitable environment for the cells of the body and to keep conditions in the blood constant.

Tissue Fluid
This bathes the body cells and is where the exchange of nutrients etcetera from the capillaries to the body cells occurs.  (see my Circulatory System blog) and where the exchange of waste products and carbon dioxide to the capillaries occurs!  This fluid and its contents are  very important as it affects the functioning of the body cells.  Excess tissue fluid drains into the Lymphatic system.

Lymph is a pale yellow or colourless fluid which carries excess tissue fluid back to the blood.  The system also transports fatty acids, some enzymes and hormones.  The Lymph also contains White Blood Cells (as mentioned last week) which help to protect the body against infection.  

Lymphatic System
This system is made up of an extensive network of vessels.  These lymphatics have very thin walls, the lymph capillaries flow into larger lymph vessels which have valves to ensure that the fluid flows in the direction of the heart.  The vessels carry excess tissue fluid back to the blood.  As well as it being essential to keep the body cell environment suitable it is also important for keeping the conditions in the blood constant.  Along the vessels there are lymph nodes, these help to protect the body against infection and disease.   
They do this by:

  • Producing and storing lymphocytes or white blood cells (WBC's) 
  • When foreign substances invade the body the WBC's multiply and engulf bacteria and secrete antibodies.  (I am planning a blog about the immune system in the future.)  The accumulation of WBC's and bacteria cause the lymph nodes to become swollen - this is particularly noticeable under the jaw or inside the thigh. 
  • Lymph nodes filter out foreign particles, bacteria and dead tissue before they enter the blood stream.

The excess tissue fluid enters the lymphatics through the thin walls (the vessels can stretch if needed).  As there is no pump (like the heart in the main circulation system) the flow depends on the valves, contraction of the vessels and external pressures like breathing, skeletal muscle and intestinal movements!  Lymph therefore moves fairly slowly.  Any blockage to the system will cause the body to swell with the excess fluid - this condition is called oedema.  

This system is obviously closely associated with the immune system so look out for a future blog about that! 

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