• What Is The Lymphatic System?
|What Is The Lymphatic System?
The lymphatic system is a network of tubes (capillaries and vessels) that drain excess fluids from the body's cells and return them to the bloodstream for eventual filtering and excretion. An easy way to picture the lymphatic system is to think of the water drainage system in a house: the pipes in your home drain water from the toilet, sink and bath and return it to the main pipe network outside your house for elimination by your local town sewage system. The pipes in your home are the lymphatic system, the main network is your bloodstream and the local town sewage system is your kidneys. If there is a problem with the lymph system it may result in edema (swelling) if excess fluid builds up. The lymph system also plays a major role in protecting the body against infections and cancer. For this reason it is part of the immune system. Additionally, the lymphatic system also plays a part in the absorption of fats from the intestines.
In order to understand the lymphatic system you need to understand what happens in the blood circulation system at tissue level. Blood travels to and from tissues throughout the body delivering nutrients and removing waste. Whole blood never leaves the capillaries (tiny blood vessels) but leucocytes and the 'passengers' (oxygen, food and water) can. Once outside the capillaries they are carried by a derivative of blood plasma called tissue fluid (or interstitial fluid). This fluid circulates throughout the tissues, delivering food, oxygen and water to the cells and collecting carbon dioxide and other waste. However, when it has finished its work and needs to return to the blood capillaries, not all of it can pass back through the capillary walls because the pressure inside the capillaries is too high. The fluid that is left is picked up by a different set of capillaries, called the lymphatic capillaries.
Lymphatic capillaries have larger pores in their walls than blood capillaries and the pressure inside them is lower. Thus, excess tissue fluid, substances made of large molecules, fragments of damaged cells and foreign matter such as micro-organisms drain away into them. The fluid, known as lymph, is filtered by the lymph nodes then collected by the lymphatic ducts before entering the right and left subclavian veins and returning to the bloodstream. At any one time an average of 1 to 2 liters of lymph fluid is circulating the body.
The lymphatic system consists of:
Structure: Each node is made of lymphatic tissue, surrounded by a wall of tough, white fibrous tissue supported by inward strands of fibrous tissue called trabecule. Lymph nodes vary in size.
The lymphatic system links to:
The lymphatic system has no pump to make the lymph fluid move. Instead fluid is circulated as a side effect of muscle movement (physical activity) and heartbeats. When the muscles in our body contract they squeeze (compress) the lymph vessels so that lymph fluid is moved on. Valves inside the vessels (which only open in one direction) ensure that the fluid always flows in the right direction.
The lymphatic system is a subsidiary circulation, helping the blood circulation to carry out its functions. It removes excess fluid from tissues and carries large particles that cannot pass through the smaller pores of the blood capillaries. Lymph nodes and the spleen filter lymph (the name of the fluid in the lymphatic system) and take out the waste materials it contains as well as producing antibodies and lymphocytes which are added to the lymph to be transported to the blood.
When you have an infection (such as a cold), the lymph nodes (sometime referred to as 'glands') in your neck or groin or under your arm may swell. This is a sign that white blood cells (lymphocytes) are fighting germs. If the infection is severe, the vessels leading from the nodes can become inflamed (lymphangitis). The following is a list of other common, and less common diseases and disorders that affect the lymph system:
• Provides a channel for transporting excess tissue fluid away from tissues and back to the blood circulation.
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