The word lymph has been derived from the Latin term "lympha", which denotes water. Hence, lymph is a watery fluid whose color varies from clear to yellow and it flows in the lymphatic system all throughout the body. Hence, it is found everywhere in our body. Circulating via the body tissues, lymph collects bacteria, fats and other redundant materials and filters these out through the lymphatic system. At times, it is possible to see this fluid, for instance when there is a cut and it weeps lymph instead of blood. The circulation of lymph all over the body via the lymphatic system is a vital part of the health of our immune system.

Lymph contains lymphocytes, which are basically white blood cells. In addition, this watery fluid also contains a small amount of red blood cells as well as proteins. Lymph has a free circulation throughout the body and bathes the cells that require oxygen and nutrients. At the same time, it picks up all harmful substances in the cell and disposes them off. Some people like to describe lymph as the body's milkman, which provides the cells with fresh supplies, while collecting the waste material for discarding them elsewhere. Similarly, a milkman supplies us fresh milk while taking away the empty bottles for processing somewhere else.

While the lymph circulates in our body, it is drawn into the lymphatic system via the widespread arrangement of blood vessels and capillaries that are connected to the lymph nodes, which are also known as lymph glands. These little nodules filter the unwanted substances in it. These nodes also generate white blood cells, thereby revitalizing the lymph before pumping the fluid into the body again. While lymph may not be as ostentatious as blood, but this fluid is also connected to a similarly complex as well as ornate vessel system.

In fact, lymph also makes it clear as to why various things like taking intramuscular shots at a doctor's chamber works. When a physician or healthcare worker injects any substances into our muscle tissue, it is first picked up by the lymph and gradually it is filtered into our bloodstream. People wearing very tight clothes or those whose circulation is obstructed may sometimes experience build up of fluids in some tissues leading to a condition known as edema. This condition can be painful as well as dangerous. In fact, edema occurs when the lymph is unable to circulate properly and draw the harmful substances out from the tissue cells.

At times, the lymphatic system can be utilized in the form of a diagnostic tool to aid physicians comprehend a disease. In fact, it is possible to biopsy lymph nodes. For instance, they are used to gather evidence about the toxins and bacterial agents in the body of a patient. There are a number of bodywork types that are meant to support healthy and free lymph circulation, which, in turn, leads to promote drainage of unwanted materials and keep the tissues healthy. Special training is required to undertake lymphatic message and different types of bodywork. This is necessary because an untrained message therapist may unintentionally cause lymphedema, a condition wherein fluids may amass in a particular limb. This condition is not only very painful, but dangerous too.

The lymphatic system is different from the cardiovascular system, as it is not closed. It has been found that in a number of reptile and amphibian species central lymph pumps exist in their lymphatic systems. These central pumps are known as lymph hearts, which usually occur in pairs. On the other hand, humans as well as other mammals do not possess any such central lymph pump. Transport or circulation of lymph is rather slow and intermittent. In spite of low pressure, movement of lymph takes place owing to peristalsis - which is forward motion of the lymph owing to smooth muscle tissues' alternate contraction and relaxation, when the neighbouring skeletal muscle compresses, valves and arterial pulsation.

Once the lymph enters the lymphatic system from the interstitial spaces, it generally does not move backwards down the vessels owing to the presence of valves. In case there is too much hydrostatic pressure inside the lymph vessels, it is possible that some fluid can leak and flow backwards into the interstitial spaces. In such cases, it can again result in edema formation.

In an average person who is in a resting state, the movement of lymph in his/her thoracic duct is usually about 100ml every hour. This is accompanied by an additional ~25ml every hour in the various other lymph vessels, taking the total flow of lymph throughout the body to roughly anything between 4 litres and 5 litres every day. However, it is possible to increase the flow of lymph by undertaking various exercises. Lymphatic massages also help in increasing the flow of lymph. It is believed that when there is no lymph flow in the body, an average person who is resting would breathe his/her last within just 24 hours.

What are lymph nodes?

Lymph nodes, also known as lymph glands, are a vital part of our immune system. They serve as "nodes" between the lymphatic vessels that are spread all over the body and connect them in a single network. These lymphatic nodes have immune cells �parked� inside them and these cells are always prepared to attack viruses, bacteria or any alien substance that invade our body. As in the case with other body areas, the lymph nodes or lymph glands are also vulnerable to various diseases like trauma, infections and even cancer. Lymph nodes play a vital role in our routine functioning of the body and, at the same time, they help to combat diseases. Below is a brief description of how these lymph glands work in our body.

As far as their arrangement is concerned, lymph nodes are bean-shaped glands. These are small glands that are found throughout the length of the lymphatic system, which are basically vessels like the arteries and veins that transport lymph instead of blood. In fact, the lymph nodes are categorized as "secondary" lymph organs, while the primary lymph organs include the thymus gland, spleen, tonsils and the bone marrow.

If you compare the primary lymph organs with courthouses, you can draw parallels between the lymphatic vessels and lengthy highways. In this case, instead of the police, the immune cells patrol the highways by surveying your body. On the other hand, the lymph nodes or lymph glands can be compared to police stations located along the highways.

While there are several hundred lymph nodes all over the body, in certain regions these lymph nodes are found in clusters.

In fact, the structure of the lymph modes is somewhat complicated. Each lymph node is separated into a number of lobules. Each of these lobules has an external cortex, which is followed by a paracortex having a medulla or core within. B lymphocytes (also known as B cells) are present inside the cortex. On the other hand, the T lymphocytes (also known as T cells) as well as the dendritic cells are found in the paracortex. The medulla or the core of the lymph nodes contains the plasma cells and macrophages. The lymph node is completely enclosed in a strong fibrous capsule protecting it from damage or any harm.

Functions of the lymph

Lymph performs multiple functions in our body. Lymph works as a mediator (middle-man) transporting various materials such as oxygen, hormones, food materials and others to the cells located in different parts of the body and brings back carbon dioxide (CO2) and other metabolic waste substances from these cells and deposit them in the blood. Eventually, these waste materials are loaded in the venous system. At the same time, the lymph helps to keep the body cells moist.

The lymph nodes also produce lymphocytes. Once the lymphocytes are produced, the lymph carries these as well as antibodies from the lymph nodes to the bloodstream. Lymph also protects us from various infections and diseases by destroying all bacteria, virus and alien substances that enter our body and found in the lymph nodes.

In the intestine, the lymph works to take up as well as transport all fats and vitamins that are soluble in fat found there. Lymph capillaries are present in the intestinal villi and they are known as lacteals. These lymph capillaries are actually associated with the absorption as well as transportation of fat and vitamins soluble in fat found in the intestines.

Lymph carries plasma protein macromolecules that have been synthesized in the liver cells to the blood. At the same time, it also brings the hormones that are produced in the endocrine glands to the bloodstream. As these are macromolecules, they are unable to enter the thin blood capillaries, but they are able to easily diffuse into the lymphatic capillaries.

Lymph also works to maintain a steady blood volume. Whenever the volume of blood decreases in the blood vascular system, the lymph immediately rushes to the blood vascular system from the lymphatic system to maintain a steady volume of blood.