How are the lymphatic system and the circulatory system related?

The lymphatic and circulatory systems are two large networks of vessels that contain fluid inside. We explain how they are related to each other and what is the function of each one.

Last update: July 11, 2021

The lymphatic and circulatory systems are two fundamental structures of the body. Both are formed by a extensive network of vessels that run throughout the body. Often they tend to think that they are independent and closed, but they are not.

The lymphatic and circulatory systems are interconnected. The main function of this connection is to control the amount of fluid present in the body. It also helps fight infections and diseases.

It can be complex to understand how they work. Therefore, in this article we explain everything you need to know about blood circulation and the lymphatic system and how they are related to each other.

What is the circulatory system?

The circulatory system is the responsible for transporting blood to tissues and organs throughout the body. It is made up of the blood vessels and the heart. The latter is the pump that allows the blood to be pushed through the vessels.

This is essential, since the blood carries the oxygen necessary for the cells of each tissue to survive. In addition, as an article by Visuals Online, with the blood other substances (nutrients, hormones and gases) are carried.

The circulatory system also contributes to the elimination of waste. For example, carbon dioxide or certain proteins. Almost 90% of all the blood that is pumped returns to the heart.

The other 10% seeps into the tissues, thanks to the capillaries. This filtered fluid is separated from most of the blood cells. Contains protein, waste, bacteria, and other microorganisms.

What is the lymphatic system?

The lymphatic system is, like the circulatory system, a network of vessels and tissues. In this case, the fluid being transported is called lymph. Lymphatic vessels are tubular structures that run throughout the body. There are between 500 and 600 lymph nodes that are distributed throughout the body.

The main function of the lymphatic system is to cleanse the lymph of abnormal cells or infectious microorganisms. That is, it plays a leading role in the immune system. The organs that are part are the tonsils, the thymus and the spleen.

All these organs are responsible for producing cells of the immune system, such as T lymphocytes and B lymphocytes. They are specializations that are responsible for fighting pathogens in a specific way. They travel with the lymph and become more concentrated in the lymph nodes, which act as a filter for potentially aggressive particles.

The lymphatic system is distributed throughout the body, reaching every tissue in the body.

How is the lymphatic system related to the circulatory system?

Many people tend to think that the lymphatic and circulatory systems are independent of each other. However, this is far from the truth. Blood vessels are not waterproof. Conversely, a small amount of liquid can leak out.

As an article by Breast Cancer, this fluid accumulates in the spaces between cells and tissues. At that time it is picked up by the vessels of the lymphatic system. In this way, lymph is formed.

The lymphatic system is not closed. That is, it can release and collect fluids. Unlike the circulatory system, it does not have any pump that drives the fluid, as the heart does. This is why the lymph moves more slowly.

The movement of the lymph occurs thanks to the pressure exerted by the muscles on the lymphatic vessels. Hence, it is stimulated with body movement, for example when walking.

Lymph circuit

The smaller lymphatic vessels are also called capillaries. The fluid is collected through them. The lymph leaves the lymphatic capillaries to go to the collecting vessels, which are larger and consist of valves.

Valves allow lymph to flow in only one direction. This fluid passes through the lymph nodes which, as we have pointed out before, are in charge of filtering the waste, toxins and microorganisms present.

Thanks to the fact that they contain cells of the immune system, they are able to fight against infections. Although the nodes are distributed throughout the body, there are areas in which they are more concentrated. For example, the armpits, groin, and neck.

Once it leaves the lymph nodes, the lymph travels to the lymphatic ducts. They drain into a large vein, so the fluid returns to the circulatory system.

Infections in the lymphatic or circulatory system

The lymphatic system has the function of purifying the fluids of the body to avoid infection. Typically, blood is a sterile fluid. The reason for this is that the circulatory system is closed.

However, sometimes there is infection in the blood. For example, through wounds, catheters, or needles. When this happens, immune cells, antibodies, and other agents fight off pathogens.

However, if the body cannot eliminate these microorganisms, they spread quickly. When there are bacteria in the blood there is bacteremia. In the case of viruses, there is talk of viremia. If infectious agents begin to reproduce and spread, the term of septicemia.

Infections in the lymphatic system

In the lymphatic system there is usually no type of microbiota either. Typically, immune cells kill any microbe early.

However, there are very virulent pathogens that can overcome these defenses. In that case, an infection occurs in the lymphatic system and a large inflammatory response appears. When this response occurs in the lymphatic vessels it is called lymphangitis.

If it is the lymph node that presents the inflammatory process, it is known as lymphadenitis. They are frequent situations in patients with immune compromise.

Lymphadenitis is more noticeable in children when it occurs, but it does not always denote a serious process.

The lymphatic system can be stimulated

The lymphatic system is essential. It is related to the circulatory system to maintain a constant amount of fluid in the body. What's more, They work together to protect the body from possible infections.

This system, unlike the circulatory system, does not have any pump that stimulates circulation. Therefore, there may be accumulation.

One of the ways to stimulate the lymphatic system is to exercise. For example, going for a walk, running or also doing strength training. In addition, there are other measures that can be beneficial and that are based on massage.

Manual lymphatic drains improve lymph circulation. They consist of applying gentle pressure to different areas of the body, following the path of the vessels. This reduces the appearance of edema and stimulates this system.