Many of the lymphatic vessels sit just under the surface of your skin. As the lymph makes its way back toward the heart, it has to pass through the lymph nodes — small, round masses that filter out bacteria, waste, and other toxins and also contain infection-fighting white blood cells.

The nodes play a key role in recognizing and destroying these substances, while also signaling the body to launch an immune response when needed. You have clusters of lymph nodes in your groin, under your arms, and in your neck, as well as more nodes located along other lymphatic pathways in the chest, abdomen, and pelvis.

As the lymph moves out of different areas of the body, it slows down to get filtered by the regional lymph nodes. For example, lymph from the hand, arm, and under the arm, as well as the chest and upper back areas, drains to the underarm also known as axillary lymph nodes to be filtered.

Eventually the lymph travels to one of two large lymphatic ducts just below the neck , where it gets dumped into a large vein and back into the bloodstream. Just as blood is always circulating throughout your body, lymph is continuously being moved out of your tissues, through the lymphatic vessels and nodes, and back to the lymphatic ducts.

Disorders of the lymphatic system. Lymphatic Disorders. Test your knowledge. An aortic dissection occurs when the inner layer lining of the aortic wall tears and separates from the middle layer of the wall. Aortic dissection is frequently fatal. Among which of the following groups is aortic dissection most common?

More Content. Thin-walled lymphatic vessels. Proteins, minerals, nutrients, and other substances, which provide nourishment to tissues. The lymphatic system may not carry out its function adequately due to. Was This Page Helpful? Yes No. Swollen Lymph Nodes.

While each of these organs and tissues fulfils protective immune functions which are related to the lymphatic system, the lymph nodes are unique amongst the lymphoid organs because they are the only organs with lymph filtering functions. The spleen is a blood-rich organ and the largest of the lymphoid organs. It is usually purple in colour, and located in the upper-left section of the abdomen.

The spleen is surrounded by the lining of the abdominal cavity on all sides except at the hilum, where the splenic artery and vein are located. The spleen lies behind to the stomach and in front of the diaphragm, near the left kidney. It is covered by a fibrous capsule which is thickest at the hilum, where the splenic artery and vein connect and transport blood into and out of the spleen.

The spleen is composed of areas of red pulp and white pulp. Most of the red pulp consists of loose tissues and blood capillaries. The splenic white pulp is made of two types of lymphocytes; T lymphocyte infection detecting and B lymphocyte antibody producing.

The thymus is a lymphoid organ located in the lower section of the throat, overlying the heart. It receives a rich supply of arterial blood from the large arteries which connect to it.

The veins which drain blood from the thymus connect to larger veins in the chest area. The thymus is divided into two lobes which each have an outer cortex and an inner medulla. The cortex sections contain T lymphocyte stem cells, while the medulla contains mature T lymphocytes which have migrated from the cortex. The thymus also contains hormone producing cells. The lymphatic system commences development during embryogenesis the period from 4—8 weeks after fertilisation, in which the fertilised egg is called an embryo.

First, several tiny sacs called lymph sacs form. These continue to grow to form lymphatic capillaries, vessels and nodes. The vessels and clusters of nodes are visible by the 5 th week of embryo development the 7 th week of pregnancy which begins 2 weeks before fertilisation occurs. However, while the foetus remains in the womb the lymphatic system remains underdeveloped and does not function. It is not until after childbirth when lymphocytes rapidly populate lymph nodes and immune functions commence.

Before entering the lymphatic system, lymph is called interstitial fluid and consists mainly of a fluid called hyaluronan.

This interstitial fluid plays an important role in giving shape and structure to the body organs, and in order to give each organ or body part the correct structure, the volume of interstitial fluid must remain constant. If interstitial fluid accumulates, swelling occurs and the shape and structure of the organ or body part changes.

So although the lymphatic system is constantly absorbing interstitial fluid from the interstitial spaces, there is always a constant volume of interstitial fluid in a given interstitial space except for example in times of inflammation and swelling. The lymphatic system only absorbs fluid when new fluid is leaked into the space to replace that absorbed into the lymphatic system. Absorption of lymph into the lymphatic vessels plays an important role in maintaining the correct amount of fluid in the interstitial spaces to ensure that swelling does not occur.

A considerable quantity of fluid leaks from the blood circulation each day. While the majority of leaked blood is reabsorbed by the blood vessels, up to 3 L per day remains in the spaces between tissues and becomes part of the interstitial fluid. Unless this fluid is absorbed by the lymphatic system, too much fluid will accumulate in the interstitial spaces and swelling will occur. Once an organ or body part is swollen, the process by which lymph and blood exchange their component parts becomes impaired.

This stops lymph and blood exchanging potentially dangerous components such as antigens e. It enables the dangerous substance to be localised kept within a particular area.

While swelling is often a necessary immune response which prevents the spread of an antigen, in some cases the immune system functions irregularly, as swelling can occur when it is not needed to protect the body. The key function of lymph is to transport blood components back to the blood stream and maintain the correct volume of blood circulation. Interstitial fluid is fluid which has leaked from the blood circulation and contains blood cells and proteins which are essential components of blood.

Once absorbed into the lymphatic system, the interstitial fluid becomes known as lymph and travels through the lymphatic vessels to the subclavian veins where it re-enters the blood circulation and maintains blood volume. Lymph is the substance in which escaped blood cells and proteins are collected and returned to the blood circulation. However, only a proportion of the interstitial fluid which enters the lymphatic capillaries will be returned to the blood stream as lymph; the remainder is broken down in the lymph nodes.

An average human body weighing 65 kg contains approximately 12 litres of interstitial fluid and produces 8—12 litres of lymph each day. Because gravity makes it harder for lymph to be transported from the legs and the lower half of the body, lymphatic capillaries which absorb lymph are more extensive in the legs compared to the arms.

Lymphatic vessels connect to the subclavian veins, which are part of the blood circulatory system and connect to the heart. Their key function is to transport excessive tissue fluid from interstitial spaces throughout the body back to the blood stream. These vessels form a unidirectional system which always directs lymph toward the heart.

The key function of the capillaries of the lymphatic system is to absorb fluid leaked from the blood vessels into the interstitial spaces. Known as interstitial fluid it is predominately water but contains a small amount of dissolved proteins and sometimes larger particles including debris e.

Together with blood vessels the lymphatic capillaries also function to ensure that circulation through the surrounding cells and tissues is sufficient to ensure each cell gets enough nutrients, and also to ensure the cells and tissues are drained so that the fluid balance is constant. The flap-like structures on the walls of lymphatic capillaries function to increase absorption when there is too much fluid in the interstitial spaces, and reduce absorption when the fluid level decreases.

When fluid levels in the interstitial spaces increase, they create pressure which causes the flap-like structures of the capillary walls to open, allowing fluid to enter the lymph capillaries.

The flaps may open up to several micrometres. As the lymphatic capillary and vessel fill with fluid, pressure inside the capillaries increases. When pressure inside the lymphatic capillary increases above that in the surrounding interstitial space, the flaps in the capillary wall close, preventing the fluid which has been absorbed escaping back into the interstitial space.

Fluid is then pushed through the lymphatic capillaries to the collecting vessels. However, the lymphatic system does not have a central pump like the heart which pumps fluid through the blood vessels.

In the lymphatic system, fluid is pushed by spontaneous contractions of the lymphatic capillaries and other lymphatic vessels. These contractions are regulated by the nervous system and some hormones, and are the force which drives lymph through the lymphatic vessels.

Collecting vessels transport lymph from the lymphatic capillaries to the lymphatic ducts, via numerous lymph nodes. Muscles in the walls of collecting vessels contract to push the lymph through the vessels. Contractions in the arteries and skeletal muscles, breathing, blood pressure and the volume of lymph in the lymphatic system also influence the rate at which lymph is pushed through the lymphatic vessels.

Valves along the walls of collecting vessels function to prevent the lymph from flowing backwards. Pre-nodal vessels transport afferent lymph to the lymph nodes. The term bacteremia refers to bacteria in the blood.

If bacteria are reproducing in the blood as they spread, this condition is called septicemia. The presence of viruses in the blood is called viremia.

Microbial toxins can also be spread through the circulatory system, causing a condition termed toxemia. Microbes and microbial toxins in the blood can trigger an inflammatory response so severe that the inflammation damages host tissues and organs more than the infection itself. This counterproductive immune response is called systemic inflammatory response syndrome SIRS , and it can lead to the life-threatening condition known as sepsis.

Sepsis is characterized by the production of excess cytokines that leads to classic signs of inflammation such as fever, vasodilation , and edema see Inflammation and Fever. In a patient with sepsis, the inflammatory response becomes dysregulated and disproportionate to the threat of infection. Critical organs such as the heart, lungs, liver, and kidneys become dysfunctional, resulting in increased heart and respiratory rates, and disorientation.

If not treated promptly and effectively, patients with sepsis can go into shock and die. Certain infections can cause inflammation in the heart and blood vessels. Inflammation of the endocardium, the inner lining of the heart, is called endocarditis and can result in damage to the heart valves severe enough to require surgical replacement.

Inflammation of the pericardium, the sac surrounding the heart, is called pericarditis. Pericarditis and myocarditis can cause fluid to accumulate around the heart, resulting in congestive heart failure. Inflammation of blood vessels is called vasculitis. Although somewhat rare, vasculitis can cause blood vessels to become damaged and rupture; as blood is released, small red or purple spots called petechiae appear on the skin.

If the damage of tissues or blood vessels is severe, it can result in reduced blood flow to the surrounding tissues. This condition is called ischemia , and it can be very serious. In severe cases, the affected tissues can die and become necrotic; these situations may require surgical debridement or amputation.

Like the circulatory system, the lymphatic system does not have a normal microbiota, and the large numbers of immune cells typically eliminate transient microbes before they can establish an infection. Only microbes with an array of virulence factors are able to overcome these defenses and establish infection in the lymphatic system. However, when a localized infection begins to spread, the lymphatic system is often the first place the invading microbes can be detected.

Infections in the lymphatic system also trigger an inflammatory response. Inflammation of lymphatic vessels, called lymphangitis , can produce visible red streaks under the skin. Inflammation in the lymph nodes can cause them to swell. A swollen lymph node is referred to as a bubo , and the condition is referred to as lymphadenitis.

Which of the following is located in the interstitial spaces within tissues and releases nutrients, immune factors, and oxygen to those tissues? Which of the following is where are most microbes filtered out of the fluids that accumulate in the body tissues? Skip to main content. Circulatory and Lymphatic System Infections.