Lymphatic System

What are lymph nodes?

Lymph is clear or white fluid that travels through vessels, moves within tissues and work to keep all the parts of the body clean.

After passing through the channels of the lymphatic system they drain into the lymph nodes.

The lymph nodes act as filters along the lymphatic system. These nodes trap germs like bacteria, viruses, toxins as well as cancer cells and ensure that these are removed from the body. (1)

Structure of the lymph nodes

The lymph nodes, also known as nodes, are small bean shaped structures that look like tiny bulbs and lie along the lymph vessels.

Lymphocytes

The lymph nodes hold the lymphocytes, a type of white blood cell. These act as fighters against foreign invasion by bacteria, viruses, cancer cells or toxins.

The lymphocytes also help control the immune response.

This function is brought about by bringing the lymphocytes in contact with foreign materials – usually protein on the germs or toxins called antigens. Once in contact with the antigens the lymphocytes are activated. (2)

These lymphocytes originate from stem cells in the bone marrow.

Types of lymphocyte

There are two major classes of lymphocytes - B cells and T cells.

The B cells fully develop in the bone marrow while the T cells are removed from the bone marrow in an immature form when they reach other organs like the thymus where they attain maturity to fight infections and foreign antigens. (2)

What is lymph?

The lymph is a clear or whitish fluid that flows through the lymph channels.

It flows through the tiniest of the blood vessels and lymph channels called capillaries and bathe the cells in the tissues of the body.

Like clean blood that flows in the arteries from the heart lymph also it carries oxygen and other nutrients.

While returning from the tissues the lymph carries away carbon dioxide and other toxins.

If lymph is not drained adequately, it might lead to swelling.

The lymph vessels gather all the lymph and send it towards the chest.

There is a large vessel within the chest that brings the lymph into a large blood vessel near the heart.

The filtered fluid, salts, and proteins that come via the lymph channels are all deposited in the blood.

What do the lymph nodes contain?

The lymph nodes contain immune cells that can attack and destroy the germs that the lymph vessels have gathered.

The node filters fluid and substances picked up by the lymph vessels.

Where are the lymph nodes located?

The lymph nodes are located at specific sites in clusters.

For example, all the lymph channels from the fingers, palm, and hand get filtered through lymph nodes at the elbow, or at the arm pits.

The lymph channels from the toes, legs and feet drain at the nodes behind the knees or at the groin.

The channels from the face, head and scalp get filtered at lymph nodes in the neck.

There are deeper lymph nodes as well located between lungs, around the coils of the intestines etc. (3)

What organs form part of the lymphatic system?

The major organs that are part of the lymphatic system are the spleen, thymus, tonsils and adenoids.

Of these the spleen lies within the abdomen (left side under the ribs), the thymus in the chest and the tonsils and the adenoids within the back of the mouth. (4)

Cancer and the lymphatic system

Another major fact is that the lymph channels serve to spread the cancer cells throughout the body. This is called cancer metastasis and frequently occurs via travelling of the cancer cells through the lymphatic system. (2)

Edited by April Cashin-Garbutt, BA Hons (Cantab)

Structure and function of lymph nodes

The lymphatic system is basically a channel that carries a clear or whitish fluid called the lymph. This lymph aids in clearing the tissues of infective organisms, toxins etc.

The basic structure and functions of the lymphatic system can be broken into the lymph channels. The lymph nodes, lymph and other organs. (1-4)

The lymph channels

These are a network of tubes or vessels much like the blood vessels that cover all the tissues of the body.

The lymphatic channels get progressively smaller as they pass in to distant organs and tissues.

For example, the vessel at the beginning of the arm is thicker. It branches into thinner tubes that progressively become thinner and thinner as they travel up to the fingers.

At the tips of the fingers the vessels may be the thinnest with places where they may be only a few cells thick. These are called lymphatic capillaries.

The walls of the capillaries are usually single cell thick. This helps in the movement of the immunity producing cells called lymphocytes (type of white blood cells), and the toxins, germs and chemicals to move in to the lymph capillaries freely.

The arteries also branch similarly at the tips of the organs. These capillaries give out a clear fluid called the plasma. This plasma bathes the tissues and enters the lymphatic channels as lymph.

The lymph channels eventually drain at a large lymphatic vessel called the thoracic duct at the chest that drains into a blood vessel.

All the filtered fluid, salts, and proteins as well as the debris thus ends up in the blood stream.

The lymph nodes

The lymph nodes are small bean shaped glands or bulbs that tend to occur in clusters much like grapes.

Along the lymph channels reside approximately 600 lymph nodes. These act as filters that sieve off the harmful substances brought by the lymphatic channels.

The lymphatic channels of the fingers, hand and arm for example comes to be filtered at the lymph nodes that lie at the elbow and the arm pit.

Similarly, those of the legs, toes and thighs drain and nodes behind the knees and the groin.

Lymph channels from the face, head and scalp drain at the nodes present at the back of the head, behind the ears and sides of the neck.

Some lymph nodes are located deeper within the body at the chest (between the two lobes of the lungs), around the coils of the intestines, in the pelvis etc.

The lymph nodes contain 2 regions within them – these include the cortex and the medulla.

The cortex contains collections of lymphocytes. These contain predominantly B-lymphocytes and some T-lymphocytes.

The B lymphocytes mature completely within the bone marrow while the T lymphocytes exit the bone marrow immature and attain maturity within the thymus.

The lymphatic vessels entering the lymph nodes are called afferent lymphatic vessels and those exiting are called efferent lymphatic vessels.

Lymph

This is a clear fluid that travels via the lymphatic channels. This contains fluid, debris, chemicals, toxins, bacteria, viruses and lymphocytes on its way back from the tissues.

Other organs and the lymphatic system

The lymphatic system also consists of other organs like the spleen that lies on the above left sided part of the abdomen.

It acts like a large filter to remove worn out and damaged red blood cells from the blood and recycle them.

The spleen also contains B lymphocytes and T lymphocytes. When blood passes through the organ these cells pick up the infections.

The lymphatic system also contains the thymus that lies behind the chest bone.

The thymus is a maturation site for T lymphocytes.

Tonsils and adenoids are also part of the lymphatic system. The lie at the back of the throat. These are sentinels that protect the digestive system and the lungs from bacteria and viruses.

Function of the lymphatic system

Functions of the lymphatic system include (3):

  • Drainage of fluid from blood stream into the tissues – The circulating blood through narrow vessels leads to leakage of fluid or plasma into the tissues carrying oxygen and nutrients to the tissues and carrying waste materials from the tissues into the lymph channels.

    The leaked fluid drains into the lymph vessels. This forms a circulatory system of fluids within the body.

  • Filtration of the lymph at the lymph nodes – The nodes contain white blood cells that can attack any bacteria or viruses they find in the lymph as it flows through the lymph nodes.

    The cancer cells may also get trapped similarly at the lymph nodes and thus lymph nodes act as indicators of how far the cancer has already spread.

  • Filtering blood – This is done by the spleen. The spleen filters out bacteria, viruses and other foreign particles.
  • Raise an immune reaction and fight infections – The lymphatic system especially the lymph nodes are over active in case of an infection the lymph nodes or glands often swell up in case of a local infection.

Edited by April Cashin-Garbutt, BA Hons (Cantab)

Swollen lymph nodes

Lymph nodes are present throughout the body. There are nearly 600 to 700 of these bean shaped glands that lie like bulbs at certain junctions of the lymphatic channels.

These are an important part of the immune system. These act as filters to remove the germs, infections, toxins etc. that the lymph brings from the tissues of the body.

Why do lymph nodes swell?

Because lymph nodes play an important part in fighting infections, in case of an infection they may swell. This may mean swelling of one or more lymph nodes.

In children a node is considered enlarged if it is more than 1 centimeter (0.4 inch) in diameter.

Where are the lymph nodes situated?

Lymph nodes lie in clusters at the –

  • Armpits
  • Groin
  • Sides of the neck, back of the scalp and behind the ears
  • Under the lower jaw and the chin

Common conditions that lead to swollen lymph nodes

There are some common conditions that lead to swollen lymph nodes, these include infections, cancer and other diseases. (1-4)

Infections

Infections, such as boils, abscesses or skin infections can cause swelling in the linked lymph node.

For example, if there is a major infection of the hand, there may be swollen glands at the armpit.

Infections are the commonest cause of swollen lymph nodes.

This type of lymph node swelling is usually painful. The nodes appear warm, red and are tender to touch.

There may be accompanying symptoms like fever with body aches, chills etc.

Some common causes include ear infections, gum or tooth abscess or infections, tonsillitis, skin infections, cellulitis etc.

The condition with swollen lymph nodes is termed lymphadenopathy. If there is accompanying inflammation of the nodes the condition is termed lymphadenitis.

Cancer

Lymph nodes may be swollen if a cancer or tumor from the end of the lymphatic channels has spread to the glands.

For example, if a breast tumor or cancer has spread to the lymph nodes that drain lymphatic channels from the breast, there may be swollen lymph nodes at the arm pit.

This type of lymph node swelling is usually painless.

Some blood cancers and those affecting lymph channels like Hodgkin’s or Non-Hodgkin’s lymphoma also lead to lymph node swelling.

Other diseases

Other diseases like Rheumatoid arthritis and HIV AIDS infection may also lead to lymph node swelling.

How long does the swelling last?

In case of infections the swollen lymph nodes usually disappears in a couple of days without treatment.

Antibiotics and over-the-counter medicines such as paracetamol (Acetaminophen) or ibuprofen may be taken to relieve the pain and inflammation.

If the glands are swollen due to viral infections like rubella (German measles), glandular fever or mononucleosis usually they may affect the glands of the whole body.

Treatment usually involves addressing the symptoms, plenty of rest and clear fluids.

However, it may be time to call the health care provider if the lymph nodes do not get smaller after several weeks or enlarge progressively.

It is also a sign of cancer if the lymph nodes feel hard, rubbery, and painless or fixed to the underlying structures.

It is especially important to contact the doctor if this swelling is accompanied by fever, night sweats, or unexplained weight loss that is a feature of lymphomas.

Edited by April Cashin-Garbutt, BA Hons (Cantab)

Lymph nodes and Disease

Lymph nodes are filters in the lymphatic system that sieve out infectious material as well as toxins that come via the lymphatic channels. These may be affected commonly by certain diseases or conditions.

The diseases or disorders of the lymphatic system and lymph nodes include lymphedema, lymphadenopathy and so forth. (1-5)

Lymphedema

Lymphedema is where Edema, or fluid collection, leads to swelling of limbs and other regions drained by the affected lymphatic channel.

The primary function of the lymph channels are to drain the fluids of the body. When this is impaired there may be swelling.

For example, if there is a blockage of the channels draining the legs, there may be excessive swelling of the leg.

It may be either primary or secondary. A primary condition is inherited and may be because of impaired or missing lymphatic vessels. This may appear at birth or may develop later in life with no palpable reasons or cause.

Secondary lymphedema usually occurs due to some acquired condition that has led to the lymphatic channel blockage or malfunctioning.

This could be after a surgery, injury or an infection. There may be damage to the channels or to the lymph nodes.

For therapy compression bandages may be tried to allow for adequate drainage of the accumulated lymph.

Lymphadenopathy

Lymphadenopathy occurs when the lymph nodes swell due to infections.

For example, an infection of the leg such as an abscess or cellulitis may lead to swelling of lymph nodes at the groin. These lymph nodes may be painful, red, warm and tender to touch.

Viral infections like measles, German measles (rubella), glandular fever, HIV AIDS etc. may also cause lymphadenopathy of all the lymph nodes.

Some conditions like rheumatoid arthritis affect the immunity and may lead to swollen lymph nodes.

Lymphadenitis

Lymphadenitis is inflammation of the lymph nodes usually caused due to infections

Lymphoma

Lymphoma is cancer of the lymphatic system. This cancer may be of various forms.

The major classes are Hodgkin’s and Non-Hodgkin’s lymphomas. These start as the lymphocytes in lymph nodes turn cancerous.

The lymphomas can begin in the stomach or intestinal lymph nodes as well.

Symptoms of lymphoma include fatigue or tiredness, fever, propensity for infections, unexplained weight loss and excessive sweating at night.

Other cancers like breast cancer (affects lymph nodes of the arm pit) may also spread to the nearest lymph nodes.

Filariasis

Filariasis is infection of the lymphatic channels by a worm or parasite

Splenomegaly

This is where the spleen is swollen due to a viral infection like infectious mononucleosis.

Tonsilitis

Tonsilitis is where the tonsils become infected, inflamed and swollen.

The tonsils normally protect the entrance of the gastrointestinal tract and the respiratory tract. The infection may lead to sore throat, fever, and severe difficulty and pain while swallowing.

Edited by April Cashin-Garbutt, BA Hons (Cantab)