Lymphatic System

Jai Ganesh · 2025-04-22 16:50:42

Lymphatic System

Gist

The lymphatic system is a circulatory system made up of lymph vessels, which are much like blood vessels. It drains extra fluid (called lymph) that has passed out of the blood and into tissues and returns it back to the blood.

Summary

The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system and complementary to the circulatory system. It consists of a large network of lymphatic vessels, lymph nodes, lymphoid organs, lymphatic tissue and lymph. Lymph is a clear fluid carried by the lymphatic vessels back to the heart for re-circulation. The Latin word for lymph, lympha, refers to the deity of fresh water, "Lympha".

Unlike the circulatory system that is a closed system, the lymphatic system is open. The human circulatory system processes an average of 20 litres of blood per day through capillary filtration, which removes plasma from the blood. Roughly 17 litres of the filtered blood is reabsorbed directly into the blood vessels, while the remaining three litres are left in the interstitial fluid. One of the main functions of the lymphatic system is to provide an accessory return route to the blood for the surplus three litres.

The other main function is that of immune defense. Lymph is very similar to blood plasma, in that it contains waste products and cellular debris, together with bacteria and proteins. The cells of the lymph are mostly lymphocytes. Associated lymphoid organs are composed of lymphoid tissue, and are the sites either of lymphocyte production or of lymphocyte activation. These include the lymph nodes (where the highest lymphocyte concentration is found), the spleen, the thymus, and the tonsils. Lymphocytes are initially generated in the bone marrow. The lymphoid organs also contain other types of cells such as stromal cells for support. Lymphoid tissue is also associated with mucosas such as mucosa-associated lymphoid tissue (MALT).

Fluid from circulating blood leaks into the tissues of the body by capillary action, carrying nutrients to the cells. The fluid bathes the tissues as interstitial fluid, collecting waste products, bacteria, and damaged cells, and then drains as lymph into the lymphatic capillaries and lymphatic vessels. These vessels carry the lymph throughout the body, passing through numerous lymph nodes which filter out unwanted materials such as bacteria and damaged cells. Lymph then passes into much larger lymph vessels known as lymph ducts. The right lymphatic duct drains the right side of the region and the much larger left lymphatic duct, known as the thoracic duct, drains the left side of the body. The ducts empty into the subclavian veins to return to the blood circulation. Lymph is moved through the system by muscle contractions. In some vertebrates, a lymph heart is present that pumps the lymph to the veins.

The lymphatic system was first described in the 17th century independently by Olaus Rudbeck and Thomas Bartholin.

Details

Your lymphatic system is a group of organs, vessels and tissues that protect you from infection and keep a healthy balance of fluids throughout your body. Lymphatic system organs include your bone marrow, thymus and lymph nodes. Swollen lymph nodes are a sign of common infections, like strep throat, but also more serious diseases like cancer.

Overview:

What is the lymphatic system?

Your lymphatic system is a network of organs, vessels and tissues that work together to move a colorless, watery fluid (lymph) back into your circulatory system (your bloodstream).

As a vital part of your immune system, your lymphatic system protects you from infection and destroys old or abnormal cells your body doesn’t need. Lymphatic system functions also include maintaining normal fluid levels in your body and absorbing fats and fat-soluble vitamins so they can make their way into your bloodstream.

Function:

What does the lymphatic system do?

Your lymphatic system has many functions. Its key functions include:

* Collecting excess fluid from your body’s tissues and returning it to your bloodstream. This supports healthy fluid levels in your body. Your lymphatic system also filters out waste products and abnormal cells from this fluid.
* Helping your body absorb fats. Most nutrients can travel through tiny openings (pores) in the walls of your capillaries, and your body can then absorb and use them. But certain fats and other molecules are too large to travel in this way. Your lymphatic system collects fluid from your intestines that contains these molecules and transports it back to your bloodstream.
* Protecting your body against invaders. Your lymphatic system is part of your immune system. It produces and releases lymphocytes (a type of white blood cell) and other immune cells. These cells look for and destroy invaders — such as bacteria, viruses, parasites and fungi — that may enter your body.

How does the lymphatic system work?

Every day, about 20 liters of plasma (the liquid part of your blood) flow out of tiny pores in the thin walls of your capillaries. Imagine water seeping out of a sponge. Where does this liquid go? It delivers oxygen and nutrients to the tissues surrounding each capillary. The tissues hungrily soak up all the nutrients while leaving behind waste (like a kid who finishes their food but leaves behind a pile of sticky napkins).

The plasma doesn’t mind cleaning up the mess — it picks up the waste and then returns to your bloodstream the same way it came, by flowing back through the pores in your capillary walls. Each day, about 17 liters of plasma return to your bloodstream in this way. Since 20 liters initially flowed out of your capillary walls, that means 3 liters are still roaming around in your body’s tissues.

That’s where your lymphatic system steps in. Tiny lymphatic capillaries pick up this remaining fluid from your tissues. The fluid changed its name during its journey: now instead of plasma, it’s called lymph. Your lymphatic capillaries move the lymph into larger tubes called lymphatic vessels.

These vessels keep the lymph moving until it ultimately reaches one of two major ducts in your upper chest. These are called your right lymphatic duct and thoracic duct, and they’re a bit like highway on-ramps. They merge into large veins called your subclavian veins and empty the lymph into them. From there, your lymph reenters your bloodstream and can flow through your body again.

Anatomy

* Different parts of your lymphatic system, including your spleen, tonsils and lymph nodes, are located in many places throughout your body.
* Many different organs and structures make up your lymphatic system. These parts all work together to help keep you healthy.

What are the lymphatic system organs?

The organs of the lymphatic system are your:

* Bone marrow. This is the soft, spongy tissue in the center of certain bones, like your hip bone, backbones and breastbone. Your bone marrow has the vital job of making white blood cells, red blood cells and platelets.
* Thymus. This organ is located in your upper chest beneath your breastbone, and it’s most active before puberty. It’s where T-cells (a type of white blood cell) fully mature. T-cells help your body fight off invaders.
* Lymph nodes. Lymph nodes are bean-shaped glands that monitor and cleanse lymph as it filters through them. They clear out damaged cells and cancer cells. Your lymph nodes also store lymphocytes and other immune system cells that attack and destroy harmful substances like bacteria. You have about 600 lymph nodes scattered throughout your body. Some are closely connected in groups called chains. You may be able to feel some lymph nodes through your skin, in areas like your armpits, groin or neck. Others are deeper inside your body.
* Spleen. This largest lymphatic organ is located on your left side under your ribs and above your stomach. Your spleen filters your blood and removes cells that are old or not working properly. It also keeps red blood cells and platelets available in case your body needs them.
* Mucosa-associated lymphoid tissue (MALT). This mucus membrane exists throughout your body in many important locations. For example, it lines your tonsils, airways, small intestine and appendix. MALT looks for and destroys germs that could harm you.

What are the other parts of the lymphatic system?

Your lymphatic system is a big team. Other key players include your:

* Lymph. Lymph, also called lymphatic fluid, is a collection of the extra fluid that drains from cells and tissues in your body and isn’t reabsorbed into your capillaries. Lymph contains many different substances, including proteins, minerals, fats, damaged cells, cancer cells and germs. Lymph also transports infection-fighting white blood cells (lymphocytes).
* Lymphatic vessels. Lymphatic vessels are tubes that form a complex network throughout your body. The smallest tubes are lymphatic capillaries, which ultimately connect to larger tubes that lead to two main ducts in your upper chest. The pulsing of nearby arteries and squeezing of nearby muscles help fluid move through your lymphatic vessels. These vessels contain one-way valves that keep lymph moving the right way.
* Collecting ducts. Two main ducts in your upper chest empty lymph into your subclavian veins. These are your right lymphatic duct and thoracic duct. These ducts are like highway on-ramps or merging points where lymph rejoins your bloodstream.
* Tonsils and adenoids. These structures trap pathogens from the food you eat and the air you take in. They’re part of your body’s first line of defense against invaders. Your tonsils are in the back of your throat. Your adenoids are just behind your nasal cavity but are only active during childhood.

Additional Information

The lymphatic system is a network of vessels, nodes, and ducts that pass through almost all bodily tissues. It allows the circulation of a fluid called lymph through the body in a similar way to blood. It is part of the immune system.

The lymphatic system is essential for fluid balance, absorption of fatty acids in the stomach, and immune system regulation.

Definition

The lymphatic system is a network of vessels, nodes, and ducts that collect and circulate excess fluid in the body.

There are 500–600Trusted Source lymph nodes throughout the body. These nodes swell in response to infection due to a buildup of lymph fluid, bacteria, or other organisms and immune system cells.

The lymphatic system is part of the immune system. It also maintains fluid balance and plays a role in absorbing fats and fat-soluble nutrients.

Function

The lymph system has three main functions.

Fluid balance

The lymphatic system returns excess fluid and proteins from the tissues that cannot return through the blood vessels. The fluid often collects in the tiny spaces surrounding cells, known as the interstitial spaces. Small lymph capillaries connect these spaces to the lymphatic system.

Around 90% of the plasma that reaches tissues from the arterial blood capillaries returns through the venous capillaries and veins. The remaining 10% travels through the lymphatic system.

A disruption of fluid processing can result in localized swelling, known as lymphedema.

Absorption

The lymphatic system plays a key role in intestinal function. It assists in transporting fat, fighting infections, and removing excess fluid.

Part of the gut membrane in the small intestine contains tiny finger-like protrusions called villi. Each villus contains tiny lymph capillaries, known as lacteals. These absorb fats and fat-soluble vitamins to form a milky white fluid called chyle.

This fluid contains lymph and emulsified fats, or free fatty acids. It delivers nutrients indirectly when it reaches the venous blood circulation. Blood capillaries take up other nutrients directly.

The immune system

The third function of lymph nodes is to defend the body from exposure to potentially hazardous microorganisms, such as infections.

The body’s first line of defense involves:

* physical barriers, such as the skin
* toxic barriers, such as the acidic contents of the stomach
* friendly” bacteria in the body

However, pathogens often do succeed in entering the body despite these defenses. In this case, the lymphatic system enables the immune system to respond appropriately.

How does the lymphatic system fight infection?

The lymphatic system produces white blood cells called lymphocytes. There are two types of lymphocytes: T cells and B cells. They both travel through the lymphatic system.

As they reach the lymph nodes, they come into contact with viruses, bacteria, and foreign particles in the lymph fluid.

Following contact, lymphocytes form antibodies and start to defend the body. They can also produce antibodies from memory if they have already encountered the specific pathogen in the past.

The lymphatic system and the action of lymphocytes form part of the body’s adaptive immune response. These are highly specific and long lasting responses to particular pathogens.

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#1 2025-04-22 16:50:42

Lymphatic System

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