Lymphatic System

Body fluids are the medium of supply in the body. In the average 70 kg adult, human total body water is about 60 per cent of the body weight or about 42 litres. Two types of body fluids are:

• Intracellular Fluid: It is present inside the body cells. About 28 of the 42 litres of fluid in the body is inside the 75 trillion cells. The intracellular fluid contains a large amount of potassium and phosphate ions and proteins, moderate quantities of magnesium and sulphate ions and only small quantities of sodium and chloride ions and almost no calcium ions.
• Extracellular Fluid: The extracellular fluid is mainly present as interstitial fluid and blood plasma. The interstitial fluid (tissue fluid) is about 11 litres and plasma contributes about 3 litres in a normal adult. Plasma includes blood plasma and lymph plasma. Lymph plasma is similar to blood plasma except that lymph plasma has lower protein content. The interstitial fluid surrounds each cell. The plasma is the noncellular part of the blood and communicates continuously with the interstitial fluid through the pores of the capillary membranes. These pores are permeable to almost all solutes in the extracellular fluid except proteins.

Transcellular fluid is known as a specialized type of extracellular fluid. All the transcellular fluids together constitute about 1 to 2 litres.

Lymph (Tissue Fluid)

Lymph is a mobile connective tissue consisting of lymph plasma (fluid) and lymph corpuscles (cells). Lymph plasma belongs to the category of blood but has not had many blood proteins, less calcium and phosphorus and high glucose concentration. Mostly globulin proteins are present which are actually antibodies. Other components of the lymph plasma also match that of blood plasma, that is organic, inorganic substances, water, etc. The organs secreting lymph are called lymphoid organs. The spleen is known as the largest mass of lymphatic tissue in the body.

Physical Properties

• Lymph is a white vascular connective tissue.
• It is a highly translucent, alkaline fluid present in the lymph vessels and between the blood capillaries and the tissues.
• It also forms the tissue fluid which surrounds the body tissues.
• The fluid that flows through the lymphatic system is called lymph tissue fluid.
• It is helpful in the maintenance of fluid balance.

 

Lymph Composition

Lymph is formed of two parts:

1. Plasma: It is a fluid matrix of lymph. It is similar to that of the blood except that it has fewer proteins, calcium and phosphorus. It is actually derived from the blood by the process of ultrafiltration.
2. Leucocytes (WBCs): These are floating ameboid cells of lymph. These also resemble those of blood. These also come from the blood by diapedesis. The main cells are lymphocytes. These are also fewer in number. So, the lymph is blood minus RBCs, Platelets and some Proteins.

Lymph Structure

The composition of the human body is lymph, lymphatic vessels, lymphatic nodes and lymphoid tissue. The lymph fluid is a non-colour, watery fluid that consists of mainly WBCs and is transported by the lymphatic system. Its production site is lymph nodes, which are small bean-shaped organs. The lymph is responsible for the collection of debris and waste products from the tissues and moves them to the bloodstream, which afterwards carries them to the liver and kidneys for elimination. Lymph also carries WBCs, which are essential in immunity, to and from the tissues.

Lymph Circulation

The lymphatic system is a circulatory system that helps in getting rid of toxins and waste products. The lymphatic system is formed of a network of thin tubes known as lymph vessels. These vessels move lymph, a fluid that contains WBCs, all over the body. Lymph vessels branch out into lymph nodes. Lymph nodes are situated throughout the body, including in the neck, under the arms, and in the groin.

The lymphatic system works with the cardiovascular system to circulate blood throughout the body. Lymph vessels help in carrying lymph alongside blood vessels. When the body’s cells want nutrients and oxygen, the blood vessels bring these things to the cells. When the cells generate waste, the lymph vessels take the waste away from the cells and to the lymph nodes. There, the waste is taken out and the lymph is cleansed before it is returned to the cardiovascular system.

Lymphoid Organs

The lymphoid organs are the spleen, thymus, and lymph nodes. The lymphoid organs produce lymphocytes, which are a type of WBC. The lymphoid organs are also responsible for the filtering of blood and the removal of foreign material. The body’s lymph system is divisible into primary lymphoid organs and secondary lymphoid organs. The primary lymphoid organs are known as the sites for the maturation of B and T cells and the secondary lymphoid organs are where these cells are further differentiated and perform their functions.

Functions of Lymph

Lymph performs the following functions:

• The lymph acts as the middleman between blood and the tissue cells as it passes on food and oxygen from the blood to tissue cells and hands over excretory wastes hormones and carbon dioxide from the body cells to the blood.
• Lymph present in the lacteals of intestinal villi helps in the absorption of fats.
• It also transports fat food from the intestine to the venous blood.
• It transports carbon dioxide and nitrogenous wastes from tissue fluid to blood.
• Lymph nodes generate lymphocytes. Lymph carries lymphocytes and antibodies from the lymph nodes to the blood.
• The lymph helps in the protection of the body against infection as it is loaded with White blood cells such as lymphocytes.
• Lymph maintains the volume of the blood.

Parts of the Lymphatic System

The lymphatic system consists of several parts such as:

• Lymph: It is also known as lymphatic fluid. It is a collection of the extra fluid that moves out from cells and tissues adding other substances. Other substances include proteins, minerals, fats, nutrients, damaged cells, cancer cells and bacteria, viruses etc.
• Lymph nodes: Lymph nodes are bean-shaped glands that inspect and cleanse the lymph as it filters through them. These nodes help in producing and storing lymphocytes and other immune system cells that attack and destroy bacteria and other hazardous substances in the fluid.
• Lymphatic vessels: Lymphatic vessels are also known as lymph vessels or lymphatics. These are thin-walled vessels or tubes, structured like blood vessels, that move lymph.
• Collecting ducts: The lymphatic vessels deplete into collecting ducts, which empty their contents into the two subclavian veins, situated under the collarbones. These veins join to form the superior vena cava, the large vein that drains blood from the upper body into the heart.
• Spleen: Spleen is the largest lymphatic organ located on the left side of the body under the ribs and stomach. Its chief function is storing and filtering blood and producing WBCs that fight against infection.
• Thymus: It is situated in the upper chest beneath the breast bone.
• Tonsils and adenoid: These lymphoid organs works by trapping pathogens from the surrounding air we breathe and the food we eat.
• Bone marrow: It is spongy tissue present inside some bones, such as hip and thigh bones. It consists of stem cells.
• Peyer’s patches: Peyer’s patches are small masses of lymphatic tissue in the mucous membrane that lines your small intestine.
• Appendix: It is believed that the appendix plays a role in housing “good bacteria” and repopulating the gut with good bacteria after the infection has cleared.

Conditions that Affect the Lymphatic System

Several conditions can affect the vessels, glands and organs that make up the lymphatic system. Some of the common diseases and disorders of the lymphatic system are as follows:

Swelling or Accumulation of Fluid (Lymphedema)

• People suffering from lymphedema are at risk for serious and potentially life-threatening deep skin infections.
• This disease can be very mild or quite painful.
• It is also often seen when lymph nodes are removed from those who had surgery or radiation to remove cancer.

Enlarged Lymph Nodes (Lymphadenopathy)

• Enlarged (swollen) lymph nodes are caused by infection, inflammation or cancer.
• Lymphadenitis refers to lymphadenopathy i.e.,  caused by an infection.
• Common infections due to enlarged lymph nodes include strep throat, mononucleosis, HIV infection and infected skin wounds.

Cancers of Lymphatic System

• When lymphocytes grow and multiply uncontrollably, a cancer of lymph nodes occurs named “Lymphoma“.
• There are numerous types of lymphoma, including Hodgkin’s lymphoma and non-Hodgkin’s lymphoma.

FAQs on Lymph (Tissue Fluid)

Question 1: What is lymph made up of?

Answer:

Lymph is a clear white fluid composed of White blood cells, especially lymphocytes, the cells that attack bacteria in the blood.

Question 2: Which is the largest lymphatic organ in the body?

Answer:

The spleen known as the largest lymphatic organ is situated on the left side of the human body. The spleen controls the numeral of red blood cells and it also helps in fighting infection.

Question 3: Give two differences between blood and lymph.

Answer:

1. Blood is a red-coloured fluid while lymph is colourless.
2. Blood transports nutrients and gases from one organ to the other whereas lymph is responsible for the maintenance of the fluid balance in the body.

Question 4: What is the function of lymph in our body?

Answer:

Lymph transports fat food from the intestine to the venous blood and maintains the volume of the blood.

Question 5: What are the components of the lymphatic system?

Answer:

The lymphatic system includes all lymphatic vessels and lymphoid organs like the lymph nodes, thymus, and spleen as well as the lymphatic tissue like Peyer’s patches and tonsils.

Question 6: Name some diseases of the lymphatic system.

Answer:

Some of the common diseases of the lymphatic system are lymphedema, lymphadenopathy and cancers of the lymphatic system.