Structure And Function Of The Lymphatic System – 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, lymphoid tissues and lymphatic network.

Lymph is a clear fluid that is carried by lymphatic vessels back to the heart to restore circulation. (The Latin word for lymph, lympha, refers to the fresh water deity “lymph”).

Structure And Function Of The Lymphatic System

The human circulatory system processes an average of 20 liters of blood per day through capillary filtration, which removes plasma from the blood. Approximately 17 liters of filtered blood is absorbed directly into the blood vessels, the remaining three liters are left in the interstitial fluid. One of the main functions of the lymphatic system is to provide an additional return route to the blood for the excess three liters.

Lymphatic System Organs, Functions, Diseases

Another main function is to strengthen the immune system. Lymph is very similar to blood plasma in that it contains waste products and cell debris along with bacteria and proteins. Lymph cells are mostly lymphocytes. Associated lymphoid organs consist of lymphoid tissue and are sites of lymphocyte production or lymphocyte activation. These include the lymph nodes (where the highest concentration of lymphocytes are found), the spleen, the thymus, and the tonsils. Lymphocytes are originally formed in the bone marrow. Lymphoid organs also contain other types of cells, such as stromal cells.

Fluid from the circulating blood leaks into the tissues of the body through capillaries, carrying nutrients to the cells. Fluid bathes tissues as interstitial fluid, collecting waste products, bacteria, and damaged cells, and flows as lymph into lymphatic capillaries and lymphatic vessels. These blood vessels carry lymph throughout the body, passing through a series of lymph nodes that filter out unwanted materials such as bacteria and damaged cells. Lymph moves into much larger lymphatic vessels called lymphatic ducts. The right lymphatic duct drains the right side of the area, and the much larger left lymphatic duct, called the thoracic duct, drains the left side of the body. The ducts empty into the subclavian veins to return to the circulation. Lymph is moved through the system by muscle contractions.

The lymphatic system consists of a conducting network of lymphatic vessels, lymphoid organs, lymphoid tissues, and circulating lymph.

Primary (or central) lymphoid organs create lymphocytes from immature progenitor cells. The thymus and bone marrow constitute the primary lymphoid organs involved in lymphocyte tissue production and early clonal selection.

The Lymphatic System 1: Structure, Function And Oedema

The bone marrow is responsible for both the creation of T-cell precursors and the production and maturation of B-cells, important cell types of the immune system. From the bone marrow, B cells immediately join the circulatory system and move to secondary lymphoid organs in search of pathogens. T cells, on the other hand, travel from the bone marrow to the thymus, where they continue to develop and mature. Mature T cells join B cells in searching for pathogens. The remaining 95% of T cells begin the process of apoptosis, a form of programmed cell death.

The size of the thymus increases from birth in response to postnatal antig stimulation. It is most active during the newborn and adolescent period. The thymus gland is located between the lower part of the neck and the upper chest. During early puberty, the thymus begins to atrophy and shrink, with adipose tissue mostly replacing the stroma of the thymus. However, residual T-cell lymphopoiesis continues throughout adulthood, providing some immune response. The thymus is where T lymphocytes mature and become the immune system. The loss or absence of the thymus gland results in severe immunodeficiency and, consequently, a high susceptibility to infection. In most species, the thymus is composed of lobules divided by septa composed of epithelium, often considered an epithelial organ. T cells mature from thymocytes, proliferate and undergo a selection process in the thymic cortex before being honed in the medulla for interaction with epithelial cells.

Studies in bony fish showed accumulation of T cells in salmon thymus and lymphoid tissue in the spleen, and showed that non-lymphoid tissues do not have many T cells.

The thymus provides an inductive virion for the development of T cells from hematopoietic progenitors. In addition, thymic stromal cells enable the selection of a functional and self-tolerant T cell repertoire. Therefore, one of the most important tasks of the thymus is the induction of central tolerance. However, the thymus is not where the infection is fought because the T cells have not yet influenced the immune response.

Solved] 6, Describe The Location, Structure, And Function Of The Following…

Secondary (or peripheral) lymphoid organs, which include the lymph nodes and spleen, maintain mature naïve lymphocytes and initiate the adaptive immune response.

Activation leads to clonal expansion and affinity maturation. Mature lymphocytes circulate between the blood and secondary lymphoid organs until they fight with their specific antig.

Sple synthesizes antibodies in its white pulp and removes antibody-coated bacteria and antibody-coated blood cells through the blood and lymph node circulation. The white pulp of the spleen ensures immune function thanks to the lymphocytes located there. The spleen also consists of red pulp, which is responsible for the release of old red blood cells and pathogens. This is carried out by macrophages residing in the red pulp. A study published in 2009 using mice showed that the spleen contains half of its reserve of monocytes in the red pulp of the body.

These monocytes migrate into injured tissue (such as the heart) to become dendritic cells and macrophages, while promoting tissue repair.

Lymphatic System Disorders

The spleen is the center of activity of the mononuclear phagocytic system and can be considered analogous to a large lymph node in that its abscess predisposes to certain infections. In particular, the spleen is important for many functions. The spleen removes pathogens and old erythrocytes from the blood (red pulp) and produces lymphocytes (white pulp) for the immune response. The spleen is also responsible for recycling some erythrocyte components and discarding others. For example, hemoglobin is broken down into amino acids, which are recycled.

Studies in bony fish have shown that the white pulp of the spleen has a high concentration of T cells.

Like the thymus, the spleen has only lymphatic vessels. Both the short gastric arteries and the splice artery supply it with blood.

In humans, up to the fifth month of pratal development, the spleen produces red blood cells; after birth, the bone marrow is solely responsible for hematopoiesis. As a major lymphoid organ and a central player in the reticuloendothelial system, the spleen maintains the ability to produce lymphocytes. Sple stores red blood cells and lymphocytes. It can store a lot of blood cells to help in an emergency. Up to 25% of lymphocytes can be stored at once.

Solved] 1. What Are The Functions Of The Lymphatic System? 2. Describe The…

A lymph node is an organized collection of lymphoid tissue through which lymph travels back to the blood. Lymph nodes are located at certain intervals along the lymphatic system. Several afferent lymphatic vessels bring in lymph, which seeps through the substance of the lymph node and is drained by the efferent lymphatic vessel. About 300 of the nearly 800 lymph nodes in the human body are located in the head and neck.

Many are grouped in different areas, such as the armpits and abdomen. Clusters of lymph nodes are usually found in the proximal ds of the limbs (groin, axillae) and neck, where lymph is collected from areas of the body that may become infected with the pathogen caused by injury. Lymph nodes are especially numerous in the mediastinum of the chest, neck, pelvis, armpits, groin, and along with the intestinal vessels.

The substance of the lymph node consists of lymphoid follicles in an outer part called the cortex. The inner part of the node is called the medulla, which is surrounded by the cortex on all sides except for a part known as the hilum. The hilum sits as a depression on the surface of the lymph node, making the otherwise spherical lymph node look bean-shaped or ovoid. The Effert lymphatic vessel exits directly from the hilum lymph node. Arteries and veins that supply the lymph node with blood and exit through the hilum. A region of the lymph node called the paracortex immediately surrounds the medulla. Unlike the cerebral cortex, which contains mostly immature T cells, or thymocytes, the paracortex contains a mixture of immature and mature T cells. Lymphocytes channel the lymph nodes through specialized high dothelial vulcans found in the paracortex.

A lymph follicle has a dse collection of lymphocytes, the number, size and configuration of which change according to the functional state of the lymph node. For example, follicles expand significantly by repelling foreign antig. The selection of B-cells, or B-lymphocytes, takes place in the germinal ctre of the lymph nodes.

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Secondary lymphoid tissue provides vironmt for foreign or altered natural molecules (antigens) to interact with lymphocytes. This

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