Lymphatic System

Lymphatic System Outline:

Lymph vessels Carry lymph from tissue spaces to the venous system, starts blindly as lymph capillaries in tissue spaces, their walls are permeable to substances of much greater size
Central Lymphoid Tissues
Bone Marrow Produces all pluripotent lymphoid cells (in adults), helps in differentiation of B-Lymphocytes
Thymus Helps in differentiation of T-Lymphocytes
Peripheral Lymphoid Organs
Lymph node Small nodules of lymphoid tissue found in the course of smaller lymph vessels, purify the lymph from harmful agents
Spleen Removes old blood cells from circulating pool, Keeps a reserve of blood for emergency, Synthesizes antibodies

Epithelio-lymphoid tissues

Lymphoid nodules in places like alimentary canal and respiratory tracts, Works as a security check agains all the incoming agents.
Lymphocytes Mature B- and T-Lymphocytes circulating in blood, protects the body against any infectious agent that enters the blood
Functions Removal of particulate matter, Production of lymphocytes, Generation of immune responses

Introduction to Lymphatic System:

Lymphatic System

Lymphatic System (Source: TheEmirr/Wikipedia)

Lymphatic system is the drainage system of human body and is accessory to the venous system. At arterial ends of capillaries fluid leaks out and at the venous end, it is absorbed back in. Some of the fluid remains in the tissue spaces. This fluid is called lymph and the system by which this lymph is returned back to blood is called lymphatic system. In addition to its drainage function, lymphatic system is also an effective defense system of the body because some organs of the lymphatic system (lympho-reticular organs) are involved in defense activities of the body.

Components of lymphatic system:

Lymphatic system is composed of the following important components.
LYMPH VESSELS:Lymph vessels are pathways for flow of lymph around the body. Lymph vessels begin as lymph capillaries that begin blindly in tissue spaces and lead to larger lymph vessels. Lymph vessels do not arise from avascular structures, brain, spinal cord, bone marrow and splenic pulp. Larger lymph vessels anastomose freely with one another and they ultimately drain the lymph into the venous system.
CENTRAL LYMPHOID TISSUE: Central lymphoid tissue consists of bone marrow and thymus.
PERIPHERAL LYMPHOID ORGANS: Peripheral lymphoid organs are lymph nodes, spleen and epithelio-lymphoid tissues (lymphoid tissue present in epithelium e.g. lymphoid tissue of alimentary and respiratory tracts).
CIRCULATING POOL OF LYMPHOCYTES: It contains mature progenies of T-lymphocytes and B-lymphocytes. They form the first line of defense of the body during antigenic emergencies.
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Functions of Lymphatic System:

  1. REMOVE PARTICULATE MATTER: Lymph capillaries absorb and remove large protein molecules and other particulate matter from tissue spaces. In this way cellular debris and other harmful particles are washed away.
  2. FILTER THE LYMPH FOR FOREIGN HARMFUL PARTICLES: Lymph nodes act as filter for the lymph and in this way they purify the lymph flowing through them.
  3. PHAGOCYTOSIS: Antigens are removed from lymph by phagocytic activity of cells of lymph node.
  4. PRODUCTION OF LYMPHOCYTES: Mature B-lymphocytes and mature T-lymphocytes are produced in lymph nodes.
  5. IMMUNE RESPONSES: Lymphatic system can induce both cellular and humoral immune responses.

Learn Lymphatic system at

Lymphatic system is explained in the following sections: