Lymphatic System

Lymphatic System

    Lymphatic circulation along with blood circulation plays a key role in maintaining the fluidity in all regions of the body. It helps to maintain fluid balance in tissues and it absorbs fat from the digestive tract. It also functions as body’s defence system against micro organisms and other harmful substances. This system includes lymph, lymphocytes, lymphatic vessels, lymph nodules, lymph nodes, tonsils, the spleen and the thymus gland.

Lymphoid Cells And Tissues :

   Lymphatic organs contain lymphatic tissues.These tissues primarily consist of lymphocytes. They also contain macrophages, dendritic cells and reticular cells. Lymphocytes are a type of white blood cells. They originate from red bone marrow and are carried by blood to lymphatic organs and other tissues. There are several classes of lymphocytes.  The B-lymphocytes or B cells synthesize antibodies for recognizing and neutralising alien macromolecules. T- lymphocytes can recognize and selectively kill cells infected with viruses. B and T lymphocytes are produced from stem cells present in the bone marrow. The T lymphocytes get matured only after entering into Thymus, a lymphoid organ through circulation. Maturation and differentiation of B cells will occur in the bone marrow itself. Thus the thymus and bone marrow are described as central or primary lymphoid organs.

The Lymphatic Circulation :
 The lymph fluid from the tissues is drained by lymphatic capillaries. These capillaries though present in many tissues are absent in epidermis, hairs, nails, cornea, cartilages, CNS and bone marrow. The lymphatic capillaries join into larger vessels. The larger vessels pass to local or remote lymph nodes. These vessels and associated lymph nodes are arranged in regional groups. Each group has its region of drainage. Nodes within a group are interconnected. Such regional groups with nodes and vessels are organised in (1) Head and neck (2) Upper limbs (3) Lower limbs (4) Abdomen and pelvis (5) thorax. The regional vessels return to the venous blood circulation via the right and left lympho venous portals. Nearly eight lymphatic trunks converge at the site of the vertebral column and open into the venous portal  nearer to the neck.