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 tiwssues and it absords fat from the digestive tract. It also functions as body's
defence system against micro orgaanisms and ;other harmful substances. This system includes Lymphocytes, Lymphatic veesels,

Lymph nodules,Lymph nodes, the spleen and the lthymus gland.
Lymphoid cells and tissues-Lymphatic organs contain lymphatic tissues These tissues primarilyl consist of lymphocytesThey

also contain macrophages, dendritic cells and reticular cells. Lylmphocyltes are a type of white blood cells. They

originate from red bone marrow and are carried by bloodto lymphatic organs and other tissues. there are several classes

oflylmphocytes. 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-T Lymphocytes are produced from stem cells

present in lthe bone marrow. The TLymphocytes get matured only after entering in to Thymus, la lymphoid organ through

circulatioooon. Maturatiooooon and differntiation of B cells will occur in lthe lbone marrow itself. Thus the thylllmus and

bone marrow are described as centrel or primary lymphoid organs.
Thymus is a rougly triangular, bilobed gland, It is located in the mediastinum. It lies between the sternum and the

pericardium. Its size varies with age. It is largest in the early part of life. At birth it weighs 10-15g. After puberty it

greatly decreases in size.
Each thymus lobe is surrounded by a thin capsule made of the connective tissue. It has two layers. The inner layer is the

medulla, the outer one is the cortex. The lymphocytes are found only in cortex layer.
Lymph nodes are small round structures. Their size ranges from 1-25mm. They are distributed throughout the course of the

lymphatic vessels. These nodes are found all over the body. However they are concentrated as aggregations in 3 regions of the

body. These are the inguinal nopdes in the groin, the axillary nodes in the axillary region and the cervical nodes of the

neck.
The lymph enters the lymph nodes through afferent lymphatic vessels and exists through efferent vessels. Thee nodes conain

open spaces called nuses. The sinuses are lined with phagocytic cells.
Spleen is roughly the size of a clenched fist. It is located on the left side of the abdominal cavity. It has a fibrous

capsule. The spleen contaains two types of lymphatic tissues, namely the red pulp and the white pulp.
Tonsils are the largest lymph nodules. They provide protection against bacteria and other harmful materials. In adults the

tonsils decrease in size and may disappear. There are 3 groups of tonsils in the pharyngeal walls. Of the three, the palatine

tonsils are usually refered to as "the tonsils." These are larger lymphoid masses on each side of the junction between the

oral cavity and the pharynx. The pharyngeal tonsil or adenoid are found near the junction between the nassal cavity and the

pharynx. The lingual tonsil is a loosely associated collection of lymph nodules on the posterior surface of the tongue.

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