Lymphatic system is supplementary system present parallel to the blood vascular system. This system is meant for returning surplus tissue fluid and tissue proteins back into vascular system. The system is composed of following structures:
Lymph Capillaries: are thin walled capillaries originating from the tissues. Their walls are similar to blood capillaries but are more permeable than capillaries (Fig 32c).
Lymphatics and lymph ducts: are wider vessels formed after joining of various lymph capillaries and these runs along the veins.
Lymph nodes: are glandular structures located along the course of lymphatics. They are associated with filtration of microorganisms from lymph and production of lymphocytes.
Lymph: is clear, colourless transparent fluid originating from tissue, circulates through lymphatics and finally mixed with blood when lymph duct joins anterior venacava.
Some important features/functions of lymphatic system are listed below:
Lymph flow is unidirectional i.e. from tissue to blood only.
Lymph flow is not active i.e. no pumping of lymph is done. It flows from tissue to blood due to pressure gradient.
By returning surplus fluid and protein to the blood, lymph maintains osmotic & fluid balance of body.
By production of lymphocytes, lymph is required for body defense activity. Obstruction to lymph flow occurs due to prolong sitting posture, resulting in swelling in legs that is development of edema.