TABLE OF CONTENTS Lymphatic system transports lymph fluid from tissues to the circulatory system.
This appendix briefly describes the human lymphatic system.
Lymphatic system is a secondary circulatory system as shown in Figure A-1:
Blood plasma leaks from the capillaries of the circulatory system due to hydrostatic pressure, and fills the space between individual cells of the tissue. As a result, blood plasma becomes interstitial fluid. About 90% of this fluid is returned to the circulatory system through capillaries by osmosis. The remaining 10%, called lymph, gradually diffuses into another set of capillaries called the lymph capillaries. Lymph diffusing into capillaries carries excess fluids from body tissues and absorbed fatty acids. This diffused lymph is processed by lymph nodes before being returned into the circulatory system. It carries fat processed from fatty acids.
Lymphatic system consists of lymphoid organs, lymph ducts, and lymph vessels. Movement of lymph in lymphatic vessels takes place by peristalsis. Lymphatic system vessels have semilunar valves that permit only one way flow of lymphatic fluid under rythmic squeezing action of skeletal muscles. This rhythmic contraction of lymphatic vessels also results in lymphatic fluid getting drawn into the lymphatic capillaries. From these capillaries, the fluid moves successively to larger vessels. Through these larger vessels, fluid from the right upper body reaches the right upper duct, and from rest of the body the fluid reaches the thoracic duct. From these ducts the fluid finally drains into the circulatory system. Lymphoid tissues such as...
