Chpt. 28: The Lymphatic System

Study of the Lymphatic System will involve three main areas: 1.The Lymphatic System 2.The Formation of Lymph 3.The functions of the Lymphatic System

1.The Lymphatic System The lymphatic system is a second circulatory system. It is a one way system of dead-ending vessels (lymph vessels). These lymph vessels collect the fluid (lymph) that surrounds each cell in the body and return it to the blood. Lymph moves very slowly in lymph vessels and is pumped by the action of ordinary body muscles.

2. The Formation of Lymph The blood in arteries is under high pressure causing some fluid to be forced out of plasma in capillaries that connect to arterioles. This fluid: - surrounds every cell in the body - allows molecules to pass in and out of cells - is called tissue fluid or extra cellular fluid (ECF) This fluid is similar to plasma except it has no platelets or red blood cells and has only small amounts of white blood cells and protein.

2. The Formation of Lymph This fluid is returned to the blood in one of two ways: 1) Most (90%) of it is reabsorbed at the venule end of the capillary by osmosis. 2) About 10% of the fluid is taken up by lymph vessels and is now called lymph. Lymph is moved through lymph vessels due to normal body movements and muscular contractions. Valves prevent lymph from flowing in the wrong direction.

2. The Formation of Lymph Lymph vessels join together to form two lymph ducts. These ducts empty the lymph back into the blood at the subclavian vein in the shoulder.

Lymph Nodes Lymph nodes: are swellings found along the lymph vessels. are found in clusters forming glands at the tonsils, neck, armpits, spleen etc. contain white blood cells. Lymph nodes fight infection in two ways: by filtering bacteria and other harmful material from lymph as it passes through. by maturing and storing large numbers of white blood cells called lymphocytes.

3. Functions of the Lymphatic System Lymphatic System has the following functions: - to absorb and transport fats to the skin and organs for storage. - to fight against infection by: - filtering bacteria - maturing and storing lymphocytes - destroying micro-organisms -to help with hearing and balance in the ear. - to collect tissue fluid and return it to the blood.