The Lymphatic System - Chp 27

Lymphatic system

one-way system of dead-ending vessels, which collect the fluid that surrounds each cell in the body and return it to the blood (second circulatory system within mammals)

What makes up the lymphatic system?

lymph, lymph vessels, lymph nodes, spleen, tonsils, adenoids, lacteals, thymmus

Lymph nodes

swellings in the lymph vessels to help the body fight infection

How does extracellular fluid arise?

blood in arteries is under very high pressure, causing some fluid and small proteins to be forced out of the blood plasma in the capillaries at the arteriole side

Another name for extracellular fluid:

• ECF
• Interstitial fluid
• Tissue fluid

Extracellular fluid

• fluid similar to plasma but without rbc, platelets and larg proteins
• surrounds all body cells and helps transport materials in and out of cells

Oedema

swelling caused by too much extracellular fluid in the tissues

What is the rate at which extracellular fluid is formed?

1 litre per hour, constantly being formed, must be removed and returned to the blood

How is extracellular fluid drained?

• 90% is absorbed back into the plasma at the venule end of the capillary, the reduced blood pressure in the veins helps it to be reabsorbed along with osmosis
• 10% is taken up by lymph vessels and is now called lymph

Lymph

made from tissue fluid and contains large amounts of white blood cells, protein and fats

Another name for lymph vessels:

lymphatics

How is lymph moved through lymph vessels

• moved slowly through the lymph vessels by the muscular walls of the vessels and general body movements
• valves ensure that lymph can only flow in one direction

What direction does lymph flow in?

towards the shoulder region to the subclavian veins

Where and how does lymph return to the blood?

• Smaller lymph vessels join together to form 2 main vessels, thoracic duct on the left side of the body, the right lymphatic duct at the right shoulder
• These ducts empty lymph into the blood at the subclavian veins near the collar bones at the shoulders

Function of lymph nodes

• contain a large number of white blood cells (lymphocytes) to fight infections in which lymph flows through
• filters bacteria from the lymph as it passes through
• phagocytes engulf and digest micro-organisms

Where are lymph nodes found?

in groups which form glands within the body e.g. tonsils, neck, adenoids (back of the nose) armpits, groin etc

Function of the lymphatic system

Drainage - collects excess tissue fluid from intercellular spaces and return it to the blood, keeping the volume of the blood constant
Defence against infection - filters germs in lymph nodes, maturing ans storting lymphocytes, phagocytes engulf micro-organisms and antibody production
Transport - absorbs and transports fatty acids and glycerol in the digestive system, Lymph is found in the lacteals in the villi of the small intestine