Chapter 28 The Lympathatic System

Learning Objectives

1.To describe the structure of the lymphatic system to include lymph nodes and lymph vessels.

2. To describe three functions of the lymphatic system

• Lymphatatic System is a second transport system in the body.

• It is a one way system of dead ending vessels called lymph vessels

• The lymph vessels collect the fluid that surrounds each cell in the body and return it to the blood.

• Lymph nodes are swellings in the lymph vessels.

• Lymph nodes help to fight infection in the body.

Tissue fluid:• Is plasma without red blood cells, platelets or

large proteins• Surrounds all body cells and helps transport

materials in and out of cells

• Tissue fluid returns to the plasma in two ways:

• most enters blood capillaries• some enters dead-ending lymph vessels where

it is called lymph. Lymph is later returned to the bloodstream

Quiz

1. What is tissue fluid?

2. What do lymph vessels do?

Answers

1. Tissue fluid is plasma without red blood cells, platelets or large proteinsSurrounds all body cells and helps transport materials in and out of cells

2. Lymph vessels collect the fluid that surrounds each cell in the body and return it to the blood

Lymph is made from tissue fluid and contains white blood cells, proteins and fats.

Valves in lymph vessels control the direction of lymph flow.

Lymph returns to the blood in the subclavian veins (near the collar bones).

Formation of Lymph• Blood in blood vessels is under higher pressure than blood in veins.• This causes some fluid and small proteins to be forced out of blood

plasma in capillaries. This fluid is called tissue fluid (extra cellular fluid ECF) and it surrounds all body cells.

• As tissue fluid is continuously being formed (about one litre an hour) it must be removed and returned to the blood. Tissue fluid is drained away by two routes:

• About 90% of the tissue fluid is drawn back into plasma in the capillaries near the veins by osmosis and by reduced blood pressure in the veins.

• About 10% of the tissue fluid enters dead ending tubes called lymph vessels (lymphatics) This fluid is now called lymph.

Lymph contains large amounts of white blood cells, proteins and fats.

Lymph Vessels• Found throughout the

body.• Lymph moves slowly

through the vessels by general body movements and the muscular walls of lymph vessels.

• Valves ensure lymph can only flow towards the shoulder region.

Lymph vessels join together to form the thoracic duct on left of body and the right lymphatic duct at the right shoulder.

These ducts empty lymph into the bloodstream at the sub clavian veins near the collar bone of the shoulder

Lymph Nodes• Small swellings found along the

lymph vessels• Contain large numbers of white

blood cells (lymphocytes)• Have many channels through

which lymph flows.• Found in clusters (groups) which

form glands in areas such as tonsils, adenoids (back of nose) and neck.

• Lymph nodes fight infection by a) filtering bacteria and other harmful materials from lymph

b) They mature and store large numbers of white blood cells (lymphocytes) which kill micro-organisms.

Functions of Lymphatic System

1.Forms a link between the different parts of the blood (i.e. plasma produces tissue fluid, tissue fluid forms lymph and lymph returns to the plasma)

1.Collects tissue fluid and returns it to the blood.

3. Defends the body against infection by filtering micro-organisms in lymph nodes, maturing and storing lymphoctyes

4. Absorbs and transports fats in the digestive system.

Quiz

1. List two functions of the lymphatic system?