Lesson 5

Learning Objectives1.Compare the structure and function of arteries, veins and capillaries2.Describe arterioles and venules.3.Describe the transfer between capillaries and tissue fluid.4.Describe lymph formation and the function of the lymphatic system.5.Describe the differences between lymph, blood plasma and tissue fluid.

Outline Blood vessels: artery, vein, capillary. Exchange of materials. Lymphatic system

Blood VesselThere are 3 types of blood vessel.

• Extremely narrow tubes.• The wall is very thin (only one cell thick).• No valve.• Lumen is very small (about the size of only

one red blood cell).

Exchange of MaterialsExchange of materials occur between capillaries,

tissue fluid and body cells.

Tissue Fluid

Tissue fluid = interstitial fluid = extracellular fluid.

It is exactly like blood plasma but without the protein and red blood cells.

Tissue fluid surrounds and bathes the body cells.

Exchange of MaterialsWhat materials are exchanged?

Oxygen, nutrients such as glucose and waste products such as carbon dioxide.

How are the materials exchanged?

Nutrients and oxygen diffuse out of the blood in the capillaries into the tissue fluid, and from there into the body cells.

Waste products formed diffuse out from the body cells into the tissue fluid and from there diffuse into the blood in the capillaries.

Movement of these substances are aided by:● The pressure from the arteriole.● Diffusion and active transport.

Lymphatic System

Lymphatic System The lymphatic system is a system of thin tubes that runs

throughout the body. These tubes are called lymph vessels or lymphatic vessels.

The lymphatic system is like the blood circulation. But the lymphatic system tubes are much finer and carry a colourless liquid called lymph.

Lymph is a clear fluid that circulates around the body tissues. It contains a high number of white blood cells (lymphocytes). Plasma leaks out of the capillaries to surround and bathe the body tissues. This then drains into the lymph vessels.

The fluid, now called lymph, then flows through the lymphatic system to the biggest lymph vessel - the thoracic duct. The thoracic duct then empties back into the blood circulation.

Lymphatic System