The Structure and Function of Blood Vessels

Session 3

Lesson Re-cap

Aims

• To describe the structure and function of blood vessels

Objectives

• Learners will be able to explain the role of blood, veins, capillaries, arteries and blood vessels

Blood Contains..• Plasma: a watery liquid which contains

calcium, salts and carbon dioxide.

• Red blood cells: carry oxygen from the lungs to our body cells

• White blood cells: are more plentiful than the red cells. Role is to fight infection and disease

• Platelets: produce clots when blood is damaged

Types of Blood Vessels• Arteries: are thick and elastic in texture.

Carry blood AWAY from the heart.• Veins: these are two layers thick. Carry

blood BACK to the heart.• Capillaries: narrow and thin. Connect

arteries and veins.• Arterioles: smallest vessels in body.

Direct blood from arteries to capillary network.

• Venules: direct blood from capillary network to the veins.

Arteries• Muscle action pushes the blood through

the arteries to relevant stops.• Carry blood AWAY from the heart• Arteries carry bright red blood! The colour

comes from the OXYGEN that it carries.

Veins• Transport blood BACK to the heart from

Upper and Lower sections of body• Receive blood from the capillaries after the

exchange of oxygen and carbon dioxide has taken place

Capillaries• Extremely small vessels • Transport blood from the arteries to the

veins • Responsible for the exchange of oxygen &

carbon dioxide between blood

Arterioles• Are like small arteries • Branch out from arteries and lead to the

capillary bed

Venules• Allows deoxygenated blood to return from

capillaries to veins• Quite simple things, with thinner and less-

developed walls

Blood flow and body temperatureThe circulatory system plays an important role in regulating body temperature.

If the body gets too hot, capillaries near the surface of the skin widen. Blood is diverted to the skin where the heat can easily radiate away. This is called vasodilation.

Water from the blood is excreted as sweat to cool the body.

CapillariesSweat gland

Thermoregulation

Blood flow and body temperature

If the body gets too cold, capillaries near the surface of the skin get narrower. Blood is diverted away from the skin to limit heat loss. This is called vasoconstriction.

Sweating stops.

CapillariesSweat gland

Blood vessels

Summary..

• Types of Blood Vessels????

• Role of Blood Vessels…

Any questions..