blood from the heart gets around

the body through blood vessels

There are 3 types of blood vessels

a. ARTERY

b. VEIN

c. CAPILLARY

Thick smooth muscle

Thin smooth muscle

Elastic layer Elastic layer

The ARTERY

thick muscle and elastic fibres

Arteries carry blood away from the heart.

the elastic fibres allow the artery to stretch under pressure

the thick muscle can contract to push the blood along.

Copyright Pearson Prentice Hall

Blood Vessels

Aorta

• Transport oxygenated blood from left ventricle to rest of body

• Forms the characteristic aortic arch• Largest artery of the body

Pulmonary arteries

• Brings deoxygenated blood from right ventricle to lungs to uptake oxygen

• The ONLY arteries that transport deoxygenated blood

• 2 pulmonary arteries – one to each lung

The CAPILLARYCapillaries link Arteries with Veins

the wall of a capillaryis only one cell thick

they exchange materials between the blood and other body cells.

The exchange of materials between the blood and the body can only occur through capillaries.

Copyright Pearson Prentice Hall

Blood Vessels

artery vein

capillaries

body cell

The CAPILLARYA collection of capillaries is known as a capillary bed.

The VEINVeins carry blood towards from the heart.

thin muscle and elastic fibres

veins have valves which act to stop the blood from going in the wrong direction.

body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel.

Copyright Pearson Prentice Hall

Blood Vessels

Copyright Pearson Prentice Hall

Blood Vessels•Large veins contain valves that keep blood moving toward the heart. •Many veins are located near and between skeletal muscles.

Valve open

Valve closed

Valves closed

• Brings deoxygenated blood from head and arms to right atrium of heart

Superior Vena Cava

Inferior Vena Cava

• Brings blood from bottom part of body into right atrium of heart

Pulmonary Vein

• Transports oxygenated blood from the lungs back to the left atrium of heart

• The ONLY vein that carries oxygenated blood• 2 pulmonary veins – one from each lung

Hydrostatic & Osmotic Pressures

• The high hydrostatic pressure on the arterial side squeezes water and nutrients out of the capillaries.

• Water leaving the capillaries builds up the osmotic pressure because the blood components have become more concentrated.

• Towards the venal end, water and waste materials are sucked into capillaries by the osmotic pressure.

Veins and Venules Capillaries Arteries and Arterioles

                                       

                  

                                       

                       

                                       

                 

Function is to carry blood from tissues to the heart

Function is to allow exchange of materials

between the blood and the tissues

Function is to carry blood from the heart to the

tissues

Thin walls, mainly collagen, since blood at

low pressure

Very thin, permeable walls, only one cell thick to

allow exchange of materials

Thick walls with smooth elastic layers to resist high pressure and muscle layer

to aid pumping

Function : Carry blood away from heart

Function : Carry blood towards from heart

Large lumen to reduce resistance to flow.

Very small lumen. Blood cells must distort to

pass through. Small lumen

Many valves to prevent back-flow

No valves No valves (except in

heart)

Blood at low pressure Blood pressure falls in

capillaries. Blood at high pressure

Blood usually deoxygenated

(except in pulmonary vein)

Blood changes from oxygenated to deoxygenated

(except in lungs)

Blood usually oxygenated (except in

pulmonary artery)

Veins and Venules Capillaries Arteries and Arterioles

Valves • Found in the heart and veins• Folds of the inner walls of heart and veins• Shaped like half moons, so called semilunar valves• Function: Prevent backflow of blood.

Textbook pg 130 NEXT

BACK

Unidirectional flow of blood

Vericose Veins

• When the valves in the veins near the surface of the skin fail to close properly

• Allow blood to accumulate in the veins• Causes vein to bulge (swollen appearance)

NEXT

BACK

Valves fail to close properly