The Circulatory System
Heart, Blood, Blood Vessels
© PDST Home Economics

The Heart
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Pump for the blood
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In the chest, between the lungs, protected by breastbone, ribs, spine.
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Size of the owners fist.

Structure of the heart
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Hollow inside
Divided in two lengthways by septum
Has 4 chambers
Upper chambers = left and right atria (atrium)
Lower chambers = left and right ventricles
Valves separate the atria from the ventricles and prevent backflow of blood

Blood Flow through Heart
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Deoxygenated blood gathered from all around the body flows into the R atrium in veins called the vena cava .
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It then flows through the tricuspid valve into the R ventricle .
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The R ventricle contracts the tricuspid closes and the blood flows out other valves into the pulmonary artery which takes it to the lungs to have oxygen added and to have carbon dioxide removed.

Blood Flow through Heart
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The oxygenated blood returns to the L atrium in the pulmonary veins .
It then goes through the bicuspid valve into the L ventricle.
The L ventricle contracts, closes the bicuspid valve and the blood goes out through valves into the aorta the largest artery in the body.
The aorta splits into many branches and takes blood to every body cell .
The cells take food and oxygen out of the blood and put carbon dioxide and other waste into it.
Then the whole process begins again.

Flow of blood through the heart

Blood circulation in the body

Coronary circulation
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The cells that make up the wall of the heart need a supply of blood.
This blood is carried by a special artery called the coronary artery a branch from the aorta.
If these blood vessels get blocked with fat a person is suffering from coronary heart disease

Coronary artery

The blood
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4-5 litres
Plasma (yellow liquid)
Red blood cells
White blood cells
Platelets

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Red blood cells
Contain a red pigment called haemoglobin
Oxygen sticks to the haemoglobin and gets carried in the bloodstream
To make haemoglobin the body needs Iron

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White blood cells
Fewer but bigger than red blood cells
They attack and kill harmful bacteria and viruses and fight diseases.
They make anti-bodies that fight disease.

Platelets
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These make the blood clot so not too much blood is lost when we get cut.

Functions of blood
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Transport: oxygen, food, waste products, heat, chemicals.
Prevents infection, fights disease.
Prevents blood loss by clotting

Blood Vessels
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Tubes that the blood flows through
Three types
Arteries, Capillaries, Veins

Arteries
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Largest vessels
Walls made of 3 layers
1 outer connective tissue
2 middle muscle
3 inner endothelium cells
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Mainly carry oxygenated blood (pure)
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Carry blood away from the heart
Blood in arteries is under great pressure so their walls need to be strong and elastic.
The pulse is the gush of the blood through an artery near the skin surface after each heartbeat.

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Capillaries
Smallest vessels
Arteries divide again and again an eventually form capillaries.
Very thin walls made of endothelial cells
Thin walls allow substances to get out of and into the blood
Capillaries join up to make veins

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Veins
Walls are thinner than arteries but lumen is bigger
Same 3 layers in walls as arteries
Blood under low pressure so valves needed to prevent backflow
Mostly carry deoxygenated blood
(impure)
Carry blood towards the heart

Take Your Pulse