I/GCSE Biology - Blood and Circulation

Blood vessel

In GCSE biology, there are three type of blood vessel will be introduced.

1. ARTERIES : carry blood away from heart 
2. VEINS : carry blood back to the heart
3. CAPILLARIES : transport oxygen, food and carbon dioxide pass in and out of the blood

Artery 

• When the heart contracts, blood is forced into arteries 
• Each beat of the heart pumps the blood along under high pressure 
• Elastic-like walls ----> stretch to take the blood
• When the walls contract and bounce back they force the blood along ----> felt as a pulse
• Thick, muscly walls

Vein

• Wider than arteries 
• Thinner walls 
• Lower pressure ----> blood flows slower 
• Blood controlled by valves to prevent blood flowing backwards

Capillaries 

• Very narrow
• Blood flows through them slowly to give time for gas exchange to occur. 
• Only one cell thick
• CO₂ passes into capillaries

Double Circulation

RIGHT side of the heart 

• Pumps blood to the lungs and then back to the heart again 
• In the lungs, the blood picks up oxygen                     
• Carries oxygenated blood
• CO₂ passes into the blood from body cells    

LEFT side of the heart 

• Pumps blood to the rest of the body, then back to the heart. 
• The blood gives up its oxygen to its body cells   
• Carries deoxygenated blood 
• CO₂ passes into theblood from the body cells 

The Heart

• 2 pumps side by side:    RIGHT SIDE ----> deoxygenated blood       LEFT SIDE ----> oxygenated blood 

• Important blood vessels in the circulation:  

1. The aorta – takes blood from the heart to the body 
2. The pulmonary artery – takes blood from the heart to the lungs 
3. The vena cava – brings blood back to the heart from the body 
4. The pulmonary vein – brings blood back to the heart from the lungs 

• Ventricles have muscular walls to pump the blood 
• The valves prevent blood flowing back into the atrium
• Left ventricle is stronger as ithas to pump the blood further 
• When the muscle contracts, thechamber gets smaller and squeezes the blood out 
• Diastole  ----> when the muscles are relaxed 
• Systole  ----> when the muscles contract
• The right ventricle pumps blood to the lungs in the pulmonary artery
• Deoxygenated blood returns to the right atrium in the vena cava 
• Oxygenated blood returns to the left atrium in the pulmonary vein 
• The left ventricle pumps blood to the rest of the body in the aorta

In this GCSE Biology article, you have to remember :

1. The types and features of different blood vessel 
2. The concept of double circulation 

That's the end of today's topic!

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