Humans have a double circulation. The right ventricle pumps deoxygenated blood to the lungs; the left ventricle pumps oxygenated blood to the body at high pressure, so its wall is thicker. Blood enters the heart into the atria, passes through valves to the ventricles, and leaves through arteries: the pulmonary artery to the lungs and the aorta to the body. Valves stop backflow. Coronary arteries supply the heart muscle itself.
Blood is made of plasma, red blood cells, white blood cells and platelets. Red cells contain haemoglobin to carry oxygen and have no nucleus. White cells fight infection. Platelets help blood clot. Plasma carries glucose, carbon dioxide, urea, hormones and heat. Blocked coronary arteries cause heart disease, treated with stents or statins.
Worked example
Why is the left ventricle wall thicker than the right?
- The right ventricle pumps blood only to the nearby lungs.
- The left ventricle pumps blood all round the body.
Answer:It needs more muscle to produce higher pressure.
Key words
- double circulation
- blood passes through the heart twice per circuit
- ventricle
- lower chamber that pumps blood out
- haemoglobin
- the protein in red cells that carries oxygen
- platelets
- cell fragments that help blood clot
New questions every time.
NGSS-referenced: HS-LS1-2