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The heart and blood
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The heart pumps blood around a double circulatory system. Blood carries oxygen, nutrients and much more.
Blood components
Red blood cells: carry oxygen using haemoglobin; no nucleus; biconcave shape.
White blood cells: fight infection.
Platelets: help blood clot.
Plasma: carries dissolved substances such as glucose, carbon dioxide and urea.
White blood cells: fight infection.
Platelets: help blood clot.
Plasma: carries dissolved substances such as glucose, carbon dioxide and urea.
Blood vessels
Arteries: carry blood away from the heart at high pressure; thick, muscular, elastic walls.
Veins: carry blood back to the heart; thin walls, valves.
Capillaries: one cell thick, for exchange with tissues.
Veins: carry blood back to the heart; thin walls, valves.
Capillaries: one cell thick, for exchange with tissues.
The heart
Right side pumps blood to the lungs; left side pumps blood to the body. The left ventricle has the thickest wall.
Order: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta.
Cardiac output = stroke volume × heart rate
Order: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta.
Cardiac output = stroke volume × heart rate
Stroke volume is 70 ml and heart rate is 72 beats per minute. Find the cardiac output.
- Cardiac output = 70 × 72
- = 5040 ml/min
Answer: 5040 ml per minute
Red cells carry oxygen, white cells fight infection, platelets clot, plasma carries dissolved substances. Arteries away, veins back with valves, capillaries for exchange. Cardiac output = stroke volume × heart rate.
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