GCSE Biology, Unit 2, Lesson 3 of 8

The heart, blood vessels and blood

GCSE Biology, Organisation: tissues, organs, digestion and circulation, 25 minutes

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The double circulation, the path of blood through the heart, arteries, veins and capillaries, the parts of the blood and cardiac output.

What you will learn

  • Trace blood through the heart and name the vessels
  • Link the structure of arteries, veins and capillaries to their jobs
  • Name the parts of the blood and what they do
  • Calculate cardiac output, heart rate and rate of blood flow

A double pump

Humans have a double circulatory system: the right side of the heart pumps deoxygenated blood to the lungs, and the left side pumps oxygenated blood to the body.

Blood goes through the heart twice on each trip round the body.

  1. Body → vena cava → right atrium → right ventricle → pulmonary artery → lungs
  2. Lungs → pulmonary vein → left atrium → left ventricle → aorta → body
  • Valves stop blood flowing backwards. A faulty valve can be replaced: a mechanical valve lasts a lifetime but the patient needs anti-clotting drugs for life; a biological valve (from a pig or a donor) needs no such drugs but wears out after 10 to 20 years, so it suits an older patient.
  • The left ventricle has the thickest wall: it pumps blood all round the body.
  • Coronary arteries supply the heart muscle itself with oxygen.
  • Cells in the right atrium act as a natural pacemaker; an artificial pacemaker corrects an irregular rhythm.

The pulmonary artery carries deoxygenated blood. Arteries carry blood away from the heart, whatever is in it.

The rest of this lesson and its 13 practice questions are locked.

In this lesson

  1. A double pump
  2. Vessels and blood
  3. Cardiac output
  4. Try it: Your first cardiac output

13 practice questions, marked as you go; about 25 minutes in all.

Key terms

Valves, Left ventricle, Coronary arteries, Natural pacemaker, Plasma, Red blood cells, White blood cells, Platelets, Heart rate

In this unit: Organisation: tissues, organs, digestion and circulation

Levels of organisation, digestion and enzymes with the amylase and food test practicals, the heart, blood and lungs, heart disease and cancer, and transport in plants.

All of Organisation: tissues, organs, digestion and circulation

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