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Medicine & The Body Medium ⚡ 10 Questions ⏱️ ~7 Mins +100 XP

The Heart and the Blood

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The circulatory system is a closed loop with a pump at one end of it, and that idea is only four hundred years old. Ten questions on the plumbing and the fluid inside it.

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~7m

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Medium

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+100

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About this topic

For fifteen centuries, European medicine followed Galen in believing that blood was made in the liver and consumed by the body like fuel. William Harvey worked out in the 1620s that there is nowhere near enough liver to manage that, and that the same blood must go round and round. He could not see the vessels linking arteries to veins, so he had to argue they existed. A microscope found them thirty years later. These ten questions cover the parts of that loop: which chamber pushes hardest, which valve sits where, and what red cells, platelets and plasma are each doing. A couple turn on the detail that trips people up most, which is that arteries and veins are named for direction of travel, not for what they are carrying.

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The Heart and the Blood: all 10 questions and answers

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1Which vessel carries blood out of the heart to the rest of the body?
- A Vena cava
- B Pulmonary artery
- C Coronary artery
- D Aorta Correct
Answer: D. Aorta

Why: The aorta leaves the left ventricle, arches over and runs down through the chest and abdomen. It is the largest artery in the body, roughly the width of a garden hose in an adult.
2Which chamber of the heart pumps blood into the aorta?
- A Left atrium
- B Right atrium
- C Left ventricle Correct
- D Right ventricle
Answer: C. Left ventricle

Why: The left ventricle has by far the thickest muscular wall because it has to drive blood around the entire body. The right ventricle pushes against much less resistance, since it only has to reach the lungs.
3Where do the pulmonary arteries carry blood to?
- A The brain
- B The lungs Correct
- C The liver
- D The kidneys
Answer: B. The lungs

Why: They are the only arteries carrying oxygen-poor blood, because an artery is defined by leading away from the heart rather than by what it holds. The pulmonary veins do the reverse, bringing oxygen-rich blood back.
4Which structure acts as the heart's natural pacemaker?
- A Sinoatrial node Correct
- B Atrioventricular node
- C Bundle of His
- D Purkinje fibres
Answer: A. Sinoatrial node

Why: The sinoatrial node, a small patch of tissue in the wall of the right atrium, generates the electrical impulse that sets the rhythm. The other three structures relay that signal onward rather than starting it.
5Which component of blood is chiefly responsible for clotting?
- A Red blood cells
- B White blood cells
- C Plasma cells
- D Platelets Correct
Answer: D. Platelets

Why: Platelets are cell fragments that clump together at a wound and set off a cascade of proteins that seals it. They are made in the bone marrow, like the other components of blood.
6Roughly what proportion of blood volume is plasma?
- A Roughly 75 per cent
- B Roughly 40 per cent
- C Roughly 55 per cent Correct
- D Roughly 25 per cent
Answer: C. Roughly 55 per cent

Why: Plasma is mostly water carrying dissolved proteins, salts, sugars and waste, and red cells make up most of the remainder. Spin a sample in a centrifuge and the two separate into visible layers.
7Which blood type is described as the universal donor for red cell transfusions?
- A B negative
- B O negative Correct
- C AB positive
- D A positive
Answer: B. O negative

Why: O negative red cells carry neither the A, the B nor the RhD antigen, so there is nothing for another person's immune system to react against. AB positive is the mirror image, the universal recipient.
8Who first correctly described the circulation of blood around the body?
- A William Harvey Correct
- B Galen
- C Andreas Vesalius
- D Marcello Malpighi
Answer: A. William Harvey

Why: Harvey set out the closed circuit in his 1628 book De Motu Cordis, using measurement rather than authority to make the case. Malpighi found the capillaries that completed the picture in 1661, under one of the first microscopes.
9What is the valve between the left atrium and the left ventricle called?
- A Tricuspid valve
- B Aortic valve
- C Pulmonary valve
- D Mitral valve Correct
Answer: D. Mitral valve

Why: The mitral valve has two flaps and takes its name from the shape of a bishop's mitre. The tricuspid valve on the right side of the heart has three.
10Which blood vessels are thin enough for oxygen to pass through their walls into tissue?
- A Veins
- B Venules
- C Capillaries Correct
- D Arteries
Answer: C. Capillaries

Why: Capillary walls are a single cell thick, so gases and nutrients cross straight through them. They are so densely spread that almost no living cell in the body sits more than a fraction of a millimetre from one.

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