6.2 The Blood System

Which feature of capillaries distinguishes them from arteries and veins?

• Narrow diameter

• Valves to prevent backflow

• Thick muscular walls

• Elastic tissue

What is an advantage of capillary walls being one cell thick in the systemic circulation?

• To allow carbon dioxide to diffuse into tissues

• To allow oxygen to diffuse out of tissues

• To allow glucose to diffuse into tissues

• To allow urea to diffuse into tissues

Which diagram represents blood flow through the mammalian heart?

• A

• B

• C

• D

What is a feature of the left atrium?

• A. Epinephrine decreases its rate of contraction.

• B. It contracts as the left ventricle contracts.

• C. It receives blood from the left pulmonary artery.

• D. Its pressure decreases as the left ventricle fills up.

Which vessel carries deoxygenated blood away from the heart?

• A. Aorta

• B. Pulmonary artery

• C. Vena cava

• D. Pulmonary vein

What helps to keep blood flowing onwards away from the heart in an artery?

• A. Valves

• B. Elastic fibres

• C. Contraction of skeletal muscles

• D. Having a wide lumen

What causes heart ventricles to fill with blood?

I. Atrial contraction

II. Closing of atrioventricular valves

III. Opening of semilunar valves

• A. I only

• B. I and II only

• C. II and III only

• D. III only

What is a role of the coronary arteries?

• A. To supply information about blood temperature to the hypothalamus

• B. To supply the heart muscle with oxygen and nutrients

• C. To carry blood away from the heart

• D. To monitor blood pH

When the left ventricle is relaxed, what is the state of the valves?

• A

• B

• C

• D

What observation did William Harvey use as evidence for the circulation of blood?

• A. The ventricles of the heart pump blood out into arteries.

• B. Valves ensure unidirectional flow of blood.

• C. Capillaries carry blood from arteries to veins.

• D. All organs of the body have a separate blood supply.