The Heart And Circulation

As an organism increases in size, which change makes diffusion alone insufficient to supply its cells?

Which feature of arteries is most directly responsible for smoothing the pulsing flow of blood between heartbeats?

A student examines a blood vessel and observes that it has a wide lumen, a thin wall, and internal valves. Which vessel is this, and why are the valves needed?

Why must red blood cells pass through capillaries in single file?

Why does the left ventricle have a thicker muscular wall than the right ventricle?

During the cardiac cycle, the AV valves close because:

At which stage of the cardiac cycle does most ventricular filling occur?

Which best explains why haemoglobin can carry up to four oxygen molecules?

The oxygen dissociation curve is sigmoid (S-shaped) because:

In actively respiring muscle tissue, what happens to the oxygen dissociation curve, and why?

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin. Which best explains the significance of this?

Approximately what percentage of carbon dioxide is transported in the blood as hydrogencarbonate ions in the plasma?

What is the role of carbonic anhydrase in red blood cells?

The chloride shift refers to:

A patient with a faulty bicuspid valve allows blood to leak backwards during ventricular systole. Which symptom would most directly result?

A mountaineer ascending to high altitude experiences a sustained fall in atmospheric pO₂. Which immediate effect on oxygen transport is most likely?

Which best describes the relationship between pressure and valve behaviour during ventricular systole?

Why does the steep middle portion of the oxygen dissociation curve give haemoglobin a functional advantage in respiring tissues?

In a patient with reduced carbonic anhydrase activity, which consequence would be expected?