The biggest fall in pressure in the circulation occurs in the arterioles, particularly those supplying the major organs. They are often called the resistance vessels.

Question 1: Why is the biggest pressure drop in the arterioles?

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The biggest fall in pressure in the circulation occurs in the arterioles, particularly those supplying the major organs. They are often called the resistance vessels.

Question 1: Why is the biggest pressure drop in the arterioles?

Answer: Their small radius produces a high resistance. Resistance is inversely proportional to the fourth power of the radius.

The pressure in the veins is low, but they hold a large proportion of the circulating blood volume: the capacitance vessels.

Question 2: When is the volume of blood in the veins reduced?

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The biggest fall in pressure in the circulation occurs in the arterioles, particularly those supplying the major organs. They are often called the resistance vessels.

Question 1: Why is the biggest pressure drop in the arterioles?

Answer: Their small radius produces a high resistance. Resistance is inversely proportional to the fourth power of the radius.

The pressure in the veins is low, but they hold a large proportion of the circulating blood volume: the capacitance vessels.

Question 2: When is the volume of blood in the veins reduced?

Answer: In hypovolaemia, when the body’s responses lead to vasoconstriction, particularly in the skin/gut with most of the blood kept in the central circulation to perfuse the vital organs.