Cambridge O Level Biology · Syllabus 5090 · Transport in Humans
Double Circulation
What is Double Circulation?
Double circulation is an arrangement in which blood passes through the heart twice during one complete circuit of the body: once through the right side on the low-pressure pulmonary circuit to the lungs, and once through the left side on the high-pressure systemic circuit to the body tissues. The low pressure in the pulmonary circuit protects the thin-walled lung capillaries, while the high pressure in the systemic circuit delivers blood rapidly to every organ.
This definition is part of the Transport in Humans chapter in Cambridge O Level Biology.
Double Circulation in context
The human circulatory system is a muscular pump (the heart), a network of blood vessels and the blood itself, with one-way valves that keep blood moving in a single direction. Blood passes through the heart twice during one complete circuit of the body, which is what makes the system a double circulation: a low-pressure pulmonary circuit to the lungs and a high-pressure systemic circuit to the rest of the body.
Common mistakes with Double Circulation
- “Double circulation means the blood goes round the body twice.” CorrectBlood passes through the heart twice during one complete circuit of the body: once on the way to the lungs and once on the way to the rest of the body.
- “Double circulation means the blood goes round the body twice.” Why wrongIt confuses the number of trips round the body with the number of visits to the pump. WriteBlood passes through the heart twice during one complete circuit of the body: once on the pulmonary circuit and once on the systemic circuit.
Questions students ask about Double Circulation
What is double circulation in humans?
Double circulation means that blood passes through the heart twice during one complete circuit of the body: once through the right side on the low-pressure pulmonary circuit to the lungs, and once through the left side on the high-pressure systemic circuit to the rest of the body.