This GCSE Biology quiz is all about the circulatory system, which includes the heart and the different types of blood vessels - arteries, veins and capillaries.
Blood is pumped through blood vessels and around the body by the heart. Blood first passes along the arteries to the organs, and veins return blood back to the heart. Joining the two are networks of microscopic sized blood vessels called capillaries. This ensures that oxygen and glucose are delivered to all cells of the body by the circulation, and carbon dioxide and waste materials are removed from cells for elimination from the the body.
The circulatory system is also an important part of homeostasis (keeping the body temperature accurately controlled). It takes heat from the core of the body to the skin when your internal temperature is too hot and, when your core temperature drops, blood flow is diverted from the surface capillaries to reduce further heat loss.
Humans have a double circulatory system. There is one circuit for the lungs and a second circuit for the rest of the body; blood must go through both circuits before it arrives back at its starting point. This ensures that the oxygenated blood from the lungs is re-pressurised before being sent round the rest of the body. To achieve this, the heart has two sides, one that sends blood to the lungs and the other for the rest of the body.
It is important to keep the circulatory system in a good condition for a healthy life. Exercise increases blood flow and strengthens the heart, but overdoing it can cause problems. It is possible to stretch the heart muscles if you excercise too hard. In most cases, they will gradually return to normal but in bad cases, they remain stretched, meaning the heart no longer works efficiently. Diet plays a large part in maintaining a healthy circulatory system. Making sure that you don't over eat, or eat too many foods with high levels of saturated fats is of great benefit. Saturated fats produce more of the type of cholesterol that clogs up your arteries. Smoking affects the circulatory system too, it can lead to heart disease. With a heart that doesn't work properly, daily life gets more difficult. Doctors use stents to treat narrowed or weakened arteries. A stent is usually in the form of a small tube.