Role of energy in the body
Energy is necessary to circulate blood, lymph and tissue fluid throughout the body; it is necessary for breathing and taking in oxygen; it is necessary for making new cells for carrying out growth and repair; it is used to transmit nerve impulses so that it can respond to changes in the environment; and it is needed to build different complex molecules such as enzymes and hormones from the simple molecules produced after digestion of food.
The heart is a muscular pump which forces blood around the body through a system of blood vessels, namely arteries, veins and capillaries. Blood carries dissolved oxygen to the body cells and at the same time removes the waste products of respiration, carbon dioxide and water. However, blood is also important in distributing heat around the body, along with hormones, nutrients, salts, enzymes and urea. It is important that the blood flows in only one direction through the heart so it is supplied with special valves to ensure that this happens.
The force blood exerts on the walls of the blood vessels it is passing through is known as the blood pressure (BP). It can be measured using a special piece of equipment called a sphygmomanometer. Blood vessels
Arteries and arterioles Arteries leave the heart and supply smaller vessels known as arterioles which, in turn, supply the smallest blood vessels, the capillaries. Arteries usually carry oxygenated blood. The exceptions are the pulmonary and umbilical arteries carrying, respectively, blood to the lungs and placenta in pregnancy for oxygenation. The digestive system
The alimentary canal is a tube that extends from the mouth to the anus. It is dilated, folded and puckered in various places along its length. Many glands are associated with the alimentary canal, and have important roles to play in digestion. When food is taken into the mouth it is mixed with saliva, chewed or masticated by the...