The blood has several main functions;
1. It carries nutrients to all the cells – mainly from the small intestine, where the food nutrients are absorbed through the intestine wall into the blood.
2. It carries waste products away from the cells. These may be broken down when the blood gets to the liver, or extracted for excretion when in the kidneys.
3. It carries oxygen from the lungs to the cells for energy; and carries carbon dioxide from the cells to the lungs for excretion.
4. In addition, the blood has various other functions – for example, it transports hormones from the special ‘endocrine’ glands where they are made, to the ‘target’ organs or areas which they are designed to affect. These affected areas could be the reproductive areas, or perhaps the kidneys.
A further function of the blood is to help regulate body temperature. For example, if you are too warm, the blood vessels dilate to help shed heat from the body and cool it down.
Lymph fluid consists of
1. The ’tissue fluid’ in which all cells are bathed, and
2. The fluid within the ‘lymph vessels’. These are ‘blood vessel’ like tubes, which connect the lymph glands of the body. The main lymph gland areas are the sides of the neck, armpits, groin and appendix.
The lymphatic system is also called the immune system. It is important to keep the lymph fluid circulating well, because it helps to carry nutrition to the cells and takes away waste products, and also-most importantly – helps to move white blood cells to where they are needed. White blood cells are the ‘cavalry’ of the body. They deal with disposing of the debris from broken down cells in the body, as well as attacking invading agents, such as poisons and bacteria.
Hence the process of circulation is necessary for continued life of the cells, tissues and even of the whole organism. Circulation begins early in fetal life. It is estimated that a given portion of blood completes its course of circulation in approximately 30 seconds.