Blood circulatory system and Lymphatic system are the two systems that play significant role in transport mechanism.
Organisms need to be able to move materials (such as respiratory gases, nutrients, waste products and heat) both into and out of, and within, themselves - that is called as transport. Let's have a look over different transport mechanisms in human body.
Blood : The blood transports substances around the body through a large network of blood vessels. In adults the body contains 5 to 6 liters of blood. It consists of two parts – a fluid called plasma and blood cells suspended in the plasma.
Plasma : This is mainly water with a wide range of substances dissolved or suspended in it. These include:
- Nutrients absorbed from the alimentary canal
- Oxygen absorbed from the lungs
- Chemical substances synthesized by body cells, eg; hormones
- Waste materials produced by all cells to be eliminated from the body by excretion.
Blood cells : There are three distinct groups, classified according to their functions.
Erythrocytes : Also known as red blood cells. They transport oxygen and, to a lesser extent, carbon dioxide between lungs and all body cells.
Leukocytes : Also known as white blood cells. They are mainly concerned with protection of the body against infection and foreign substances and often referred as 'soldiers of human body' . There are several types of leukocytes, which carry out their protective functions in different ways, which we have covered in detail in the topic 'Immune system'. These cells are larger and less numerous than erythrocytes.
Platelets : Also known as thrombocytes. These are tiny cell fragments that play a significant part in blood clotting.
The heart and circulatory system make up the network that delivers blood to the complete body. The circulatory system, also called the cardiovascular system, is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon, hormones, and blood cells to and from the cells in the body to provide nourishment and help in fighting, stabilize temperature and pH, and maintain homeostasis.
The lymphatic system includes a network of vessels that transports fluids. Lymphatic vessels carry excess liquids that accumulate in tissues and return them to the bloodstream. The lymphatic system plays a key role in immunity by attacking toxins and cancer cells.