The function of a human’s circulatory system is to transport blood around the body. The blood itself carries numerous other substances, which the body requires to function. It is circulated through a network of vessels throughout the body to provide individual cells with oxygen and nutrients, maintaining homeostasis and the immune system. It is made up of plasma, red blood cells, white blood cells and platelets. The heart pumps the blood through the blood vessels.

The main substance being Oxygen, carried by a protein called haemoglobin, found inside red blood cells. White blood cells are also vital in their role of fighting disease and infection. Blood contains platelets, which are essential for clotting the blood, which occurs following an injury to stop blood loss. Blood also carries waste products, such as Carbon Dioxide away from muscles and organs in order to be dispelled by the lungs.

Functions of blood and circulation:

Circulates oxygen, hormones and removes Carbon Dioxide

Supplying oxygen to the body is an important function of the circulatory system. Throughout inhalation, air enters the lungs and oxygen are absorbed through the air sacs into the blood. This oxygen-rich blood is pumped through the heart into the blood vessel circulation. Within the capillaries, oxygen diffuses out of the blood and into the cells of the body’s organs and tissues. At constant time, carbon dioxide -a waste product produced by cells is absorbed into the blood and transported to the lungs through the blood vessel circulation. Once this oxygen-rich blood reaches the lungs, carbon dioxide diffuses through the air sacs and is then exhaled.  Hormones are also transported throughout the body via the blood’s liquid plasma.

Provides cells with nutrients excretory and removes the waste products of metabolism

Delivering nutrients to the body is another feature of the circulatory system. When food is digested inside the stomach and intestines, its issue nutrients are absorbed into the bloodstream. Oxygen, nutrients diffuse from the blood into body cells through the capillaries. Moreover, to carbon dioxide, the circulatory device picks up metabolic waste products and toxins and transports them to the liver, kidneys and lungs for remaining removal from the body.

·         Tissue fluid

By the time blood reaches the capillary beds from an artery, it is at high pressure and this forces blood plasma out. The plasma leaves the capillary and becomes tissue fluid. As the blood plasma moves through the capillary bed towards the vein, pressure drops and stops plasma being squeezed out. Tissue fluid acts as a bridge in the diffusion of chemicals between the capillaries and the cells of the tissue. Oxygen and glucose diffuse from the blood into the tissue fluid and then into the cells. Carbon dioxide and urea diffuse from the cells into the tissue fluid and then into the blood. Since the convective supply of oxygen depends directly on blood flow, the regulation of tissue oxygenation depends critically on the regulation of blood flow. The cardiovascular system controls blood flow to individual organs by maintaining the input pressure to each organ within narrow limits by the mechanisms designed to regulate arterial pressure and by allowing each organ to adjust its vascular resistance to blood flow to an appropriate value. 

Helps regulate body temperature and pH

Body temperature regulation is a usually overlooked however important perform of the circulatory system. Blood vessels help maintain a stable body temperature by controlling the blood flow to the surface of the skin. Blood vessels near the skin’s surface open during times of overheating to allow hot blood to dump its heat into the body’s surroundings, for example, dilate and increase in size. This is vasodilation. The increased blood flow to the surface tissues under the skin means that more heat is lost. This allows the body to free itself excess heat through the skin. Conversely, if the heating temperature of the body drops, surface blood vessels constrict to conserve body heat only to vital organs in the body’s core. When body temperature is, too low vasoconstriction occurs as it reduces the blood flow to the surface tissues under the skin. As a result, less heat is lost. Blood also helps balance the body’s pH due to the presence of bicarbonate ions, which act as a buffer solution.

Clotting stops bleeding after injury

Blood clotting is managed by the platelets of the blood. Platelets normally remain inactive in the blood until they reach damaged tissue or leak out of the blood vessels through a wound. Platelets release chemical clotting factors and begin to produce the protein fibrin to act as a structure for the blood clot. The two liquid tissues of the body, the blood and lymph have separate but interrelated functions in maintaining this balance.  They combine with a third system, the immune, to protect the body against pathogens that could threaten the organism’s viability, so they defend the body against disease using the immune response.

Diffusion distance/rates in humans

Diffusion is the spreading of particles of gas or other substances in solution where they are moved from a region of a higher concentration to lower concentration. The greater the difference in concentration, the faster the rate of diffusion.  For example in these diagrams below;