The main function of the respiratory system is to inhale oxygen and exhale the waste product carbon dioxide. Oxygen is breathed through the mouth and nostrils into the lungs. The gas then diffuses through the alveolar walls and into the red blood cells. Carbon dioxide carried back within erythrocytes diffuses back through the alveolar walls and is exhaled out through the mouth.
The cardiovascular system has a role of circulating blood around the body. The contents of blood being circulated include nutrients, gases and waste products. The main organs involved within this process are blood, arteries, veins, heart and the lungs.
The function of the digestive system is to absorb and adapt key nutrients which are required to maintain and regulate other systems in the body. Enzymes secreted within the digestive system have a role of breaking down food from proteins into amino acids, starch into glucose and fats into a mixture of fatty acids and glycerol.
It can be analysed that the two body systems work together. Which are the respiratory system and the cardiovascular system. Oxygen is inhaled and enters the respiratory system. It travels down into the lungs through the trachea. Once inside the lungs, the gas enters the alveoli and diffuses through the alveolar wall. After it diffuses through the capillary wall, it enters the cardiovascular system. Oxygen then binds with haemoglobin forming oxyhaemoglobin and is then transported around to cells within the body. Carbon dioxide is transported as a waste product within red blood cells through the cardiovascular system. This needs to be exhaled