Answer the following questions in your own words.

Explain the functional correlation of circulatory system with respiratory, digestive and excretory system.

The functional correlation between circulatory system with respiratory, digestive and excretory system is as follows:

We already know that during respiration exchange of gases occurs in the lungs. The respiratory system causes the diffusion of oxygen into the blood and the diffusion of CO₂ out of the blood. The oxygen is then transported to cells of the body via the circulatory system.

The digestive system is responsible for producing nutrients by breaking complex molecules into simpler ones. The circulatory system then transports these nutrients to different cells and tissues.

The excretory system is responsible for the elimination of waste products from the body.

These waste products are transported by blood to the excretory system.

Explanation: In a multi-cellular organism the levels of organisation are: cells, tissues, organ, organ system, and organism (from smallest to largest). All parts are specialised having a particular structure to complete a particular function. However, all the organ systems work together for the good of the whole.

The respiratory system is composed of lungs. Its main function is the in-taking of oxygen and exhaling of CO_2.

The O₂ that is inhaled by the respiratory system is delivered to the rest of the body via circulatory system. The haemoglobin in the RBCs attaches to the oxygen. As the blood travels through the veins and arteries, it drops off the O₂ from the lungs to the cells and picks up the CO₂ from the cells and delivers it to the lungs to be exhaled.

Some of the O₂ that is inhaled by the respiratory system and delivered by the circulatory system is used during the digestive processes of cellular respiration in the digestive system. In the process, food (glucose) combines with oxygen to produce carbon dioxide, water and energy.

C₆H₁₂O₆ + 6O₂→ 6CO₂ + 6H₂O + Energy (38ATP)

Hence some of the CO₂ that the blood carries to the lungs is produced during the breakdown of organic materials in the digestive system.