Catabolic reactions can be described as one of the two types of metabolic reaction (other being anabolic) which occur within cell when complex organic molecules are broken down to form simpler, smaller molecules.
For example - Respiration, which involves glucose breakdown in order to form carbon dioxide and water. Generally they are type of hydrolysis reactions, which include water to break bonds present in complex molecules.
Large amount of energy is also released during these reactions.
The circulatory system transports blood throughout the body through the veins. The circulatory system works with the respiratory system because it transports oxygen through the body as well. It works with the digestive system because it transports waste so it can be disposed.
