Endorespiration, also known as tissue respiration, can be referred to as internal respiration when oxygen is exchanged between capillaries and tissues. Endorespiration is a process in which tissues use oxygen to provide energy to the body. The oxygen carried in the blood will pass through the capillary walls during endorespiration and then enter the tissues, thus allowing the oxygen to be used by the tissues. During the metabolic process the tissues produce carbon dioxide, which then passes through the capillaries of the blood, and with the flow of the blood the carbon dioxide reaches the lungs, and through external respiration the carbon dioxide is expelled from the body. The respiratory process of the human body has a total of three interrelated links, namely, gas transport and exchange in the blood, internal respiration and external respiration, external respiration includes pulmonary ventilation and pulmonary ventilation, pulmonary ventilation refers to the exchange of gas between the blood and alveoli, and pulmonary ventilation refers to the exchange of gas between the external environment and the lungs.