What is a Promise Ring. A promise ring, sometimes known as a pre-engagement ring, is a simple piece of jewelry that is given as a symbol of a committed, monogamous relationship. In some cases, the promise ring symbolizes purity and a decision to remain celibate until marriage.
Noun. 1. external respiration-the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation. breathing, respiration, ventilation. artificial respiration-an emergency procedure whereby breathing is maintained artificially.
External respiration is an exchange of gases by diffusion, which takes place in the lungs. Oxygen goes into the blood, in exchange for CO2, through the bronchiole into the capilleries. Internal respiration is an exchange of gases which takes place in the tissues.