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. Gas exchange between alveolar capillaries and the alveoli (oxygen movement from the alveoli into the blood, carbon dioxide movement from the blood into the alveoli). Transport of respiratory gases. Oxygen from lungs to tissues, carbon dioxide from tissues to lungs.