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.
Internal respiration, in contrast, is the exchange of gases in body tissues. External respiration is the exchange if oxygen and carbon dioxide between the blood and air in the lungs, and internal resparation is the exchange of gases between blood cells of the body. External respiration is the exchange of gases between the alveoli and lung capillaries. Oxygen diffuses from the alveoli into the blood, while carbon dioxide moves from the blood in the alveoli.