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.
Commonly known as external respiration this refers to the process of gas exchange between the lungs and 'external' environment. Read this page and find out how it all happens and why our blood is sometimes referred to as 'blue'. Once pulmonary ventilation (inhaled a breathe of air) has taken place and the lungs are filled with air, the second stage of respiration takes place, pulmonary gas exchange.