trigraph. noun. 1  Three letters spelling one consonant, vowel, or diphthong, such as Sch in Schiller or igh in high or thigh. 2  A group of three letters, especially of frequent occurrence in a given language, as the or ing in English or gli in Italian.3  Any combination of three letters of an alphabet. 4  Also called trigram.rigraph. noun. 1  Three letters spelling one consonant, vowel, or diphthong, such as Sch in Schiller or igh in high or thigh. 2  A group of three letters, especially of frequent occurrence in a given language, as the or ing in English or gli in Italian. 3  Any combination of three letters of an alphabet. 4  Also called trigram.
Oxygen-carbon dioxide-The process by which oxygen passes from the air in the LUNGS to the HEMOGLOBIN in the BLOOD, and carbon dioxide from the hemoglobin passes into the air in the lungs.Oxygen-carbon dioxide exchange is fundamental to life and is the primary function of the lungs.Oxygen-carbon dioxide exchange takes place between the alveoli, the tiny bubblelike sacs deep within the lungs, and the capillaries, the tiniest blood vessels of the cardiovascular system.xygen and carbon dioxide molecules (as well as the molecules of other gases such as nitrogen and highly toxic carbon monoxide) can easily pass through the walls of the alveoli and the capillaries, moving in the direction of least resistance. Oxygen molecules move from the alveoli into the capillaries with inhalation.
The air we breathe contains oxygen and other gases. Once in the lungs, oxygen is moved into the bloodstream and carried through your body. At each cell in your body, oxygen is exchanged for a waste gas called carbon dioxide.Your bloodstream then carries this waste gas back to the lungs where it is removed from the blood stream and then exhaled. Your lungs and respiratory system automatically perform this vital process, called gas exchange.In addition to gas exchange, your respiratory system performs other roles important to breathing.our lungs and respiratory system automatically perform this vital process, called gas exchange. In addition to gas exchange, your respiratory system performs other roles important to breathing.