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 primary function of the respiratory system is to exchange oxygen and carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli. The layers of cells lining the alveoli and the... The primary function of the respiratory system is to exchange oxygen and carbon dioxide. Inhaled oxygen enters the lungs and reaches the alveoli. The layers of cells lining the alveoli and the...