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.
Gas exchange. The air sacs (alveoli) have a very large total surface area and a very good blood supply. There is an exchange of gases between the air sacs and their surrounding capillary blood vessels. Oxygen diffuses from the air sac into the blood.Carbon dioxide diffuses from the blood into the air sac. These four features are particularly important to our lungs efficient for gas exchange.as exchange. The air sacs (alveoli) have a very large total surface area and a very good blood supply. There is an exchange of gases between the air sacs and their surrounding capillary blood vessels. Oxygen diffuses from the air sac into the blood.