. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Release of Energy aoc (c) Bronchi.—The trachea usually branches into two bronchi, that resemble it in structure with the exception of being smaller in size and in having weaker skeletal rings. There are three bronchi in certain ruminants, pigs, and whales, but in most snakes, with the degeneration of one lung as an accommodation to the extraordinarily elongated shape of the body, there remains only one bronchus. (d) Bronchioles.—Bronchioles, which cont
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. The Release of Energy aoc (c) Bronchi.—The trachea usually branches into two bronchi, that resemble it in structure with the exception of being smaller in size and in having weaker skeletal rings. There are three bronchi in certain ruminants, pigs, and whales, but in most snakes, with the degeneration of one lung as an accommodation to the extraordinarily elongated shape of the body, there remains only one bronchus. (d) Bronchioles.—Bronchioles, which continue and multiply the air passages from the bronchi, have only limited cartilaginous supports which are in the form of rings. These supports become progressively smaller, and the mucous cells of the linings of the bronchioles fewer, until both are com- pletely absent from terminal bronchioles. The latter serve simply as ducts leading the way into the ultimate air chambers, or alveoli, in which respi- ration occurs. In mammals generally the bronchioles arise like the twigs of a tree and diverge from each other, but in crocodiles and birds they run together, forming intercommunicating loops instead of terminal twigs, from the sides of which alveoli are given off. - Endothelium Blood in Capillary Respiratory. Air in ^s> Epithelium Alveolus Fig. 338. Diagram showing relation of capillary, carrying blood, to alveolus, containing air. (e) Alveoli.—The alveolar sacs, or the respiratory part of the whole system of air passage-ways, are hemispherical enlargements at the ends of the bronchioles. They have exceedingly thin delicate highly elastic walls over the outside of which, like vines over a trellis, extends a closely woven maze of capillaries (Fig. 338). It is estimated that in a pair of human lungs there may be more than six million of these tiny chambers, all in ultimate communication with the outside atmosphere through the air-passages which unite in the trachea. The amo
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte