Quain's elements of anatomy . layer ; &, muscular layer; c, mucous membrane in longitudinal folds, withnumerous longitudinally running elastic fibres cut across ; d, ciliated epithelium; /, sur-rounding alveoli. L L 2 616 THE LUA^GS. they contain the same elements as the larger air-passages, they are reducedgradually to a state of gTeater tenuity, but possess certain peculiaritiesof structure. Thus, the cartilages no longer appear as imperfect ringsrunning only upon the front and lateral surfaces of the air-tube, but aredisposed over all sides of the tubes in the form of irregularly shapedplat
Quain's elements of anatomy . layer ; &, muscular layer; c, mucous membrane in longitudinal folds, withnumerous longitudinally running elastic fibres cut across ; d, ciliated epithelium; /, sur-rounding alveoli. L L 2 616 THE LUA^GS. they contain the same elements as the larger air-passages, they are reducedgradually to a state of gTeater tenuity, but possess certain peculiaritiesof structure. Thus, the cartilages no longer appear as imperfect ringsrunning only upon the front and lateral surfaces of the air-tube, but aredisposed over all sides of the tubes in the form of irregularly shapedplates and incomplete rings of various sizes. These are most developedat the points of division of the bronchia, where they form a sharp con-cave ridge projecting inwards into the tube. They may be traced, be-coming rarer and rarer and more reduced in size, as far as bronchia onemilhmeter in diameter. The filrous coat extends to the smaUest tubes,becoming thinner by degrees and degenerating into areolar tissue. In Fiff. Fig. 446. DiAGRAilllATIC REPRESENTATION OF THE TERJIINATION OF A BROJfCHIAL TUBE IN AGROUP OF INFUNDIBULA. () it are mucous glands which send theirducts to open on the mucous occur most numerously in thelarger tubes; in those which measure lessthan 1 mm. they are rarely if everfound. The mucous memhrane, whichextends throughout the whole system ofair passages, is also thinner than in thetrachea and bronchus, but it retains its ciliated columnar epithelium(figs. 444, 445, cl). The longitudinal bundles of elastic fibres (c, in thetransverse sections) are very distinct in both the large and smallbronchia, and may be followed by dissection as far as the tubecan be laid open, and by the microscope into the smallest tubes. Themuscular fibres, which in the trachea and bronchi are confined tothe back part of the tube, surround the bronchial tubes with a con-tinuous layer of annular fibres, lying inside the cartilaginous plates(&) ; they are found,
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Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
