Textbook of normal histology: including an account of the development of the tissues and of the organs . annuli fibrosi—composed of supplementary-masses of fibro-elastic tissue. The auricular muscle is continued intothe valves for about one-third of their width, following closely thegeneral contours of the fold. Within the larger chordae tendineasthe papillary muscles extend for some distance, in addition to whichisolated muscle-bundles are also sometimes present. The semilunarvalves possess a thinelastic layer on thearterial surface, aug-mented by a thickstratum of connectivetissue, the bundl
Textbook of normal histology: including an account of the development of the tissues and of the organs . annuli fibrosi—composed of supplementary-masses of fibro-elastic tissue. The auricular muscle is continued intothe valves for about one-third of their width, following closely thegeneral contours of the fold. Within the larger chordae tendineasthe papillary muscles extend for some distance, in addition to whichisolated muscle-bundles are also sometimes present. The semilunarvalves possess a thinelastic layer on thearterial surface, aug-mented by a thickstratum of connectivetissue, the bundles ex-tending parallel withthe margin of thevalve; increasedstrength is secured bya nbro-elastic nodule,or corpus Arantii,which occupies themiddle of each the ventric-ular endocardium, inmany animals (deer,sheep, calf, pig, horse,goat, dog, certainbirds, etc.), but not inman, peculiar bands—the fibres of Purkinje—occur; these aremuscular fibres whosetransverse striationsare limited to the pe-ripheral zone, whiletheir centre is occupiedby a large continuousmass of nucleated pro-. Section of the heart, including a leaflet of the semilunar valveof the pulmonary artery of child : a, a, cardiac, b, b, arterial,surface ; c, recess behind the valve (/), constituting part of asinus of Valsalva; d, free border of valve ; e, thickening nearedge of valve corresponding to a corpus Arantii ; g, endothe-lium, h, intima, i, media, k, adventitia, of the pulmonary artery ;the adventitia is continuous with the principal fibrous layer ofthe endocardium ; m, cardiac muscle ; n, areolar tissue. toplasm. The fibres of Purkinje represent an embryonal condition of the muscular tissue,since the peripheral part of the fibre alone has undergone differen-tiation, while the central portion has remained indifferent some lower vertebrates, as fishes, a similar condition of themuscle-fibres is constant. 102 NORMAL HISTOLOGY. The muscular tissue of the heart possesses the
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Keywords: ., bookauthorpiersolgeorgeageorgea, bookcentury1800, bookdecade1890
