The development of the human body; a manual of human embryology . RP Fig. 189.—Portion of a Sectionthrough an embryo . op the^Fourth Week. A, Aorta; DC, ductus Cuvieri; L,lung; O, oesophagus; RP, parietalrecess; VOm, omphalo-mesentericvein.—(Toldt.) THE LUNGS. 353 and since this lower end lies, with the oesophagus, in themedian attached portion of the dorsal edge of the septumtransversum, the lobes, as they enlarge, project into thedorsal parietal recesses (Fig. 189), and so become enclosedwithin the peritoneal lining of the recesses which laterbecome the pleural cavities. The lobes, which rep
The development of the human body; a manual of human embryology . RP Fig. 189.—Portion of a Sectionthrough an embryo . op the^Fourth Week. A, Aorta; DC, ductus Cuvieri; L,lung; O, oesophagus; RP, parietalrecess; VOm, omphalo-mesentericvein.—(Toldt.) THE LUNGS. 353 and since this lower end lies, with the oesophagus, in themedian attached portion of the dorsal edge of the septumtransversum, the lobes, as they enlarge, project into thedorsal parietal recesses (Fig. 189), and so become enclosedwithin the peritoneal lining of the recesses which laterbecome the pleural cavities. The lobes, which represent the lungs, do not long remainsimple, but bud-like processes arise from their cavities,three appearing in the right lobe and two in the left ( Fig. 190.—Reconstruction of the Lung Outgrowths op Embryos op (A) 10, (B) , and (C) mm. Ap, Pulmonary artery; Ep, apical bronchus; Vp, pulmonary vein; I-II, primary bronchi.—{His.) 190, A), and as these increase in size and give rise to addi-tional outgrowths, the structure of the lobes rapidly be-comes complicated (Fig.: 190, B and. C). In the formationof new outgrowths the terminal enlarged part of each pro-cess divides as if to give rise to two equal bronchi, butlater as the new bronchi elongate, one grows more rapidlythan the Other and places itself so as to be in the line of thestem from which it arose, its fellow seeming to be a lateralbranch from it. As a result of this method of growth a3° 354 THE DEVELOPMENT OF THE HUMAN BODY. main bronchus traversing the entire length of the lung isformed, and into it there open numerous lateral branches,which may be termed secondary bronchi, arranged in amore or less definite and similar manner in the two main stem of
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
