The practice of obstetrics, designed for the use of students and practitioners of medicine . Figs. 84, 85, 86, 87.—Fetal Skulls of the First Third of Pregnancy (Two-thirdsNatural Size).—{Authors collection.) blood-vessels, take their origin from the mesoderm; but while the problemsinvolved in a full consideration of the mesoderm and ccelom are fundamentalin character, they are very complex and, moreover, have not been satisfactorilyworked out in their finer details. (For the heart and vascular system, see sec-tions on Nutrition and Circulation.) The urogenital system is derived from a cord of
The practice of obstetrics, designed for the use of students and practitioners of medicine . Figs. 84, 85, 86, 87.—Fetal Skulls of the First Third of Pregnancy (Two-thirdsNatural Size).—{Authors collection.) blood-vessels, take their origin from the mesoderm; but while the problemsinvolved in a full consideration of the mesoderm and ccelom are fundamentalin character, they are very complex and, moreover, have not been satisfactorilyworked out in their finer details. (For the heart and vascular system, see sec-tions on Nutrition and Circulation.) The urogenital system is derived from a cord of tissue lying between thesomites and the coelom (Fig. 69). This early forms the Wolffian or pronephricduct, which gives rise to tubules forming the primitive excretory apparatus,the mesonephros or Wolffian body In lower vertebrate forms a fetal kidney,. Figs. 88, 89, 90.—Fetal Skulls of the Middle Third of Pregnancy (Two-thirdsNatural Size).—{Authors collection.) called the pronephros, precedes the mesonephros. It exists in a very rudi-mentary condition in the human embryo. With the exception of its duct itentirely disappears to make way for the mesonephros. This structure projectsfar into the coelom and its mesothelial covering cells which give rise to theMullerian duct, and to the ova or zoospores, the essential parts of the ovaryor testis. The mesonephros disappears, gradually giving place to the definitekidney or metanephros, but its duct at the caudal end gives rise to the ductand tubules of the true kidney. In the male it produces the vas deferens. GERM-LAYER. 61 In the female the Miillerian ducts are transformed into the Fallopian tubesand caudally, by their union, into the uterus and vagina. The limbs arise asmere pads of indifferent mesodermic tissue covered by ectoderm. Into themgradually extend outgrowths of the myotom
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectobstetrics, bookyear1
