. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. a?2 Biology of the Vertebrates with only a single papilla (Fig. 363), are never lobed, since the number of pyramids determines the number of lobes. The true multilobed condition of the human kidneys, which is most plainly apparent at about the fourth fetal month, is masked by the growth of parts which eventually fill in the inter- stices between the lobes. The relation of all these parts is described in the following section dealing with the microscopic st
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. a?2 Biology of the Vertebrates with only a single papilla (Fig. 363), are never lobed, since the number of pyramids determines the number of lobes. The true multilobed condition of the human kidneys, which is most plainly apparent at about the fourth fetal month, is masked by the growth of parts which eventually fill in the inter- stices between the lobes. The relation of all these parts is described in the following section dealing with the microscopic structure of a single urinary unit or nephridial apparatus, and its position in the Malpighian Fig. 363. Evolution of pyramids in different kidneys. At the left is the unipyramidal type; in the center a iobulate kidney with several pyramids; and at the right, a kidney composed of several pyramids but tissue filled in between them so that it is no longer externally Iobulate. (After Nuhn.) 4. A Urinary Unit A urinary unit is a transformed nephridium that has gained an intimate connection with the blood system and established an avenue of drainage to the outside. The various parts of such a unit are pictured in Figure 364. The junction where the nephridial tube makes contact with the blood stream is called the renal corpuscle (Fig. 365). It consists of a spherical tuft or knot of arterial capillaries, the glomerulus, enveloped by a double cup of epithelial cells, Bowman's capsule, between the double layers of which is the cavity of the renal tubule, or nephridium. The formation of Bowman's capsule around the glomerulus at the tip of the renal tubule is brought about when the glomerulus comes into contact with the tip of the tubule and pushes it in from the outside, like the finger tip of an empty glove. The delicate inner cup of Bowman's capsule is thus closely adherent to the glomerulus so that the blood in the glomerular capil- laries is separated from the cavity at the
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
