52 



MORPHOLOGY OF THE VERTEBRATE BODY 



f. od 



OT 



In its ventral aspect, as seen from dissection (Fig. 30), the urino- 

 genital system consists of the paired kidneys and their ducts, 

 the ureters; the ovaries in the female, and the testes in the 

 male, with their respective connections to the outside; and' 

 certain accessory parts hke the urinary bladder. The kid- 

 neys are flattened organs lying dorsally but separated from the 



dorsal body wall by the sub- 

 vertebral lymph sinus (Fig. 19, 

 p. 40), and having their ventral 

 surfaces covered with perito- 

 neum after the manner shown. 

 The ureters, which convey the 

 urine from the kidneys, leave 

 the outer edge of either kid- 

 ney and enter the dorsal surface 

 of the cloaca. The urinary 

 bladder is a bi-lobed sac con- 

 nected with the ventral surface 

 of the cloaca opposite the 

 openings of the ureters. The 

 urine, which flows from the 

 ureters into the cloaca, enters 

 the bladder as the only place 

 Fig. 30.-Urino-genital organs of frog available, because the large in- 

 from ventral view, showing ovary and testine is closed or filled with 

 oviduct to left as in female, and testis faeces and the anus is never 

 and rudimentary oviduct to right as in open except when the fiBCes or 



urine is being extruded. From 



duct; k, kidney; m.t., mesentery of testis; ^^^ bladder the Urine is pCH- 



post-cavai odically discharged by way of 



the anus. These conditions in 



the frog are simpler than those 



found in mammals, where the 



ureters lead directly to the bladder and the latter discharges by 



a separate opening instead of by the anus. 



Microscopically, the kidneys of any vertebrate animal are com- 

 posed of numerous tubules (Fig. 31 B), each of which begins blindly 

 as an enlarged cup-hke portion, known as Bowman's capsule and 

 containing a coil of small arteries, the glomerulus. These 

 tubules wind about somewhat irregularly, but each one empties 



male. 



an, anus; cl, cloaca; f.od., funnel of evi- 

 ct; k, kic 

 od, oviduct; ov, ovary; p-c.v., 

 vein; r.od., rudimentary oviduct; r.v., renal 

 vein; sod., ovisac; te, testis; u.bl., urinary 

 bladder; ut, ureter. 



