Section V—Urogenital System
Urinary and reproductive structures should be examined next, but do not injure mesenteries and vessels in doing so. Postpone detailed tracing of the structures until the vessels have been studied.
Lift the coils of the small intestine in the posterior part of the peritoneal cavity to locate one of the paired gonads.
FIGURE 5.12 Pleuroperitoneal cavity of the mudpuppy in ventral view, with the liver reflected to the right and stomach pulled to the left.
FIGURE 5.13 Pleuroperitoneal cavity of the mudpuppy in ventral view, with the liver and stomach reflected to the right.
FIGURE 5.14 Pleuroperitoneal cavity of the mudpuppy in ventral view, with the posterior end of the liver reflected to the left.
Male Urogenital System
In males the testis is an elongated organ posteriorly in the pleuroperitoneal cavity lying ventral to the kidney (Figure 5.15). It is supported by the mesorchium. The kidney, longer than the testis, is considerably wider posteriorly than anteriorly. Its narrow anterior part is genital in function, while the wider posterior portion is urinary.
The archinephric duct is a longitudinal tube that runs along the lateral margin of the kidney. The portion along the genital part of the kidney is coiled, but its more posterior part, lying along the urinary portion of the kidney, is straight. Numerous small collecting tubules may be observed leading to the duct from the kidney. Trace the duct posteriorly to its entrance into the cloaca. In males the duct carries sperm from the testis, as well as urine from the urinary portion of the kidney.
Sperm reaches the duct by way of ductules efferentes, which lead into the genital portion of the kidney and thence to the archinephric duct. The vestigial oviduct is a dark thread-like structure along the lateral edge of the archinephric duct. It has no connection with the latter and continues anteriorly on its own. The margins of the cloaca bear numerous cloacal papillae. Skin the region on one side of the cloaca to expose the cloacal gland, which consists of numerous tiny tubules and is involved in clumping sperm to form spermatophores.Female Urogenital System
In females the elongated ovary, supported by the mesovarium, may be quite large (Figure 5.16). The presence of numerous eggs within follicles gives the ovary a lob- ulated or granular appearance, in contrast to the more regular surface of the testes. The follicles and eggs vary in size depending on their stage of maturity, being quite large in some specimens (Figure 5.12) and smaller in others (Figures 5.14 and 5.16). The archinephric duct lies along the lateral margin of the kidney but is straight and narrower than in the male. In the female it carries only urine from the kidney. Follow it posteriorly to its entrance into the cloaca.
The oviduct, supported by the mesotubarium, is the long, prominent, and convoluted tube lying between the ovary and kidney and extending nearly the length of the peritoneal cavity. At its anterior end is the open, funnel-shaped ostium, into which the eggs pass after they have been released into the coelom by the ovary. Follow the oviduct posteriorly to its entrance into the cloaca. Cloacal glands and papillae are absent in the female.
Key Terms: Urogenital System
archinephric duct cloacal gland cloacal papillae kidney mesorchium mesotubarium
mesovarium ostium ovary oviduct testis