Question

Mesorchium in frog refers to
a. Fold of peritoneum between a kidney and a testes
b. Internal tissue of testes
c. Capsules of testes
d. None of the above

Answer 1

Hint: The mature male frog is mostly smaller than the feminine, starting from 60 to 110 mm. long from snout to anus. The identifying features which distinguish it from the feminine are a darkened thumb pad which changes thickness and color intensity because the breeding season approaches; a definite low, guttural croaking sound with the accompanying swelling by air of the lateral vocal sacs located between the tympanum and therefore the forearm; a more slender and streamlined body than that of the female..

Complete answer: In order to answer this question we need to go through reproductive characters of male frog:

Primary Sexual Characters: The testes of the frog are paired and internal organs and are suspended to the dorsally placed kidneys by a double fold of peritoneum referred to as the mesorchium. This mesentery surrounds each testis and is continuous with the peritoneal epithelium which covers the ventral face of every kidney and contours the complete body cavity. The testes are whitish and ovoid bodies lying ventral to and near the anterior end of every kidney. The tubule, ducts from the testes, pass between the folds of the mesorchium and into the mesial margin of the adjacent kidney. During the breeding season these ducts become more apparent because of the presence in them of whitish masses of spermatozoa in suspension. Each duct is connected directly with a variety (8 to 12) of Malpighian corpuscles of the kidneys, by way of the Bowman's capsules. These connections are permanent so many of the anterior uriniferous tubules of the frog kidney will contain spermatozoa during the breeding season.

The presence of spermatozoa within the kidney can also be achieved artificially by injecting the male frog with the ductless gland sex-stimulating hormone. Since these anterior Malpighian corpuscles carry both spermatozoa (during the breeding season) and excretory fluids (at all times), they're truly urogenital ducts having a dual function. The spermatozoa are produced in subdivisions of the testes referred to as seminiferous tubules.

Spermatogenesis: After the traditional breeding season within the spring for Rana pipiens, the spermatogonium, which has ceased all mitotic activity, enters upon a period of rest but not inactivity. During this, the nucleus passes through a sequence of complex changes which represent an extended prophase. This is often in anticipation of the 2 maturation divisions that finally produce the haploid spermatid which metamorphoses into a spermatozoon.

Spermatogenesis within the frog is seasonal and is completed within the testes. The walls of the seminiferous tubules produce spermatogonia which undergo mitotic divisions so the series of nuclear changes. By the time of hibernation (October) all the spermatozoa that are to become available for the subsequent spring breeding season will have matured. At now the testis will exhibit only these spermatozoa and comparatively few spermatogonia, without the intervening maturation stages. The spermatogonia are found near the basement membrane of the tubule. These then await their communication to undergo the maturation changes necessary for the assembly of spermatozoa which is able to be ready for the breeding season a year and a half thereafter. The elongated and filamentous tails of the clustered mature spermatozoa project into the lumen of every tubule.

The spermatogonia are located around the periphery of tubules. Spermatocytes tend to be irregularly spherical, possessing large and vesicular nuclei. Secondary spermatocytes have a darkly staining nucleus, and therefore the cytoplasm could also be tapered toward one side. The spermatid, following another division, is even smaller and possesses a condensed nucleus of irregular shape. Clusters of spermatids appear as clusters of granules, the dark nucleus being almost as small because of the cross section of a sperm head. The metamorphic stages from spermatid to spermatozoa are difficult to spot with ordinary magnification, and are often confused with the spermatids themselves. During this alteration the inner of two spermatid centrioles passes into the nucleus while the outer one gives rise to the tail-like flagellum. The mature spermatozoon averages about 0.03 mm. in length. It’s an elongated, solid-staining head (nucleus) with an anterior acrosome, pointing outward toward the periphery of the tubule. The short middle piece generally isn't visible but the tail appears as a gray filamentous extension into the lumen, about four or more times the length of the sperm head. The mature spermatozoon relies upon external sources of nutrition so it joins from 25 to 40 other spermatozoa, all of whose heads is also seen converging into the cytoplasm of a comparatively large, columnar-type basal cell referred to as the Sertoli cell. This can be functionally a nurse cell, supplying nutrients to the clusters of mature spermatozoa. Reproductive Behavior It has been proved definitely that the adenohypophysis hormone causes the discharge of the mature spermatozoa from the testis. But this hormone also releases other maturation stages. It’s therefore probable that there are smooth muscle fibers, either among the interstitial cells or within the tunica albuginea of the testes, which fibers contract to force the spermatozoa from the seminiferous tubules.

Responding to sex stimulation, spermatozoa become free from their sertoli cells and are forced from the lumen of the tubule into the related collecting tubule. These collecting tubules are small and are lined with closely packed cuboidal cells. They join the tubule which leaves the testis to pass between the folds of the mesorchium and then into the Malpighian corpuscles of the kidney. From this time the spermatozoa surpasses the excretory ducts, the uriniferous tubules, and into the mesonephric duct (ureter) which can be found attached to the lateral margin of the kidney. They’re carried passively down the ureter to the slight dilation near the cloaca, referred to as the cyst. Within the vesicle the spermatozoa are stored briefly in clusters until amplexus and oviposition occur. At oviposition the male ejaculates the spermatozoa into the neutral or slightly alkaline water where they're activated then are able to fertilize the eggs as they emerge from the cloaca of the feminine.

Therefore the answer is a, fold of peritoneum between a kidney and a testes.


Note:
Accessory Structures In the male frog the ureter isn't directly connected with the bladder, because it is in higher vertebrates. The male frog also features a duct, homologous to the oviduct of the feminine, called the "rudimentary oviduct" or Miillerian duct. This duct normally has no lumen. At the anterior end of the testes there could also be found an undeveloped ovary referred to as Bidder's organ. This structure responds to removal of the adjacent testis or to the injection of female sex hormones by enlarging to become structurally like an ovary. To the anterior end of testis of the hibernating frog there are finger-like fat bodies which represent stored nutrition for the long period of hibernation, and for the pre-breeding season when food is scarce