Urogenital system of a frog and reproductive systems are inextricably linked and collectively referred to as the urinogenital system of frog. It is primarily responsible for assisting the frog in urine excretion and reproduction. Frogs are ureotelic animals because urea is their main excretory product.
Male and female frogs have the same excretory system, but their reproductive structures are different. In frogs, excretion is primarily carried out through the kidneys (which filter blood), ureters (which transport urine from the kidneys to the bladder), cloaca (which is a structure where eggs/sperm, urine, and faeces leave the body), and urinary bladder (stores urine).
Frogs have separate sexes, so they are dioecious. That is, male and female frogs can only be distinguished/identified externally during the breeding season. This is due to males developing a copulatory or nuptial pad on their first forelimb digit. Female frogs do not exhibit this trait. Males also have vocal sacs, which allow them to produce louder sounds. As a result, the male and female urogenital systems of frogs are studied independently.
Parts of the Urogenital System of Frog
Male Frog Urogenital System
Male urogenital system of the frog: The following are the structures of the urogenital system of a frog in males are: Kidney, Urinary bladder, Ureter, Testis, Bidders canal, Vasa efferentia, and Cloaca.
Male Frog Urogenital System Diagram Labeled
Both kidneys are elongated, compact, flattened, and dark red. These can be found in the lymph spaces (subvertebral lymph sinuses) above the coelom on either side of the vertebral column. Tadpole kidneys are pronephros, whereas adult kidneys are mesonephros. The peritoneum covers these ventrally.
(ii) Urinary Bladder
It is a large, thin-walled, distensible bilobed structure. It also has a sphinctered aperture that opens into the ventral wall of the cloaca. Its aperture is below and opposite the ureter openings. The bladder’s inner surface is lined with a three-cell-thick layer of epithelium. The bladder’s middle layer is made up of a network of smooth muscle fibres, and outside of this layer is a thin sheet of connective tissue that is covered by the peritoneum.
In frogs, two ureters are connected to kidney. In male frog, the urters opens into cloaca and helps in passing the urine and sperm. In female frog, it opens separately into cloaca and helps in excrete urine.
The testis is light yellow, rounded or ovoid bodies that are attached to the antero-ventral surfaces of the kidneys by a double fold of peritoneum called the mesorchium.
Each testis is surrounded by peritoneum, which extends dorsally as a double membrane, the mesorchium, to the dorsal side of the body cavity, where it joins the general coelomic lining. Attached yellowish finger-like processes are found just in front of each testis. They act as a sort of nutrient storage facility for developing spermatozoa and during hibernation.
(v) Bidders canal
The bidder canal is a vital organ of the frog’s male reproductive system (Anura). It aids in the transport of sperm from the testis to the water. This canal runs longitudinally through the middle of a male frog’s kidney.
(vi) Vasa efferentia
The vasa efferentia are a group of slender tubes that arise from the inner margin of the testis and extend within the mesorchium before entering the inner margin of the kidney and opening into the Bidders canal. Through the collecting tubules of the kidney, the Bidders’ canal communicates with the ureter. Sperms enter the ureter of the kidney via vasa efferentia in this manner. Bidders canal and tubules for collecting bids The vasa efferentia are outgrowths of the walls of the Malpighian corpuscles that connect to the testis.
It is a small, medium-sized sac that houses the anus, urinogenital apertures, and the urinary bladder opening. The cloaca opens to the outside world through a cloacal aperture located at the posterior end of the body between the two hindlimbs.
Female Frog Urogenital System
The kidneys, ureters, and urinary bladder are common structures in both male and female urogenital systems in frogs, and their functions are the same. The structures of the female urogenital system of the frog are: Kidney, Urinary, bladder, Ureter, Ovaries, Oviduct, and Cloaca.
Female Frog Urogenital System Diagram Labeled
It is a paired structure found near the kidneys. The mesovarium is a fold of peritoneum on the outer side of the kidneys that contains these yellow-colored structures. They produce ova through the process of oogenesis. A mature female can produce between 2500 and 3000 eggs all at once.
A long, coiled glandular and ciliated oviduct, or Mullerian duct, runs down each side. A thin-walled ciliated coelomic or oviducal funnel begins near the base of the lung. Each oviduct dilates at the posterior end near the cloaca to form a thin-walled ovisac called the uterus, which opens through a narrow aperture on a papilla in the cloaca.
The oviduct’s cilia direct the eggs posteriorly, and glands secrete an albuminous coat around each egg as it descends. Just before the breeding season, the oviducts become greatly enlarged and coiled. The eggs escape from the ovary’s surface into the coelom, where they are directed by cilia into the oviduct and temporarily stored in the ovisacs.
Each egg is spherical with a diameter of about 1.75 mm. Its upper black pigmented half is the animal hemisphere, which contains the nucleus, and its lower white yolk-containing half is the vegetal hemisphere. The egg is surrounded by a thin vitelline membrane and a thick albuminous coat.
Blood Supply to Kidneys
The kidneys are supplied with blood via the renal portal veins and renal arteries. As an excretory product, blood primarily consists of urea. The renal artery divides in the kidney and redivides to form the afferent arteriole, which has a larger diameter than the efferent branch. The detoxified blood from the kidneys is carried away by the renal veins on the other side.
The renal portal veins branch into the kidney, and these branches, along with the efferent arteriole, form a mesh of capillaries near the uriniferous tubules, eventually forming the renal venule.
Role of Urogenital System
Urogenital system of a frog primarily excretes urea, which is carried into the kidney by the blood and eventually distilled and excreted. As a result, the renal structures of this system remove urea from the frog’s body. This system’s reproductive or genital structures produce sex cells that are ready to be delivered outside of the body for the process of external fertilisation.