Frog: Excretory system.

 In Frog, it consists of a pair of kidneys, a pair of ureters, a urinary bladder and Cloaca.

• Kidneys: Two Kidneys lie Posteriorly outside abdominal Coelom in  Subvertebral lymph  sinus attached one on either side of vertebral Column. They are Covered with peritoneum on their ventral surface only.  They are mesonephric in nature. They are elongated, flat and reddish brown structures. on ventral surface of each kidney an elongated narrow yellow Coloured adrenal gland is present. on
anterio-ventral surface of each kidney gonad (testis in male and ovary in female) and several finger like fat bodies are present which stores reserve food.

Histologically, each kidney is compact mass of about 2000 highly twisted microscopic uriniferous tubules or nephrons and blood vessels embedded in Connective tissue. Nephrons are functional units of Kidney. The proximal end of tubule is double walled cup like structure called Bowman's capsule which encloses a bunch of network of capillaries called glomerulus.

The distal end of tubule opens into a collecting tubule running transversely across the Kidney near dorsal Surface. All transverse Collecting tubules open into a longitudinal Bidder's Canal which continues out from posterior end of kidney as ureter.

ventral surface of each Kidney many ciliated funnels Called nephrostomes are present. They drain wastes from body Cavity and Connect to renal veins in Frog while with uriniferous tubules in tadpoles.

• Ureters: From posterior Outer margin of each kidney a urinary or wolffian duct also Called ureter emerges out. It is fine White duct which extends backward and open into the dorsal wall of cloaca on papillae. In male Frog, the ureters are Called urinogenital duct as they carry both Urine and sperm.

• urinary bladder: A large transparent, bilobed , thin walled and elastic urinary bladder opens into the ventral wall of cloaca by sphinctered aperture opposite and below the openings of Ureters.
• Cloaca: It is a small median Chamber into which open the anus, urinogenital apertures and urinary bladder. The cloaca opens outside by a Sphinctered cloacal aperture lying at the posterior end of body in between two hindlimbs.

# Frog is ureotelic i. e. primary nitrogenous metabolic waste is urea.
# Pronephric kidneys are present in tadpole.

# Tadpole is Ammonotelic.