Each kidney of toad is formed by the combination of numerous fine coiled renal tubules. In each kidney, there are about two thousand such coiled microscopic tubules. These tubules are called nephrons. Each nephron is divided into two portions.
a) Malpighian body or organ
b) Renal tubules.
(A) Malpigbhian organ: It is the anterior rounded part of the nephron. This organ is again formed of two parts, such as Bowman’s capsule and Glomerulus.
Bowman’s capsule and Glormerulus: At the free end of each renal tubule there is a closed cup-like part called the Bowman’s capsule. The wall of this cup is formed of an epithelial cell layer. branch of the renal artery enters the cavity of the Bowsman’s capsule. This branch of the artery is known as the afferent artery. Inside the cavity of Bowman’s capsule the afferent artery form a cluster of blood capillaries.
(B) Renal tubules: The duct-like tubule behind the Bowman’s capsule is called the renal tubule. This tubule being turned into coil opens into the collecting duct. The collecting duct ultimately opens into the ureter. The tubule is surrounded by the branches of the efferent artery.
Ureter: From the outer end of each kidney a whitish elastic duct originates and goes towards the posterior part of the body. This duct is known as the ureter. The ureters of the two sides meet and form a common renal duct and open into the cloaca through a common renal aperture.
Urinary bladder: The thin, incompletely divided sac situated on the ventral side of the cloaca is called urinary bladder. Urine is stored here temporarily. The urinary bladder opens into the cloaca through an aperture.
Cloaca: The cloaca is situated behind the rectum. It is a narrow chamber. The urinary bladder opens into the cloaca through the renal aperture. Through it, urine passes towards the cloacal aperture.
Cloacal aperture: The cloacal aperture is situated at the posterior end of the body. Through this aperture stool, urine, sperms and ova are discharged outside.