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The kidney of the frog is an opisthonephros. The kidneys are seen as two elongated, red organs in this image. The opisthonephros is the functional adult kidney in lampreys (cyclostomes), most fishes, and amphibians. [1] It is formed from the extended mesonephros along with tubules from the posterior nephric ridge. [2]
Wolffian tubules are labeled to the right. The mesonephros persists and forms the anterior portion of the permanent kidneys in fish and amphibians, but in reptiles, birds, and mammals, it atrophies and for the most part disappears rapidly as the permanent kidney ( metanephros ) begins to develop [ 2 ] during the sixth or seventh week.
The amount of entrained water the frog can ingest is related to its ability to actively increase its body volume. The frog's buccopharyngeal cavity (the cavity connecting the mouth and the pharynx) is very distensible and can expand substantially. It uses its entire trunk to rapidly enlarge the cavity, which expands into the lower end of the trunk.
The development of the kidney proceeds through a series of successive phases, each marked by the development of a more advanced kidney: the archinephros, pronephros, mesonephros, and metanephros. [1] The pronephros is the most immature form of kidney, while the metanephros is most developed. The metanephros persists as the definitive adult kidney.
The nephron is the functional unit of the kidney. [3] This means that each separate nephron is where the main work of the kidney is performed. A nephron is made of two parts: a renal corpuscle, which is the initial filtering component, and; a renal tubule that processes and carries away the filtered fluid. [4]: 1024
The glomerular basement membrane of the kidney is the basal lamina layer of the glomerulus.The glomerular endothelial cells, the glomerular basement membrane, and the filtration slits between the podocytes perform the filtration function of the glomerulus, separating the blood in the capillaries from the filtrate that forms in Bowman's capsule. [1]
In lungfish and tetrapods, the renal portal vein is joined by a vein traveling upwards from the abdominal vein, [4] which can bring venous blood from the hind limbs and ventral body wall into the renal portal system, or alternatively, enable blood from the tail and groin to pass into the hepatic portal system, already served by blood from the gut, via the hepatic portal vein, and from the hind ...
The collecting duct system is the final component of the kidney to influence the body's electrolyte and fluid balance. In humans, the system accounts for 4–5% of the kidney's reabsorption of sodium and 5% of the kidney's reabsorption of water. At times of extreme dehydration, over 24% of the filtered water may be reabsorbed in the collecting ...