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What is the uriniferous tubule? How does it function?

Last updated date: 18th Jun 2024
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Hint: This is the basic kidney structural and functional unit that controls water and soluble substances by filtering and reabsorption in the blood, and excreting the rest as urine.

Complete answer:
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A kidney consists of a large number of uriniferous tubules (also known as nephrons, or kidney tubules). It is regulated by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone in the neuroendocrine system.

Nephrons are the kidney's structural and functional components. There are tubules of tiny minutes found in the kidneys. It includes the proximal tube, the loop of Henle, the distal tube, and the collecting duct.

Its function is important for blood flow, blood pressure, and plasma osmolarity homeostasis It is used to filter the blood and isolate the liquid component from the blood. Water is also reabsorbed in the uriniferous tubule.

Additional information:
The glomerulus (a capillary tuft, which receives its blood supply from an afferent renal circulation arteriole). The glomerulus is surrounded by Bowman's capsule also called the glomerular capsule (fluid and solutes are pumped out of the blood and into space).

The proximal tubule is the first site that water is reabsorbed into the bloodstream and the location where the most water and salt reabsorption occurs. Owing to both passive diffusion across the basolateral membrane, and active transport from $Na^{+} / K^{+} - ATPase$ pumps that actively transport sodium across the basolateral membrane, water reabsorption occurs in the proximal convoluted tubule.

Henle's loop is a U-shaped tube consisting of a downward limb and an ascending limb. It moves fluid from the proximal tubule to the distal. The descending limb is extremely permeable to water but entirely impermeable to ions, allowing reabsorption of a significant amount of water.

The distal tubule and collecting duct is the final site of nephron’s reabsorption. Its water permeability varies depending on the hormone stimulation to enable the complex control of blood osmolarity, volume, pressure, and pH. After passing through the collection duct, the fluid is transferred through the ureter where it exits the kidney as urine.

Note: There are 85% cortical nephrons, deep in the renal cortex, while the remaining 15% are juxtamedullary nephrons, which lie close to the renal medulla in the renal cortex.