Which part of nephron allows the selective reabsorption of useful substances like glucose, amino acids, salts and water into the blood capillaries?

General
1

which part of nephron allows the selective reabsorption of useful substances like glucose, amino acids, salts and water into the blood capillaries?

2

Which part of the nephron allows the selective reabsorption of useful substances like glucose, amino acids, salts, and water into the blood capillaries?

Answer:
The nephron is the basic structural and functional unit of the kidney. It plays a crucial role in filtering waste products from the blood and reabsorbing useful substances back into the bloodstream. The specific part of the nephron responsible for the selective reabsorption of substances such as glucose, amino acids, salts, and water is the proximal convoluted tubule (PCT).

  1. Proximal Convoluted Tubule (PCT):

    • The PCT is the first segment of the nephron after the Bowman’s capsule, where the initial filtrate from the blood enters.

    • Selective Reabsorption: The PCT is lined with epithelial cells that have microvilli, which increase the surface area for reabsorption. Here, nearly all of the filtered glucose and amino acids, along with a significant amount of sodium, chloride ions, and water, are reabsorbed into the bloodstream.

    • Mechanism:

      • Active Transport: Glucose and amino acids are reabsorbed via active transport mechanisms. For example, glucose reabsorption occurs through sodium-glucose co-transporters (SGLTs).
      • Osmosis: Water reabsorption occurs primarily through osmosis, driven by the concentration gradient created by the reabsorption of solutes.
      • Facilitated Diffusion: Some substances are reabsorbed by facilitated diffusion through specific transport proteins.
      \text{\textbf{Overall Process in the PCT:}}
      • Glucose reabsorption:
        \text{Glucose} + \text{Na}^+ \rightarrow \text{SGLT} \rightarrow \text{Capillaries}
      • Amino acids reabsorption:
        \text{Amino acids} + \text{Na}^+ \rightarrow \text{Na+-dependent transporters} \rightarrow \text{Capillaries}

  2. Other Nephron Segments:

    • While the PCT is the primary site for the reabsorption of glucose, amino acids, and a significant portion of salts and water, other parts of the nephron also play roles in reabsorption and concentration of urine:
      • Loop of Henle: Mainly involved in the reabsorption of water (descending limb) and sodium chloride (ascending limb), contributing to the concentration gradient in the kidney medulla.
      • Distal Convoluted Tubule (DCT) and Collecting Duct: Further adjustments in ion and water reabsorption occur, regulated by hormones such as aldosterone and antidiuretic hormone (ADH).

Final Answer:
The part of the nephron that allows the selective reabsorption of useful substances like glucose, amino acids, salts, and water into the blood capillaries is the proximal convoluted tubule (PCT).