Question

Antidiuretic hormone makes distal tubules and collecting tubules more permeable to_____.

Short answer

Water.

Step-by-step solution

Understanding the Role of Antidiuretic Hormone (ADH)

Antidiuretic hormone (ADH) plays a crucial role in regulating water balance in the body. Its primary function is to conserve water by increasing the permeability of certain kidney tubules to water. It acts mainly on the distal convoluted tubules and the collecting ducts, promoting water reabsorption back into the bloodstream.

Identifying the Targeted Tubules

The hormone specifically targets the distal tubules and the collecting tubules in the kidney. These parts of the nephron are typically less permeable to water without the influence of ADH.

Determining the Effect of ADH on Permeability

ADH increases the water permeability of the distal tubules and the collecting ducts by inserting aquaporins, which are water channels, into their membranes. This allows more water to be reabsorbed from the filtrate back into the bloodstream, thus concentrating the urine and diluting the blood.

Conclusion on Permeability Change

Given the role and action of antidiuretic hormone, it specifically makes the distal tubules and collecting tubules more permeable to water. This increase in permeability helps in water retention and regulation of the body's hydration levels.

Key concepts

Water Balance Regulation

Water balance regulation is a fundamental process in the human body that maintains homeostasis. This process ensures that the body maintains an optimal balance between water intake and water loss.

Several mechanisms are involved in regulating water balance, but among the most critical is the role of antidiuretic hormone (ADH). ADH helps the body retain water and prevent dehydration by reducing urine output. By acting on the kidneys, particularly targeting specific parts of the nephrons, ADH fine-tunes water conservation and adjusts urine concentration. Through these mechanisms, the body keeps its internal environment stable, even in varying conditions.

This regulation is crucial for many bodily functions, including temperature control, nutrient transport, and metabolic processes.

Kidney Tubules Permeability

Kidney tubules are essential structures within the nephron where filtration and absorption occur. The permeability of these tubules to water and various solutes greatly affects kidney function.

Permeability is critical because it dictates how much water and solutes get reabsorbed into the bloodstream versus being excreted as urine. Without hormone regulation, the distal and collecting tubules are less permeable naturally. ADH plays an essential role by increasing the permeability of these tubules to water, enabling efficient reabsorption when necessary.

By altering permeability, the kidneys can respond quickly to the body's changing hydration needs, demonstrating adaptability and the complex regulation of bodily fluids.

Aquaporins

Aquaporins are specialized proteins that form channels in cell membranes, specifically facilitating water movement across these barriers.

These channels are critical in the kidneys because they allow rapid and selective water reabsorption. Under the influence of ADH, aquaporins are inserted into the membranes of the distal convoluted tubules and collecting ducts, exponentially enhancing water permeability.

Through aquaporins, the body can efficiently reabsorb water from the filtrate produced in the kidneys back into the bloodstream, concentrating urine, and conserving water. In this way, aquaporins are vital in maintaining water balance and ensuring that body fluids are appropriately regulated.

Water Reabsorption

Water reabsorption is a crucial kidney function, allowing the body to reclaim water from the filtrate processed by the kidneys. This process ensures that vital fluids are retained.

ADH significantly impacts water reabsorption by making kidney tubules more receptive to water passage. With more aquaporins present due to ADH action, water escape into blood vessels is facilitated, thus reducing urine output.

This conserved water helps maintain blood volume and pressure, demonstrating the importance of water reabsorption in systemic homeostasis. Proper reabsorption processes are essential for balanced hydration in the body.

Distal Convoluted Tubules

The distal convoluted tubules play a vital role in the nephron's filtration and absorption processes. Situated after the loop of Henle, these tubules continue processing the tubular fluid from the nephron.

In the absence of hormones like ADH, these tubules have limited permeability to water. However, when ADH is present, it specifically targets these areas to enhance water permeability.

By facilitating the insertion of aquaporins into the cell membranes, ADH enables increased reabsorption from the distal convoluted tubules. This effective mechanism is part of the nephron's broader ability to fine-tune the body's fluid balance and respond to its hydric needs.

Collecting Ducts

Collecting ducts receive the processed filtrate from various nephrons and are pivotal in the final urine concentration process. These ducts converge to form larger channels that lead the urine towards the renal pelvis and eventually the bladder.

In response to ADH, the collecting ducts become more permeable to water through the addition of aquaporins, allowing more reabsorption back into the bloodstream.

This adaptability of collecting ducts is essential for conserving water, especially in conditions of dehydration, providing the body with the ability to concentrate urine and maintain fluid homeostasis. As a result, collecting ducts are paramount to the kidney's function in water conservation and balance.