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Chapter 10: Problem 7

Explain how a hypertonic urine can be formed, detailing where and how salt and water move, and the influence of hormones on the process. (pages \(218-20\) )

Short Answer

Expert verified
Hypertonic urine is a concentrated urine with higher solute concentration, formed to conserve water in the body during dehydration. The nephron, the functional unit of the kidney, plays a vital role in determining urine concentration through its structure and function. The Loop of Henle concentrates the urine by reabsorbing water in the descending limb and actively transporting ions in the ascending limb. Hormones, such as Antidiuretic hormone (ADH) and Aldosterone, regulate water and sodium reabsorption, respectively, to further increase urine concentration. Overall, this process helps the body conserve water when experiencing dehydration or water scarcity.

Step by step solution

01

Define hypertonic urine

Hypertonic urine is a concentrated urine with a higher solute concentration (especially of salts) than the normal concentration found in the body. It is formed to conserve water in the body when it's dehydrated.
02

Role of Nephron in Urine Formation

The nephron is the functional unit of the kidney responsible for filtering blood and producing urine. It consists of the glomerulus, proximal convoluted tubule, Loop of Henle, distal convoluted tubule, and collecting duct. It has a vital role in reabsorption and secretion processes that determine urine concentration.
03

Loop of Henle Function

The Loop of Henle is a U-shaped structure in the nephron that helps concentrate the urine. It has two limbs: the descending limb (permeable to water) and the ascending limb (impermeable to water). - In the descending limb, water leaves the filtrate by osmosis and enters the surrounding interstitial fluid due to the high osmolarity in the medulla. - In the ascending limb, ions (like Na+ and Cl-) are actively transported out of the filtrate, increasing the osmolarity in the interstitial fluid but not letting water follow, making the filtrate progressively more dilute as it moves upward.
04

Hormonal Influence

Two hormones mainly influence the formation of hypertonic urine: 1. Antidiuretic hormone (ADH) or Vasopressin: Secreted by the posterior pituitary gland, it makes the collecting duct walls more permeable to water, allowing more water to be reabsorbed into the interstitial fluid and blood. 2. Aldosterone: Secreted by the adrenal cortex, it enhances the reabsorption of sodium in the distal convoluted tubules, making the filtrate more hypertonic before reaching the collecting duct.
05

Summarizing the Process

To form hypertonic urine, the nephron structure, specifically the Loop of Henle, facilitates solute concentration. Hormones like ADH and aldosterone regulate water and sodium reabsorption to increase urine concentration. This process helps the body conserve water when dehydration or water scarcity occurs.

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Most popular questions from this chapter

Sodium is actively extruded from which part of the nephron? a. descending portion of the proximal convoluted tubule b. ascending portion of the loop of the nephron c. ascending portion of the distal convoluted tubule d. descending portion of the collecting duct

When tracing the path of filtrate, the loop of the nephron follows which structure? a. collecting duct b. distal convoluted tubule c. proximal convoluted tubule d. glomerulus e. renal pelvis

The function of erythropoietin is a. reabsorption of sodium ions. b. excretion of potassium ions. c. reabsorption of water. d. to stimulate red blood cell production. e. to increase blood pressure.

Which portion of the nephron has cells with a brush border and many mitochondria? a. glomerular capsule b. proximal convoluted tubule c. loop of the nephron d. distal convoluted tubule e. collecting duct

Which of the following is a structural difference between the urinary systems of males and females? a. Males have a longer urethra than females. b. In males, the urethra passes through the prostate. c. In males, the urethra serves both the urinary and reproductive systems. d. All of these are correct.
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