Question

Figure 12.4 Which of the following statements about the nephron is false? a. The collecting duct empties into the distal convoluted tubule. b. The Bowman's capsule surrounds the glomerulus. c. The loop of Henle is between the proximal and distal convoluted tubules. d. The loop of Henle empties into the distal convoluted tubule.

Short answer

a) The collecting duct empties into the distal convoluted tubule. b) The Bowman's capsule surrounds the glomerulus. c) The loop of Henle is between the proximal and distal convoluted tubules. d) The loop of Henle empties into the distal convoluted tubule. Answer: a) The collecting duct empties into the distal convoluted tubule.

Step-by-step solution

1. Understand the structure of the nephron

To determine which statement is false, we should first understand the structure of the nephron. The nephron consists of several parts such as the Bowman's capsule, the proximal convoluted tubule, the loop of Henle, the distal convoluted tubule, and the collecting duct.

2. Analyze statement a

"The collecting duct empties into the distal convoluted tubule." Analyzing the nephron's structure, the collecting duct actually empties not into the distal convoluted tubule, but into the renal pelvis and then into the ureter leading to the bladder. This statement is false.

3. Analyze statement b

"The Bowman's capsule surrounds the glomerulus." This statement is true. The Bowman's capsule is a cup-shaped structure surrounding the glomerulus, which is a network of capillaries involved in the initial filtration of blood within the nephron.

4. Analyze statement c

"The loop of Henle is between the proximal and distal convoluted tubules." This statement is true. The loop of Henle is a long U-shaped structure between these two tubules. It plays a crucial role in the concentration and dilution of urine by reabsorbing water and electrolytes.

5. Analyze statement d

"The loop of Henle empties into the distal convoluted tubule." This statement is true. The loop of Henle indeed empties into the distal convoluted tubule, which modifies the filtrate by reabsorbing some substances and secreting others. Answer: The false statement among the given options is (a) "The collecting duct empties into the distal convoluted tubule."

Key concepts

Bowman's capsule

The Bowman's capsule is an essential component of the nephron, the basic functional unit of the kidney. It acts like a tiny, cup-shaped structure and plays a pivotal role in the filtration process of the blood. This capsule surrounds the glomerulus, which is a network of capillaries, and together they start the process of filtering the blood to form urine.

The Bowman's capsule encloses the glomerulus snugly, creating a Bowman’s space where the filtered fluid collects. It's this structure that captures the initial filtrate that includes water, electrolytes, waste products, and other small molecules while preventing larger proteins and cells from passing.

• Functions primarily to initiate the filtration process.
• Works with the glomerulus to filter out unwanted substances from the bloodstream.
• Forms the initial step in urine formation within the nephron.

Loop of Henle

The loop of Henle is a vital part of the nephron that significantly contributes to the concentration of urine. It is situated between the proximal and distal convoluted tubules, creating a U-shaped loop. Its main function is to enable the reabsorption of water and salts, which is crucial for maintaining the body's fluid and electrolyte balance.

The loop of Henle has two parts: the descending limb and the ascending limb. These sections have different permeabilities to water and ions. The descending limb allows water to leave, making the filtrate more concentrated, while the ascending limb allows ions to be pumped out but retains water, diluting the filtrate once more.

• Concentrates urine by reabsorbing water and vital ions.
• Uses countercurrent exchange to maximize efficiency.
• Essential for regulating the osmotic balance of the urine.

Distal convoluted tubule

The distal convoluted tubule is another critical segment of the nephron, following the loop of Henle in the order of components. Its primary roles include the selective reabsorption of certain ions and water, as well as the secretion of ions, acids, and other substances. The distal convoluted tubule works with a high level of responsiveness to hormones like aldosterone, which regulates sodium and potassium balance, and antidiuretic hormone (ADH), which manages water retention. This tubule prepares the filtrate for its final passage into the collecting duct, making additional changes to achieve the proper balance of salt and water.

• Performs selective reabsorption and secretion.
• Modulates urine concentration under hormonal control.
• Adjusts ionic and water balance before filtrate enters the collecting duct.