Question

Glucose reabsorption in the nephron occurs in the A. loop of Henle. B. distal convoluted tubule. C. proximal convoluted tubule. D. collecting duct.

Short answer

C. Proximal Convoluted Tubule.

Step-by-step solution

Understand Glucose Reabsorption

Glucose reabsorption is the process by which the nephron removes glucose from the filtrate and returns it to the blood.

Identify Nephron Segments

The nephron consists of the glomerulus, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and the collecting duct. Each segment has specific functions.

Determine the Reabsorption Site

Glucose is primarily reabsorbed in the proximal convoluted tubule. This is because the proximal convoluted tubule has transporters specifically for glucose reabsorption.

Match Correct Answer

Now compare the options with the information from Step 3: A. Loop of Henle - Incorrect B. Distal Convoluted Tubule - Incorrect C. Proximal Convoluted Tubule - Correct D. Collecting Duct - Incorrect

Key concepts

proximal convoluted tubule

The proximal convoluted tubule (PCT) is a key component of the nephron, the basic functional unit of the kidney. It is where the initial stage of reabsorption happens. After the blood gets filtered through the glomerulus, the filtrate passes into the PCT. Here, essential substances like glucose, amino acids, sodium, and water are reabsorbed back into the bloodstream.

The PCT is highly efficient and handles a significant amount of reabsorption:

• Approximately 100% of glucose reabsorption
• Around 65%-70% of sodium and water reabsorption
• Other essential nutrients and ions

The transporters in the PCT are specialized to ensure that glucose and other vital substances are reabsorbed entirely. When these transporters become saturated, excess glucose may spill into the urine, a condition observed in diabetes mellitus.
The PCT's significant role highlights its importance in maintaining the body's electrolyte balance and preventing nutrient loss.

nephron segments

The nephron is divided into several segments, each with unique functions that contribute to the overall role of the kidney in filtering blood and producing urine. The main segments include:

• Glomerulus: Where blood filtration begins. A tuft of capillaries filters water and solutes from the blood.
• Proximal Convoluted Tubule (PCT): Reabsorbs essential nutrients, ions, and water.
• Loop of Henle: Concentrates urine by creating a gradient in the medulla through its descending and ascending limbs.
• Distal Convoluted Tubule (DCT): Fine-tunes the reabsorption of sodium, potassium, and calcium, under hormonal control.
• Collecting Duct: Final adjustments to urine composition, focuses on water reabsorption, and acid-base balance.

Each segment contributes to carefully balancing fluids, electrolytes, and waste products.
Studies on these segments provide insights into various kidney-related diseases and help develop targeted medical treatments.

kidney function

The kidneys perform several essential functions that maintain internal homeostasis. Their primary roles encompass:

• Filtration of blood to remove waste products such as urea, creatinine, and ammonia.
• Regulating blood pressure through the renin-angiotensin-aldosterone system (RAAS).
• Balancing electrolytes like sodium, potassium, and calcium.
• Maintaining acid-base balance by excreting hydrogen ions and reabsorbing bicarbonate.
• Producing hormones, including erythropoietin (stimulates red blood cell production) and calcitriol (active vitamin D).

Regularly, the kidneys filter about 180 liters of blood daily, but only about 1-2 liters of urine are excreted. This indicates an immense capacity for reabsorption and filtration.

Disruptions in kidney function can lead to serious health problems. Recognizing symptoms like swelling, fatigue, and changes in urine output can help with early diagnosis of kidney diseases. Routine check-ups and a healthy lifestyle can safeguard kidney health and ensure they function effectively.