Question

About \(65 \%\) of the glomerular ultrafiltrate is reabsorbed in a. the proximal tubule. b. the distal tubule. c. the nephron loop. d. the collecting duct.

Short answer

The proximal tubule (a) is responsible for reabsorbing approximately 65% of the glomerular ultrafiltrate.

Step-by-step solution

Identify the given percentage

In this problem, we are given that 65% of the glomerular ultrafiltrate is reabsorbed in one of the parts of the nephron. This will be the key information we use to determine the correct answer to the problem.

Review the function of each part of the nephron

To determine which part of the nephron is responsible for reabsorbing 65% of the glomerular ultrafiltrate, it's essential to review the function of each section briefly: a. Proximal tubule: Reabsorption of water, glucose, amino acids, and essential ions, as well as secretion of certain substances (e.g., hydrogen ions, creatinine) b. Distal tubule: Further reabsorption of water and essential ions and secretion of certain substances (e.g., potassium, hydrogen ions) c. Nephron loop (Loop of Henle): Regulation of water and electrolyte balance and concentration of the urine d. Collecting duct: Final regulation of water, electrolyte balance, and acid-base balance, as well as further water reabsorption

Determine which part of the nephron reabsorbs 65% of the glomerular ultrafiltrate

Taking into consideration the functions of each part of the nephron, we can determine that the proximal tubule (a) is responsible for reabsorbing approximately 65% of the glomerular ultrafiltrate. The proximal tubule is the first part of the tubular system and plays a significant role in reabsorbing water, essential ions, glucose, and amino acids. Therefore, the correct answer is: a. the proximal tubule.

Key concepts

Proximal Tubule

When learning about the proximal tubule, it's important to understand that it is the first segment of the renal tubule system within the nephron, immediately following the Bowman's capsule. This site is critical for reabsorption, as it efficiently recovers a vast majority of small molecules initially filtered into the kidney.

In terms of renal physiology, the proximal tubule's role is multifaceted. It reabsorbs about 65% of the glomerular ultrafiltrate, including water, electrolytes, glucose, and amino acids, using both active and passive transport mechanisms. This reabsorption ensures the body retains vital substances while excess ions and waste are excreted. Additionally, the proximal tubule performs the secretion of waste products like creatinine and hydrogen ions. These processes highlight the complex interplay of filtration, reabsorption, and secretion essential for maintaining homeostasis.

Nephron Structure

Exploring the nephron structure is like taking a journey through the kidney's functional units. Each nephron begins with a filtration component, the glomerulus, enclosed by Bowman's capsule, where blood plasma is filtered. Following filtration, the liquid, now referred to as the ultrafiltrate, travels through a series of tubular structures.

These structures include the proximal tubule, the loop of Henle, the distal tubule, and finally the collecting duct. The proximal tubule, as the exercise indicates, reabsorbs a significant portion of the ultrafiltrate, making it indispensable in the urinary system. The nephron's architecture - meticulously designed for sequential filtering, absorbing, and concentrating - is a testament to its sophisticated role in renal physiology and the body's fluid and electrolyte balance.

Renal Physiology

In discussing renal physiology, we delve into the dynamic processes that keep our body's internal environment stable. One of the most remarkable aspects of kidney function is the process of creating urine. This involves filtering the blood, reabsorbing necessary substances, and excreting waste products.

Within this context, the role of the proximal tubule—which reabsorbs around two-thirds of the ultrafiltrate volume—is crucial. Reabsorption in the kidneys isn't just about volume; it also includes essential solutes like sodium, which follows an osmotic gradient affecting water movement. The remaining structures within the nephron, such as the loop of Henle and distal tubule, fine-tune the urine's concentration and composition, while the collecting duct finalizes urine formation. Together, these processes maintain body fluid homeostasis, a core tenet of renal physiology.