Problem 44 - Objective Biology for NEET

Question

A part of Nephron is situated in cortex completely A. Malpighian Corpuscle B. PCT C. DCT D. Loop of Henle E. Collecting duct (a) \(\mathrm{A}, \mathrm{B}\) and \(\mathrm{C}\) only (b) B and C only (c) \(\mathrm{A}, \mathrm{B}, \mathrm{C}\) and \(\mathrm{D}\) only (d) D and E only

Step-by-Step Solution

Answer

The correct answer to the exercise is option (a).

Step 1: Identify the Parts of the Nephron Situated in the Cortex

The Malpighian Corpuscle, the PCT, and the DCT are the parts of the nephron that are completely situated in the cortex of the kidney.

Step 2: Match the Identified Parts with the Options

Match the identified parts with the provided options in the exercise. The options that include only the Malpighian Corpuscle, the PCT, and the DCT are the correct answers.

Step 3: Select the Correct Answer

According to the analysis, the correct answer is option (a), as it includes the Malpighian Corpuscle, the PCT, and the DCT only which are completely situated in the cortex of the kidney.

Key Concepts

Malpighian Corpuscle

The Malpighian Corpuscle, also known as the renal corpuscle, is an essential component of the nephron, the functional unit of the kidney. It plays a vital role in the filtration of blood, serving as the initial step in the formation of urine.

The Malpighian Corpuscle consists of two main parts:

• The glomerulus - a tangled, ball-like structure composed of tiny blood vessels called capillaries.
• The Bowman's capsule - a cup-shaped structure that encases the glomerulus.

Blood enters the glomerulus through an afferent arteriole and leaves through an efferent arteriole. As blood passes through the glomerulus, fluid and small molecules are filtered out, leaving larger molecules and blood cells behind. This filtrate enters the Bowman's capsule and then moves onto the next part of the nephron for further processing.

Located exclusively in the kidney's cortex, the Malpighian Corpuscle is responsible for the ultrafiltration of the plasma, which is a critical step in excreting waste while retaining important substances such as proteins and blood cells.

Proximal Convoluted Tubule (PCT)

The Proximal Convoluted Tubule (PCT) is a significant section of the nephron that continues the process of filtering blood after the initial filtration done by the Malpighian Corpuscle.

In the PCT, the filtrate from the Bowman's capsule is further processed through reabsorption and secretion. Here's what happens in this part of the nephron:

• A large proportion of reabsorption occurs in the PCT, where essential nutrients, such as glucose, amino acids, and ions like sodium and potassium, are reabsorbed back into the bloodstream.
• It is also the site where a considerable amount of water is reabsorbed, a process driven by osmosis due to the reabsorption of solutes.
• Toxins and waste products, including hydrogen ions and urea, are secreted into the tubular fluid to be eliminated from the body.

The PCT has a convoluted structure that increases its surface area, making it highly effective in reabsorption. It is located entirely in the kidney's cortex, and its functions are vital for maintaining the body's internal balance of fluids and electrolytes, known as homeostasis.

Distal Convoluted Tubule (DCT)

Next in line within the nephron, following the PCT, is the Distal Convoluted Tubule (DCT). The DCT is a critical structure within the nephron that fine-tunes the reabsorption and secretion of various substances to maintain the body's electrolyte and acid-base balance.

It differs from the PCT in that it performs more selective reabsorption based on the body's needs, which is regulated by hormones such as aldosterone and parathyroid hormone (PTH). Here's what sets the DCT apart:

• The DCT regulates the reabsorption of sodium, chloride, and calcium ions, thus playing a crucial role in managing blood pressure and bone health.
• It adjusts the pH of the body fluids by reabsorbing bicarbonate and secreting hydrogen ions and ammonium.
• It is also the site of action for several diuretics, which are medications that increase urine production to treat conditions like hypertension.

Similar to the PCT, the DCT resides entirely within the kidney's cortex. Unlike the previous tubular sections, the DCT transports its contents to the collecting duct, which ultimately leads to the concentration and excretion of urine.