Problem 162 - Objective Biology for NEET

Question

Assertion: PCT reabsorbs nearly all essential nutrients and 70 to 80 per cent of the electrolyte and water from filterate. Reason: PCT is lined with brush border epithelium.

Step-by-Step Solution

Answer

Assertion and reason are both true and relate to each other. PCT is able to reabsorb nearly all essential nutrients and a substantial amount of electrolyte and water because of its lining with brush border epithelium, which increases its surface area, thereby aiding in the reabsorption process.

Step 1: Understand Assertion

Assertive statement 'PCT reabsorbs nearly all essential nutrients and 70 to 80 per cent of the electrolyte and water from filterate' is explaining about the function of Proximal Convoluted Tubule (PCT) part of the kidney, which majorly deals with the reabsorption of filtered components. PCT absorbs nearly all essential nutrients along with a considerable amount of electrolyte and water.

Step 2: Understand Reason

Reasoning part 'PCT is lined with brush border epithelium' is bringing the characteristics of PCT: the lining of brush border epithelium. These brush border cells have several microvilli on their apical surface which increase the surface area, helping in the reabsorption process.

Step 3: Correlation Between Assertion and Reason

Now, comparing the Assertion and the Reason, it can be deduced that the Reason is explaining why the Assertion is true. The lining of PCT with brush border epithelium enhances its ability to reabsorb nutrients, electrolytes, and water from the filtrate that has been formed.

Key Concepts

Kidney Function

The kidneys are vital organs in the human body that serve several essential functions. One of their primary roles is to filter blood and remove waste products. The Proximal Convoluted Tubule (PCT) is a crucial component of kidney function. It is responsible for reabsorbing valuable substances from the filtered fluid back into the blood. This process ensures that essential nutrients and a significant amount of water and electrolytes are not lost from the body.

• The kidneys help maintain fluid and electrolyte balance.
• They play a role in detoxifying the blood.
• The production of urine is one of their primary functions.

By maintaining the internal environment, the kidneys contribute to body homeostasis. Their efficient filtration and reabsorption capabilities are vital for a healthy metabolic balance.

Reabsorption Process

Reabsorption is a fundamental process occurring in the kidney's PCT that ensures essential substances are retained in the body. During filtration, blood is filtered to form a fluid called "filtrate." This filtrate initially contains water, electrolytes, and various nutrients. However, not all of these substances should be excreted. In the PCT, reabsorption involves:

• The uptake of almost all essential nutrients such as glucose and amino acids.
• 70 to 80 percent of electrolytes like sodium and water being reabsorbed into the bloodstream.

This efficient reabsorption process allows your body to conserve vital nutrients while selectively excreting waste products. Without this function, valuable nutrients could be lost excessively.

Brush Border Epithelium

The lining of the Proximal Convoluted Tubule is made up of special cells known as brush border epithelium. This unique structure is characterized by the presence of multiple microvilli on the surface of the epithelial cells. These tiny hair-like structures serve an important purpose:

• Microvilli greatly increase the surface area of each cell.
• This increased surface area enhances the kidney's capacity to efficiently reabsorb substances.

Thanks to the brush border epithelium, the PCT can absorb substances more effectively. By providing a large area for absorption, the brush border epitomizes the body's intricate design for maintaining health and efficiency through the reabsorption process.