Question

Assertion (A) : The parietal cells of gastric glands secrete Castle's intrinsic factor in man.
Reason (R) : Castle's intrinsic factor is essential for the absorption of cyanocobalamin.
Identify the correct option from the following

• (A) and (R) are true. (R) is correct explanation for (A).
• (A) and (R) are true. But R is not correct explanation for (A).
• (A) is true, but (R) is false.
• (A) is false, but (R) is true.

Hint:

Parietal cells in the stomach are crucial for two functions: secreting HCl for digestion and intrinsic factor for Vitamin B12 absorption. The latter is a specific carrier protein without which Vitamin B12 cannot be absorbed.

Answer 1

The Correct Option is A

Step 1: Analyze Assertion (A). Assertion (A) states: "The parietal cells of gastric glands secrete Castle's intrinsic factor in man." Parietal cells (also known as oxyntic cells) are indeed found in the gastric glands of the stomach. Their two main secretions are hydrochloric acid (HCl) and intrinsic factor (also known as Castle's intrinsic factor). This statement is True. Step 2: Analyze Reason (R). Reason (R) states: "Castle's intrinsic factor is essential for the absorption of cyanocobalamin." Cyanocobalamin is the synthetic form of Vitamin B12. Intrinsic factor is a glycoprotein that binds to Vitamin B12 (including cyanocobalamin) in the stomach and facilitates its absorption in the ileum (the final section of the small intestine). Without intrinsic factor, Vitamin B12 cannot be properly absorbed, leading to conditions like pernicious anemia. This statement is True. Step 3: Evaluate if Reason (R) is the correct explanation for Assertion (A). Assertion (A) states \textit{what} parietal cells secrete (intrinsic factor). Reason (R) states \textit{why} intrinsic factor is important (for Vitamin B12 absorption). The secretion of intrinsic factor by parietal cells is precisely for its function in Vitamin B12 absorption. The cell secretes it because it has this essential role. Therefore, Reason (R) directly explains the physiological importance and thus the reason for the existence and secretion of intrinsic factor by parietal cells. This establishes a cause-and-effect relationship where the function (R) explains the existence/secretion (A). Thus, (R) is the correct explanation for (A). Step 4: Conclude the correct option. Both (A) and (R) are true, and (R) is the correct explanation for (A). The final answer is $\boxed{\text{(A) and (R) are true. (R) is correct explanation for (A).}}$.