**Question:** Intrinsic Factor of Castle is secreted by which of the following cells in gastric glands:

A. G cells
B. D cells
C. ECL cells
D. Fundic cells

**Correct Answer:** **D. Fundic cells**

**Core Concept:** Intrinsic Factor (IF) is a glycoprotein essential for the absorption of vitamin B12 in the terminal ileum. It plays a crucial role in the synthesis of methionine and DNA, as well as the maintenance of the neural and myelin sheaths.

**Why the Correct Answer is Right:** Fundic cells are a type of chief cells found in the gastric glands of the stomach. They secrete various substances, including intrinsic factor, which is responsible for binding to vitamin B12 and facilitating its transport through the gastric juice into the small intestine.

**Why Each Wrong Option is Incorrect:**

A. G cells: These cells secrete gastrin, which stimulates the secretion of gastric acid, but not intrinsic factor.
B. D cells: D cells secrete somatostatin, which inhibits gastric secretion but also does not produce intrinsic factor.
C. ECL cells: ECL cells are responsible for producing and releasing histamine, which stimulates gastric acid secretion, but not intrinsic factor.

**Why Each Wrong Option is Incorrect:**

A. G cells: These cells secrete gastrin, which stimulates the secretion of gastric acid, but not intrinsic factor.
B. D cells: D cells secrete somatostatin, which inhibits gastric secretion but also does not produce intrinsic factor.
C. ECL cells: ECL cells are responsible for producing and releasing histamine, which stimulates gastric acid secretion, but not intrinsic factor.

**Clinical Pearl:** Intrinsic factor plays a vital role in maintaining proper gastrointestinal function and preventing vitamin B12 deficiency, which can lead to serious neurological complications. A deficiency of intrinsic factor may occur in cases like pernicious anemia, where the stomach becomes inflamed and damages the parietal cells (D cells) that produce gastric acid, leading to achlorhydria (absence of gastric acid).

**Clinical Pearl:** Achlorhydria, which is a state of absent gastric acid secretion, can cause severe vitamin B12 deficiency and lead to pernicious anemia. Pernicious anemia is characterized by a deficiency of intrinsic factor, resulting from the damage to parietal cells (D cells) and the absence of gastric acid production. This condition can cause neurological complications due to vitamin B12 deficiency.