## **Core Concept**
Intrinsic factor is a glycoprotein produced in the stomach that plays a crucial role in the absorption of vitamin B12. It binds to vitamin B12 from food and facilitates its absorption in the ileum. The production of intrinsic factor is essential for preventing vitamin B12 deficiency.

## **Why the Correct Answer is Right**
The correct answer, **parietal cells**, are responsible for secreting intrinsic factor. Parietal cells, also known as oxyntic cells, are found in the gastric glands of the stomach lining. They secrete hydrochloric acid (HCl) and intrinsic factor. The intrinsic factor produced by parietal cells is critical for the subsequent absorption of vitamin B12 in the terminal ileum of the small intestine.

## **Why Each Wrong Option is Incorrect**
- **Option A: Chief cells** - Chief cells, also known as peptic cells or gastric chief cells, primarily secrete pepsinogen, which is converted into pepsin, an enzyme that breaks down proteins. They do not produce intrinsic factor.
- **Option C: Mucous cells** - Mucous cells produce mucus, which protects the stomach lining from the acidic environment and digestive enzymes. They are not involved in the production of intrinsic factor.
- **Option D: Enterochromaffin-like cells (ECL cells)** - ECL cells produce histamine, which stimulates parietal cells to secrete hydrochloric acid. They do not produce intrinsic factor.

## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that autoimmune destruction of parietal cells can lead to a deficiency in intrinsic factor production, resulting in pernicious anemia, a condition characterized by vitamin B12 deficiency. This is an important cause of megaloblastic anemia.

## **Correct Answer:** B. parietal cells