Intrinsic factor is secreted by
**Core Concept**
Intrinsic factor is a glycoprotein produced in the stomach that plays a crucial role in vitamin B12 absorption. It binds to vitamin B12 in food and facilitates its absorption in the terminal ileum.
**Why the Correct Answer is Right**
The correct answer is secreted by the parietal cells in the stomach. Parietal cells use the enzyme proton pump (H+/K+ ATPase) to secrete hydrochloric acid, which creates an acidic environment necessary for intrinsic factor production. The acidic environment allows the intrinsic factor to bind to vitamin B12. The intrinsic factor-vitamin B12 complex is then released into the small intestine, where it is absorbed by the ileal mucosa.
**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because parietal cells, not chief cells, secrete intrinsic factor. While chief cells produce pepsinogen, an enzyme that breaks down proteins, they do not produce intrinsic factor.
**Option B:** is incorrect because G cells, which are found in the stomach antrum, secrete gastrin, a hormone that stimulates gastric acid secretion, but they do not produce intrinsic factor.
**Option C:** is incorrect because the pancreas produces digestive enzymes, such as amylase and lipase, but it does not produce intrinsic factor.
**Clinical Pearl / High-Yield Fact**
Intrinsic factor deficiency is a key feature of pernicious anemia, a condition characterized by vitamin B12 deficiency due to impaired intrinsic factor production.
**Correct Answer:** C. Parietal cells.