All of the statements are true about ileum except –
**Core Concept**
The ileum is the final and longest segment of the small intestine, playing a crucial role in the absorption of bile salts and vitamin B12. Its unique structure and function enable the breakdown and absorption of nutrients from the food we consume.
**Why the Correct Answer is Right**
The ileum is indeed the primary site for the reabsorption of bile salts, which are produced in the liver, stored in the gallbladder, and released into the small intestine to facilitate fat digestion. The ileum's walls are richly supplied with specialized cells called enterocytes, which contain microvilli that increase the surface area for absorption. Additionally, the ileum is responsible for the absorption of vitamin B12, a process that involves intrinsic factor, a glycoprotein produced by the parietal cells of the stomach.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, so we will address the others.
**Option B:** This option is incorrect because the jejunum, not the ileum, is primarily responsible for the absorption of carbohydrates, proteins, and fats.
**Option C:** This option is incorrect because the ileum does not have a significant role in the absorption of water and electrolytes, which is primarily facilitated by the large intestine.
**Option D:** This option is incorrect because the ileum is not the primary site for the absorption of glucose, which is mainly absorbed in the jejunum.
**Clinical Pearl / High-Yield Fact**
A classic exam trap is the confusion between the jejunum and ileum. Remember that the jejunum is responsible for the bulk of nutrient absorption, while the ileum specializes in the reabsorption of bile salts and vitamin B12.
**Correct Answer: B. The jejunum is primarily responsible for the absorption of carbohydrates, proteins, and fats.**