Question

Which of the following is absorbed in the proximal intestine?
A. Iron
B. Sodium
C. Bile salts
D. Vitamin ${{\text{B}}_{12}}$

Answer 1

Hint: Digested food gets absorbed in millions of tiny villi like structures present in the lumen of the small intestine. These villi are tiny finger-like projections meant to increase the surface of absorption. They give lumen of the small intestine a brush border like appearance.

Complete answer:
Small intestine is divided into duodenum, jejunum and ileum. Duodenum is also referred to as the proximal intestine because it is the beginning of the intestines. It is in connection with the stomach and pancreas. The villi like structure of the small intestine begins from here which starts absorption of nutrients from the partially digested food that is passed on from the stomach. It has mucosa, submucosa and muscularis layers and is C shaped.

As duodenum obtains partially digested food so it mechanically digests it with the help of bile and pancreatic enzymes. It neutralises the acidic gastric juices present in the food which are poured into it by the stomach. Absorption of nutrients, water and electrolytes start here.

Hence, the correct answer is option (A).

Additional information:
• Brunner’s gland is the speciality of proximal intestine/duodenum. The secretions of this gland protects the intestine walls from the acidic gastric juices produced by the stomach.
• Duodenum is divided into – Ascending, descending, superior and horizontal duodenum.
• Amino acids, sugars and fatty acids are absorbed by the jejunum.
• Ileum absorbs ${{\text{B}}_{12}}$ and bile salts.

Note: The length of duodenum is 25-30 cm which is approximately 12 fingers’ length and it is present in the upper part of the abdomen. It is rich in goblet cells which produce mucus that aid in the lubrication of the food.