Question

During the process of digestion, food is exposed to a range of $pH$ . The relative $pH$ of fluids in $I,II$ and $III$ regions of the alimentary canal represented in this diagram is

• A. $I>II<III$
• B. $I>II>III$
• C. $I<II<III$
• D. $I<II>III$

Answer 1

Answer: (A)

The alimentary canal of human beings is divided into various parts, where several types of organs are associated. Several digestive glands are also associated with assisting the process of digestion. The enzymes secreted by these glands are specific for the pH available at the organ on which they are working.
1. In the mouth, salivary glands secrete slightly acidic saliva. Salivary glands like the parotid glands, submaxillary glands. Submandibular glands secrete saliva. The pH of saliva is nearly 6.8. Ptyalin or salivary amylase helps in the digestion of starch at this pH.
2. The Parietal cells of the stomach secrete HCl. This makes the gastric juice highly acidic and the pH falls to nearly 2.8 to 3.2. At this pH, the food is churned and pepsin digests the protein to peptone.
3. In the small intestine, the acidic pH is neutralized by the bile salts, alkaline mucus, and the pH is brought to a slightly alkaline range. Trypsin, Chymotrypsin, etc. help in the digestion of protein at a pH of 8.2 to 8.5 in our small intestine.