Question

Where does the process of digestion begin? Are nutrients absorbed from the large intestine?

Answer 1

Mouth or buccal cavity is the part where the digestion starts. The mouth contains saliva and teeth. No, nutrients are not absorbed from the large intestine. Villi is important for the absorption of nutrients from the small intestine.

Complete answer:
When we smell food, the secretion of saliva occurs in the buccal cavity or mouth. When we eat the food, teeth present in the mouth chew the food and break it down into smaller pieces making it easy to be digested. The saliva on the other hand helps the smaller pieces to get absorbed in the body. The tongue on the other hand helps to push the smaller pieces of the food mixed with saliva to the throat from where it passes to the esophagus then to the stomach. Thus, it can be said that the process of digestion starts from the mouth.
The Small intestine secretes many digestive enzymes.
Moreover, the surface of the small intestine contains villi (finger-like projection) and at the same time, the surface area of the intestine is very large. These three factors play a vital role in the absorption of nutrients from the small intestine. The large intestine on the other hand does not secrete any digestive enzyme or does not have villi for absorption of nutrients. The main function of the large intestine is to take up or absorb water and minerals left over after absorption by the small intestine and also to enhance or assist the process of excretion. So it is clear that the nutrients are not absorbed from the large intestine.

Note:
There are a total of $32$ teeth in both jaws. The types of teeth include –Incisors, Canine, Molar, and Premolar. The saliva of humans contains amylase (helps in starch digestion), lingual lipase (important for fat digestion), mucus, and electrolytes. Villi of the small intestine contain lacteals which are responsible for absorption. Some of the digestive enzymes secreted by the small intestine include – maltase, peptidase, lipase.