Question

Why do you think the stomach is structured like a bag rather than a tube like an oesophagus​?

Answer 1

Stomach and oesophagus are the important parts of the digestive system. The food from the mouth passes to the stomach through the oesophagus. Stomach is the organ where the digestion of food takes place.

Complete answer:
The alimentary canal is the system where the complete digestion and elimination of food takes place. It starts with the mouth where the food is masticated, partially digested and converted into bolus. The oesophagus is a tube-like structure through which the food/bolus is passed to the stomach. The oesophagus is a tube-like structure which is lined by the mucus. It has this structure because it acts like a channel for passing down the food easily to the stomach. The mucus reduces the friction and also kills any type of microorganism present.

The stomach is a sac-like muscular structure where digestion and temporary storage of food takes place. It has an acidic environment for the better functioning of the digestive enzymes. The food stays in the stomach for a greater duration. At the stomach the digestion of proteins by the pepsin enzyme takes place. This structure provides maximum surface area so that proper digestion of food takes place.
The tube-like structure facilitates the proper movement of the food and the bag-like structure enables the better digestion of food.

Note: The food after digestion in the stomach moves to the intestine where the food is completely digested and the reabsorption of the nutrients takes place. Digestive enzymes play an important role in breaking down food into simpler substances. The undigested food is eliminated through the rectum.