HiiiIt's first made acidic medium becoz to activate the Pepsin enzyme.. then it's make alkaline medium which help the bile juice from liver in DUODENUM..Hope it's help u

Introduction:
The digestive system is responsible for breaking down food into simpler compounds that can be absorbed and utilized by the body. This process mainly occurs in the alimentary canal, which consists of various organs that work together to digest food. One of the unique features of the digestive system is the fluctuation in pH levels that occur during digestion.

Acidic and Basic Environment:
The alimentary canal has different pH levels at different stages of digestion. It starts with an acidic environment in the stomach, where hydrochloric acid is secreted by the stomach lining to break down food and kill harmful bacteria. The pH in the stomach can be as low as 1.5, which is highly acidic.

After the stomach, the food enters the duodenum, the first part of the small intestine. The acidic food from the stomach needs to be neutralized before it can enter the small intestine, which is an alkaline environment. The pancreas secretes bicarbonate ions that neutralize the acidic food, raising the pH level to around 7-8, which is alkaline.

Reason for Fluctuation in pH:
The reason for this fluctuation in pH is that different enzymes work best at different pH levels. For example, pepsin, an enzyme in the stomach, works best in an acidic environment and breaks down proteins into smaller molecules. On the other hand, enzymes in the small intestine, such as pancreatic amylase and lipase, work best in an alkaline environment and break down carbohydrates and fats, respectively.

Conclusion:
In conclusion, the fluctuation in pH levels in the alimentary canal is essential for proper digestion. The acidic environment in the stomach helps to break down food, while the alkaline environment in the small intestine is necessary for the enzymes to work efficiently. This process ensures that the body can absorb and utilize the nutrients from the food we eat.