Pancreatic and intestinal enzymes operate optimally at a pH that is slightly alkaline, yet the chyme entering the duodenum from the stomach is very acidic. How is the proper pH for the functioning of the pancreatic-intestinal enzymes ensured?

By the help of the fluid delivered from the pancreas.

Explanation:

The human body is a very complex system consisting of many organ and organ system.

One of those systems is the the digestive system. By the help of this system the digestion and absorption of food takes place.

There are numerous number of enzymes involved in the digestion of the food released by various organs. The pancreatic and intestinal enzymes are secreted that work at alkaline pH, but the chyme that is secreted from the deodenum is slightly acidic yet they work together.

This is because pancreas pour enzyme into small intestine which is alkaline  and it then secretes huge amount of sodium bicarbonate which neutralizes the acidity of the stomach and makes the pH optimum for the digestion of food.

they deliver oxygen to the blood

helicase, i think thats it