What is the functions of plicae circulares?

Answer 1

The plicae circulares slow down the food passing along the intestines. Because of their shape there is an increase in the surface area between the food and the walls on the intestines which allows more efficient absorption of nutrients from the chyme - the stuff that comes from the stomach.

Answer 2

Plicae circulares slow down the passage of the chyme along the intestines, therefore increasing the availability for the process of segmentation. They can also increase the surface area for fat absorption.