Identify the location and function of the following:
$(1)$ Villi
$(2)$ Oxyntic cells

(N/A) $(1)$ Villi: Located in the mucosa of the small intestine. They provide a large surface area for the absorption of digested food components.
$(2)$ Oxyntic cells (Parietal cells): Located in the gastric glands of the stomach. They secrete dilute $HCl$ and intrinsic factor,which is essential for the absorption of vitamin $B_{12}$.