Write the function of the following in the human alimentary canal:
(i) Saliva (ii) HCl in stomach
(iii) Bile juice (iv) Villi

Explanation

(i) Saliva contains a digestive enzyme called salivary amylase which breaks down starch into sugar.
(ii) Secrtion of HCl makes the food soft and acidified for pepsin to act unpon food.
(iii) Bile juice down the fats which are present in food in the form of large globules (which make it difficult for enzyms to act on them) mechanically into smaller globules which increases the efficiency of fat digesting enzymes.
(iv) Villi in the small intestine inceare the surface area of the absorption of food .Villi in the larger intestine incrase the surface area for the absorption of water .