Pancreas : The pancreas is a is a exocrine as well as endocrine gland. The pancreas has two types of cells :

(a) Pancreatic gland cells : These cells secrete enzymes.

(b) Islets of Langerhans : These are the endocrine part of the pancreas.  These cells are further of following types :

Fig. A part of the section of pancreas to show an islent of Langerhans.

(i) Alfa cells : These secrete glucagon. The glucagon converts glycogen into glucose. This process is called glycogenolysis.

(ii) Beta cells : These secrete insulin. It converts glucose to glycogen in liver. This process is called glycogenesis.

(iii) Delta cells : These secrete somatostanin hormone which controls the rate of absorption of food.