Thepancreasis the organ responsible for secreting insulin directly into the bloodstream. Insulin is a hormone that regulates blood glucose levels by facilitating the uptake of glucose into cells for energy production or storage as glycogen. The pancreas contains clusters of cells known as the islets of Langerhans, which include beta cells that produce insulin.

Gallbladder: Stores bile produced by the liver.

Colon: Part of the large intestine, involved in water absorption and feces formation.

Liver: Produces bile, detoxifies substances, and stores glycogen, but does not produce insulin.