Final answer:
The pancreas, located in the upper retroperitoneum, functions as a heterocrine gland with both endocrine and exocrine tissues; it secretes digestive enzymes and hormones such as insulin and glucagon.
Step-by-step explanation:
Located in the upper retroperitoneum, the pancreas is composed of both endocrine and exocrine tissues. The soft, oblong, glandular pancreas lies transversely behind the stomach. Its head is nestled into the c-shaped curvature of the duodenum with the body extending to the left and ending as a tapering tail in the hilum of the spleen. The pancreas is unique as it functions as a heterocrine gland, performing both exocrine actions, such as secreting digestive enzymes, and endocrine functions, which include releasing hormones like insulin and glucagon into the blood.