Final answer:
The pancreas is the organ that lies in the retroperitoneal space. It has a complex role in the body, containing both exocrine glands that secrete digestive enzymes and endocrine glands that release important hormones such as insulin. Thus, the option B is the correct answer.
Step-by-step explanation:
The structure that lies in the retroperitoneal space is the pancreas. The soft, oblong, glandular pancreas is situated transversely in the retroperitoneum, located behind the stomach. Its anatomy includes a 'c-shaped' curve of the duodenum around its head, with the body of the pancreas extending to the left and ending as a tapering tail in the hilum of the spleen. Moreover, the pancreas performs a dual role, with both exocrine functions (secreting digestive enzymes into the small intestine) and endocrine functions (releasing hormones such as insulin and glucagon into the bloodstream).
The retroperitoneal space contains several organs that are posterior to the peritoneum, and the pancreas is one such organ. The pancreas is not only crucial for digestion due to its exocrine role but also plays a vital role in regulating blood sugar levels through its endocrine function.