Certified Tumor Registrar (CTR) Practice Exam

The primary role of the islets of Langerhans in the endocrine system is to produce insulin and glucagon. These islets are clusters of cells located in the pancreas, and they play a vital role in glucose metabolism and maintaining blood sugar levels. Insulin is a hormone that facilitates the uptake of glucose by cells, lowering blood sugar levels, while glucagon has the opposite effect, promoting the release of glucose into the bloodstream when levels are low. This balance is crucial for energy regulation in the body.

In contrast, the other options pertain to functions not related to the endocrine role of the islets of Langerhans. Filtering blood is a function associated with the kidneys, transporting oxygen is the primary role of red blood cells, and storing bile is a function of the gallbladder. Each of these processes is important to the body, but they do not involve the production of hormones essential for glucose regulation like the islets do.