Insulin is secreted by which part of the body?

Insulin is secreted by the Islets of Langerhans, which are clusters of cells located in the pancreas. These islets contain different types of cells, with beta cells specifically responsible for producing and releasing insulin in response to elevated blood glucose levels. Insulin plays a crucial role in regulating glucose metabolism, facilitating the uptake of glucose by cells for energy, and helping to maintain blood sugar levels within a normal range.

The other options indicate incorrect locations for insulin secretion. The gallbladder, which stores bile produced by the liver, does not have a role in hormone production or secretion. The kidneys are primarily involved in filtering blood and maintaining fluid and electrolyte balance, although they can produce some hormones, they do not secrete insulin. Lastly, the liver, while essential in carbohydrate metabolism, does not produce insulin; instead, it responds to insulin's effects and stores glucose in the form of glycogen.