Insulin is secreted by which cells?

• A. Beta-cells in the islet of Langerhans in the pancreas tail
• B. Alpha-cells in the islet of Langerhans
• C. Delta-cells
• D. Acinar cells

Answer: (A)

Insulin is secreted by beta cells in the islets of Langerhans in the pancreas. These endocrine cells respond to rising blood glucose by releasing insulin, which promotes glucose uptake into muscle and adipose tissue and inhibits glucose production by the liver, helping to lower blood sugar. The other cell types have different roles: alpha cells produce glucagon, which raises blood glucose; delta cells secrete somatostatin, which modulates endocrine release; acinar cells are part of the exocrine pancreas and secrete digestive enzymes, not hormones.