Q.'Glucagon' hormone is secreted by:

Insulin, secreted by the beta cells of the pancreatic islets of Langerhans in response to rising blood glucose after a meal, lowers blood glucose precisely by stimulating liver and muscle cells to convert glucose into glycogen (glycogenesis) for storage — so A is true and R is its correct mechanistic explanation.

After a meal, blood glucose rises as carbohydrates are digested and absorbed. This rise directly stimulates the pancreas to secrete insulin. Insulin then acts on target cells (mainly liver and muscle) in several coordinated ways: it increases glucose uptake into cells (via GLUT4 transporters, especially in muscle and adipose tissue), and — most relevant here — it activates the enzyme glycogen synthase, driving the conversion of free glucose into glycogen, the storage polysaccharide, in liver and muscle cells. By pulling glucose out of the bloodstre …

The pancreas is both an endocrine and an exocrine gland, so the answer is (C).

The pancreas is a heterocrine (mixed) gland:

• Exocrine part — acini secrete pancreatic juice (digestive enzymes) that is carried through a duct into the small intestine. …

Glucagon, the hyperglycaemic hormone, is secreted by the alpha cells of the pancreatic islets of Langerhans.

The pancreas is a heterocrine gland: its exocrine part secretes digestive enzymes, while its endocrine part consists of clusters of cells called the islets of Langerhans. These islets contain:

• Alpha (α) cells — secrete glucagon, which raises blood glucose level by stimulating glycogenolysis (breakdown of liver glycogen to glucose) and gluconeogenesis.
• Beta (β) cells — secrete insulin, which lowers blood glucose by promoting glucose uptake and glycogen synthesis. …

β cells of the pancreatic islets secrete insulin; α cells secrete glucagon.

The pancreas has an endocrine portion made up of clusters of cells called the islets of Langerhans, which contain two major cell types:

• α (alpha) cells, which secrete glucagon, a hormone that raises blood glucose levels (by promoting glycogen breakdown and glucose release from the liver). …