This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology and abdominal wall layer, Subject name: Anatomy
Pancreatic islets consist of alpha, beta, and delta cells, which secrete glucagon, insulin, and somatostatin, respectively. These cells are derived from 
Select and explain. 
A. Mesoderm, B. Endoderm, C. Ectoderm, D. Neuroectoderm
B: Endoderm
Answer: B: Endoderm 
Explanation: Pancreatic islets form as isolated clumps of cells that bud from endodermal tubules. As pa of embryonic development, the pancreas forms as two buds from the foregut, an embryonic tube that is a precursor to the gastrointestinal tract. It is therefore of endodermal origin