Why are the islets of Langerhans?
D000311:Adrenal Glands / Q000502:physiology; D000717:Anatomy, Comparative; D000818:Animals; D005075:Biological Evolution; D004702:Endocrine Glands / Q000378:metabolism; D005088:Exocrine Glands / Q000378:metabolism; D005399:Fishes / Q000196:embryology; D007515:Islets of Langerhans / Q000378:metabolism* / Q000502:physiology; D010179:Pancreas / Q000196:embryology