State the exact location of the following structures:
Islets of Langerhans
Topic: Location of the islets of Langerhans
Answer
Scattered as small groups of cells throughout the PANCREAS, which lies in the loop of the duodenum just below the stomach.
The islets are the ENDOCRINE portion of the pancreas — isolated patches of hormone-secreting cells embedded among the much more numerous cells that make digestive enzymes. The word ISLETS (little islands) describes exactly that arrangement.
Within them: BETA cells secrete INSULIN (lowers blood glucose), ALPHA cells secrete GLUCAGON (raises it).
This makes the pancreas a HETEROCRINE or mixed gland: the exocrine part pours pancreatic juice into the duodenum through a DUCT, while the islets release their hormones DIRECTLY INTO THE BLOOD with no duct at all. It is the standard example when a question asks for such a gland.