Describe the structure of the pancreas,its location,and discuss its hormonal role.

(N/A) The pancreas is a composite gland that acts as both an exocrine and an endocrine gland.
$\Rightarrow$ The endocrine part of the pancreas consists of 'Islets of Langerhans'.
$-$ There are about $1$ to $2$ million Islets of Langerhans in a normal human pancreas,representing only $1$ to $2 \%$ of the pancreatic tissue.
The two main types of cells in the Islets of Langerhans are $\alpha$-cells and $\beta$-cells. The $\alpha$-cells secrete a hormone called glucagon,while the $\beta$-cells secrete insulin.
Glucagon is a peptide hormone that plays an important role in maintaining normal blood glucose levels.
Glucagon acts mainly on liver cells (hepatocytes) and stimulates glycogenolysis,resulting in increased blood sugar (hyperglycemia).
In addition,it also stimulates the process of gluconeogenesis,which contributes to hyperglycemia.
Glucagon reduces cellular glucose uptake and utilization. Thus,glucagon is a hyperglycemic hormone.
Insulin is a peptide hormone that plays a major role in the regulation of glucose homeostasis.
Insulin acts mainly on hepatocytes and adipocytes and enhances cellular glucose uptake and utilization. As a result,there is a rapid movement of glucose from the blood into hepatocytes and adipocytes,resulting in decreased blood glucose levels (hypoglycemia).
$-$ It also stimulates the conversion of glucose to glycogen (glycogenesis) in the target cells.
The glucose homeostasis in the blood is thus maintained jointly by the two hormones: insulin and glucagon.
Prolonged hyperglycemia leads to a complex disorder called diabetes mellitus,which is associated with the loss of glucose through urine and the formation of harmful compounds known as ketone bodies.
Diabetic patients are successfully treated with insulin therapy.