**Question:** Pancreas secretes all of the following except

A. Insulin
B. Glucagon
C. Stomach acid (HCl)
D. Pancreatic Kallikrein

**Core Concept:**
The pancreas is an essential endocrine and exocrine organ responsible for maintaining glucose homeostasis, digestion, and other physiological processes. It is composed of two main parts: the exocrine pancreas and the endocrine pancreas.

**Why the Correct Answer is Right:**
The pancreas produces hormones that help regulate blood glucose levels:
1. Insulin: lowers blood glucose by promoting glucose uptake in target tissues such as muscle, liver, and adipose tissue. Insulin is not involved in digestion.
2. Glucagon: raises blood glucose levels by stimulating glycogenolysis and gluconeogenesis in the liver, promoting glycogen breakdown and glucose production respectively.
3. Stomach acid (HCl): Secreted by gastric chief cells, not by pancreatic acinar cells. Pancreatic Kallikrein is an enzyme involved in the activation of other digestive enzymes, not a hormone or gut hormone.

**Why Each Wrong Option is Incorrect:**
A. Insulin: Although insulin is secreted by pancreatic beta cells, it plays a role in glucose homeostasis, not digestion.
B. Pancreatic Kallikrein: This enzyme is involved in the activation of other digestive enzymes, not a hormone or gut hormone.
C. Stomach acid (HCl): Secreted by gastric chief cells, not by pancreatic acinar cells.

**Clinical Pearl:**
The pancreas has distinct cells and functions within its different parts. While insulin and glucagon are hormones regulating blood glucose levels, pancreatic Kallikrein is an enzyme involved in the activation of other digestive enzymes. Stomach acid (HCl) is secreted by gastric chief cells, not pancreatic acinar cells.