Gall bladder contractions and Pancreatic secretion are triggered by

The correct option is cholecystokinin.

Here is a step-by-step educational explanation of why this is correct:

1. Understanding the Role of Cholecystokinin (CCK):
Cholecystokinin is a peptide hormone synthesized and secreted by the enteroendocrine I-cells located in the mucosal lining of the duodenum (the first part of the small intestine). Its release is primarily stimulated by the presence of hydrochloric acid, amino acids, and fatty acids entering the duodenum from the stomach.

2. Gallbladder Contractions:
Once released into the bloodstream, cholecystokinin acts on the gallbladder, causing it to contract. This contraction forces stored bile out of the gallbladder, through the common bile duct, and into the duodenum. Bile plays a critical role in emulsifying fats, breaking them down into smaller droplets so they can be digested more efficiently by lipases.

3. Pancreatic Secretion:
Simultaneously, cholecystokinin stimulates the acinar cells of the pancreas. This stimulation triggers the secretion of a digestive juice rich in pancreatic enzymes, including amylase, lipase, and proteolytic enzymes (such as trypsinogen and chymotrypsinogen). These enzymes are vital for digesting carbohydrates, lipids, and proteins in the small intestine.

4. Evaluating Other Options:
- Enterogastrone: A hormone secreted by the duodenal mucosa that mainly inhibits gastric secretion and motility.
- Enterocrinin: A hormone that stimulates the secretion of intestinal juice (succus entericus) from the glands of the small intestine.
- Gastrin: A hormone produced by G-cells in the stomach that stimulates the secretion of gastric acid (HCl) by the parietal cells of the stomach mucosa.

Therefore, cholecystokinin is the specific hormone responsible for triggering both gallbladder contractions and the secretion of enzyme-rich pancreatic juice.