Human Digestive System

Answer is option A i.e. "Gastrin"
Stimuli in the stomach and small intestine activate or induce gastric juice production. The gastrin in digestive acid secretion is induced by the mechanical and chemical stimulation of stomach.

Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility. It is released by gastric cells in the pyloric antrum of the stomach, duodenum, and the pancreas. Gastrin is directly responsible for the release of gastric acid, which breaks down the proteins in the food you eat.

•  Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is produced in many tissues of vertebrates including the gut, pancreas, intestine and suprachiasmatic nuclei of the hypothalamus in the brain. Hence, VIP hormone is produced in Pancreas and Intestine. 

Answer is option A i.e. "Duodenum and pancreas"
Secretin is a hormone that regulates water homeostasis throughout the body. Duodenum and pancreas are associated with secretion and stimulation of secretin hormone in following way: when hydrochloric acid passes from the stomach into the duodenum, secretin is released into the bloodstream and stimulates the duct cells of the pancreas to secrete water and bicarbonate.

• Vasoactive intestinal polypeptide (VIP), a 28-amino-acid polypeptide secreted by cells throughout the intestinal tract. 
• It stimulates the secretion of electrolytes and water by the intestinal mucosa.
• Some pancreatic islet-cell tumours secrete excessive amounts of VIP (a condition called Verner-Morrison syndrome, or pancreatic cholera). VIP-secreting tumours cause severe, intractable, debilitating watery diarrhoea and an associated loss of large quantities of potassium. The resulting dehydration may be life-threatening. Hence, VIP hormone stimulates the Intestinal secretion of water and electrolyte.
So, the correct answer is 'Intestinal secretion of water and electrolyte'.

• Cholecystokinin is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. 
• Cholecystokinin, officially called pancreozymin, is synthesized and secreted by enteroendocrine cells in the duodenum, the first segment of the small intestine. 
• Cholecystokinin also increases the release of fluid and enzymes from the pancreas to break down fats, proteins and carbohydrates.
•  Cholecystokinin seems to be involved with appetite by increasing the sensation of fullness in the short-term, that is, during a meal rather than between mealsHence, Cholecystokinin involves in Controlling appetite.
So, the correct answer is 'Controlling appetite'.

• Cholecystokinin, officially called pancreozymin, is synthesized and secreted by enteroendocrine cells or I-cell in the duodenum, the first segment of the small intestine.
•  Its presence causes the release of digestive enzymes and bile from the pancreas and gallbladder, respectively, and also acts as a hunger suppressant. Hence, I cell secretes cholecystokinin hormone.

Gastric inhibitory peptide inhibits gastric acid secretion in the stomach.
Cholecystokinin is a  small intestinal hormone that stimulates the secretion of pancreatic enzymes and bile. Secretin is a small intestinal hormone secreted by epithelial cells od small intestine epithelial cells; stimulates secretion of bicarbonate-rich fluids from the pancreas and liver. Hence Gastric inhibitory peptide, Cholecystokinin, and Secretin hormones regulate the secretion of digestive juices and help indigestion
So, the correct option is 'All of the above'.

Secretin is a hormone that regulates water homeostasis. It is secreted by the duodenum. When hydrochloric acid passes from the stomach into the duodenum, secretin is released. It stimulates the acinar cells of the pancreas to secrete water and bicarbonate into the pancreatic duct. This water and bicarbonate is then drained into the duodenum.

• Gastric inhibitory polypeptide (GIP) or gastro inhibitory peptide, also known as the glucose-dependent insulinotropic peptide, is an inhibiting hormone of the secretin family of hormones. 
• While it is a weak inhibitor of gastric acid secretion, its main role is to stimulate insulin secretion.  
• It is synthesized by K cells, which are found in the mucosa of the duodenum and the jejunum of the gastrointestinal tract. Hence, the GIP  hormone stimulates the lipase activity

• Duocrinin is a postulated gastrointestinal hormone that is liberated by the contact of gastric contents with the intestine and that stimulates the secretory activity of the duodenal glands (Brunner glands). Hence, Duocrinin  the hormone whose secretion is stimulated by the acidic chyme in intestine.

CCK is cholecystokinin and secretin are released by duodenum cells and CCK acts upon gallbladder for the secretion of bile while secretin stimulates stomach and they both stimulate the pancreas to secrete enzymes and hydrogen bicarbonate that neutralize acidic chyme.

Secretin is a hormone that regulates water homeostasis throughout the body and influences the environment of the duodenum by regulating secretions in the stomach, pancreas, and liver. It is a peptide hormone produced in the S cells of the duodenum, which are located in the intestinal glands. Secretin primarily functions to neutralize the pH in the duodenum, allowing digestive enzymes from the pancreas (e.g., pancreatic amylase and pancreatic lipase) to function optimally. Secretin targets the pancreas; pancreatic centroacinar cells have secretin receptors in their plasma membrane.

Enterogastrone is a hormone released by the duodenum that inhibits gastric motility and the secretion of gastric juice to slow down digestion when fats are present.