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Secretin is a peptide hormone produced in the S cells of the duodenum in the crypts of Lieberkühn. Its primary effect is to regulate the pH of the duodenal contents via the control of gastric acid secretion and buffering with bicarbonate. It was the first hormone ever discovered.
Secretin stimulates the secretion of bicarbonate (base) from the liver, pancreas, and duodenal Brunner's glands in order to buffer the incoming protons of the acidic chyme. It also enhances the effects of cholecystokinin. It is known to promote the normal growth and maintenance of the pancreas.
It also reduces acid secretion from the stomach by inhibiting gastrin release from G cells. This helps neutralize the pH of the digestive products entering the duodenum from the stomach, as digestive enzymes from the pancreas (eg, pancreatic amylase and pancreatic lipase) function optimally at neutral pH.
In 1902, William Bayliss and Ernest Starling were studying how the nervous system controls the process of digestion. It was known that the pancreas secreted digestive juices in response to the passage of food into the duodenum. They discovered (by cutting all the nerves to the pancreas in their experimental animals) that this process was not, in fact, governed by the nervous system. They determined that a substance secreted by the intestinal lining stimulates the pancreas after being transported via the bloodstream. They named this intestinal secretion secretin. Secretin was the first such "chemical messenger" identified. This type of substance is now called a hormone, a term coined by Bayliss in 1905.
- Asimov, Isaac; The Human Brain: Its Capacities and Functions.
|Hormones and endocrine glands - edit|
Hypothalamus: - TRH - CRH - GnRH - GHRH - somatostatin - dopamine | Posterior pituitary: vasopressin - oxytocin - lipotropin | Anterior pituitary: GH - ACTH - TSH - LH - FSH - prolactin - MSH - endorphins - lipotropin
Thyroid: T3 and T4 - calcitonin | Parathyroid: PTH | Adrenal medulla: epinephrine - norepinephrine | Adrenal cortex: aldosterone - cortisol - DHEA | Pancreas: glucagon- insulin - somatostatin | Ovary: estradiol - progesterone - inhibin - activin | Testis: testosterone - AMH - inhibin | Pineal gland: melatonin | Kidney: renin - EPO - calcitriol - prostaglandin | Heart atrium: ANP
Digestive system, physiology: gastrointestinal physiology
|Enteric nervous system|
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