GI Tract Control: Gastrin, CCK, Secretin, Motilin and Gastric Inhibitory Peptide (Updated Audio!)

In this video 5 hormones will be discussed that play important roles in the regulation of digestion in the Gastrointestinal tract.
This is a reupload of a video I uploaded some years ago, which had a robotic voice as "Voice Over". Because I agreed with the feedback that this was distracting and often hard to follow, I reupload the video now with a better Voice Over. I hope you like it.

Old version of the video: https://www.youtube.com/watch?v=80mTUNgXhfg

First we will shortly discuss some basic principles. With over thirty different hormones
identified as being produced in the gastrointestinal tract, the gut has been described as ‘the largest endocrine organ in the body’. For the purpose of a correct definition: Hormones are chemical messengers secreted into blood that modify the physiology of target cells. So hormones are not secreted into the lumen of the gastrointestinal tract, but into the circulatory system, which will transport them to their destination. The definition of a target cell for a particular hormone is a cell that has receptors for that hormone and can thus respond to it.
The endocrine cells within the gastrointestinal tract are referred to collectively as the 'enteric endocrine system'. Some of the best-studied enteric hormones are: Gastrin, Cholecystokinin, Secretin, Motilin and Gastric inhibitory polypeptide, which is also known as glucose dependent insulinotropic peptide. These are the 5 hormones that will be discussed in this video.
Another thing you must realize is the following: in contrast to endocrine glands like the anterior pituitary gland, in which essentially all cells produce hormones, the enteric endocrine system is diffuse. single hormone-secreting cells are scattered among other types of cells in the mucosa of the stomach and small intestine.

1. Gastrin
The primary action of gastrin is: stimulation of gastric acid secretion.
Gastrin is secreted by “G” cells, these are located in the antrum of the stomach (and actually some in the duodenum as well).

2. Cholecystokinin.
Cholecystokinin is the principle stimulus for delivery of bile and pancreatic enzymes into the small intestine, hereby stimulating the digestion of fat and proteins.
As mentioned previously, cholecystokinin and gastrin are highly similar peptides. Cholecystokinin (or CCK) is secreted by specialized gut endocrine cells called “I” cells in the mucosa of the duodenum and jejunum mainly in response to digestive products of fat, fatty acids, and monoglycerides in the intestinal contents. CCK mediates digestion in the small intestine various functions. It stimulates the acinar cells of the pancreas to release digestive enzymes and stimulates the secretion of a juice rich in pancreatic digestive enzymes.

3. Secretin.
Secretin functions as a type of fireman: in response to acid, it stimulates the pancreas and bile ducts to release a flood of bicarbonate base, which neutralizes the acid, and the secretion of secretin is turned off.
Secretin was the first gastrointestal hormone discovered and is secreted by specialized enteroendocrine cells called “S” cells in the mucosa of the duodenum in response to acidic gastric juice emptying into the duodenum from the pylorus of the stomach. Secretin has a mild effect on motility of the gastrointestinal tract and acts to promote pancreatic secretion of bicarbonate which in turn helps to neutralize the acid in the small intestine.

4. Motilin
Motilin is released cyclially and stimulates waves of gastrointestinal motility called migrating motor complexes, which move through the stomach and small intestine every 90 minutes in a fasted person.
Motilin is secreted by endocrine “M” cells in the duodenum and jejunum during fasting, and the only known function of this hormone is to increase gastrointestinal motility.

5. Gastric Inhibitory Peptide.
It stimulates insulin secretion in a glucose dependent manner and inhibits gastric acid secretion and motor activity of the stomach.

Видео GI Tract Control: Gastrin, CCK, Secretin, Motilin and Gastric Inhibitory Peptide (Updated Audio!) канала TheMedicalZone