GI Tract Flashcards
How long is the gi tract?
About 8 long.
What organs make up the GI tract?
Stomach, small and large intestines, pancreas and gallbladder
What is the function of the GI tract?
Efficient digestion and absorption of ingested nutrients
What quantity of food and water enter the small intestine and what quantity reaches the large?
~10mL enters the small intestine and only ~1.5mL reaches the large
What is digestion?
Digestion is the chemical processing of food into absorbable substance
Where does digestion begin?
In the mouth
What are the three phases of the digestive process?
Neurogenic
Gastric
Intestinal
What happens in the neurogenic phase of digestion?
Sight, smell and taste of food stimulates the brain. The brain sends impulses to the stomach via the vagus nerve and this nerve innervates the stomach inducing peristalsis and gastric secretion of HCl and gastrin
What nerve in from the brain stimulates the stomach to release HCl and gastrin?
Vagus nerve
What does the vagus nerve stimulate in the stomach?
Peristalsis and gastric secretion of HCl and gastrin
What is the second phase of the digestive process?
Gastric phase
What phase in the digestive process is initiated by the entry of food into the stomach and stomach distention?
Gastric phase
How is the gastric phase initiated?
By the entry of food into the stomach and stomach stretching.
What is the pH of HCL?
1-2
What cells release HCl? Why?
The parietal cells of the stomach. Due to cell stimulation, stretching and gastrin release
What is the major digestive hormone of the stomach?
Gastrin
What cells release gastrin?
G cells
What is the function of gastrin hormone?
Gastrin causes enzyme and gastric fluid to be released, and the start of stomach motility/churning
This hormone causes enzymes and gastric fluids to be released, and the start of stomach motility.
Gastrin
What is the major digestive enzyme of the stomach?
Pepsin
What cells release pepsin?
Gastric chief cells
This enzyme released by gastric chief cells serve in the hydrolysis of proteins.
Pepsin
Food mixed with gastric fluid is called?
Chime
What phase of the digestive process begins when chime enters the duodenum?
The intestinal phase
What is cholecystokinin (CCK)?
A hormone produced by the intestinal mucosa to stimulate the gallbladder, pancreas and intestinal motility
What is the purpose of secretin?
To neutralize pH
What happens during digestion in the small intestine?
Bile and pancreatic enzymes enter the duodenum to further degrade carbs and proteins, and solubilize fats for absorption into bloodstream.
What intestine absorbs water, sodium and potassium, and contains bacteria to form stool?
Large intestine
What cells produce CCK?
Intestinal mucosa cells
What stimulates the secretion of CCK by the intestinal mucosa cells?
The presence of aa and gastric HCl entering intestine
What are the functions of CCK?
Controls the contraction of the gallbladder
Stimulates pancreas to secrete more digestive enzymes in duodenum
Increase motility of small intestine
List the GI tract hormones.
CCK Gastrin Secretin GIP VIP
What cells produce secretin?
Intestinal S cells
Secretin hormone is produced by S cells of the intestine in response to what?
Increase acid in duodenum
What are the functions of secretin?
- Helps inhibit gastric H+ by stimulating HCO3 secretion from pancreas
- Decrease bile secretion from liver/gallbladder
- Inhibits stomach motility
Gastrin hormone is produced by the G cells in the stomach in response to what?
Distention of stomach and presence of proteins
What are the functions of gastrin?
Aid in gastric motility
Stimulate pancreatic secretions and gallbladder emptying
Stimulate secretion of gastric acid, intrinsic factor to protect Vitamin B12 in stomach
What hormone stimulates secretion of intrinsic factor to protect vitamin B12 in the stomach?
Gastrin
Where is Gastric inhibitory polypeptide secreted from?
Duodenum and Jejenum
What is the function of GIP?
Stimulate insulin release from pancreas
Reduces gastric acid secretion and motility
Where is vasoactive intestinal peptide secreted from?
From entire small and large intestines nervous system