Digestive Physiology Flashcards
Chemical and physical breakdown of food is referred to as what?
Digestion
What happens during absorption?
Nutrients are taken into the blood
What contributes to the high rate of surface area for absorption in the small intestine?
Convoluted surface area of the lumen
What is the difference between endocrine and exocrine?
Endocrine is secretions into the blood and exocrine is secretions into the digestive tract
What is regulated by the stomach contents and volume?
GI processes
What are the 4 ways that the GI processes are regulated?
Distension of stomach walls, osmolarity of chyme, chyme acidity and the concentration of digestive enzymes in the chyme
How do emotional states and hunger influence the GI system?
Emotional states trigger the CNS which innervates the smooth muscles, response in the gastrointestinal lumen
Sublingual, submandibular and parotid are 3 types of what?
Salivary glands
What are the contents of saliva?
Mucus, water, HCO3- and enzymes
Which enzymes are in saliva?
Lysozyme, salivary lipase and salivary amylase
What does salivary amylase do?
Breaks down carbs
What does salivary lipase do?
Breaks down fat
What is the purpose of saliva?
Lubricate food, buffer acidity
Increased salivary gland activity by increased blood flow to the salivary glands is under control of what?
Parasympathetic activity
Decreased salivary gland activity is under the control of what?
Sympathetic activity
What causes heartburn?
Acid reflux into the cardiac sphincter
What are the two sphincters in the esophagus?
Upper esophageal sphincter and lower esophageal sphincter
How does regurgitation of chyme into the esophagus happen?
Esophageal sphincters don’t always close properly during and following swallowing, allows chyme into esophagus
The wave of contractions to bring food downward is referred to as what?
Peristalsis
What are the 3 types of cells in the stomach?
Parietal cells, chief cells and G cells
Which cells secrete pepsinogen in the stomach?
Chief cells
Which cells secret HCl and intrinsic factor in the stomach?
Parietal cells
Where does the HCl in the stomach come from?
The bicarbonate buffer system, secreted by parietal cells
Which cells in the stomach secrete gastrin?
G cells
Where does gastrin go after secretion?
Into the blood
Out of carbs, fats and proteins, which macromolecule gets partially digested in the stomach?
Proteins
The increase of proteins in the stomach lumen stimulates what?
Gastrin release and the insertion of H/K Atpase pumps, ultimately means increased acidity
How is stomach acidity increased in the stomach?
Insertion of H/K ATPase pumps into the parietal cells
What shuts off gastrin?
Too much acidity - example of negative feedback
How much protein digestion occurs in the stomach?
About 20%
Why is pepsinogen inactive in the small intestine?
Requires a low pH
Where is the pyloric sphincter located?
At the junction of the stomach and the small intestine
What does the pyloric sphincter do?
It only allows a small amount of chyme into the small intestine at a time
How does increased fat presence affect gastric emptying?
It inhibits/slows it down
What is the whole volume of the stomach?
0.5-4L
Where is the brush border?
Fancy apical membranes of the small intestine
What are the 3 parts of the small intestine?
Duodenum, jejunum, ileum
What is secreted by the pancreas?
Bicarbonate, zymogens (ex: trypsinogen)
Which cells secrete trypsinogen?
Acinar cells in the pancreas
What converts trypsinogen to trypsin?
Enterokinase
Why is HCO3- secreted by the pancreas?
Needs to buffer acidity of the chyme, too much acidity would inactive the zymogens
Increased acid from stomach increases the secretion of what from the small intestine?
Secretin
What does secretin do?
Stimulates HCO3- secretion, increases plasma secretin
What is CCK production stimulated by?
Increased fatty acids and amino acids in the small intestine
What does CCK do?
Increases enzyme secretion from the Acinar cells of the pancreas
What is bile composed of?
HCO3-, cholesterol, phospholipids, bile pigments and bile salts
What does bile do?
Solubilizes dietary fats (mechanical digestion)
How is bile brought into the small intestine?
It gets taken up by transporters in the ileum
What does CCK do?
Signals gallbladder and pancreas to contract, results in release of bile
Glucose and galactose take what transporter into the epithelial cell?
sGLUT
Fructose takes what transporter into the epithelial cell?
GLUT
Do glucose, fructose and galactose take the same transporter out of the epithelial cells or travel separately?
They take the same GLUT transporter out
Which gradient is amino acid transport into the epithelial cell associated with?
Na+
Which ion gradient is small peptide transport into the epithelial cell paired with?
Hydrogen
What converts small peptides into amino acids in the lumen?
Brush border enzymes
What converts small peptides into amino acids in the epithelial cell?
Peptidase
What breaks triglycerides into monoglycerides and fatty acids?
Pancreatic lipase
How do dietary fats get into the intestinal epithelial cell?
Diffusion
What happens to dietary fats in the intestinal epithelial cells?
They’re converted into triglycerides by the smooth ER, then transported into lymphatic circulation as chylomicron
Which vitamins are fat soluble?
Vitamins A, D, E, and K
How do water soluble vitamins get absorbed?
Diffusion and mediated transport
What is the name of the sphincter between the small and large intestines?
ileocecal
How is the defecation reflex triggered?
Distension of the walls of the rectum
What are some functions of the gut microbiota?
Vitamin K synthesis, metabolic aid, and education of the immune system
What does gluten do in Celiac’s disease?
Damages the epithelial cells and decreases surface area for absorption of nutrients
What bacteria causes ulcers?
Heliobacter pylori
What are two drugs that help ulcers?
Histamine receptor blockers (cimetidine) and H/K pump inhibitors (omeoprazol)
What does histamine do?
Increases acid production
