Digestion Flashcards
General functions of digestion?
Ingestion/motility
Digestion/secretion
Absorption
Regulation of GI function
What three things control movement of food throughout GI tract?
Intrinsic enteric nervous system
Extrinsic nervous system
Reflexes
At what point does enteric nervous system start along GI tract?
In esophagus
What cells constitute the enteric nervous system?
Pacemaker interstitial cells of cajal
What does cells of cajal dictate?
Maximum frequency/the strength of contractions independent of nerves and hormones
What does the number of spike potentials indicate?
The strength of the contraction
What aspect of the ANS increases peristalsis?
Parasympathetics
What aspect of the extrinsic nervous system is present in GI tract?
Myenteric plexus
Name the 5 types of contractions myenteric plexus causes?
Tonic contractions
Giant migrating complexes
Migratory motor complexes
Mixing contractions
Peristalsis
What territory is vagus nerve responsible for?
Esophagus to splenic flexure of large intestine
What do g ain’t migrating complexes allow for?
Contractions over long distances
What increases giant migrating complexes (like in bowel movements?)
Serotonin
What increases migratory motor complexes?
Motilin
What cells perform peristalsis?
Interstitial cells of cajal
What innervation is responsible for digestion, secretion and absorption?
Meissner’s plexus
Where is meissner’s plexus located?
In submucosa
What effect does chewing have on food?
Increases surface area
What nutrients are digested in the mouth?
Carbs and fats
What enzyme digests carbs in the mouth?
Amylase
What does amylase do?
Digests starch to maltose
What enzyme is responsible for fat digestion in mouth?
Salivary lipase
What does salivary lipase do?
Digests triacyglycerols to glycerol plus fatty acids
Three phases of swallowing?
Voluntary
Pharyngeal
Esophageal
What is the primary function of the pharyngeal stage?
Block trachea as food passes so breathing is inhibited
What relaxes during the pharyngeal stage?
Upper spinchter
What begins in pharyngeal stage?
Peristalsis
Upper 1/3 esophagus muscle?
Striated
What is upper esophageal sphincter responsible for?
Keeping air from entering esophagus
Where is primary peristalsis initiated?
Medulla
Where is secondary peristalsis initiated?
Enteric nervous system
What is responsible for the stomach mixing movements?
The high pressure antral pump
What nutrients are digested in the stomach?
Proteins and fats
What enzyme digests proteins in stomach?
Pepsin
What does pepsin do?
Converts proteins to peptides
What is required to make pepsin?
HCl and pepsinogen
Where is HCl released from?
Parietal cells
Where is pepsinogen released from?
Chief cells
What enzyme digests fats in the stomach?
Gastric lipase
What does gastric lipase do?
Digests TAGs to glycerol plus fatty acids
What does emptying of the stomach cause the release of?
Gastrin
What does gastrin do?
Assists in emptying stomach
Where is gastrin released from?
G-cells
What duct enters at duodenum?
Common bile duct
What sphincter does the common bile duct enter through?
Spinchter of odi
What does the sphincter of odi allow for?
Bile and pancreatic enzymes to enter the duodenum
What is bile necessary for ?
Action of pancreatic lipase for fat digestion
How are proteins absorbed?
They enter the portal blood as amino acids
Primary role of jejunum of small intestine?
Absorption of digested proteins, carbs, and lipids
How are carbs absorbed?
They enter the portal blood as monosaccharides
How are fats absorbed?
They enter the lymph as chylomicrons containing TAGs
What in GI tract is sensitive to ischemia?
Villi of small intestine
What is absorbed in ileum?
Vitamin B12
What is required for vitamin B 12 to be absorbed?
Intrinsic factor
What connects the small and large intestines?
Ileocecal valve
What is the primary function of the large intestine?
Absorption of water and electrolytes
What is produced and absorbed by intestinal bacteria in the large intestine?
Vitamins like vitamin K and biotin
Where do mass movements occur?
From transverse colon to rectum to push food through large intestine
What does chyme help with?
Electrolyte absorption
What causes CCK to be released?
Fatty chyme and amino acids in the duodenum
5 actions of CCK?
Contraction of gallbladder to release bile
Release pancreatic enzymes
Relaxation of sphincter of odi
Decreases gastric emptying
Causes brain to feel satiated
What causes secretin release?
Acid in duodenum
5 actions of secretin?
Release of bicarbonate from Brunner’s glands
Release of pancreatic fluid
Increases liver ductal secretion
Decreases gastric emptying
Inhibits motility
What causes GIP to be released?
Glucose in duodenum
2 actions of GIP?
Larger insulin release with oral glucose
Delays gastric emptying
What causes gastrin to be released?
Stretch in stomach
3 actions of gastrin?
Secretion of acid from gastric cells
Increase motility
Stimulate growth of gastric mucosa
What initiates release of VIP?
Myenteric plexus
4 actions of VIP?
Relax sphincter
Dilate blood vessels
Inhibit gastric acid secretion
Increase motility
When is motilin released?
Cyclically between meals
Actions of motilin?
Mediates migratory motor complexes
Moves undigested food towards colon