Gastrointestinal Physiology Flashcards
What are the barriers that control the movement of food at the GIT?
Sphincters
What are the four layers of the gut?
mucosa, submucosa, muscularis externa, serosa
What is the innermost layer that mainly consists of epithelial cells, lamina propria, and muscularis mucosae?
mucosa
Which layer of the gut contains blood and lymph vessels?
submucosa
Which layer propels food in the GIT and contains an inner circular and outer longitudinal muscle layer?
muscularis externa
What is the function of the serosa?
prevents friction
What are the 3 layers of the muscularis externa?
outer longitudinal, middle circular, inner oblique
What is the the three strips of outer longitudinal muscle found in the colon called?
taenia coli
What is motility?
mixing and propulsion of food in the GIT
Mixing occurs at which part of the GI tract?
distal stomach + intestine
What is the relaxation and contraction of muscles in the stomach and colon?
reservoir
What are the “pacemakers of the GIT” formally called?
Interstitial Cells of Cajal
What enzymes at the mouth begin digestion?
amylase and lipase
Amylase is responsible for the breakdown of what?
starch
Mucin and glycoproteins found in the mouth are responsible for what?
lubrication and protection
What kinds of secretion helps maintain tooth integrity?
inorganic compounds like ions and CA2+
What buffers can be found in the mouth?
HCO3- (for lingual lipase and salivary amylase to act) + Amphoteric protein
What are the three pairs of salivary gland?
parotid gland, sublingual gland, submandibular gland
Primary secretions (saliva) are nearly isotonic to a person’s plasma. However, after tubular modifications by the _____ cells, it becomes hypotonic.
duct
What is the texture of saliva produced by the sympathetic nervous system?
thick, scanty, and viscous
What is the texture of saliva produced by the parasympathetic nervous system?
watery and has a large volume
What factors can affect the decrease in saliva production?
sleep, dehydration, fear/anxiety
What are the 4 stages of swallowing?
oral, pharyngeal, esophageal, esophagus
From when food touches the tip of the tongue up until it is forced to enter the pharynx, what stage of swallowing is observed? (hint: voluntary)
oral phase
The elevation of the larynx and closer of glottis is part of which stage of swallowing? (hint: entirely reflex)
pharyngeal phase
What are the two peristaltic movements generated in the esophagus?
Primary and Secondary
The contractions of the esophagus are controlled by which nerve?
vagus nerve
In relation to proteins, what function do gastric secretions have?
turns pepsinogen to pepsin
Why is the intrinsic factor important?
it’s essential in binding Vit B12
What cell produces acid and the intrinsic factor?
parietal cells
What does chief cells produce?
pepsinogen + gastric lipase
What do parietal cells secrete?
inorganic compounds via the proton pump
Enterochromaffin-like cells produce what?
histamine
G cells are stimulated by what to produce gastrin?
GRP - gastrin releasing peptide
What is the pH of the surface of the gastric epithelial cell?
7
What is the ratio of the bicarbonate : proton during the chloride bicarbonate exchange?
1 bicarbonate goes out = 1 proton goes out
What is the pH of the lumen?
1-2
Prostaglandin has what net effects?
- inhibit gastric acid secretion
- stimulate bicarbonate and mucus secretion
- promote gastric mucosal blood flow
- epithelial regeneration
Which part of the stomach grinds food?
distal part
What are the two functional regions of the stomach?
proximal (fundus) and distal (pylorus)
What pancreatic cells synthesizes and secretes digestive enzymes?
acinar cells
Ductal cells secrete what?
HCO3
What activates trypsinogen into trypsin?
enterkinase
What triggers the secretion of CCK?
fatty chyme at the duodenum
Cholecystokinin (CCK) is mainly responsible for what?
gallbladder contraction, relaxation of the sphincter of Oddi, and inhibits gastric emptying + food intake
Bile acid is synthesized by what?
hepatocyte
What is the end product of digestion and also gives the primary color of gallbladder secretion?
bilirubin
This part of the duodenum receives both bile duct and main pancreatic duct (hint: guarded by a sphincter of Oddi)?
Ampulla of Vater
These are the small bowel folds (circular) that start from the second part of the duodenum.
Valves of Kerckring
What gland produces secretions that neutralize acidic stomach content and also produces enterokinase?
Brunner’s gland (mucous gland)
What gland produces succus entericus (intestinal juice) and is rich in epithelial cells that aid digestion and absorption?
Crypts of Lieberkuhn
In a fed state, mixing contractions are _________.
ring-like
During a propulsive contractions, a wave of contraction is preceded by relaxation. What is this contraction also known as?
peristalsis
This is a set of rhythmic contractions of the small bowel that can clean the gut in periods of fasting between meals and in sleep.
Migratory Motor Complex (MMC)
Describe the contractions during Phase II of a normal MMC.
intermittent and irregular low amplitude contractions
Describe the contractions during Phase III of a normal MMC.
short bursts of regular high amplitude contractions + 10 mins of strong contractions that sweep all contents down the colon
Digestion occurs in an ________ enviornment.
aqueous environment
Bile emulsification is considered to be mechanical or chemical digestion?
mechanical
Luminal digestion occurs in the lumen. Which organs are part of this?
mouth, stomach, small intestine
Luminal digestion is incomplete, what step is necessary to fully digest food?
Membrane (Brush Border) Digetsion)
Where does membrane digestion occur?
surface of the small intestine + epithelial cells (microvilli)
What enzyme breaks maltose into glucose?
maltase
Why is there a need for our digestive system to breakdown molecules into monosaccharides?
because the small intestine can only absorb monosaccharides
What protein uses a sodium gradient to facilitate transport? This is located at the brush border and is responsible for the absorption of glucose and galactose alongside sodium.
SGLT-1
Found at the brush border, this protein transports fructose into the enterocyte. It is considered inefficient as it is not coupled with Na+.
GLUT-5
Where is GLUT-2 located at?
basolateral membrane
What is the exit point for monosaccharides into the blood stream via GLUT2?
basolateral membrane
What is the dietary protein requirement?
0.5-0.7/kg
What kind of proteins come from the GIT and are the secretory proteins and desquamated cells?
Endogenous proteins
What kind of protein comes from food?
Exogenous protein
True or False. Amino acids cannot be synthesized in a person’s body.
True
What are the essential amino acids?
- phenylalanine
- valine
- tryptophan
- threonine
- isoleucine
- methionine
- histidine
- leucine
- lysine
(PVT TIM HaLL)
Where does protein digestion start?
gastric lumen
Where does fat digestion start and what enzyme breaks it down?
mouth; lingual ligase
Gastric ligase completely hydrolyzes fat. True or False.
False
Chylomicrons enter the bloodstream through what?
thoracic duct
In the absorption of water in the small intestine, sodium is absorbed through what antiporters?
sodium hydrogen 3 antiporter + chloride bicarbonate antiporter
Medium chain fatty acids can easily diffuse into the enterocyte’s tight junction and can directly enter the bloodstream. Why?
it’s water-soluble
What vitamins does the large intestine produce?
Vitamin B and K
What are the functions of the proximal and distal large intestines?
proximal = absorb water, ion, vitamins
distal = storage of fecal material
What are the secretions of crypts of lieberkuhn?
mucus and bicarbonate
Short chain fatty acids are produced by what?
bacteria carbohydrate fermentation at the large intestine
What transport short chain fatty acids?
SMCT1
Where does electrogenic Na absorption mainly occur?
distal colon
What are the 2 kinds of colonic movement?
haustralations + mass movements
A greater anal rectinal angle would increase what?
better defacation
What structure helps in keeping in your poop?
External Anal Sphincter (EAS)
When the IAS relaxes but EAS contracts, the urge to poo might go away. Why?
rectum learns to accommodate
What muscles relaxes to increase anal rectal angle?
puborectalis muscle
During a flatus, the puborectalis muscle is relaxed or contracted?
contracted