digestive physio Flashcards
the process of breaking polymers into monomers/components that can be used by the body.
digestion
this process takes digested monomers into the bloodstream to be allocated.
absorption
digestive tract functions 6
motility, secretion, digestion, absorption, storage/elimination, immune barrier
a muscular pocket that propels food into the esophagus
pharynx
a muscular tube that moves food by peristaltic contraction into the stomach
esophagus
these muscular rings control the ingress & egress of food or gastric contents
upper & lower esophageal sphincters
a spasm of the UES can lead to what?
dysphagia
a laxity of the LES can lead to what outcome?
gastroesophageal reflux disease (GERD) –> cancer
the secretory & absorptive epithelial layer; Contains muscle that forms folds
mucosa
a very vascular tissue to transport nutrients; also has some glands, innervated
submucosa
smooth muscle; responsible for peristalsis and segmentation; innervated
muscularis
the outer protective layer of GI organs; allows for reduced friction during movement
serosa
a reservoir that chemically & mechanically preps food for intestinal digestion
stomach
20 ft of coiled loops that primarily aids in nutrient absorption and has a large surface area
small intestine
what three features allow for an increase surface are of the small intestine?
plicae
villi
microvilli
3 segments of small intestine
duodenum, jejunum, ileum
receives bile & pancr. secretions; short that immediates starts from the stomach
duodenum
how long is the jejunum
8 ft
how long is the ileum
12 ft
what are 3 components of villus structure
columnar epithelium, goblet cells, intestinal crypts
what two cells are found in the intestinal crypts of small intestine villi?
stem cells and paneth cells
secrete protective mucus – helpful but not perfect
goblet cells
actively divide and migrate toward the tip of the villus.
stem cells
secrete antibacterial molecules; found in the villi
paneth cells
colon bacteria consists of what percent of dry fecal weight?
90%
the microflora of the colon produce what?
vitamin K, folic acid, short chain FAs
how much water is absorbed from the colon a day
1.5 liters
wavelike contractions of the GI tract; often with direction
peristalsis
non-directional churning of GI organs
segmentation
both peristalsis and segmentation are modified by what?
Autonomic nervous system
gastric emptying time
2-6 hours
small intestine transit time
5 hrs
the stomachs pacemaker cells that spontaneously depolarize @ 3 per min
interstitial cells of Cajal
5 gastric glands
mucous neck cells
chief cells
parietal cells
endocrine cells
enterochromaffin-like cells
parietal cells secrete:
HCL & intrinsic factor
secreted by parietal gastric gland cells that binds to vitamin B12 to prevent its digestion + increase absorption
intrinsic factor (IF)
endocrine cells of the stomach secrete:
gastrin, ghrelin, and somatostatin
hormone secreted by gastric endocrine cells that regulate digestion and increase the release of histmaine
gastrin
hormone secreted by gastric endocrine cells that acts as an appetite stimulant
ghrelin
hormone secreted by gastric endocrine cells that decrease overall gastric secretion
somatostatin
this is an acid an food solution created by the digestive processes of the stomach
chyme
these are paracrine regulators secreted by ECL cells in the stomach
serotonin and histamine
H+ is pumped into the stomach via ______ of the parietal cells
H+/K+ ATPase
what is the pH of stomach acid
~2
what protects the epithelium of the stomach from digestive acids?
mucosa
the HCl and acidic environment of the stomach converts this enzymatic precursor into pepsin
pepsinogen
this hormone is released by ECL cells and stimulates parietal cells to secrete HCl
histamine
the low pH of the stomach triggers this; decreases gastrin and H+ secretion
enterogastric reflex
inactive forms of digestive enzymes (ex. pepsinogen)
zymogens
what is the optimal pH for trypsin (an intestinal enzyme) function?
~6-7
these are the regions of the pancreas that perform endocrine function
Islets of Langerhans
The Islets of Langerhans secrete what endocrine hormones?
insulin, glucagon, somatostatin
These are the cells of the pancreas that perform exocrine function by secreting HCO3- and 20 zymogens
acinar cells
what do acinar cells secrete?
HCO3- and 20 zymogens
what are 3 of the 20 zymogens secreted by the pancreas into the duodenum?
trypsin, lipase, amylase
this is a pancreatic enzyme that breaks down proteins
trypsin
this is a pancreatic enzyme that breaks down fats
lipase
this is a pancreatic enzyme that digests starch
amylase
What does the high bicarbonate secretion from the pancreas do to the chyme from the stomach?
neutralizes it to create ideal pH for pancreatic enzyme activation
this vessel picks up nutrients from the small intestine and delivers them to the liver
hepatic portal vein
once the contents from the hepatic portal vein reach the liver, what happens to the blood?
detoxified, decontaminated, receives digestive enzymes, and distributed
heme groups from dead RBCs are converted into protein bound what?
bilirubin
how is bilirubin excreted?
- liver secretes bilirubin in bile
- converted into urobilirubin (via bacteria)
- some is reabsorbed
- most is secreted by kidneys
these are formed from excess cholesterol and AAs; form micelles with fats to aid in excretion
bile salts
what percentage of bile salts are reabsorbed in the ileum and returned to the liver?
95%
this is the circulation of bile salts from use by the intestines and then recycling back to the liver
enterohepatic circulation
what are 3 complication of gallstone formation
cholecystitis
bile duct obstruction
pancreatitis
triglycerides are complexed with proteins and cholesterol to form this; repackaged as LDLs
chylomicrons
these are other enzymes secreted by the pancreas to aid in the digestion of complex sugars
sucrase, lactase, maltase
