chapter 20.2b gastro Flashcards
what is the order of the GI tract
mouth, pharynx, esophagus, stomach, small intestine, colon, rectum, anus
muscular tube from pharynx to stomach
esophagus
upper 1/3rd esophagus vs lower 1/3rd
upper - skeletal m
lower - smooth m
empty volume stomach vs full volume
empty - 50 mL
full - 1000 mL
thickest muscle layer and produces the strong contractions responsible for gastric mixing and emptying
antrum
secreted by chief cells; precursor of pepsin
pepsinogen
enzyme that digests proteins
pepsin
secreted by parietal cells; maintain acidic environment of stomach
hydrogen ions
secreted by parietal cells; necessary for absorption of B12
intrinsic factor
secreted from G cells (hormone)
gastrin
secreted from neck cells
mucus
pH of the stomach
2
primary site of digestion and absorption
small intestine
three divisions of the small intestine
duodenum, jejunum, and ileum
pancreatic juices enter the
duodenum (bicarbonate to neutralize acidic chyme)
epithelial cells in crypts secrete bicarbonate rich fluid - crypts called
crypts of lieberkuhn
absorbed nutrients travel in the blood to the ____ before entering the general circulation
liver
liver function
detoxify substances and processes certain nutrients
large intestine consists of
cecum, colon, and rectum
concentrates wastes into feces, absorbs most water
colon
four sections of the colon
ascending, transverse, descending, sigmoid
secretes saliva
salivary gland
secretes pancreatic juice
pancreas
secretes bile
liver
what enzymes are present in saliva
salivary amylase and lysozyme
___ portion of pancreas produces pancreatic juice
exocrine
secretes more protein than any other tissue in the body
pancreas
enzymes present in pancreas
pancreatic amylase and lipase, proteases, nucleases
(liver) glucose ->
glycogen
(liver) amino acids ->
fatty acids
what stores bile
gallbladder
regulates flow from pancreas and gallbladder to duodenum
sphincter of oddi
___ secrete bile into bile canaliculi, on the side opposite of the sinuosoids
hepatocytes
lining of lumen of GI tract
mucosa
connective tissue of GI tract
submucosa
smooth muscle of GI tract
muscularis externa
deep connective tissue of GI tract
serosa
submucosal plexus
Meissner’s plexus (part of ENS)
myenteric plexus
Auerbach’s plexus (2nd part of ENS)
ENS
- myenteric (auerbach plexus)
- submucosal (meissner plexus)
intrinsic control
ANS
- para (stimulate Ach)
- sym (inhibit Ach)
extrinsic control
plexus is to control GI motility
- stimulatory influences: increase tone and propulsion
- inhibitory influences: decreased sphincter tone
myenteric (auerbach) plexus
plexus is to local control of GI
- secretion
- absorption
- contraction of muscularis mucosa
submucosal (messiner) plexus
parasympathetics ___ ENS
excite
parasympathetics pre gang vs post gang length
pre gang - long
post gang - short (all ENS)
sympathetics pre gang vs post gang length
pre gang - long (T5-L2 via prevertebral ganglia)
post gang - long terminate in ENS
inhibitory influences on sympathetics
decreasing activity of ENS, direct effect to inhibit SM
pre gang efferent neurons
Ach
post gang efferent neurons
PNS - Ach
SNS - NO
ENS excitatory vs inhibitory NT
excite - Ach, substance P, serotonin
inhibit - VIP, NO
____ reflex controls gastric motor and secretory activity
vagovagal reflex
____ reflex overall inhibitory of GI tract
pain reflex
only ____ of carbs are absorbed
monosaccharides
what enzymes break down starch
salivary and pancreatic amylase
limit dextrins -> glucose
dextrinase
polysaccharides -> glucose
glucosamylase
sucrose -> fructose + glucose
sucrase
lactose -> galactose + glucose
lactase
maltose -> 2 glucose
maltase
absorption of glucose and galactose
- 2nd active transport across apical membrane
2. facilitated diffusion across basolateral membrane
absorption of fructose
facilitated diffusion across both membranes
typical diet carbs, protein, and fats amount
carbs- 500
protein - 125
fats - 50
protein digestion products
amino acids, dipeptides, tripeptides
split polypeptides at interior peptide bonds into small peptide fragments
endopeptidases
cleave amino acids from one end of polypeptide
exopeptidases
inactive storage form of proteases
zymogens
protein digestion begins in the
stomach (pepsin)
___ cleaves pepsinogen to pepsin
HCl
what secretes HCl
parietal cells
pancreatic proteases in small intestine
trypsin, chymotrypsin, carboxypeptidase
absorption of amino acids
cross apical membrane by Na linked 2ndary active transport or facilitated diffusion
absorption of dipeptides and tripeptides
cross the apical membrane by ACTIVE transport
lipid enzyme
lipase (secreted by pancreas)
emulsify fat
bile salts
what makes up triglycerides
monoglyceride + 3 fatty acids
lipids enter ____ to be packaged into chylomicrons
Golgi appartatus
secreted by exocytosis into interstitial fluid and enter lymphatic system via lacteal
chylomicrons
what vitamin is only bound to intrinsic factor
B12
Na is actively absorbed where
jejunum, ileum, and colon
passively follows Na absorption
chloride
secreted when lumenal concentrations are very low
K
actively absorbed in duodenum and jejunum
Ca
____ increases Ca absorption by increasing the concentration of Ca binding protein
1,25 (OH)2 D3
transferrin is secreted by enterocytes into the lumen of the small intestine
iron
water in GI secretions L vs intake L
secretions - 7L/day
intake - 2 L/day
