ch 23 digestive system p2 Flashcards
cardia of stomach
portion leading right out of the esophagus
fundus of stomach
dome shaped portion of stomach on top
body of stomach
midportion of stomach
pyloric portion of stomach
inferior funnel shaped portion of stomach, leads right into small intestine, has the pyloric sphincter
pyloric sphincter
thick tissue controls release of food from stomach to intestine
omenta
mesenteries extending from greater and lesser curvature of stomach
lesser vs greater omentum
lesser is from liver to stomach and greater is stomach to intestines (its like a purse to hold intestines and spleen with many lymph nodes)
the autonomic innervation of stomach, parasympathetic vs symp
parasympathetic- via vagus nerve, increase digestion and muslce walls contract for rest and digest
sympathetic- decrease digestion, less stomach activity bc fight or flight thoracic splanchic nerves
stomach has 3 layers of muscle what n why
circular, longitudinal, oblique, allows each organ to have their own function
oblique muscle layer
provides extra muscle layer to generate force. stomach twists like a towel, shortens and widens. helps break down food by churning literally, moves the food and pummels Into smaller pieces to increase SA
mucosa of stomach has what
surface epithelia, simple columnar cells that secrete a lot of mucous with a basic pH
lining of the mucosa has what
gastric pits, which leads to gastric glands and secretes gastric juices.
mucous neck cell stomach
produces acidic and thin mucus, may protect other cells bc its more acidic
parietal cells stomach
secretes HCl and intrinsic factor
HCl makes it really acidic! 1.5-3.5
activates protein digestive pepsin which breaks down the plant cell walls
pepsin
breaks down plant cell walls and kills bacteria, activated with HCl starts the proteins digestion which denatures protein!!!
intrinsic factor stomach
necessary for vitamin B12 absorption in small intestine. B12 is a coenzyme for manny reactions such as ATP. also for erythropoiesis
chief cells stomach
produces pepsinogen, which is converted to pepsin, which as we know starts protein digestion in stomach
enteroendocrine cells of stomach
releases hormones, histamine and serotonin and somatostatin and gastrin!
histamine from enteroendocrine cells
stimulates parietal cells to release HCl
serotonin from enteroendocrine cells
stimulates contraction of muscle in stomach wall
somatostatin from enteroendocrine cells
slows gastric function, plays several inhibitory roles in stomach and other organs
gastrin from enteroendocrine cells
increases HCl secretion, stimulates contraction. of intestinal muscle, releases ileocecal valve, stimulates mass movement of materials
mucosal barrier of the stomach
protects stomach from its own gastric juice, bc low pH would corrode the stomach itself
the 3 mechanisms of protection for the stomach
thick alkaline mucus on internal surface of stomach (physical barrier), epithelial cells joined by tight junctions (ensures gastric juices can’t leave stomach), damaged epithelial cells are replaced fast (undifferentiated stem cells in gastric pits replace damaged cells, mitosis ensures that protection)
smooth muslce is thickest where
bottom of the stomach, the strongest contractions occur here for greater mixing and churning
retropulsion
as food is mixed and churned in the pylorus, small liquid and food particles can pass through pyloric valve, making chyme that will die (some of it) and not pass through pyloric valve.
chyme
gastric juice and partially digested food together that will remain in stomach until gets smaller or die
how is the rate of contraction established in the stomach
enteric pacemaker cells, very slow, APs are sent to smooth muslce cells slowly. NOT FORCE OF CONTRACTION
what determines force of contraction of the stomach muscle
intiric pacemaker cells
what does the rate of emptying stomach depend on
S/L in the stomach L is faster in digestion, how distended is the stomach (stronger contractions is more chyme to small intestine), contents of 1st part of small intestine
contents of 1st part of small intestine regulating stomach emptying
duodenum receptors react to food, suppress gastric secretions to slow gastric emptying. ensure small intestine has good chyme. suppresses pyloric contractions in stomach and slows it down, fatty chyme makes fat take more time to digest than carbs
liver
accessory to small intestine, has 4 lobes (right left caudate and quadrate)
falciform ligament of liver
divides L from R, suspends liver from diaphragm, prevents movement
round ligament of liver
remnant of umbilical vein its always there q
how do liver products drain from lobes
common hepatic ducts, bile from liver drains
is the liver hollow
no, has liver lobules densely packed with hepatocytes
hepatocytes functions
many functions, bile secretions and process blood borne nutrients, stores fat soluble vitamins and detoxifies blood.
only organ that regenerates
liver!
each corner of lobule has portal triad, which has. a
hepatic artery branch, hepatic portal brach, and bile duct.
liver sinusoids
drain blood from portal triad, empties into central vein.
what happens to blood traveling through liver sinusoids
blood gets cleansed by sinusoid capillaries, hepatocytes clean it up!
bile canaliculi
drain bile secreted by hepatocytes and enters bile duct of portal triad, then drained into duodenum
function of central vein that runs through the center of each lobule
takes blood ad brings it to hepatic vein for general circulation where it can be exposed to other organs
blood vs bile where does it travel q
blood from portal triad to center, bile from portal triad to be dumped
bile is
yellow green alkaline solution produced by hepatocytes
bile components
bile salts and bilirubin
bile salts from bile
component of bile aids in digestion n absorbs fats. does the digestive function. bile salts never leave body just get recycled and saves energy so we don’t need to produce more bile
bilirubin
bile pigment formed by heme breakdown, absorbed from blood in liver, excreted into bile, metabolized in small intestine by bacteria.
bilirubin circulation
circulates until liver, dumps bilirubin to bile, then removes via solid waste
gallbladder
accessory organ to liver and small intestine. helps digest fats bc liver stores bile in the gallbladder. inferior surface and green in color, absorbs water and ions from bile.
how does gallbladder empty bile
via cystic duct into common bile duct then small intestine.
gall stones
crystallized bile salts, painful af
pancrea
accessory to small intestine, secretes substances that help digest wide variety of foodstuff.
exocrine part of pancreas
secretes pancreatic juce, has
acini- synthesized and stores digestive enzymes, as well as secreting them.
ducts- transports acini secretions
why is it necessary to have inactive digestive enzymes in the exorcrin pancreas
if they were active, pancreas would digest itself. only active with low pH chyme.
endocrine part of pancreas
contains pancreatic islets, has alpha cells and beta cells
alpha vs beta cells in endocrine part of pancreas
alpha- secretes glucagon to increase blood glucose levels (hyperglycemic)
beta- secretes insulin to decrease blood glucose levels (hypoglycemia)
composition of pancreatic juice
water, enzymes, and electrolytes, alkaline in nature.
how is the pH of pancreatic juices important to the small intestine.
pH neutralizes chyme, so pancreatic enzymes can digest protein n fats n carbs
