Digestive System Flashcards
Where is the main site of absorption?
the small intestine
How is digestion in the small intestine aided?
secretion from the liver (bile salts) and secretions from the Pancreas (bicarbonate enzymes)
What are the four layers of the wall of the GI tract?
muscosa, submucosa, musclaris externa, serosa
What are Enteroendocrine cells?
they secrete hormones into the blood stream
What are exocrine cells?
secrete enzymes, mucus etc. Goblet cells secrete mucus and paneth cells secrete antimicrobial compounds
What is the Enteric Nervous System?
it is the neurons that are like the second brain
What does myenteric plexus do?
regulates motility via the enteric nervous system
what does the submucosal plexus do?
regulates secretion and absorption via the Enteric nervous system
What does the parasympathetic control do to ENS?
increase gut muscle activity, relx sphincters, increase secretion, secrete Ach
What does the sympathetic control do to ENS?
release noradrenaline, inhibit gut movements, constrict sphincters, reduce secretions
what vessesls bring blood to and from the digestive system?
splanchnic circulation
what artery supplies the stomach with blood?
celiac artery
artery for small intestine?
superior mesenteric artery
large intestine artery?
superior and inferior mesnteric arteries
Describe the activity of smooth muscles cells
they have pacemaker activity via interstitial cells of cajal, which generate slow ave potentials that do not always reach threshold and contract
Parasympathetic control ______ and therefore caus___ action potentials. While Sympathetic control _____ and has more ____ waves.
depoolarizes a more, hyperpolarizes
motilin is secreted by
m cells in the crypts in duodenum and jejunum
what is the duodenum and jejunum?
ebegning and end of small intestine
What does motilin do?
increase and regulates migrating motor complex
what is he difference between voluntary and involuntary swallowing?
voluntary involves the glossopharyngeal nerve and does not involve the faciel nerve
What is secondary peristalsis?
it happens when food gets stuck, it is the contraction to propel food through GI tract
what is the brain to stomach reflex called?
vagovagal reflex
What is the Ileocecal valve?
it controls emptying of small intestine to large intestine and prevents back flow
What happens during emesis from vagus, spinal nerves, phrenic nerve and stomach?
vagus - enhances salivation, relaxes esophagus, LES, body contract pylorus
spinal nervse - inspiration, contract abdominal muscles
phrenic nerve- diaphragm descends
stomach - undergoes reverse peristalsis
What increases surface area in the stomach?
rugae and gastric pits
what increases surface area in the small intestine?
villi and crypts of lieberkuhn
what increases surface area in the large intestine?
haustra, crypts of lieberkuhn
what does short microvilli mean?
malabsorption, immune disease allergy to gluten
where is saliva produced?
parotid gland, sublingual gland, submandibular gland
What is in saliva?
water, electrolytes, bicarbonate, mucus, IgA antibodies, lysozyme, defensins, enzymes
what is the function of saliva?
protection, lubrication, taste, digestion
What is the parasympathetic response in relation to saliva?
lots of watery saliva
What is the sympathetic response in relation to saliva?
small amount of thick saliva
What is secreted from the stomach?
mucous cell, parietal cells, chief cells, enterochromaffin-like cells, dcells, g cells
What are mucous cells?
mucus, bicarbonate
what are parietal cells?
HCL, intrinsic factor
what are chief cells?
pepsinogen, gastric lipase
what are enterochromaffin-like cells?
histamine
what are D cells?
somatostatin
what are G cells?
gastrin
What happens with people with Zollinger-ellison syndrome?
hyper-acidic stomach and damges stomach lining, release too much gastrin from a tumour in pancreas
What does HCI do?
kills bacteria, denatures proteins, activates pepsinogen
what does instrinsic factor due?
ensures the absorption of vitamin B12 in ileum
What does pepsinogen do?
it is the inactive form of pepsin that is activated by stimach acid, pepsin then breaks down proteins into peptides and or amino acids
What does gastrin do?
increases HCI, histamine, pepsinogen, mucus, stomach motility and mass movements
What pancreatic secretion enter the small intestine?
acinar and duct cells
what are acinar cells?
release by pancreas to small intestine, they include pancreatic amylase, pancreatic lipase, inactive proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase, proelastase)
what are duct cells?
pancreatic secretions to the small intestine that release sodium, bicarbonate and water
What activates pancreatic enzymes in the small intestine?
enterokinase
What facilitates the transfer of water and bicarbonate in the small intestine?
cystic fibrosis transmembrane regulator
Why do people with cystic fibrosis have to ingest pancreatic enzymes?
because there no luminal bicarbonate to break down the thick mucus, so the enzymes can’t travel to the small intestine
What is secreted from the liver into the small intestine via the gall bladder?
bile salts, lecithin, cholesterol, bilirubin, bicarbonate
What hormones are released from the small intestine?
Secretin, CCK, GIP, motilin, GLP-1
What does secretin do?
to decrease stomach acidity by increasing the release of pancreatic bicarbonate, and decreasing gastric acid secretion/gastric emptying
What does CCK do?
contraction of the gall bladder, increases the release of pancreatic enzymes, and decrease gastric acid secretion
what does does glucagon-like peptide 1 (GLP-1) do?
fatty acids and carbs in small intestine, helps to feel satieted, increases insulin, and beta cell growth,, decreases glucagon and gastric acid secretion and emptying
Why is pancreatic amylase more effeective?
because it can withstand the acidity in the small intestne and it has more mre brush broader enzymes
what is the order to carb absrption?
galactose, glucose and fructose
When does the digestion of protein begin?
in the stomach - with pepsinogen, acid pepsin to break them down
What do brush border enzymes do?
facilitates the transfer of carbs and proteins and fat
Why do people with zolinger- syndrome have malnutrition?
becaus e high acidity kills everything even fat, so no nutrients get absorbed to the rest of the body
What breaksdown fat in the mouthy and stomach?
lingual lipase and gastric lipase
What breaksdown fat in the small intestine?
bile salts from cholesterol, create larger surface area for enzymes to access the fat, along with pancreatic lipase and colipase it turns them into micells
What are chylomicrons?
triglycerides assemble with proteins, that are delievered out of cells to get absorbed in the lymphatic system, store energy and can be taken up by the liver
What are fat soluble vitamines?
A, D, E, K
What are water soluble vitamins?
C and B
What increases calcium absorption?
calbindin, this is increased by calcitriol and vit d
what increases iron absorption?
ferroportin - levels DEcreased by hepcidin from the liver
What is the cephalic phase?
seeing, smelling, tasting or thinking about food. Vagus stimulates stomach secretion and then pancreatic secretion
What is GERD? what aggravates it and how to change it?
Acid-reflex, causes by fatty meal, alcohol, caffeine, chocolate, peppermint all increase relaxation of LES. Treated with lifestyle changes like weight loss, eat small meals, eat earlier in the day, stop smoking, reduce acid secretion or enhance stomach emptying via drugs
What is the gastric phase?
when food is in the stomach
What is the regulation of stomach secretions?
gastrin stimulates stomach acid directly though direct action and histamine, acid stimulates short reflex secretion or pepsinogen, somatostatin release H+ to decrease stomach acid and pepsin
What are gastric ulcers?
from H. pylori, secondary causes: drugs, excess acid (zollinger Ellison) organ stress
How do h. pylori survive in the stomach?
they make bicarbonate to surround themselves to protect from stomach acid
How do you test for H. Pylori?
A breath test, by drinking urea with 14C isotope, and the measure 14CO2 in breath, if it’s in the breath than it is a yes
How do you treat H. Pylori?
you can give an antibiotic but need something else to decrease the pH
What is the intestinal phase?
there is a presence of chyme, distension of the small intestne, secretin from S cells stimulates fluid and bicarbonate secretion. CCK from I cells stimulates secretion of pancreatic enzymes
