phys1020 > Gastrointestinal - week 25 > Flashcards

Gastrointestinal - week 25 Flashcards

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1
Q

what is pancreas

A

has exocrine and endocrine functions
- connected to upper portion of small intestine via 2 ducts
- where pancreatic juices come in contact with chyme

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2
Q

anatomy of pancreas

A
  • exocrine secretions made by pancreatic cells, mixed through body of pancreas via the pancreatic duct
  • this joins the common bile duct which is connected to liver and gallbladder
  • hepatopancreatic sphincter (sphincter of oddi) - need to allow exocrine secretions to enter into dudenum
  • minor accessory pancreatic duct: allows for secretions of the pancreas to enter into first part of small intestine
  • pancreatic islets: make endocrine secretions
  • acinar (secrete pancreatic amylase which digests starch (amylose) and pancreatic lipase which digests triglyceride) and ductal (secretes bicarbonate and water) cells: make exocrine secretions
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3
Q

what is a zymogen

A

inactive substance which is converted into an enzyme when activated by another enzyme

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4
Q

how to activate zymogens

A
  • most enzymes secreted by acinar cells and as inactive zymogens
  • zymogens activated once they enter lumen of small intestine
    • begin with activity of brush border enzyme enterokinase aka enteropeptidase
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5
Q

where are trypsinogen and chymotrypsinogen secreted from

A

pancreatic acinar cells

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6
Q

what are trypsin and chymotrypsin

A

active protein-digesting enzymes derived from zymogens

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7
Q

where must trypsinogen and chymotrypsinogen be secreted for activation

A

into lumen of small intestine

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8
Q

what enzyme activates trypsinogen into trypsin

A

enterokinase - in small intestine

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9
Q

how are other zymogens like chymotrypsin activated

A

by the enzymatic activity of trypsin

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10
Q

what does trypsin do after it is activated

A

converts all remaining zymogens into their active enzyme forms

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11
Q

what is colipase

A

formed form the inactive protein - procolipase

  • not an enzyme but an enzyme helper
  • helps pancreatic lipase enzyme digest triglycerides more efficiently
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12
Q

what is pancreatic amylase

A

enzyme

digests the starch amylase

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13
Q

lipase

A

enzyme

digests lipids - triglycerides

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14
Q

trypsinogen

A

zymogen - converts into trypsin enzyme

trypsin digests protein

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15
Q

chymotrypsinogen

A

zymogen - converts into enzyme chymotrypsin

chymotrypsin digests proteins

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16
Q

procarboxypeptidase

A

zymogen - converted into enzyme carboxypeptidase

carboxypeptidase digests proteins

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17
Q

proelastase

A

zymogen - converts into elastase enzyme

  • elastase digests protein
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18
Q

prophospholipase

A

zymogen - converted into phospholipase enzyme

phospholipase digests phospholipids

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19
Q

liver function

A

removes waste products from body

converts ingested nutrients into other useable forms for body

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20
Q

define metabolism

A

biotransformation of waste products for excretion

convert absorbed carbohydrate into other useable forms such as lipids

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21
Q

anatomy of liver

A

main cell type: hepatocytes - make bile solution

bile collected within liver by hepatic ducts

there are a left and right hepatic duct connect together to form the common hepatic duct

cystic duct and common hepatic duct connect to common bile duct

secretions from pancreatic duct connect to the common bile duct
- secretions are collected and when hepatopancreatic sphincter opens, secretions collected in the common bile duct and can enter into duodenum

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22
Q

vasculature of the liver

A

2 blood vessels bring blood to liver
1. hepatic artery - carries oxygenated blood
2. hepatic portal vein - brings nutrient rich blood coming from GI tract

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23
Q

what are sinusoids

A

permeable capillaries
- where blood vessel pool their contents

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24
Q

what is the liver lobule

A

basic structural unit of liver
- organized in a hexagonal shape
- hepatocytes make majority of lobule

corners of lobule: 3 diff. vessels
1. hepatic artery
2. hepatic portal vein
3. bile duct

at the center of each lobule there is a central vein - collects blood that passes through the sinusoids

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25
what is bile canaliculi
small vessels that collect bile solutions that is made from hepatocytes
26
what are hepatocytes
produce bile - within a liver lobule, hepatocytes are organized into a single plate of cells - exposed to both blood via sinusoids and bile collecting vessel - because sinusoids are very leaky, there is a good exposure to mixed arterial-portal venous blood and therefore can easily absorb and metabolize nutrients hepatocyte membrane facing sinusoids - sinusoidal membrane hepatocyte membrane that faces bile collecting vessels is called calicular membrane
27
what is the gallbladder
- pear-shaped sac - made of smooth muscle - lies beneath liver - connected to liver through cystic duct (leaves gallbladder and joins to hepatic duct, forming common bile duct)
28
gallbladder function
store and concentrate bile solution produced by liver until needed
29
what is bile solution
- aids in metabolism of lipids - vehicle to excrete waste products such as bilirubin (break downs products from hemoglobin)
30
bile salts
amphipathic molecules made by hepatocytes - function as detergents to solubilize lipids
31
define amphipathic
have both hydrophobic and hydrophilic regions
32
gallstones
as bile solution concentrates in gall bladder, components of solution can be hyper-concentrated and start to form small crystals if crystals big enough, form gallstones usually formed by cholestrol
33
gallstone blockage - cystic duct
bile produces and released directly from liver but can be painful for patient
34
gallstone blockage - common bile duct
more serious and leads to additional symptoms since liver secretions are also prevented from entering duodenum
35
symptoms of gallstones
painful - pain generally occurs after meal when gallbladder has been stimulated to squeeze - higher the fat content in the meal, more forcefully and frequent gallbladder will contract
36
what is cholecystectomy
removal of gallbladder - surgical procedure
37
enteric nervous system relationship to autonomic nervous system
- SNS- fight or flight - PSNS - rest and digest - ENS - third division of ANS - can function on its own but it shares and receives info from both SNS and PSNS
38
ENS function
control of digestive tract motility carefully regulated - mostly due to the activity of myenteric plexus neurons within muscularis externae layer of digestive tract - another process: secretions of digestive tract
39
sensory neurons of ENS
mechanoreceptors chemoreceptors nociceptors
40
mechanoreceptors
detect how much digestive organ is stretching - if there are any contents in lumen of digestive tract - can detect how solid vs. liquid the lumen contents are
41
chemoreceptors
- can detect contents if bolus or chyme - including nutrient density and types of macroutrients init - such as proteins amino acids and lipids
42
nociceptors
transmit pain - identify damaging events such as injury or inflammation
43
what are short loop reflexes
local reflexes that can begin and end within the wall of GI tract of ENS (no CNS needed)
44
what are long loop reflexes
incorporate CNS - info sent to CNS and sensory info can be integrated by brain and result in action - sensory info can originate within digestive tract (presence of food) - can also be outside of of digestive tract such as smell, sight or thought of food long loop can reinforce short loop
45
gastrin
peptide hormone secreted by G cells of stomach - triggered for release due to activation by neurotransmitter acetylcholine - stretching of stomach due to bolus and presence of protein or amino acids in bolus
46
somatostatin
peptide hormone secreted by D cells of stomach - triggered for release due to low pH
47
cholecystokinin (CCK)
peptide hormone secreted by I cells of small intestine - triggered for release due to presence of protein or lipis in chyme
48
secretin
peptide hormone secreted by S sells of small intestine - triggered for release due to low pH
49
glucose dependent insulinotropic peptide (GIP)
peptide hormone secreted by K cells of small intestine - triggered for release due to presence of carbohydrates, lipids and proteins in chyme
50
salivary gland regulation
both branches of ANS positively regulate salivary secretion stimulation of SNS with cause saliva production and PSNS will initiate large volume
51
parotid gland innervation
PSNS innervation of parotid gland by glossopharyngeal nerve
52
submandibular gland and sublingual gland innervation
innervated by facial nerve
53
SNS innervation of salivary glands
innervated by thoracic spinal nerves T1-T3
54
regulation of stomach motility
stomach has pacemaker like cells found within muscularis externa layer called interstitial cells
55
stomach pacemaker cells
cells generate electrical signals that spreads through connected smooth muscle cells without any neural or hormonal input self generating electric signals known as basal electrical rhythms (BERs)
56
basal electrical rhythms
self generating electric signals if BERs reaches threshold then a muscle contraction can occur in absence of bolus, slow peristalsis like wave initiated in body of stomach and ripple down towards antrum, then through small intestine
57
function of MMC
ensure no remaining meal contents remain, can be pushed through a more opened pyloric sphincter
58
what are the 3 signals needed for parietal sells to secrete max levels of acid
1. gastrin 2. histamine 3. acetylcholine
59
what inhibits acid release from parietal cells
somatostatin - released by D cells which are stimulated to rease somatostatin when pH of stomach is low
60
signals that increase gastric emptying (open pyloric sphincter)
1. increased vagus nerve activity 2. gastrin in the circulation
61
signals that decrease gastric emptying (cause less pyloric sphincter opening)
1. increased sympathetic nerve activity 2. CCK in circulation
62
regulation of small intestine motility
absence of chyme: slow waves of contractions moving down small intestine. occurs due to MMC that is first initiated in the stomach when bolus in stomach: pattern of stomach changes. MMC stops in small intestine as well. once chyme starts to enter small intestine, motility patterns change to segmentations and peristalsis
63
regulation of pancreatic secretions
- ductal cells modify secretions by adding bicarbonate and water - CCK will stimulate acinar secretions - zymogens and enzymes - secretin stimulates ductal secretions - bicarbonate and water - both ductal and acinar cells are neurally regulated
64
regulation of bile secretions
CCK stimulates gallbladder contraction and relaxation of hepatopancreatic sphincter and stimulates production and secretion of bile salts PSNS stimulates gallbladder contractions secretin stimulates secretions of bicarbonate and H2O from ductal cells that live in common bile duct
65
phases of digestive tract:
cephalic phase gastric phase intestinal phase
66
cephalic phase
stimulated by thought or smell of food - neural centers in cerebral cortex and center in hypothalamus are activated - this activates facial, glossopharyngeal and vagus nerve - all this to increase salivary secretions by salivary glands, increase acid secretion by parietal cells, and increase motility of stomach
67
gastric phase
stimulus: presence of a bolus in the stomach causing stretching, pH of stomach contents inc. - caused by presence of peptides -- detected by chemoreceptors amino acids stimulate G cells to release gastrin into bloodstream hormonal and neural ccontrol increases secretions from stomach (HCl) and intestine (mucus) and increased motility of stomach leading to increased gastric emptying
68
intestinal phase
stimulus is presence of chyme in the small intestine neural and hormonal control increase secretions from intestine, pancreas and increased motility of intestine and gallbladder contractions which releases bile there are also decreased secretions from stomach and decreased motility of stomach and decreased gastric emptying
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