Gastrointestinal Physiology Flashcards
what are the four processes of digestion?
- secretion
- digestion
- motility
- absorption
what is secretion?
- enzymes being secreted in tubes of digestive tracts
- saliva in mouth and acid in stomach
- enzymes used to break down food
what is amalase?
enzyme that breaks down carbs
what are the two types of digestion?
mechanical (big to small through chewing) and chemical (uses enzymes, needed to absorbed nutrients)
what is motility?
moving food from mouth to rectum (movement at a carefully controlled speed; peristalsis)
what is absorption?
how to get nutrients into bloodstream (once small enough, moves through epithelial cells and becomes absorbed for nutrients)
what are three accessory organs of the digestive system?
gallbladder, liver and pancreas
what is the job of the oral cavity?
secretion
what does secretion do?
- lubricates
- helps with ability to taste our food
- protects mouth and teeth
- aids with speech
describe saliva composition
- mostly water and ions such as sodium and chlorine
what are the three salivary glands?
- parotid gland
- submandibular gland
- sublingual gland
where is the parotid gland found?
cheeks area
where is the submandibular gland found?
under mandible
where is the sublingual gland found?
under tongue
describe the three types of salivary glands
parotid gland = watery
submandibular gland = music and watery saliva
sublingual gland = mostly mucus
what is the term used to describe mechanical digestion through chewing?
mastication
chemical digestion in the oral cavity is done by what salivary enzyme?
amylase
is lingual lipase active when in the oral cavity?
NO, lingual lipase is activated in the stomach
(oral cavity) three steps of motility :
- mastication (chewing); mechanical motility, movement from back to front of mouth
- swallowing (only cavity to the esophagus)
- peristalsis : top to bottom of esophagus
“co-ordinate contraction of the muscles in the esophagus, involuntary control, propels bolus towards the stomach” is all used to describe…
peristalsis
what are the two “movements” of peristalsis and what does it do”?
- longitudinal (push it down)
- circular (constrict)
what is absorbed in the oral cavity (bare minimal absorption) and where does it mostly occur?
glucose / drugs and mostly occurs under the tongue
what organ acts as a reservoir for bolus before it enters the intestine?
stomach
what liquid/acid is found in the stomach?
hydrochloric acid
how does bile become chyme?
it mixes with the acid in stomach
what part of body leads into the stomach?
esophagus (through diaphragm)
where does the esophagus attach?
to the cardia
what does the lower esophageal sphincter do?
stops stomach acid from coming up?
which side of the stomach has a bigger curve?
left side (greater curvature)
what happens if too much acid is getting pushed up?
- acid reflex (sphincter isn’t closed all the way)
- increase abdominal pressure
what part of the stomach attaches to the small intestine?
antrum
what is the sphincter at the end of the stomach?
pyloric sphincter
when does the pyloric sphincter open?
only opens when food needs to go into the intestine
what are the four layers of the stomach?
- muscosa
- submucosa
- smooth muscle (muscular externa)
- serosa
describe the mucosa?
- innermost
- protect stomach from bacteria and acid
describe the submucosa? (stomach)
- neural network (info being sent)
- has submucosal plexus (helps with mucous excretion)
describe the smooth muscle?
- muscular contractions of the stomach
- circular and longitudinal muscle to change shape of stomach
contains a neural network (myenteric plexus; peristalsis)
describe the serosa?
- protective layer
- dense connective tissue
- outermost
which layer of the stomach is responsible for muscular contractions of the stomach?
smooth muscle (muscular externa)
what layer protects the stomach from bacteria and acid?
mucosa
which layer has a submucosal plexus that is responsible for helping with mucous excretion, etc.
submucosa
what are the three exocrine cells of the stomach?
- mucous neck cells
- chief cells
- parietal cells (oxyntic cells)
what is the endocrine cell of the stoamch?
G cells
what does mucus neck cells do?
secrets mucous and bicarbonate (to protect stomach)
what do chief cells do?
secretes pepsinogen and gastric lipase
what is pepsinogen?
the inactive version of pepsin
what is the endocrine cell of the stomach?
G cells
what do G cells do?
secrete the hormone gastrin
what does gastrin do?
releases HCl and stimulates gastric acid
what do parietal cells do?
secretes H+ and Cl - (HCl) and intrinsic factor
what is intrinsic factor?
helps absorb B12 and terminal ileum
what are the three movements of digestion in the stomach?
propulsion, grinding and retropulsion
describe the direction of propulsion, grinding and retropulsion …
- propulsion = moving foward
- grinding = circular contraction
- retropulsion = pushing backwards as we let little amounts move through
how does bolus become chyme through chemical digestion?
- secreted gastric juices contain HCl
- secreted pepsnogen converted to pepsin
what does pepsin do?
pepsin is the active for of pepsinogen and it is an enzyme that aids in protein digestion in the stomach
name the 6 functions of acid in the stomach
- activation of lingual lipase (lipid digestion can occur)
- activation of pepsin (from pepsinogen)
- inactivation of salivary amylases
- kills microbes (with HCl)
- denatures proteins
- stimulates secretion of hormones
where does carbohydrate digestion completely stop?
in the stomach
what are the three parts of the small intestine?
- duodenum
- jejunum
- ileum
where does nutrient absorption occur?
small intestine
what is the job of the duodenum?
decreasing acidity of chyme
what is the job of the jejunum?
absorption (increase SA)
what is the job of the ileum?
responsible for absorption and digestion of nutrients and vitamins like B12, etc and everything else not absorbed prior
where does most absorption in the small intestine occur?
jejunum
what does villi in the jejunum do?
increases surface area for optimal absorption
what are the four layers of the small intestine?
- mucose
- submucosa
- smooth muscle (musularis)
- serosa
what’s the difference between layers of the stomach and the small intestine?
- the mucosa of small intestine is responsible for mucus secretion
- the mucosa of the stomach is responsible for protects the stomach from bacteria and acid
- serosa is opposite of each other (small intestine very thing and stomach thick)
what does the myenteric plexus do?
controls the muscles (peristalsis)
what are the two movements of motility of the small intestine?
segmentation and peristalsis
what it segmentation?
mixing back and fourth, allowing for touching (increases the interactions of particles of food in chyme with absorptive cells of the mucosa layer)
name the 7 cell types of the small intestine?
- absorptive cells
- goblet cells
- K cells
- intestinal gland cells
- paneth cells
- S cells
- CCK cells
what do absorptive cells do?
helps absorption of nutrients (epithelial cells with microvilli)
what do goblet cells do?
secretes mucus
what do intestinal gland cells do?
secretes alkaline watery mucus and helps protect from acid of stomach
what do paneth cells do?
secretes lysozyme (helps fight against pathogens)
what do S cells do?
secretes secretin
what do CCK cells do?
secretes cholecystokinin
what do K cells do?
secretes (GIP)
what does secretin tell the liver/pancrease to do and is it a hormone/enzyme?
- hormone not an enzyme
- tells liver and pancreas to separate its enzymes
what does GIP do ?
stimulates insulin to be secreted
what does cholecystokinin (CCK) do ?
tell pancreas to secrete enzymes and gall bladder to contract
where is bile created and stored?
created in the liver and stored in gallbladder
what does microvilli do?
increases surface area for absorption of nutrients
what is the very last step in regards to chemical digestion?
microvilli
what are brush border enzymes
cells on the microvilli (which have enzymes)
what are the 6 brush border enzymes?
- lactase
- sucrase
- malatase
- aminopeptidase
- dipeptidase
- enteropeptidase
what is lactose broken down by?
lactose is broken down by lactase into glucose + galactose
what is sucrose broken down by?
sucrose is broken down by sucrase into glucose and fructose
what is maltose broke down by?
maltose us broken down by maltase into glucose and glucose
where are brush border enzymes mostly found?
in duodenum
what does aminopeptidase do?
removes one amino acid from the end of a protein
what does dipeptidase do?
cuts a dipeptide into two single amino acids
what does enteropeptidase do?
cuts trypsinogen into trypsin
what does the large intestine do?
- completes absorption (usually water)
- highly populated by bacteria
- beneficial for completing nutrient extraction
- reabsorbes water
what are three points of motility of the large intestine
- gastroileal reflex
- haustraul churning
- peristalsis and mass peristalsis
what does the gastroileal reflex do?
presence of food in the stomach stimulates the opening of the ileocecal valve (neural reflex)
what does haustral churning do?
responsible for mixing of elements and allows for optimal absorption of mostly water from lumen contents
what does peristalsis and mass peristalsis do?
unidirectional movement of lumen contents out of the large intestine (into rectum) (feeling of having to go to the washroom)
what organ has both endocrine and digestion function?
pancreas
what are the names of epithelial cell clusters and the cells that form the ducts that together make exocrine secretions ?
acinar and ductal cells
where does the pancreas secrete directly into?
the duodenum
what comes from ductal cells?
bicarbonate
what does bicarbonate do?
neutralizes the acid from the stomach
what 7 enzymes come from acinar cells ?
- pancreatic amylase
- pancreatic lipase
- trypsinogen = trypsin
- chymtrypsinogen = chymotrypsin
- procarboxypeptidase = carboxypeptidase
- prophospholipase = phospohlipase
- procolipase = colipase
what type of carbohydrate is amalose?
complex carbohydrate
what is pancreatic amylase?
enzyme from pancreas breaking down
what is pancreatic lipase?
enzyme that breaks down lipids
what is trypsinogen?
inactive form that is further turned into trypsin (active form) used for the breakdown of proteins
what is chymotrypsinogen?
trypsin converts chymotrypsinogen into chymotrypsin which is used in the breaking down of proteins found in chyme
what converts procarboxypeptidase into carboxypeptidase?
trypsin converts procarboxypeptidase into carboxypeptidase
what is prophospholipase?
prophospholipase is the active form from procarboxypeptidase
what happens to the amino group during carboxypeptidase?
take off amino group @ end of carboxy
what does colipase do?
works as cofactor with pancreatic lipase
what is used to turn chymotrypsinogen, procarboxypeptidase and prophospholipse into its active form?
trypsin
what does trypsin do?
activates enzymes that cuts proteins
where do acinar cells come from?
pancreatic duct
what are the three islets of langehans?
- insulin
- glucagon
- somatostatin
what type of cells does insulin come from?
beta cells
what type of cells does glucagon come from?
alpha cells
what type of cells does glucagon come from?
delta cells
what does insulin do?
monitors glucose levels in the blood (hyper; too much)
what does glucagon do?
too little glucose in bloodstream; converts into glucose (hypo; too little)
what does the liver do ?
- clean blood
- duo portal system
- take all bad things and excrete them
** liver can regenerate
what are the arteries that go to the stomach ?
digestive tract arteries
what is the “bed”called that has oxygen, nutrients, glucose, etc?
sinusoids (capillary bed)
anything leaving the liver exists through the…
hepatic vein
blood going towards liver that delivers lots of oxygen …
hepatic vein
sinusoids join together to form what?
the central vein, and then the hepatic vein
where does bile get secreted by?
hypothalmus
what do hepatocytes do?
secrete bile into a vessel called a bile canaliculus
small vessels in the liver gather together and join to form the …
bile duct
bile ducts come together to form …
hepatic ducts
what are hepatocytes?
main liver cell that decides what goes where (makes decisions)
four functions of the liver…
- synthesis of bile
- excretion of bilirubin
- metabolism of carbohydrates, lipids and proteins
- processing drugs and hormones
what are the components of bile salts?
- bile salts
- cholesterol
- bile pigments (bilirubin)
- water and ions
what does bile do?
help with lipid digestion
what is bilirubin?
waste product that gives the colour of urine
bilirubin leads to the breakdown of …
haemoglobin (red blood cells)
what are the two types of cholesterol ?
GOOD = HDL (high)
BAD = LDL (low)
what is the sphincter at the end of the gallbladder called
sphincter of oddi
is the sphincter of oddi usually open or closed?
closed all the time until needed to open at the right time to let things through
what does the gallbladder do?
stores bile
what happens when you eat a high fat meal?
contraction of gallbladder, pushes bile out and help with lipid digestion (CCK)
what does the common bile duct do ?
carries bile from liver to the pancreas and then into the small intestine
where does bile solution become concentrated?
gallbladder
what is the cystic duct?
tube that carries bile from the gallbladder
what two ducts come together to form the common bile duct?
cystic and hepatic duct
bile solution enters into the duodenum through the opening of …
the sphincter of oddi
what does CCK do to the gallbladder?
causes the gallbladder to squeeze and the sphincter of oddi opening to be released into the duodenum
what are the three phases of coordination of the gastrointestinal tract?
- cephalic phase (brain)
- gastric phase (stomach)
- intestinal (small intestine)
what happens when there is a slower rate (motility) in the large intestine?
diarrhea
what is the stimulus of the cephalic phase
sight, smell and taste of food (anticipation of food through neural control)
neural control of the cephalic phase is through the …
medulla oblongata
where is the medulla oblongata found ?
in the brainstem
(cephalic stage) increased secretions come from:
- salivary glands (saliva)
- stomach (HCI)
- small intestine (mucus)
what is the stimulus of the gastric phase?
presence of bolus (food) in the stomach causing stretching, presence of amino acids
neural control of the gastric phase is through …
sensory information to the submucosal plexus and the myenteric plexus
what is the term that “helps with the emptying of the stomach into the small intestine” ?
motility
hormonal control of the gastric phase is …
gastrin (G cells)
what type of cells are gastrin?
G cells
gastric phase causes increased secretions from :
- stomach (HCl)
- intestine (mucus)
what is the stimulus of the intestinal phase?
presence of chyme in the intestine
neural control of small intestine is through …
sensory information to the submucosal plexus (secretions) and myenteric plexus (motility)
hormonal control of the intestinal phase is …
secretin (S cells), CCK (CCK cells), GIP (K cells)
what does GIP do?
tells pancreas to release insulin (needed in blood)
increased motility of intestinal phase is through …
- intestine (segmentation and peristalsis)
- gallbladder contraction
what phase inhibits another phase?
the intestinal phase inhibits the gastric phase
what are the two types of carbohydrate sources?
simple and complex
simple carbohydrates are either called __ or __ :
monosaccarides or disaccharides
what are the three monosaccharides ?
glucose, galactose and fructose
what are the three disaccarides ?
lactose, sucrose and maltose
complex carbohydrates are either called __ or __ ?
starch or glycogen
where does starch come from ?
plant storage of glucose
where does glycogen come from?
animal storage of glucose
where does carbohydrate digestion occur?
mouth
where is carbohydrate digestion completely inhibited?
stomach
what enzyme is inactive in the stomach due to acid in the stomach (carbohydrate digestion)
salivary amylase
where does carb digestion further continue after the stomach?
the pancreas (pancreatic amylase present)
where does chemical digestion of carbs occur?
mouth and small intestine
what does finer do?
help with digestion, motility and function
salivary amylase turns starch into what?
maltose
how does fructose move through cell?
fructose moves alone (symporter)
what cotransporter does glucose and galactose need?
sodium
describe the concentration gradient of sodium…
sodium is always higher on the outside and lower in the inside
when sodium exists the cell what enters it?
potassium
what is a uniporter?
transport protein that moves a single species of substrate across a membrane
what is needed for the exchange of Na and K ?
ATP
which organ in body will help with the digestion of fructose?
large intestine
what happens if theres too much fructose in the large intestine?
constapation / GI upset
what are allergies vs intolerance
- allergies = immune system will attack the good & make sick
- intolerance = not feeling great, upset & uncomfortable
how many amino acids are there
20
how many essential and nonessential amino acids are there?
9 essential & 11 nonessential
what is an essential amino acid?
one the body cannot create / must be consumed
what is a nonessential amino acid?
one the body can create naturally
what is a di, tri and poly - peptide?
di = 2 amino acids bonded together
tri = 3 amino acids bonded together
poly = many amino acids bonded together
where does protein digestion occur?
stomach
what enzyme is used in the stomach for protein digestion?
pepsin (active form that comes from pepsinogen)
aminopeptidase is in what organ?
small intestine
what breaks pepsin, trypsin and chymotrypsin into smaller fragments?
endopeptidase
what is a further break on the aminopeptidase side called?
amino terminus
what is a break on the carboxypeptidase side called?
carboxy terminus
how do we classify protein digesting enzymes that cut somewhere in the middle?
endopeptidase
how do di and tri-peptides enter the cell?
bring themselves in
how do amino acids enter the cell?
needs a co transporter (Na)
once di and tri-peptides enter the cell what breaks them down into amino acids?
peptidase
what is a tryglyceride?
type of fat
what is the composition of a triglyceride ?
glycerol and 3 fatty acids
what is the variable length in fatty acids ?
4 - 24 carbons
what is considered the most common number of carbons in a fatty acid?
18 carbons
what are saturated fats?
- more unhealthy
- no double bond present
- more solid
what are unsaturated fats?
- healthier
- double bond present
- more fluid (liquid)
in order to break more double bonds in unsaturated fats what must be present?
more energy (lose more calories)
what are trans fats?
found in processed food, more LDL (worst type of fat)
where does lipid digestion occur?
small intestine
what enzyme is in the mouth responsible for little bit of lipid digestion?
lingual lipase
where do tryglerides gets digested ?
stomach and small intestine
what are bile salts?
component of bile
where are bile salts found?
lipids (fats)
what is jaundice disease?
condition that involves having too much bilirubin
who tends to have jaundice disease?
alcoholics/drug users/babies
what pushes bile salts apart so that the lipase can touch the surface of the small lipid droplet ?
colipase
what form lipid droplets?
triglycerides
what part of tryclerides face the outside of lipid digestion?
hydrophobic heads
what is wrapped around liquid droplets?
bile salts
what is a diglyceride?
one fatty acid is off
what is a monoglyceride?
two fatty acids off
what is a free fatty acid?
no head present just tails
what is a michelle?
small fat droplet covered with bile
where do Michelles happen?
small intestine
in what situation can bile be in the stomach ?
vommiting
what “helps package lipids in order to move around the body”?
chylomicrons
what are chylomicrons ?
help pack lipids in order to move around the body
where does the best fat digestion occur?
small intestine
what are two classifications of vitamins ?
fat soluble and water soluble vitamins
what are examples of fat-soluble vitamins?
- vitamin A
- vitamin D
- vitamin E
- vitamin K
what are examples of water-soluble vitamins?
- vitamin C
- vitamin B
- B12
what does vitamin C do?
help with immune function
what occurs in the cytoplasm during digestion ?
glycolysis and pyretic acid
what is glycolysis?
breakdown of glycologen
what does pyretic acid turn into?
lactic acid
what does lactic acid do?
breakdown of muscles and glucose
what occurs in the mitochondria during digestion?
pyretic acid, acetyl CoA, CoA, citric acid cycle … electron transport system
what does the citric acid cycle do?
trying to produce ATP (for aerobic respiration)
what is the primary source of energy ?
carbohydrates
what happen to carbs in our body?
- ATP production
- amino acid synthesis
- glycogen synthesis
- triglyceride synthesis
what is glycolysis ?
breakdown of glucose by enzymes, releasing energy and pyruvic acid
what is amino acid synthesis ?
converted to some amino acids if needed (protein creation)
what is glycogenesis ?
formation of glycogen without the use of glucose (storage of glucose)
what is lipogenesis ?
formation of fat
what does triglyceride synthesis mean in regards to glucose ?
too much glucose
what does glucose uptake mean?
cells of the body take glucose from the blood in order to use for the production of ATP
through what concentration gradient does glucose move?
region of high concentration (blood) to a region of low concentration (cell)
in what state does carbohydrate fates glycogenesis occur?
fed state
what 2 cell types have a large capacity to store glucose as glycogen?
skeletal muscle and liver
where does glycogenesis happen?
liver
how does glucose become glycogen?
glucose -> 6- phosphate (G6P) -> glycogen
what is added to glucose to form bonds to create glycogen?
phosphate
in what state of carbohydrate fates glycogenolysis occur?
fasted state
how does glycogen become glucose?
glycogen -> G6P -> liver -> glucose
how does the liver create new glucose molecules?
through non carb sources (amino acids, lactic acid and glycerol)
in what state does gluconeogenesis occur?
fasted state
what is “any fat you see on you body” ?
adipose tissue
_____ is the fat right under skin; used on energy storage for starvation
adipose tissue
what are the 4 fates (what happens in our body) of lipids ?
- stored in adipose tissue as fat deposits
- oxidizes to produce ATP
- formation of structural molecules
- triglyceride storage
what do myelin sheaths do?
speed up transduction
where is majority of our energy needed daily stored ?
trigylerides
what is lipolysis ?
breakdown of triglycerides into glycerol and fatty acids
in what state does lipolysis occur?
fed state
“most simple form of alpha keto acid”
pyruvic acid
what happens if theres too much fat in the body?
leads to weight gain
in what state does lipogenesis occur?
fed state
what is an alternate energy source in the body?
ketones
what is ketogenesis?
creation of ketone bodies by breaking down fatty acids and ketogenic amino acids
how are ketone bodies formed?
by joining two acetyl coenzyme A molecules together
what are liver cells called?
hepatocytes
can liver cells make ketone bodies ?
yes ! which later diffuse into the blood
in what state does ketogenesis occur?
fasted state
what cell types prefer ketone bodies to produce ATP?
heart and kidney cortex
“depleting yourself of glucose”
ketones
how do organisms produce ketone bodies ?
organisms produce ketone bodies by breaking down fatty acids and ketogenic amino acids
what is protein anabolism ?
formation of proteins from amino acids
what is protein catabolism?
breakdown of proteins into amino acids
in what state does protein anabolism occur?
fed state
in what state does protein catabolism occur?
fasted state
what components of our bodies are made up of proteins?
enzymes, hormones, structural components, transporters
amino acids from proteins can be converted into …
fatty acids, glucose and ketone bodies
what organ coverts amino acids into fatty acids, ketone bodies and glucose?
liver
