physiology Flashcards
is the muscualris externa in the rectum/ anus thick or thin
thin
what happens to the micelle when it reaches the acid microclimate of the small intestine brush border
breakdown releasing its contents to diffuse across the plasma membrane
which 2 ducts join to form the common bile duct
common hepatic duct form the liver
cystic duct from the liver
How are amino acids transported into the cell
SAAT1
sodium coupled amino acid transporter
(Na/ K ATPase)
Once CO2 is inside a parietal cell, what chemical reaction takes place
CO2 + H20 –> H2CO3
carbonic anhydrase
what prevents gastric acid corrosion and pepsin digestion in the stomach
mucous
what are place circulares
folds in the mucous membrane of the small intestine
which vitamins are water soluble
B C folic acid
which vein does the interior mesenteric drain into
splenic
how are digestive enzymes stored in acinar cells
inactive form (zymogen)
How does sympathetic innervation effect secretion and motility
Decrease secretion
Decrease motility
what motility happens in the gut while food is being processed
Segmentation
what separates the right and left lobes of the liver
falciform ligament
which transporter transports glucose/ galactose into the cell
SGLT1 - coupled to sodium
what happens to the stomach contents that don’t leave the pyloric sphincter when it contracts
forced back into body for further mixing with pepsin and acid
what are enterogastrones released in response to
acid
hypertonic solutions
fatty acids
monoglycerides
which minor lobe of the liver is superior in your drawing
quadrate
where are the mucous glands in the oesophagus
submucosal
what happens to the bicarbonate made inside a parietal cell
transported out BL membrane in exchange with a Cl ion - which exits through Cl channel on apical membrane
Why does the stomach store food
constant energy supply between meals
What does the lamina propria contain
glands, blood vessels, lymph
what is the purpose of the backwards and forwards movements of segmentation
thorough mixing of contents with digestive enzymes
brings chyme into contact with absorbing substance
What enzymes hydrolyse peptide bonds
protease
peptidase
what is the max storage of glycogen
3 miles - after it is tired as fat
what does bile aid in
fat digestion and absorption in the small intestine
what muscles control chewing
skeletal muscles of mouth and jaw
in the pharyngeal phase of swallowing, what triggers the relax of contractions by the pharyngeal muscles
sense bolus
where are monosaccharides broken down
small intestine
where is NaCl absorbed in the intestine and what does this mean
ileum - chyme is dehydrated as water follows sodium out
what happens to fatty acids and monoglycerides that are not absorbed across the plasma membrane
released back into micelles (dynamic equilibrium - constant supply of free molecules)
what is silly about the production of gastrin
it is produced in the antrum but has to go through the full bloodstream to be utilised in the body
which anal sphincter is smooth muscle
internal anal - autonomic
How does parasympathetic innervation by the vagus nerve effect secretion and motility
Increase secretion
Increase motility
what type of muscle are the UOS and LOS
smooth
how does the stomachs receptive relaxation work
vagal reflex - thin elastic smooth muscle of gastric fundus/ body allowing it to balloon
which nerves innervate the salivary glands
glossopharyngeal
facial
why is secretin released in response to acid in the duodenum
increases bicarbonate
what is different about the muscularis externa in the stomach
has an oblique layer of muscle (inner)
which vitamins are fat soluble
A D E K
what do the serous and mucous glands in saliva excrete
serous - protein (amylase)
mucous - mucous
mixed - both
What is the animal storage of glucose
glycogen
what do pancreatic duct cells secrete to keep enzymes at optimum pH
HCO3
what is muslin in saliva
protein
mucin + water = mucus - lubricant
what are chylomicrons
extracellular fat droplets containing phospholipids, cholesterol & fat soluble vitamins
how does unabsorbed iron travel in the blood
bound to transferrin
are micelles absorbed across the small intestine epithelium
no
what produces oscillations in the membrane potential of pacemaker cells that causes depolarisation
BER - basic electrical rhythm
what kind of saliva does the parasympathetic nervous system produce
lots of watery saliva
Which electrolyte does a rise in gastrin produce that increases the action of the proton pump to make more acid
Calcium
what 4 things are contained in a micelle
monoglyceride
fatty acid
bile salt/ phospholipid (emulsifying agents)
how is bilirubin added to bile
extracted from blood by hepatocytes and secreted into bile
What are disaccharides
2 monosaccharides linked by glycosidic bonds
what section of the liver is not covered by visceral peritoneum
bare area
what is a crypt of lieberkuhn
villi that extend into the lamina propia
how does ferritin leave the body
black faeces
What are the contents of saliva
water, mucin, alpha-amylase, electrolytes, lysozyme
What are the endocrine glands of the pancreas called
islets of langerhans
what does the ileocal sphincter do in response to distension of the colon by a bolus
contracts to prevent reflux
How are the glucose linked in cellulose
unbranched linear chains linked by beta- 1,4 glycosidic bonds
where is gastrin produced
the antrum of the stomach
what does alpha amylase do in saliva
catalyses breakdown of polysaccharides (starch, amylase) into disaccharides
what neutralises acid in the duodenum
HCO3
What is the law of the intestine
If intestinal smooth muscle is distended - muscle on the oral side contracts and muscle on the anal side relaxes
mediated by neurones in the myenteric plexus
what does the UOS do once food has entered the oesophagus
contracts to prevent reflux
What are the 3 pairs of salivary glands
Parotid
Sublingual
Submandibular
Which organs does the superior mesenteric artery supply
small intestine, caecum, ascending colon, transverse colon
How does histamine increase the action of the protein pump (make more HCl)
stomach has unique receptor with Gs coupled to AC which converts ATP –> cAMP which acts on the pump
Which membrane does CO2 in the blood diffuse over to get inside the parietal cell
Basolateral
what stimulates the cephalic phase of gastric acid production
sight, smell and taste of food
what circulation recycles secreted bile salts
enterohepatic (liver –> bile duct –> duodenum –> ileum (5% lost) –> portal vein –> liver (5% synthesis)
what are hepatic sinusoids
spaces beween hepatic chords with a blood channel for dead cells
when is GIP released (gastric inhibitory peptide)
fat in the duodenum
What muscle makes up the muscularis externa
2 concentric thick layers of smooth muscle
What tissue is the submucosa made up of
Thick, irregular connective tissue
what do the electrolytes in saliva do (ions in solution)
control tonicity and pH by selectively releasing NaCl/ bicarbonate
why does peristalsis need neural and hormonal control to induce an AP
depolarisation is sub threshold
What breaks down disaccharides
brush border enzymes in small enzymes
what are the constituents of triaglycerol
glycerol + 3 fatty acids
what neural response helps increase the frequency of APs in peristalsis (PNS/ENS)
reflex from distension of stomach wall
where does the bulk of digestion are place
duodenum
Which two plexus make up the enteric nervous system
Myenteric and submucosal
what do the enterogastrones act together to do
prevent further acid build up - maintain pH for pancreatic enzymes
which transporter transports fructose into the cell
GLUT 5
where is secretin released from in response to acid in the duodenum
S cells in duodenum
pancreas and liver
What is the epithelium in the stomach, small intestine and large intestine
simple columnar
What turns off the protein pump that helps to make gastric acid
prostaglandins - receptor coupled to inhibitor G protein (Gi) that turns off AC
why does emulsification speed up fat digestion
increases surface area of the lipids and accessibility to lipase action
what percentage of saliva is water
99%
what initiates segemntation
depolarisation from pacemaker cells in longitudinal muscle layer
list some enterotoxigenic bacteria
vibrio cholera
escherichia coli
Describe the process of emulsification
large lipid droplets broken into smaller droplets by mechanical disruption from contraction of the smooth muscle in the muscularis externa - grinds and mixes lumenal contents
how are water soluble vitamins absorbed
passive diffusion or carrier mediated transport
where is iron absorbed
duodenum
what channel does Cl pass out of the cell into the intestinal lumen
CFTR - cystic fibrosis transmembrane conductance regulator
what kind of saliva does the sympathetic nervous system produce
small volume
viscous saliva (dry mouth)
alpha 1 - high mucous beta 2 - high amylase
Where in the GI tract is water absorbed
large intestine
what is the surface area of the small intestine
200m2
What type of blood is carried via the portal system
venous - rich in nutrients
in the gastric phase, what causes the vagal and enteric reflexes to fire ACh
distension of the stomach by the arrival of food
how is the absorption of fatty acids and monoglycerides enhanced
micelles
list the 4 functions of the stomach
temporary store of ingested food
dissolve food particles (initiate digestion)
control delivery of contents to small intestine
Produce intrinsic factor (vit B12 absorption)
are large lipid droplets soluble in water
no
what attaches the small intestine epithelial cells
tight junction complex
Which nerve is used for sympathetic innervation of the gut
splanchnic
Where are bile salts produced
the liver
how is there voluntary delay of defaecation
descending pathways to external sphincter – grow with age
what happens in the chewing phase of swallowing
molecule size reduced (bolus)
what is in the centre of each hexagonal lobule in the liver
central veins –> hepatic veins –> IVC
Where does the inferior mesenteric artery leave the abdominal aorta
L3
which transporter transports glucose out of the cell
GLUT 5
Which is the inner layer of the muscular external and what does it do
Circular - constricts the lumen
which receptors counteract saliva
chemoreceptors - chemicals in food
pressure receptors - distension of mouth/ tongue
how is water important for normal digestion
maintains contents in liquid state
promotes mixing with enzymes
aids nutrient presentation to absorbing surface
dilutes and washes away potentially harmful substances
which 3 mechanisms control gastric acid secretion
neurocrine - Ach vagus
endocrine - gastrin
paracrine - histamine
what do intestine crypts secrete
Cl and H20
what is the only essential (non - compensated for) function of the stomach
produce intrinsic factor for Vit B12 absorption
What tissue is the lamina propria
smooth connective tissue sheath
what are the 3 hormones released from gland cells in the duodenal mucosa (enterogastrones)
secretin
GIP
CCK
which hormone initiates the MMC
motilin
what is the predominant pigment of bile pigments
bilirubin (yellow)
which anal sphincter is skeletal muscle
external anal - voluntary
What does the gall bladder do to bile
stores and concentrates it
what is the only nutrient that the gut regulates
iron
what is a micelle
extracellular structure that encapsulates the fat to keep it away from water (fat taxi)
what causes MMC to sop
arrival of food in the stomach (segmentation begins)
how does the body respond to anaemia
decrease in ferritin level - more iron in good
how is pepsin stored and what is this method of storage called
pepsinogen in chief cells
zymogen storing
what response does the sight, smell and taste of food have
vagus nerve fires - ACh on parietal cells, stimulates G cells to produce gastrin which acts on parietal cells
what condition is caused by a Vit b12 deficiency
pernicious anaemia
describe the transportation of pancreatic enzymes to the duodenum
acinar cells –> lobules –> intercalated ducts –> interlobular ducts –> main pancreatic duct (meets with common bile duct) –> sphincter of oddi
how is paracellular movement described
down leaky channels
what do stomach chief cells secrete
pepsinogens
What motility happens in the gut after finishing food
peristalsis
what is the blood level of glycogen
5 mmol/L
Where is the majority of bacteria in the GI tract
large intestine
which receptors does acetylcholine act on
muscarinic cholinergic
what do stomach mucous neck cells secrete
mucous
How does ACh act to increase the action of the protein pump on parietal cells and produce more HCL
intracellular Ca
what so the lysozyme is saliva do
bacteriocidal- cleave polysaccharide component of bacterial wall to sterilise
How does the vagus nerve effect salivation
it doesn’t
How long is the gut tube
8m
what muscles layer produces haustra in the large intestine
circular layer
Which 2 veins make the portal vein
splenic
superior mesenteric
what happens to the soft palate and nasopharynx during the pharyngeal phase of swallowing
soft palate - reflected back and up
nasopharynx - closed to prevent regurgitation
where is the swallowing centre located
medulla - next to respiratory
what generates the peristaltic rhythm in the stomach
pacemaker cells in longitudinal muscle layer near oesophageal opening
how does the gall bladder concentrate bile by 5-20 times
absorbs Na so H2O follows
What 3 monosaccharides can be absorbed
Glucose
Galactose
Fructose
which 2 ducts join to make the common hepatic duct
right and left hepatic
what pH do intestinal enzyme work at
neutral
When does the motilin hormone rise to start the MMC
when nutrient content in the blood lows
which section of the gut has the fastest segmentation and what does this allow
intestine –> rectum
slow migration of chyme toward rectum
What are the 3 sections of the small intestine called
duodenum
jejunum
ileum
how does the dehydration of chyme occur to form solid faecal pellets
active transport of Na from lumen into blood causes the osmotic absorption of water
what causes the release of secretin
acid in the duodenum
What is lactose broken down to and by what
glucose + galactose
lactase
what happens to fatty acids and monogycerides after they enter epithelial cells
enter smooth ER for enzymes to reform them to triacylglycerol
transported through cells in vesicles
processed in golgi apparatus
exocytosed into extracellular fluid at basolateral membrane (as chylomicrons)
what is cellulose a constituent of
plant cell walls
What is exopeptidase
Break peptide ponds at terminal end, one amino acid at a time
aminopeptidase - amyl end
carboxypeptidase - carboy end
How are the glucose arranged in glycogen
alpha- 1,4 glycosidic bonds
what do pancreatic islets produce (endocrine)
insulin (alpha cells)
glucagon (beta cells)
somatostatin
What does the longitudinal layer (outer) do
shortens tube
Where are the digestive enzymes stored
pancreas
what does GIP do
inhibit gastrin secretion / stop stimulation of parietal cells/ decrease secretion of Hal
What are the 4 functions of the alimentary system
Digestion
Secretion
Absorption
Motility
where are 95% nutrients absorbed
jejunum
What direction doe segmentation move
backwards and forwards
what cells make up the exocrine portion of the pancreas
acinar cells
what happens to bile when the sphincter of Oddi is contracted
bile forced back into gallbladder where it is concentrated
what divides the liver into hexagonal lobules
septa (vessels, ducts and nerves follow)
What prevents bacterial colonisation of the small intestine
MMC - migrating motility complex
what is the alimentary role of the liver
production of bile
what is the outer connective tissue layer of the gut tube called outwith the peritoneal cavity
Adventitia
what cells produce intrinsic factor
parietal cells
What muscle is the muscular mucosae and what is its function
smooth - insignificant
what are the 2 phases of gastric acid production
cephalic phase
gastric phase
why is pepsin stored as an inactive precursor
prevent cellular digestion
How is the gut maintained at an acidic environment to create a constant supply of hydrogen ions
NHE3 pumps them out the cell - coupled to sodium
Na/ K ATPase
what are bile acids synthesised from
cholesterol in liver
how do you treat enterotoxigenic bacteria
sodium glucose solution
drives water absorption = rehydration
How often are the MMC waves
as one ends in terminal ileum another begins
Which 2 organs contain submucosal glands
oesophagus - saliva
duodenum - bicarbonate
how does the H/K ATPase pump work
1 for 1 exchange - keeps cell neutral
where is food reduced to liquid form
stomach
how are dipeptides transported into the cell
PEPT1 - hydrogen coupled
which membrane is the proton pump that makes gastric acid
apical - into lumen
Where does the superior mesenteric artery leave the abdominal aorta
L1
what are the main functions of hepatocytes
bile synthesis
nutrient storage
conversion of nutrients (when required)
detoxification
which movement occurs in the oesophagus during the oesophageal phase of swallowing
peristalsis - open in front and contract behind
what lies between cells in the hepatic cords that radiate form the central veins
bile canaliculi
how does emulsification prevent reformation of droplets
polar tails repel each other
where is enterokinase found and why
brush border of duodenal cells - so digestive enzymes can only be active there
What neurones does the submucosa contain
submucosal plexus - parasympathetic
what does vit B12 do to blood cells
allows them to mature to concave shape - optimum for carrying oxygen
What are the 3 layers of the mucosa
Epithelium
Lamina propria
Muscularis mucosal
describe the epithelium of the anus
Junctional - simple columnar –> stratified squamos
what are some associated symptoms of constipation
headaches
nausea
loss of appetite
abdominal distension
what causes diarrhoea
pathogenic bacteria protozoans viruses/ toxins food - e.g. lactose intolerance stress
What transporter is essential for the transportation of monosaccharides
Na/K ATPase
what happens in the voluntary oral phase of swallowing
bolus pushed to back of mouth by tongue
what is contained in each portal triad
hepatic portal vein
hepatic artsy
hepatic duct
what causes haustra appear in the large intestine
contractions of teniae coli
why determines the frequency of segmentation
BER
what happens to bile once it is modified by bacterial enzymes in the large intestine
turns brown - faeces
how does water move through parietal cells
paracellular transport
why is the epithelium of the oesophagus
stratified non keratinised squamous
What acts as an emulsifying agent during emulsification
bile salts and phospholipids - secreted from bile in liver
what does the ileocal sphincter do in response to increased segmentation in the ileum
opens to allow chyme to enter the large intestine
how much water does the small intestine secrete per day (crypts of lieberkun)
1.5 L water
Which organs does the inferior mesenteric artery supply
descending colon, sigmoid colon, rectum
what does bacterial fermentation of undigested carbohydrates make
short chain fatty acids - energy source
vitamin K - blood clotting
Gas - flatulence
how is the secretion of water in the small intestine from cryptos lieberkuhn passive
osmotic gradient of the active secretion of Cl into intestinal lumen
how is the gastric phase of gastric acid production inhibited
decrease in pH from the increase in HCl turns off the production of gastrin (which turns of the production of more gastrin)
what environment does pancreatic lease act in
aqueous only- at surface of droplet
which phase prepares the stomach for any food by inducing the parietal cells to make more HCl
Cephalic phase
which nerves innervate the liver
hepatic plexus on inferior surface
What converts trypsinogen to its active form trypsin
enterokinase - CCK
what are the functional cells of the gut called
interocytes
roughly how much bacteria is in the large intestine
1 x 10^14
what happens to the LOS when the bolus reaches the stomach
relaxes
which transportation method do most crypts use to absorb nutrients
Na coupled secondary active transport
Why are the peristaltic waves in the stomach slow
basic electrical rhythm - spontaneous depolarisation and repolarisation through gap junctions
in what circumstances is pepsinogen made into pepsin by acid hydrolyses
pH < 3
what are the 2 monomers of starch and how are they different
alpha-amylase - straight chains
amylopectin - highly branched structure
Where is the apical membrane on the small intestine epithelial cells
outside
basolateral inside
where are the gastric pits of the stomach
surface epithelial mucus cells
describe the epithelium of the large intestine and what does it not have
simple columnar epithelium
no villi or folds
flat and smooth
where are the portal triads
each corner of hexagonal lobule
What is located in between the longitudinal and circular layers of the muscularis externa
myenteric plexus
What is triacylglycerol broken down into and by what
monoglyceride and 2 fatty acids
pancreatic lipase
What is endopeptidase
Break bonds of middle amino acids, leaving 2 chains
where is the peristaltic wave in the stomach most powerful
antrum - thick muscle
how is cellulose digested
dietary fibre - no digestion enzymes
Which two nerves innervate salivation
Facial (VII)
Glossopharyngeal (IX)
Which organs does the celiac trunk supply
stomach, small intestine, pancreas, liver
what do stomach parietal cells secrete
HCl, intrinsic factor
where is bicarbonate secreted in the duodenum
Brunner’s glands in submucosa
What is the purpose of producing saliva
acts as a lubricant
how are fat soluble vitamins absorbed
same as fat
what type of muscle is present in the top 1/3 of the oesophagus
skeletal (voluntary - swallowing reflex)
Where does the coeliac trunk leave the abdominal aorta
T12
how do the enterogastrones prevent acid build up in the duodenum
inhibit gastric acid secretion
reduce gastric emptying (reduce motility/ contract pyloric sphincter)
how do enterotoxigenic bacteria cause profuse watery diarrhoea
produce protein enterotoxins which elevate intracellular secondary messengers to turn on Cl production from crypt cells which increases water secretion
(swamps absorptive capacity of villas cells)
what nutrients are stored in hepatocytes
glycogen
fat
vit B12, A, D, E, K
Cu and Fe
what are the effects of an increase of CCK in the circulation
delayed gastric emptying
increased pancreatic enzymes
Sphincter of oddi relaxes
increased gallbladder contraction
how does the self limiting negative feedback of secretin work
neutralisation of the duodenum inhibits production
what cells do gastrin/ Ach stimulate to produce histamine in the cephalic phase
ECL cells
what converts all inactive digestive enzymes to their active form
trypsin
where are the goblet cells in the large intestine
crypts
What is the epithelium in the mouth, oesophagus and anal canal
stratified squamous (non keritonised)
where are gut stem cells found
crypts of lieberkuhn
what are the components of bile
bile acids Lecithin cholesterol bile pigments (bilirubin) toxic metals bicarbonate
What do the lymphatics in the submucosa do
Take away fat as it doesn’t mix with water
during constipation is there absorption of toxins form faecal material
NO
what is a lacteal
lymphatic capillary that removes dietary fats
what does somatostatin do
controls insulin and glucagon levels
what is CCK released in response to
fatty and amino acids in the duodenum
how long is a peptide
3-10 amino acids
what does the sphincter of Oddi control
the delivery of bile and digestive enzymes to the duodenum
What is sucrose broken down to and by what
glucose + fructose
sucrase
What stimulates G cells to produce gastrin
peptides in the lumen
where is the HCl made in the stomach and where do the components come from
stomach lumen
H - dissociation of HCO3 from CO2
Cl - exchange transport with bicarbonate, exits through Cl channel
which nerves control the defaecation reflex
parasympathetic
How do chylomicrons pass through endothelial cells
through lacteals and then through lymphatic system
what is the primary role of the duodenum
gastric acid neutralisation
What is maltose broken down to and by what
Glucose + glucose
maltase
when is the production of pepsin inhibited
neutral pH - raise to stop
describe starch
glucose storage in plants
Glucose monomers linked by alpha-1,4-glycosidic bonds hydrolysed by amylases
what is the migrating motility complex
Pattern of peristaltic activity starting in antrum and travelling down small intestine
what is the pH of the blood
7.4
what neural response controls the pancreatic function
vagal/ local reflex triggered by arrival of nutrients in duodenum
List 3 polysaccharides
Starch, Glycogen, Cellulose
What would happen to the gut if the stomach didn’t store food
water influx
what type of muscle is present in the middle 1/3 of the oesophagus
skeletal and smooth
what does the enterogastric reflex do in response to acid in the duodenum
inhibit gastrin secretion / stop stimulation of parietal cells/ decrease secretion of Hal
does the autonomic nervous system have any effect on the gut
no - constant movement when processing food
What are the 4 layers of the gut tube
Mucosa
Submucosa
Muscular externa
Serosa (below diaphragm) / Adventitia
What links the amino acids in proteins
peptide bonds
if the main pancreatic duct is obstructed , how will digestive enzymes reach the duodenum?
accessory pancreatic duct
define diarrhoea
too frequent passing of faeces which are too liquid
what is the purpose of chewing
defence against respiratory failure
prolong taste experience
why do parietal cells only produce Hal when necessary
Very energy dependent - K/ H pump
where is glycogen stored
liver
how does the body respond to hyperaemia
increase in ferritin level - more iron stored
what happens to the cephalic phase of gastric acid production when you stop eating
decrease vagal activity - inhibit acid production
how is gastric mucus cytoprotective
protects mucosal surface from mechanical injury and neutralised pH (HCO3)
how is iron stored in a cell
ferritin - ions can’t leave
where is mucous produced in the stomach
surface epithelial cells and mucus neck cells
what 3 cells are contained in a gastric pit
neck, parietal, chief
describe the epithelium of the rectum
simple columnar
how are phospholipids amphiphatic
polar tail (water soluble) and non-polar head (fat soluble)
what is the pH of the stomach of the stomach lumen
<2
how long is the oesophagus
about 25cm
how is Vit B12 absorbed
binds to intrinsic factor from the stomach
specific transport mediated system in distal ileum and moved to liver for storage
what hormone helps increase the frequency of APs in peristalsis
gastrin
describe the reflex of chewing
contraction of jaw muscles increase pressure food against gums, hard palate and tongue mechanoreceptors fore inhibit jaw receptors decrease pressure
what type of muscle is present in the lower 1/3 of the oesophagus
smooth
what is a feature of the submucosa of the stomach
folded rugae
Once it is produced, what does carbonic acid immediately dissociate to once its inside the cell?
H and HCO3
what happens during swallowing when the bolus reaches the oesophagus
UOS relaxes and epiglottis covers opening to larynx (stops food entering teaches/ inhibits breathing)
which muscle layer in the muscularis externa is incomplete in the large intestine
Longitudinal
what molecules can’t pass the membrane
polar - water soluble
charged
