8. GI Physiology Flashcards
Gastric acid secrtion
which cells
where in stomach
Parietal cell secrete H and CL
located fundus and body stom
also secrete intrisnic factor
necc abs B12 term Il
How is H prod
how secrete
Rxn Co2 + H20 by carbonic anhydrase
active tpor by h k atpase
hco3 bl membrane exchange Cl - antiport
Max H grad accross
Ph 7.4 and gastric Ph 1.4 - gradient 6 ph units
H grad 1,000,000 (10^6)
max grad could be higher as ph can be as low .87
What is the alkaline tide
agstric resp quiotient
Alakine state gastric ven blood - suffc prod alk urine
lvel gastric acid resul large amt bic - secrete vessel drain stom
max acid secretion in partietal - net consump co2 sotmahc
resp quitient - negative neg co2 production
Humoral factos act parietal stim gatric acid secretion
Hist H2 rec
(AC )
Ach M1
Gastrin gastrin rec -
act BLMembr
Ach & gastrin - increase intra cell Ca
both Ca inc and cAMP increase - act pro kin increase act H pump
PGE2 inhbi AC via Gi - decrease gastric secretion
Where is gastrin produced
Main action
Gastrin prod G cell - located antrum
neuroendocrine cell - derived neural crest
Stim acid sec - partietal into lum
stim pensinoogen - chief cell in lumen
Main actions gastric acid
Activate pensinogen to prod pepsin
assit protien dgiestion pepsin req low pH acivity
Help rpevent infectio
Inhib gastri antral G cell
Increase secretion bile and panc juice
Fail iron absorption
Bile acids
whats bile
Fluid secreted by the liver into th ehpeatic ducts
comppostion undergoes modifcation in the gallbladder
Contrains Water Salts Pigments Electrolytes
What are the bile salts
Steroid compound prod liver from cholesterol
conj taurine / glycine and excreted in bile
Form Salts Na + K
BIle acids classify intro primary and secodnary bile acids
Primary bile acids
Secondary bile acids
Primary - produce liver
cholic acid
chenodeoxycholic acid
daiyl syhtn - .5g day - may net faecal loss acids
PRod intest action bacteria - prim small int normally no except ileum colon - huge bac load secondary acids deoxycholic litholchilic acid
Whats the circulation of acids
95% reabs term ileum return liver in portal vein - maint low prod
If lost (eg fistual) - liver can increase rate synthesis of salts
TOtal bile acid pool 2.5 -3gm
Pool circ 2-3 per meal for 2 meals d - effective bile acid pool 27g day
What is the fxn of bile acid
Facil absorption lipds sml int
abesence 50% ignested fat in faceas
1 Emulsifying - detergnet action on fats
monoglyc plip - fat to break into large number - minute fat partciles
decrease surf tension fat particles
2 Formation of lipid micells
Cause fat form sml highly solube discs micells
acid amphipathic
hydrohpilic outside - tport bruse border lipid diffuse across lip membrane
Fat sol bitains
ADEK
Defici - abesent bile salt
Functions of liver
1 Lipid metab
-fatty acid oxid
synth chol + PLipd
prod ketoacids
2 Carb metab
Glycogen metab
gluconeo
glucstat fxn
3 protein metab
aa metab
turonvover prote
synthesis - alb coag carri
4 Urea
5 Bile
6 Drugs & xenobitiics
7 RES - kupffer
8 Endocrine synth 25 hydroxycalc inact some hormone precursos sythn metaob steroid somatemedins epo
9 Haemotopoesis
10 Blood resevoir
11 Storage xn
12 Role AB bal
Nearly all plasma prot cept ig - prod liver
How does liver act as a resevoir
10% tbv normall liver
hypervol/rhf increase to 15000
hypo - exercise / ep sym stim deliver 350 mls
What is reticuloendothelial system
Tissue macrophage and monocytes - distrb various sties around body
Moncyote - bm progenitor cell - rel bstream migrat tissue differentiate to cell RES
Tissue macrophage in system -
Kuppfer cell lining hepatic sinusoids
Macrophage lining sinusoids bm + spleen
Pulmonary alveolar macrophage
Macrophage in LN
Migrolial cell CNS
Osteoclasts
Major fxn
1 antigen process and presse esp cII MHC
Phagocytosis - Bact cell dbri
R/O bacteria old RCC other debri
Secr vary cytokine - response infect regulation haemoeisis
maco - attract acute inflam - involved paho savengin antigen process
How are liver and spleen involved
Kuppfer in liver - improtant component of RES _ line sinusoids - effective removing all ivnetivale number colonic bact enter portal bood
SPelen - senecent red cell and plt
Kuppfer - iron recycle
Liver in ab metab
Net prod / consuer H ion
CO2 prod - oxidation
20% use o2 = 20% co2 production
Metab acid anion
Lactate / keto or citrate tfusi
endog - not result prod H - exog = prod bic
AA metab - incomp metab net fix acid prod
Ammonium Nh4 to rurea -
Vomiting
what diff bom reguarg
Vom active muscular contract
regurg - passive
VOm centre
autonom sym / nausea
Inspire - hold breat mid insp glottis closed - prtect airway
soft palat - eleavted nasal airway soil
LOesSph + Up releax
abdominal muscle cotnrat - rise IAP compress stomach - gatri content force expell oes exit motuh
Whats Nausea
Unpleasant concious sensation a.w vomiting
occur prodmal to vom
Vom Can also occur without N
WHat stimli cause vom
how act
what causees vom if swallow gastric irritant
BOdy mech rid gastric and bowel content - adbant ingest toxin
Most stim bowel brain
bowel - mus irrital trav vom - sym vagal aff - CTZ not involved
SOme circ chem - CTZ
Vestibular system - ctz and driect to vom
anticholinergic more effective rx type nausea
Other area - ptoent input
odours
psyhogenic / pain
Wht CTZ
ARea postream later wall 4th venticle
lies outside BBB circunticular organ
Var sub circ stim CTZ = vom
What is the adeverse conseq persistent vomiting
Water electrolyte and ab balncetypical finding vom pyoloric steno -
hypoCl
Na
K
Met alk
hypovl
VOm direct loss fluid acid - contract alkaslois
RAAS _ active secon hypoaldo
kidney conserve water Nad NA presisten - loss K
hypo - due to renal loss
ACid base effect
Met alk
Plasam bic elvated
Nroamlly kidney excrete bic but there is avolme contract
cl defic - impair kid excrete
Loss gastric acid initate alkolis
second effect kidney maint high bic
