GI 5 Flashcards
SI: electro & H2O abs at the Villi
Na-coupled w/nutrient 1:1
-Driven by electrochem grad, against conc grad
H-coup: Pept1 & PAT1
-driven by pH gradient: acidic surf & alk interior
Electroneutral NaCl abs: NaH & Cl:HCO3 coupling
Uncoup NaH & Cl:HCO3: adjusts lumen pH
- Up JJ: ⬆️NaH=net [H] secr➡️ recover HCO3
- ileum: ⬆️Cl:HCO3= alk il effluent➡️ buffers VFA
Most fl enter GIT is
Endogenous secr
Intestines recover 98% of fl.
Pept1
Main AA assimilation path
♻️ [H+] via NaH exchanger
Euvolemia
Dig& abs➡️PSNS: cAMP/Ca2+ ➡️
⛔️NaH & Cl:HCO3 exchange ➡️⛔️NaCl abs & ✳️NaCl&HCO3 secr for digestion
Bacterial enterotoxins ⬆️⬆️cAMP➡️secretory diarrhea
Hypovolemia
SNS➡️⛔️PSNS euvolemia➡️ ✳️rapid NaCl & H2O abs
LI: salt & H2O abs at surf epi
Prox LI: electroneut NaCl abs
-uncoup NaH➡️ ♻️[H] for VFA&Na abs
Dist LI: electrogenic Na abs
- Na scavenging: ENaC (~DT) abs Na against conc grad ➡️ net [K] secr
- reg by ALDO: ⬆️ENaC expression
Intestinal crypt secr: NaCl & H2O
Electrogenic Cl & HCO3 secr: LI &SI
⬆️Cl via NKCC1 & ⬆️HCO3 via NBC at BL mem
- both use Na gradient
- Cl:HCO3 secr via CFTR & Cl:HCO3 exchanger ➡️♻️Cl ➡️ ⬆️HCO3 secr
H2O (osm) & NaCl (eg) follow
PSNS & ENS ➡️
✳️crypt fl secr
⛔️fl abs at villi/surf epi
SNS &EEinterneurons
⛔️ENS➡️ ⬆️fl abs ⬇️fl secr
Antidiarrheals: alpha-Ach= also ⛔️motility➡️ infx
Syn opiates= segmentation & aboral prog
Mucosal BB enz
High Lactase➡️ digest milk
Low everything else⛔️ digestion of IgM
CHO Digestion
Efficient due to Monosacc digest on surf next➡️ Na-coup Hexose transport ➡️ Portal V
Protein dig & abs
Stomach (polypeptide AA)➡️ intestinal lumen protease (oligo AA)➡️ intestinal BB peptidase (di/tri peptides)➡️ NaH-coup AA transport
Complex 3D structure
Fat dig & abs
TG duodenum➡️✳️CCK➡️✳️pancr enz & GB contraction➡️ bile emulsify ➡️micelles ⬆️SA for lipase:✳️ hydrolyze ester bonds 1&3
Lipids passively diffuse at BB epi➡️ re-ester to TG➡️ chylomicra➡️ BL➡️ lacteals of villi
Irreversible injury to SI
Removal of bowel sect➡️✳️Remaining villi ⬆️length
Max x2
Req crypt stem cells
Nutrients presence
SI Resection
Jejunum: ⬇️dig/abs protein
Ileum: ⬇️fat abs (site of bile abs) & ⬇️Vitamin B12 abs
Modify protein & fat intake & VB inj
Colon Resection
⬇️VFA abs & ⬇️fl+electrolyte abs
Compensate:✳️⬆️cecum size in eq
Intestinal Motility Pattern
ISSP
Ileus: dysautonomia ⛔️contraction
Spasm: ⛔️inhibition ➡️✳️⚪️smM contracted
Segmentation: normal ON&OFF➡️propulsive peristalsis
Peristalsis: main propulsive & MMC
Peristalsis
Aboral to bolus: SLEEVING
Ach+VIP/NO/ATP➡️✳️Long M & ⛔️⚪️smM ➡️open lumen
Oral to bolus: default state
✳️⚪️smM & relaxed LongM➡️ closed
⛔️reflux
Pacemaker: SI-myogenic
LI-neurogenic
ssp. LI Segmentation
Humans, horse, pig: haustra movements
- taenia longit M
- huastration ⚪️smM
Slows digesta but aboral progression occurs
spp. Reverse peristalsis
O: midcolon Slows aboral flow Midcolonic Pacemaker ✳️reverse peri & normal peri Eq: pelvic flexure ⛔️dog
spp Cecal retropulsion
Ruminants, rabbits, rodents:
Slows passage, adaptation of rev.peri ➡️ repel digesta into cecum
⛔️eq: strong cecocolic sphincter
spp Cecal motility
Equine
LI mass movment
✳️⚪️M contract cupola➡️digesta pass to colon
Gas ⬆️wall tension➡️CNS:✳️base cecum:gas➡️cupola distension➡️ lowers fl level: gas➡️ostium
Mass mov ➡️colon
Mod peri mov➡️Prep defecation
CNS long reflex& peristalsis waves➡️try to fill rectum
Gastrocoloic reflex
Colonic filling
Colonic irritation
Defecation reflex
Filled rectum sensed local & CNS➡️✳️ENS & PSNS long reflex
Invol: ✳️rectal peri & relax int sphincter
Vol: ✳️valsalva & relax ext sphincter (nAch Pudendal N)
Rabbit Cecotrophy
Cecum 40% GI Vol
Enlarged Prox colon & haustra
Fusi coli sphincter ➡️ colonic retropulsion soft digestible matter➡️ moar fermentation
Hard day stools
Soft cecotrophs 8hrs later in rectum➡️✳️ licking
-rich VitaB & K & bacteria protein
Avian digestion
Crop- storage ~prox stomach
Proventriculus- gl stomach
Ventric/gizzard- non gl stomach
⛔️JJ
Thin gizz M: peristalsis waves
Thick gizz M: grind & reflux ➡️provent
Reg provent peri➡️gizz & rev peri duodenum ➡️gizz
Colonic:
Constant rev peri ➡️paired ceca
⛔️rev peri➡️✳️defecation
