Intestinal Fluid and Electrolyte Balance Flashcards
(17 cards)
Label cross section of the gut
Lec slide
Compare villi in small intesting to larger intestine
Smaller intestine villi are longer finger like projections
Label the intestine structures and the cells in the villi and where are they located down the villi/crpyt
Lecture Slide
Vilious absorptive cell, Goblet, enteric endocrine, stem cell, paneth cell, undiffereniated cell
Surface of small intestine is amplified (folded) at 3 levels. What are they
*Folds of Kerchring
*Microvilli and crypts of Lieberkuhn
*Submicroscopic microvilli
Surface of Large intestine is amplified (folded) at 3 levels. What are they
*Semilunar folds *Crypts, but no villi *Microvilli
Small vs large intestine
Length
Area of apical plasma membrane
Folds
Villi
Crupyts/glands
microvilli
nutrient absorption
Active Na asb
Active K+ secretion
Small
Length: 6m
Area of apical plasma membrane:~200m2
Folds: Y
Villi: Y
Crupyts/glands: Y
microvilli: Y
nutrient absorption: Y
Active Na abs: Y
Active K+ secretion: N
Large
Length: 2.4m
Area of apical plasma membrane:~25m2
Folds: Y
Villi: N
Crupyts/glands: Y
microvilli: Y
nutrient absorption: N
Active Na abs: Y
Active K+ secretion: Y
What does the small and large intestine abs and secerete
The small intestine absorbs net amounts of water, Na+, Cl- and K+ and secretes HCO3-, whereas the large intestine absorbs net amounts of water, Na+, Cl- and secretes both K+ and HCO3-
Intestinal Epithelial cells are Nonpolar or Polar
Polar
Describe the flow in intestinal epithelial cells
Lecture Slide for diagram
Glucose + 2 Na enter the apical surface of cell through Na -glucose symporter (driven by high Na conc)
At Basal surface
3 Na will exit the Na/K+ ATPase and 2 K will enter (to make inside cell Na defiencent)
Glucose leaves through glucose uniporter GluT2
Transepithelial movement of water and solutes…
-route types
-What is transcellular vs paracellular
Either absorptive or secretory
Transcellular or paracellular
Transcellular, must move across 2 membranes in series
Transcellular: solutes, across at least one membrane is active
Paracellular: movement passive via tight junctions
Absorption of water
- via what type of movement
- what route? through (transcellular) or around cells (paracellular)
- What route dominates in jejunum
Osmosis
Coupled by solute movement
Occurs via transcellular or paracellular routes
Paracellular predominant mode of absorption primailry in the jejunum
Na+ absorption
- where does it occur
- mediated by
- -maintains?
- How does Na move across apical surface
Occurs in villus epithelial cells of the small intestine and surface epithelial cells of the large intestine
All transcellular Na absorption mediated by Na-K pump (Na-K ATPase) on basolateral membrane
Maintains a low intracellular Na concentration
Provides force for Na movement from diffusion from lumen across apical membrane
Apical transport mediated by Na+ coupled transporters (e.g. Na/glucose transporters) or Na+ channels dependent on fasting/postprandial state and GI region)
Control of fluid abs and secretion
Enteric nervous system- release of Ach, VIP and other Secretagogues
Endocrine system- Aldosterone
Paracrine System- 5HT
Osmotic diarrhoea vs secetroy
Osmotic diarrhoea: Results from disturbances of abs
secetory: results from disturbances in secretion
Small intestine: Volumious
Large: Small volume diarrhoea
Osmotic diarrhoea
cause
examples
2 diseases that cause this type of diarrhoea
caused by macronutrients malabsorption retaining osmotic pressure in the lumen and therefore water is retained in the lumen
Examples: pancreatic disease (protease, lipase, amylase), large intakes of sugar alchols, fructose or lactose intolerance, celiac disease
Lactose intolerance:
Lack of lactase enzyme
Celiac:
AID to gluten causing destruction of epithelial cells and severe bluting of villi causing nuteirnt malabsorption
Seceretory diarrhoea
what is it
cause
cellular process
An increase in active seceretion
Cause is E coli or cholera toxin exposure
Enterotoxins produced by bacteria raise intracellular conc of cAMP,cGMP, calcium
Leads to stimulation of anion secretion, especially CL-. To maintain a charge balance in the lumen Na+ is carried with it, along with water.
Oral rehydration therapy and purpose
Give Na, Cl and water
Given in IV
Correct loss of electrolytes
Restore fluid loss
Restore Na balance across brush border
to aid osmotic reabs in lumen
