Monogastric pt 8 Flashcards
What are the mechanisms of Na absorption?
- Na/ substrate transport (proximally)
- Na/ H and Cl/HCO3 in ileum and proximal colon
- Passive facilitated diffusion (ENaC) distal colon
What are the mechanisms of Cl absorption?
- Paracellular Cl absorption due to lumen negative
- Na/H and Cl/HCO3 in ileum and proximal colon
- Direct apical Cl/HCO3 exchange, ileum (villous cells) and colon (epithelial cells)
Where is HCO3 recovered?
- Pancreatic secretions
- Residual after neutralization of H+
- Incidental to Cl absorption
How does HCO3 get recovered?
Converted to CO2 by CA and then turns back to HCO3 and Na/H pumps proton out and bicarb leaves via Na/HCO3 cotransporter (SI and colon)
Where does water move?
Whatever direction is required to maintain iso-osmotic ingesta
How is K absorbed?
Paracellular diffusion in the ileum due to H2O absorption
What is the effect of diarrhea on K absorption?
K loss due to no gradient being built
Describe the growth of intestinal epithelium?
Stem cells proliferate and differentiate and migrate to the villous tips and are subsequently shed every 4-7 days and the process keeps going?
What regulates the rate of growth of the intestinal epithelium?
- Hormones
- Diet
- Feed intake
- Environment
Why do we need to have a delay in acid and pancreatic secretions in neonates?
Need to transfer antibodies from colostrum so you do not want them to degrade them. Want to transcytose intact proteins
What does inhibits the breakdown of proteins in colostrum?
Trypsin inhibitors
What is gut closure?
After 24 hrs no longer to transcytose intact proteins
What happens to lactase as neonates develop?
Starts to switch to maltase because there is less milk sugar
When do you get diarrhea?
From disease that causes mismatch of secretion and absorption
Enterotoxins have what effect?
Secretory mismatch: increased crypt secretion
