Luminal and membranous phase of digestion

LUMINAL AND MEMBRANOUS PHASE OF DIGESTION


Luminal phase

  • In luminal phase of digestion, alpha amylase  is secreted by  the salivary glands (eg. pig, dog and  rabbit), and pancreatic amylase  hydrolyses starches to yield oligosaccharides (a -dextrins, maltotriose, maltose  without free glucose),whereas fibrous carbohydrates (eg. Cellulose and hemicellulose) can not be hydrolysed by alpha amylase of mammals. 
  • Hydrolysis of amylopectin produces branched-chain oligosacchrides, limit dextrins and alpha 1, 6-linked disaccharide, isomaltose. 

Membranous phase

  • The oligosaccharides, di- and tri-saccharides are hydrolysed by saccharidases enzymes like maltase, isomaltase, sucrase and lactase in the membranous phase.
  • In the glycocalyx of enterocytes, these enzymes hydrolyse the oligosaccharides (eg. maltose, sucrose and lactose)  to monosaccharides (glucose, galactose, and fructose).

  • Most of the monosaccharides are absorbed into the portal blood and carried to liver. some are also absorbed through lymph stream. 

Phase
Last modified: Thursday, 9 June 2011, 5:12 AM