Digestion 5 small intestines and large

Two structures; Brunners gland and crypts of Lieberkuhn

BRUNNERS; mucus to protect SI mucosa from dmage by stomach acid.

LIEBERKUHN’S; from two different cellular types;

    i. Cryptic goblet cells; mucus to lubricate food and protect intestinal mucosa

   ii. Cryptic enterocytes; fluids that add to intestinal chyme and aid in digestion and absorption( fluid similar to ECF in terms of electrolyte composition). Ion movement is bidirectional and occur via trnascellular and paracellular routes

        iii. Paneth cells; produce antimicrobial substances that protect the intestinal tract from pathogens and contribute to overall gut health.

                1. paracellular is passive, in response to gradients(conc,electric,osmotix and hydrostatic)

                 2. transcelluar is active and passive transport mechanism

Driving froce of secretion of fluid is thr cl- moving from serosal to lumen.

The (NA+ - K+ - 2Cl-) carrier in basolateral helps accumulate Cl- in the cell. Cl- then exists the cell at apical membrane via (CFTR) Cl- channel. Na+ and K+ regulated by Na+ pump and a basolateral K+ channel.

These transporters regulated by Ca2+, cAMP and cGMP

SI digestive enzyme aanchored in brush border membrane of epithelial cell

LARGE INTESTINES

Colonic glands limited to that of mucus; it lubricates forming stool,protects intestinal mucosa and prevents overgrowth of fecal bacteria.

Mucus also has HCO3- from non mucus secreting epithelial cells

Bacteria produce acid and is remived from its epithelial cells by

    1 Cl- / HCO3- exchanger. 2 Na+ / H+ exchanger

Its mucus can also secrete large amounts of H20 and electrolytes to dilute and was away the irritant.