SMALL INTESTINE H.3

SMALL INTESTINE STRUCTURE SHORT DUODENUM-LIVER & PANCREATIC JUICES ENTER TWO LONG SECTIONS-JEJUNUM & ILLEUM 2 LAYERS OF SMOOTH MUCSLE (CIRCULAR & LONGITUDINAL)

MUSCLES CONTRACT & MOVE FOOD ALONG (PERISTALSIS) MUCOSA FORM VILLI EACH VILLUS HAS A CAPPILLARY BED & A LACTEAL (SMALLEST VESSEL OF LYMPHATIC SYSTEM)

ABSORPTION EACH VILLUS HAS MANY MICROVILLI THEY INCREASE SURFACE AREA FOR ABSORPTION SOME MOLECULES ARE ABSORBED BY ACTIVE TRANSPORT EPITHELIAL VILLI CELLS ARE ABUNDANT IN MITOCHONDRIA

PINCYTOTIC VESICLES ARE NEAR THE PLASMA MEMBRANES & ALSO ABSORB MOLECULES INTO VILLI CELLS FROM LUMEN

TIGHT JUNCTIONS EPITHELIAL CELLS HAVE TIGHT JUNCTIONS BETWEEN ECAH CELL SO THAT NOTHING MOLECULES MOVE IN BETWEEN THE CELLS ONLY COMPLETELY DIGESTED MOLECULES CAN ENTER THE BLOOD & LYMPH SYSTEM VIA LACTEAL

JUNCTIONS SHARE CELL PROTEINS & ARE SEALED

MECHANISMS FOR ABSORPTION FACILLITATED DIFFUSION – PROTIEN CHANNELS ALLOW FOR CONCENTRATION GRADIENTS TO DIFFUSE MOLECULES FROM INTESTINAL LUMEN INTO CYTOPLASM OF VILLI CELLS

ACTIVE TRANSPORT – USED WHEN A MARKED CONCENTRATION GRADIENT DOES NOT EXIST & ENERGY IS NEEDED TO TRANSPORT THE MOLECULES INTO THE VILLI CELLS

PINCYTOSIS – ALLOWS SMALL DROPLETS OF FLUIDS TO ENTER THE VILLI CELLS & THEN CONTENTS ARE RELEASED INTO CYTOPLASM & DIFFUSE INTO LACTEAL

WHAT’S NOT ABSORBED? CELLULOSE LIGNIN BILE PIGMENTS (COLON TO FECES) BACTERIA (NORMAL INTESTINAL INHABITANTS) INTESTINAL CELLS (BROKEN OFF AS FOOD MOVES THRU LUMEN)

LARGE INTESTINE REABSORBS H₂O & IONS NATURALLY OCCURRING BACTERIA RECEIVE NUTRIENTS, WARMTH, & WATER BACTERIA SYNTHESIZE VITAMIN K UNDIGESTED MATERIAL IS ELIMINATED AS SOLID WASTE