The document summarizes gastrointestinal absorption in the small intestine and large intestine. It describes the folds, villi, and microvilli that increase the surface area for absorption. It explains the active transport of nutrients like sodium, calcium, and proteins through epithelial cells and their transport across membranes. Finally, it briefly outlines the composition of feces and factors that determine its color and odor.

1. GASTROINTESTINAL ABSORPTION
• FOLDS OF KERCKRING: THREEFOLD, EXTEND
CIRCULARLY, 8 mm INTO LUMEN
• VILLI: ON THE EPITHELIAL SURFACE OF
SMALL INTESTINE ,1 mm, 1O FOLDS,
• BRUSH BORDERS: EACH EPITHELIAL CELL ON
EACH VILLUS, 1000 MICROVILLI,
PROTRUDING INTO INTESTINAL CHYME, 20
FOLDS
• COMBINATION OF FOLDS OF KERCKRING,
VILLI, MICROVILLI: 1000 FOLLDS

3. LONGITUDINAL SECTION OF VILLUS
• VASCULAR SYSTEM FOR ABSORPTION AND DISSOLVED MATERIAL
INTO PORTAL BLOOD
• CENTRAL LACTEAL LYMPH VESSELS
• PINOCYTIC VESICLES: (PORTIONS OF ENTEROCYTES MEMBRANE),
ABSORBED FLUIDS ENTRAPPED IN VESICLES
• EXTENDING FROM EPITHELIAL CELL INTO MICROVILLUS: MULTIPLE
ACTIN FILAMENTS, CONTRACT, CONTINUALLY MOVEMENT OF THE
MICROVILLI, EXPOSED TO NEW QUANTITIES OF INTESTINAL FLUID

4. ABSORPTION IN SMALL INTESTINE
• SEVERAL HUNDRED GRAMS CARBOHYDRATE, 100 GM FAT, 50-100
GM AMINOACIDS, 50 -100 GRAMS IONS, 7-8 LITERS WATER/DAY
ABSORPTION OF WATER
THROUGH INTESTINAL TO BLOOD: OSMOSIS
CHYME DILUTED: WATER ABSORBED INTO BLOOD BY OSMOSIS
HYPEROSMOTIC FLUID: WATER TRANSFERRED FROM PLASMA INTO
CHYME

5. SODIUM IS ACTIVELY TRANSPORTED THROUGH THE INTESTINAL
MEMBRANE
• 25- 35GMS OF SODIUM ABSORB
• SODIUM ACTIVELY TRANSPORTED FROM INSIDE OF EPITHELIAL CELLS
INTO PARACELLULAR SPACES THROUGH BASOLATERAL MEMBRANE
• REDUCE SODIUM CONC INSIDE THE CELL AND HIGH IN CHYME SO
SODIUM MOVES THROUGH CHYME TO BRUSH BORDERS OF
EPITHELIAL CELLS INTO EPITHELIAL CELL CYTOPLASM
ALDOSTERONE GREATLY ENHANCES SODIUM ABSORPTION
DEHYDRATION, INCREASE SODIUM ABSORPTION BY INTESTINAL
EPITHELIUM
• ALDOSTERONE CONSERVE SODIUM CHLORIDE AND WATER IN BODY

6. ABSORPTION OF CHLORIDE IONS
• ABSORPTION OF CHLORIDE BY DIFFUSION, ABSORPTION OF SODIUM
IONS THROUGH EPITHELIUM CAUSES ELECTRONEGATIVITY IN THE
CHYME AND ELECTROPOSITIVITY IN PARACELLULAR SPACES B/W
EPITHELIAL CELLS
• CHLORIDE ALSO ABSORBED ACROSS BRUSH BORDERS MEMBRANE IN
ILEUM AND LARGE INTESTINE
ABSORPTION OF BICARBONATE IONS FROM UPPER SMALL INTESTINE
SODIUM IONS ABSORBED, H ION SECRETED INTO GUT, WHICH
COMBINE WITH BICARBONATE IONS FORM CARBONIC ACID,
DISSOCITAD CO2 AND WATER, CO2 EXPIRED THROUGH LUNGS AND
WATER REMAIN AS PART OF CHYME

7. SECRETION OF BICARBONATE IONS IN ILEUM AND LARGE INTESTINE
• EPITHELIAL CELLS ON SURFACE OF VILLI(SMALL INTESTINE) AND
LARGE INTESTINE: SECRETING BICARBONATE IONS IN EXCHANGE OF
ABSORPTION OF CHLORIDE IONS
 ALKALINE BICARBONATE NEUTRALIZE ACID FORMED BY BACTERIA IN
LARGE INTESTINE

8. ACTIVE ABSORPTION OF CALCIUM, IRON, POTASSIUM,
MAGNESIUM AND PHOSPHATE
CALCIUM IONS: ACTIVELY ABSORBED INTO BLOOD FROM DUODENUM,
CALCIUM ION ABSORPTION CONTROLLED DAILY NEED OF THE BODY,
PARATHYROID HORMONE ACTIVATE VIT D AND ENHANCE CALCIUM
ABSORPTION
IRON IONS: ACTIVELY ABSORBED FROM SMALL INTESTINE, IRON
ABSORPTION IN PROPORTION TO BODY NEED FOR IRON
POTASSIUM, MAGNESIUM, PHOSPHATE AND OTHER IONS: ACTIVELY
ABSORBED THROUGH INTESTINAL MUCOSA
MONOVALENT IONS: ABSOPTION IN GREAT QUANTITIES AS COMPARE
TO BIVALENT

9. ABSORPTION OF NUTRIENTS
CARBOHYDRATES ARE MAINLY ABSORBED AS MONOSACHARIDES
GLUCOSE IS FINAL DIGESTION PRODUCT OF MOST OF CARBOHYDRATE
ABSORBED BY ACTIVE TRANSPORT PROCESS
GLUSOSE IS TRANSPORTED BY A SODIUM Co-TRANSPORT MECHANISM
• TWO STAGES IN THE TRANSPORT OF SODIUM THROUGH INTESTINAL
MEMBRANE
• FIRST ACTIVE TRANSPORT OF SODIUM IONS THROUGH BASOLATERAL
MEMBRANES OF INTESTINAL EPITHELIUM CELLS INTO THE BLOOD
• SODIUM FROM INTESTINAL LUMEN MOVE THROUGH BRUSH BORDER
OF EPITHELIAL CELLS TO INTERIOR BY SECONDARY ACTIVE TRANSPORT

10. TRANSPORT PROTEIN
• SODIUM ION COMBINES WITH A TRANSPORT PROTEIN, COMBINE
WITH OTHER APPROPRIATE SUBSTANCE, GLUCOSE, TRANPORTED
TOGETHER TO INTERIOR OF CELL, THEN INTO THE BLOOD
• GALACTOSE TRANSPORTED BY SAME MECHANISM AS GLUCOSE
• FRUTOSE IS TRANSPORTED BY FACILITATED DIFFUSION THROUGH
INTESTINAL EPITHELIUM,
• RATE OF TRANSPORT IS ABOUT ONE HALF THAT OF GLUCOSE OR
GALACTOSE

11. ABSORPTION OF PROTEIN AS DIPEPTIDES, TRIPEPTIDES OR AMINO
ACIDS
• LUMINAL MEMBRANES OF INTESTINAL EPITHELIAL CELLS
• ENERGY SUPPLIED BY SODIUM Co TRANSPORT MECHANISM
• BIND WITH CELL'S MICROVILLUS MEMBRANE WITH SPECIFIC
TRANSPORT PROTEIN REQUIRE SODIUM BINDING BEFORE
TRANSPORT
• MOVES DOWN ITS ELECTROCHEMICAL GRADIENT TO INTERIOR OF
CELL, PULLS AMINO ACIDS ALONG WITH IT, Co TRANSPORT
• SPECIAL MEMBRANE TRANSPORT PROTEINS IN LUMINAL MEMBRANE
AND TRANSPORTED BY FACILITATED DIFFUSION
• MULTIPLE TRANSPORT PROTEINS B/C DIVERSE BINDING PROPERTIES
OF AMINO ACIDS

12. ABSORPTION OF FATS
• DIGESTIVE END PRODUCTS, DISSOLVE IN LIPID PORTIONS OF
MICELLES
• BILE MICELLES CARRIED TO SURFACES OF MICROVILLI OF INTESTINAL
BRUSH BORDER, PENETRATE INTO SPACES B/W THE MOVING
MICROVILLI
• MONOGLYCERIDES AND FATTY ACIDS DIFFUSE OUT OF MICELLES INTO
INTERIOR OF EPITHELIAL CELLS, CELL'S SMOOTH ENDOPLASMIC
RETICULUM USED TO FORM TRIGLYCERIDES
• FLOW THROUGH THORACIC LYMPH DUCT AND EMPTY INTO
CIRCULATING BLOOD
• SHORT CHAIN FATTY ACIDS ABSORBED DIRECTLY INTO PORTAL
BLOOD, DIRECT DIFFUSION OF SHORT CHAIN FATTY ACIDS, FROM
INTESTINAL EPITHELIAL CELLS INTO CAPILLARY BLOOD OF INTESTINAL
VILLI

13. ABSORPTION IN LARGE INTESTINE
• I.5 LITER CHYME PASS
• MOSTLY WATER AND ELECTROLYTES ABSORBED, 100 ML FLUID AND
FEW SODIUM AND CHLORIDE IONS LOST IN FECES
• HIGH CAPABILITY FOR ACTIVE ABSORPTION OF SODIUM
• TIGHT JUNCTIONS B/W EPITHELIAL CELLS PREVENT BACK DIFFUSION
OF IONS, ALDOSTERONE ENHANCE SODIUM TRANSPORT CAPABILITY
• CHLORIDE IONS ABSORBED DUE TO ELECTRICAL POTENTIAL GRADIENT
• BICARBONATE IONS SECRETE, EQUAL NUMBER OF CHLORIDE IONS
ABSORBED
• DUE TO OSMOTIC GRADIENT, WATER ABSORPTION

14. COMPOSITION OF FECES
• THREE-FOURTHS: WATER
• ONE-FOURTH: SOLID MATTER
• DEAD BACTERIA,FAT, INORGANIC MATTER,PROTEIN,UNDIGESTED
FOOD, DIGESTED SECRETION (BILE PIGMENT), EPITHELIAL CELLS
• COLOUR: STERCOBILIN, UROBILIN
• ODOR: BACTERIAL ACTION, DEPEND ON PERSON'S COLONIC
BACTERIAL FLORA AND TYPE OF FOOD