Digestion and Absorbtion - Dr A

"Malabsorption" Malabsorption - clinically definition for _____ unlike carbohydrates and proteins, fat can be measured easily in _______ Motility disorders - moving through too _________ Digestion disorder - pancreatitis/cystic fibrosis - (not enough _________) Absorption disorder - tropical and non-tropical sprue - resection of _________ __________

"Malabsorption" Malabsorption - clinically definition for fats unlike carbohydrates and proteins, fat can be measured easily in stool. Motility disorders - moving through too rapidly Digestion disorder - pancreatitis/cystic fibrosis - (not enough lipase) Absorption disorder - tropical and non-tropical sprue - resection of small intestine

Abnormalities of Carbohydrate Assimilation _________ ____________ - most common Symptoms - abdominal cramps, bloating, diarrhea, and flatulence Diagnosis - feed lactose - look for _____________ in plasma Cause - absence of ______ ________ _________ Lack of glucose/galactose carrier - rare diagnosed at _____ feed __________

Abnormalities of Carbohydrate Assimilation Lactose Intolerance - most common Symptoms - abdominal cramps, bloating, diarrhea, and flatulence Diagnosis - feed lactose - look for glucose in plasma Cause - absence of brush border lactase Lack of glucose/galactose carrier - rare diagnosed at birth feed fructose

Abnormalities of Protein Assimilation Pancreatic _____________ Pancreatitis or _________ _________ Decreased absorption - __________ in stool Congenital absence of _________ No trypsin - no other proteolytic enzymes Protein malabsorption Hartnup's disease cannot absorb _________ ________ ______ Neutral amino acids can still be absorbed as ___- and ____- peptides

Abnormalities of Protein Assimilation Pancreatic insufficiency Pancreatitis or cystic fibrosis Decreased absorption - nitrogen in stool Congenital absence of trypsin No trypsin - no other proteolytic enzymes Protein malabsorption Hartnup's disease cannot absorb neutral amino acids Neutral amino acids can still be absorbed as di- and tri- peptides

Absorption of Carbohydrates _____________ is rate limiting step in carbohydrate assimilation Glucose and galactose - _________ _________ _____________ compete for membrane carrier (________) energy from ????? Fructose - __________ diffusion (________) does not require _______ requires concentration gradient

Absorption of Carbohydrates Absorption is rate limiting step in carbohydrate assimilation Glucose and galactose - secondary active transport compete for membrane carrier (SGLUT-1) energy from Na+ - K+ ATPase Fructose - facilitated diffusion (GLUT-5) does not require energy requires concentration gradient

Digestion of Carbohydrates Starch digestion - Begins with ________ in saliva (___ digestion in mouth, up to ____ in stomach) Continues in small intestine with ________ _______________ Final digestion occurs at ______ ____________ Lactose and sucrose - digestion only occurs at ________ ___________

Digestion of Carbohydrates Starch digestion - Begins with -amylase in saliva (5% digestion in mouth, up to 40% in stomach) Continues in small intestine with pancreatic amylase Final digestion occurs at brush border Lactose and sucrose - digestion only occurs at brush border

Absorption of Vitamins Fat-soluble vitamins (_______) require _____ _______ to facilitate micelle for efficient absorption They are then incorporated into _____________ and enter the bloodstream via the lymphatic system. Water-soluble vitamins are absorbed by ____-dependent co-transport system B12 is released from dietary proteins by _________ _______ It then binds to ___ proteins, which are secreted in saliva. In the duodenum, trypsin digests the R protein, liberating ____, which then forms a complex with __________ __________ This B12-IF complex is resistant to the effects of t_______ and travels to the _________ _______, where it binds to specific receptors and is absorbed.

Absorption of Vitamins Fat-soluble vitamins (A,D,E,K) require bile salts to facilitate micelle for efficient absorption They are then incorporated into chylomicrons and enter the bloodstream via the lymphatic system. Water-soluble vitamins are absorbed by Na+-dependent co-transport system B12 is released from dietary proteins by gastric acid. It then binds to R proteins, which are secreted in saliva. In the duodenum, trypsin digests the R protein, liberating B12, which then forms a complex with intrinsic factor (IF). This B12-IF complex is resistant to the effects of trypsin and travels to the terminal ileum, where it binds to specific receptors and is absorbed.

Absorptive Pathway of Nutrients A nutrient must cross 8 barriers to be absorbed by blood or lymph (8)

Absorptive Pathway of Nutrients A nutrient must cross 8 barriers to be absorbed by blood or lymph 1. Unstirred layer 2. Glycocalyx 3. Apical cell membrane 4. Cytoplasm of enterocyte 5. Basolateral cell membrane 6. Intercellular space 7. Basement membrane 8. Wall of capillary or lymph vessel

Anatomical Basis for Absorption Total surface area of small intestine is _____________ m2 Small intestine - ___ m long Folds of Kerckring - ___-fold Villi - ___-fold Microvilli - _______-fold

Anatomical Basis for Absorption Total surface area of small intestine is 250 - 400 m2 Small intestine - 5 m long Folds of Kerckring - 3-fold Villi - 10-fold Microvilli - 1000-fold

Basic Steps of Lipid Assimilation Most dietary lipid is neutral fat or ____________. 3 main processes must occur for triglyceride to be absorbed into blood: ____________ - large aggregates of dietary triglyceride are broken down. ___________ _____________ - to yield monoglyceride and fatty acids. Both can diffuse into enterocyte. ____________ of triglyceride and chylomicron formation

Basic Steps of Lipid Assimilation Most dietary lipid is neutral fat or triglyceride. 3 main processes must occur for triglyceride to be absorbed into blood: Emulsification - large aggregates of dietary triglyceride are broken down. Enzymatic digestion - to yield monoglyceride and fatty acids. Both can diffuse into enterocyte. Reconstitution of triglyceride and chylomicron formation

Ca2+ ions are actively absorbed in the _________ _________ __________ and passively by ____________diffusion in the rest of the small intestine. The active absorption is dependent upon 1,25-dihydrocholecalciferol (1, 25-(OH)2-D3), the active form of ________, which is synthesized the kidney.

Ca2+ ions are actively absorbed in the proximal small intestine and passively by paracellular diffusion in the rest of the small intestine. The active absorption is dependent upon 1,25-dihydrocholecalciferol (1, 25-(OH)2-D3), the active form of vitamin D, which is synthesized the kidney.

Cl- is absorbed via cotransport with ____ or Cl-/_______ exchange

Cl- is absorbed via cotransport with Na+ or Cl-/HCO3- exchange

Cycle of small intestine enterocytes: Villi house a self-renewing population of epithelial cells with a ______ turnover Mechanism of absorption: ________ __________ (primary & secondary), passive __________, _________ _________ (endocytosis)

Cycle of small intestine enterocytes: Villi house a self-renewing population of epithelial cells with a 5-day turnover Mechanism of absorption: Active transport (primary & secondary), passive diffusion, facilitated diffusion (endocytosis)

Digestion: Involves breakdown or hydrolysis to nutrients to smaller molecules that can be absorbed in _______ ________) - (process?)

Digestion: Involves breakdown or hydrolysis to nutrients to smaller molecules that can be absorbed in small intestine) - carbs → monosaccharides, proteins → small peptides & aa's, fats → monoglycerides & fatty acids, vitamins → fat & water soluble, electrolytes

Familial lipoprotein lipase deficiency A rare genetic disorder characterized by _________ __________ of (_________ ___________) that breaks down fat molecules causes the accumulation of large quantities of fat (_____________) in the blood.

Familial lipoprotein lipase deficiency A rare genetic disorder characterized by deficient activity of (lipoprotein lipase) that breaks down fat molecules causes the accumulation of large quantities of fat (lipoproteins) in the blood.

Fluid Entering and Exiting the Gut An average adult ingests _______ of water per day, but the fluid load to the small intestine is _________. Most absorption of water and electrolytes occurs in the ______ __________, with some water absorbed in the colon as well.

Fluid Entering and Exiting the Gut An average adult ingests 1-2 L of water per day, but the fluid load to the small intestine is 9-10 L. Most absorption of water and electrolytes occurs in the small intestine, with some water absorbed in the colon as well.

Ingested ferric ions (Fe3+) are reduced to __________ ______ (Fe2+) by acid in the stomach by ________ _________ on the brush borders of the _________ __________ _________

Ingested ferric ions (Fe3+) are reduced to ferrous ions (Fe2+) by acid in the stomach by ferric reductase on the brush borders of the proximal small intestine

K+ is absorbed passively in the ________ _________. Most of its movement is _________ As ____ and _____ are absorbed, the volume of the luminal contents __________, resulting in an increase in [K+], ________ __________.

K+ is absorbed passively in the small intestine. Most of its movement is paracellular. As Na+ and H2O are absorbed, the volume of the luminal contents decreases, resulting in an increase in [K+], passive diffusion.

Lipid absorption: Most dietary lipids are neutral fat or triglycerides, before being absorbed into blood must have emulsification, enzymatic breakdown & reconstitution of triglyceride & chylomicron formation → _______ ______ _______ & glycerol - abnormalities are familial ____________ _______ _________, malabsorption (fat can be easily measured in ______ - _________ disorders, digestion disorders, absorption disorders)

Lipid absorption: Most dietary lipids are neutral fat or triglycerides, before being absorbed into blood must have emulsification, enzymatic breakdown & reconstitution of triglyceride & chylomicron formation → free fatty acids & glycerol - abnormalities are familial lipoprotein lipase deficiency, malabsorption (fat can be easily measured in stool - motility disorders, digestion disorders, absorption disorders)

Na+ is absorbed from the ______ into enterocytes by _______ _________ through Na+ channels cotransport with __________ and ______ ______, Na+/H+ exchange, neutral Na+/Cl- cotransport

Na+ is absorbed from the lumen into enterocytes by passive diffusion through Na+ channels cotransport with glucose and amino acids, Na+/H+ exchange, neutral Na+/Cl- cotransport

Protein Digestion and Absorption Luminal digestion produces ___ amino acids and ____ small peptides Amino acids secondary active transport (Na+ dependent) facilitated diffusion Di/Tripeptides different carrier system than amino acids absorbed faster than amino acids hydrolyzed to amino acids in cytoplasm

Protein Digestion and Absorption Luminal digestion produces 40% amino acids and 60% small peptides Amino acids secondary active transport (Na+ dependent) facilitated diffusion Di/Tripeptides different carrier system than amino acids absorbed faster than amino acids hydrolyzed to amino acids in cytoplasm

Protein digestion/absorption: Digestion occurs in intestinal lumen (stomach & small intestine), brush border & cytoplasm of mucosal cells; luminal digestion produces 40% of aa's & 60% of small peptides, aa absorbed via secondary active transport & facilitated diffusion, di/tripeptides absorbed via different carrier system - abnormalities are pancreatic insufficiency, congenital absence of trypsin (protein malabsorption), Hartnup's disease (cannot absorb neutral aa's unless as di/tri-peptides)

Protein digestion/absorption: Digestion occurs in intestinal lumen (stomach & small intestine), brush border & cytoplasm of mucosal cells; luminal digestion produces 40% of aa's & 60% of small peptides, aa absorbed via secondary active transport & facilitated diffusion, di/tripeptides absorbed via different carrier system - abnormalities are pancreatic insufficiency, congenital absence of trypsin (protein malabsorption), Hartnup's disease (cannot absorb neutral aa's unless as di/tri-peptides)

Sites of Absorption Stomach - (3) Duodenum and Jejunum - (4) Ileum - ______ _____ and __________ ___ - major ________ significance Colon - _______ and ______________ Rectum - drugs such as __________ and _____________

Sites of Absorption Stomach - ethanol, NSAIDs, aspirin Duodenum and Jejunum - nutrients, vitamins, various ions, water and electrolytes Ileum - bile salts and vitamin B12 - major clinical significance Colon - water and electrolytes Rectum - drugs such as steroids and salicylates

Sodium Electrochemical Gradient Single most important process in _________ __________ to make absorption of nutrients possible is the: establishment of electrochemical gradient of sodium across epithelial cell boundary of lumen (_______ membrane).

Sodium Electrochemical Gradient Single most important process in small intestine to make absorption of nutrients possible is the: establishment of electrochemical gradient of sodium across epithelial cell boundary of lumen (apical membrane).

Sprue Diseases that result in decreased ______________ caused by ______________ even when food is well digested are often classified as "sprue" - - Non-tropical sprue - also called ________ _________ - allergic to gluten (wheat, rye) - destroys __________ and sometimes _____ - Tropical sprue - bacterium (______) - treated with antibacterial agents - _____, folate and iron deficiency

Sprue Diseases that result in decreased absorption caused by inflammation even when food is well digested are often classified as "sprue" - - Non-tropical sprue - also called celiac disease - allergic to gluten (wheat, rye) - destroys microvilli and sometimes villi - Tropical sprue - bacterium (E coli) - treated with antibacterial agents - B12, folate and iron deficiency

Sprue: Diseases that result in decreased absorption caused by inflammation even when food is ______ ______________ - nontropical (celiac disease, allergic to ________) or tropical (__________ infection)

Sprue: Diseases that result in decreased absorption caused by inflammation even when food is well digested - nontropical (celiac disease, allergic to gluten) or tropical (bacterial infection)

Types of Digestion Luminal/cavital digestion: Occurs in lumen of ___ tract, enzymes from where can do what? Membrane/contract digestion: Enzymes on ????

Types of Digestion Luminal/cavital digestion: Occurs in lumen of GI tract, enzymes from salivary glands/stomach/pancreas, pancreatic enzymes can do all Membrane/contract digestion: Enzymes on brush border of enterocytes

Villi house self-renewing population of ___________ cells with a 5-day turnover Cell types in villus include: (4) Cells in enterocyte lineage divide and differentiate as they migrate up the ______, becoming ________ _______ _________ Enterocytes are shed into lumen to become part of _____________ to be digested and absorbed

Villi house self-renewing population of epithelial cells with a 5-day turnover Cell types in villus include: secretory cells, endocrine cells, goblet cells, and mature absorptive epithelial cells Cells in enterocyte lineage divide and differentiate as they migrate up the crypts, becoming mature absorptive cells Enterocytes are shed into lumen to become part of ingestants to be digested and absorbed