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NUTR 4320 MIDTERM STUDY GUIDE
Absorption in the small intestine - Answers - kerckring folds, villi, microvilli Surface area of the small intestine - Answers - tennis court Peristalsis is mediated by - Answers - longitudinal and circular muscles Enterocytes - Answers - intestinal epithelial cells Colonocytes - Answers - colon epithelial cells Apical membrane - Answers - faces the lumen of the small intestine Basolateral membrane - Answers - faces the lamina propria Lacteals - Answers - sites of lipid absorption and lymphatic vessels Apical junctional complexes - Answers - hold intestinal epithelial cells tightly together Goblet cells are - Answers - dispersed through the intestinal epithelial cell barrier Goblet cells secrete - Answers - mucin Mucus - Answers - mucin mixes with water to create Lamina propria (and blood vessels and lymphatics) - Answers - below the epithelial barrier Amplifying zone - Answers - where stem cells differentiate into mature cells types as they move up the crypt Cell turnover occurs at - Answers - the top of the villi (old cells slough off and are lost in the feces) The intestinal epithelial barrier is replaced - Answers - about twice a week (every 2- 3 days) High rate of cell turnover = - Answers - high risk of cancer Layers of the small intestine (inner- to outer-most) - Answers - mucosa, submucosa, muscularis externa, serosa Mucosa is important for - Answers - nutrient absorption, protection, mucosal immune cells
Submucosa is made up of - Answers - connective tissue and contains lymphatic and blood vessels Muscularis externa is a - Answers - smooth muscle layer Serosa is - Answers - an outer connective tissue layer that functions in protection The small intestine has - Answers - crypts and villi The colon has crypts - Answers - but no villi Compared to the small intestine, the colon has a - Answers - thicker mucus layer Microbiota - Answers - all the bacteria that reside in an established environment Microbiome - Answers - all the genetic material found within the microbiota Symbiotic relationship - Answers - gut microbiota and human host LGR+ - Answers - marker for colonic stem cells Lactose is a - Answers - disaccharide (galactose + glucose) 1 L milk = - Answers - 48 g lactose Lactase is expressed in - Answers - the small intestine (jejunum and ileum) Transports galactose and glucose (not fructose) across the apical border with two sodium molecules (sodium-dependent) - Answers - SGLT1 (sodium glucose-linked transporter 1) Four (two per monosaccharide unit of the disaccharide) - Answers - SGLT1 requires how many sodium molecules per molecule of lactose Transports fructose across the apical border by facilitated diffusion (sodium- independent) - Answers - GLUT5 (glucose transporter 5) Transports all monosaccharides across the basolateral membrane by facilitated diffusion (sodium-independent) - Answers - GLUT2 (glucose transporter 2) Low [Na+] inside the cell and high [Na+] outside the cell - Answers - concentration gradient The Na+/K+ pump has continuous activity to - Answers - continuously remove sodium from inside the cell
Activators of lactase gene expression - Answers - Oct-1, HNF1-alpha, Cdx-2, GATA- 4/5/ HNF1-alpha, Cdx-2, GATA-4/5/6 - Answers - bind to the lactase gene and increase mrna expression Oct- 1 - Answers - binds to both the MCM6 and lactase gene Pdx- 1 - Answers - transcription repressor that binds to the lactase promoter (decreases lactase expression) Higher methylation of lactase gene in individuals with lactase - Answers - non- persistence (methylation also increases with age) Bacterial fermentation of undigested lactose in the large intestine produces - Answers - short-chain fatty acids and gases Acids produced in lactose intolerance - Answers - lactic acid Scfas produced in lactose intolerance - Answers - acetic acid, propionic acid, butyric acid Gases produced in lactose intolerance - Answers - hydrogen, carbon dioxide, and methane gas Some bacteria in the large intestine express - Answers - beta-galactosidase, which breaks the glycosidic bond in lactose to free glucose and galactose Bacteria in the large intestine that ferment the disaccharide lactose or it's monosaccharides - Answers - enterobacter, citrobacter, klebsiella, escherichia coli, serratia, streptococcus Non-lactose fermenting bacteria - Answers - salmonella, shigella Acids in the colon lumen - Answers - decrease ph In the colon, undigested lactose acidifies - Answers - leading to an increased osmotic load (increased water) Variability in the symptoms of lactose intolerance - Answers - transit time, genetics, lactase expression and activity, microbial composition Diagnosing lactose intolerance - Answers - exclusion diagnosis and breath hydrogen test Breath hydrogen test - Answers - > 20 suggests lactose intolerance
Treatment of lactose intolerance - Answers - aversion, calcium and vitamin D supplements, lactase enzyme supplements Fats - Answers - slow gastric emptying Lactase deficiency is seldom - Answers - total (patients often retain some ability to digest lactose) Unpasteurized dairy has - Answers - bacterial beta-galactosidase activity that survives the low ph in the stomach Pasteurization destroys - Answers - beta-galactosidase activity Strepococcus lactis and streptococcus cremoris are - Answers - lactose fermenters found in cultured milk products Sweet acidophilus milk - Answers - non-fermented milk that is supplemented with lactobacillus acidophilus (can be used as a probiotic) Osteoporosis - Answers - decreased bone mineral density, bone quantity, and bone quality due to changes in bone structure Risk factors for osteoporosis - Answers - female, old, inactive, malnutrition DXA - Answers - determines bone strength and mineral density to diagnose osteopenia and osteoporosis Osteopenia - Answers - reduced bone mass and mineral density Trabecular bone - Answers - spongy bone Cortical bone - Answers - compact bone Calcium, all of it, is provided through - Answers - diet Bone (including teeth) - Answers - 99% of calcium stores in the body are in 9 - 10 mg/dl - Answers - blood calcium levels should be maintained around What is calcium used for - Answers - skeletal and smooth muscle contraction, as a second messenger, needed for neurons Calcium is absorbed in the - Answers - small intestine Calcium is reabsorbed in the - Answers - kidney
Passive diffusion (paracellular transport) or calcium channels (TRPV6) - Answers - calcium uptake from the intestinal lumen and across the apical membrane occurs through Passive diffusion of calcium across the apical membrane only works with - Answers - the consumption of a large amount of calcium; mechanism decreases as lumen calcium concentration decreases Calbindin - Answers - binds calcium together and shuttles it in two directions: from the apical to the basolateral membrane and to and from intracellular stores in the mitochondria and ER Calcium is moved across the basolateral membrane and into the bloodstream by - Answers - sodium-calcium exchanger and calcium pump Sodium-calcium exchanger - Answers - 3 sodium in for every calcium out Calcium pump - Answers - one hydrogen in for every calcium out (ATP-dependent) Parathyroid hormone inhibits bone-forming reactions - Answers - type-1 collagen formation and osteocalcin production in osteoblasts Active parathyroid hormone is stored in - Answers - vesicles Pre-pro PTH is transcribed in the - Answers - ribosome Pre-pro PTH has it's signal cleaved and then - Answers - pro PTH moves into the endoplasmic reticulum Activates a signaling pathway that stops parathyroid hormone release - Answers - binding of calcium to the casr (calcium-sensing receptor) Mutation in casr and dysfunction in TRPV5 - Answers - familial hypercalcemic hypocalciuria Makes it unresponsive to changes in blood calcium levels, meaning that parathyroid hormone and bone resorption are sustained - Answers - mutation in casr (FHH) Excess calcium is not moved into the urine, it stays in the kidney and forms kidney stones - Answers - dysfunction of TRPV5 (FHH) Cortical bone - Answers - 80% of bones mass Trabecular bone - Answers - undergoes constant turnover Osteoblasts - Answers - bone-forming (ossification)
Osteoclasts - Answers - bone-resorbing Osteocytes - Answers - old osteoblasts embedded in the bone matrix Osteocytes sense - Answers - mechanical stress on bone and secrete growth factors that stimulate new osteoblast and bone formation Stem cells --> - Answers - osteoblast --> osteocyte M-CSF (macrophage colony stimulating factor) is a - Answers - secreted protein and not a transcription factor M-CSF stimulates - Answers - RANK expression RANK - Answers - a cell surface receptor on pre-osteoclasts RANK - Answers - RANK ligand binds Osteoblasts - Answers - RANK ligand is secreted by Osteogenic cell can mature into - Answers - hematopoietic stem cells (pre-osteoclasts -- > mature osteoclasts) or mesenchymal stem cells (pre-osteoblasts --> mature osteoblasts) Bone resorption, matrix formation, mineralization, resting - Answers - bone remodeling cycle Give bone its tensile strength and stability - Answers - type 1 collagen fibres Provide sites for nucleation of hydroxyapatite crystals - Answers - chondroitin sulfate and hyaluronic acid
