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Digestive System.docx

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PHGY 210
K.Andrew White

Digestive System Gastrointestinal Tract Provides nutrients to maintain homeostasis Site of nutrient processing providing raw materials for growth, repair, function & regulation Anatomy Earthworm o Hollow tube with lumen (central cavity) Mammals o Hollow tube with lumen o Communication with external environment @ both ends o 3X longer then height of person Extreme folding Up to 9X longer in cadaver o Interior lining 600X > exterior lining 200-250m (1/2 tennis court) o Sequence of specialized organs that are interconnected Serosa o Thin tough layer of connective tissue o Surrounds tube Muscularis externa o Muscular layer Straited Oral cavity Pharynx Upper 1/3 esophagus External anal sphincter Smooth Between upper 1/3 of esophagus & external anal sphincter Outer layer Longitudinal fibers Inner layer Circular fibers Submucosa o Loose connective tissue Nerce cell bodies Ganglia Blood vessels Lymphatics Mucosa o 3 distinct smaller layers Muscularis mucosae Smooth muscle Lamina propria Loose connective tissue Epithelial layer Absorption Endocrine secretion Exocrine secretion Functions Motility/Propulsion Pressure gradient - Variations in - resistance Segmentation Myogenic response to distension ENS organizes Parasympathetic Sympathetic Alternating relaxation & contraction Peristalsis Propagated wave Ring moves along Narrowing lumen 8-10 seconds Smooth Frequency of swallowing Flow under normal Slow conditions Aboral Little to no resistance Secretion How Glandular activity Result Chemical breakdown via enzymes & fluids Where In mucosa Absorption Regulation Local enteric reflexes Vagal-vagal interactions Hormones Quantities of 50% ions circulate daily exchange 80g proteins released in lumen daily 9L fluids absorbed daily 7L absorbed by small intestine 2L absorbed in colon Mal-absorption Dehydration & electrolyte imbalance Where Sites of exchange need abundant blood supply Colon Water & ions Small intestine Duodenum o Fe, Ca, CHO, proteins, lipids, water, Na Jejunum o CHO, proteins, lipids, water, Na Ileum o Vitamin B12 & bile acids (not fat!) How Simple diffusion Facilitated diffusion Active transport Pinocytosis Osmosis Requirements Adequate digestion Enzymes activated by enterokinases for proteases pH level Ion Sufficient breakdown Adequate size <50% surface area Distal ileum for bile salt absorption & intrinsic factor Adequate transport time 2-6 hours Adequate co-factors Intrinsic factor for B12 Co-lipase for pancreatic lipase Specific transporters Results 99% carbs = absorbed 95% fats = absorbed 92% proteins = absorbed Highly efficient system ! 0! ! 7E! ! ! ! : KY!QK]M!eXQPOOTMU!a!. #" #!a#; ' 2 !2 )6( ' m#b! Myenteric Interconnection between plexuses o Muscle cells o Epithelial cells o Allows for single stimulus to activate a lot of cells Pre-programmed relay between ganglia Relaxation at one point = ! contraction at anotherVOHPU!ZO\P!WMNXUMU!QTSQM`! Result of single stimulus #WT\MRQ!VMRU! ! !!!!! ! T^ Q'_TS'PVON'QU] \\Q'T'PXZPRN'P'OV!_XPVR'd'T_'Q'W o 9KMFWKH]KQL LI !QY!^MZ MP!]QP]Q' ! 6OTL XQMI /' ! )P\T^TMI /' o 3QP!\QS!KMQNQTHP!Q!HP!HTP!^X!VHPKQVTHP!Q!QPH\K' ! ' U!KUXO!HJP]RM!TL XXU'
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