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PHGY 210 (301)
Lecture

Digestive System.docx

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Department
Physiology
Course
PHGY 210
Professor
K.Andrew White
Semester
Winter

Description
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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