Download Science Textbooks Books for FREE. All formats available for PC, Mac, eBook Readers and other mobile devices. Large selection and many more categories to. Download Human Anatomy and Physiology PDF 37P Download free online book chm pdf. Welcome to MedbooksVN formally medbooksvn. Free Medical Books site, which has been built up with all our heart and brain. We are proud of spreading free. With a focus on human integrative and translational physiology, the European Journal of Applied Physiology publishes original research that is considered likely to. Physiology Books Pdf' title='Physiology Books Pdf' />Medical PhysiologyGastrointestinal PhysiologySecretions Wikibooks, open books for an open world. Secretions in the GI tracteditAbout 9 liters of fluid pass through the gastrointestinal system each day, and only about 2 liters are ingested, the rest represent secretions from the system itself. About half, 3. 5, liters is secreted from the exocrine glands, the salivary glands, the pancreas and the liver, the other half is secreted by the epithelial cells of the of the digestive tract it self. Nearly all this fluid is absorbed, so the pellets of feces only contain a significant amount of fluid in diarrhea. To put this in perspective a 7. Kilogram man has about 4. The circulation contains about 3. Failures of absorption of the intestinal secretions can thus lead to rapid dehydration and electrolyte imbalance. The secretions consist of digestive enzymes, mucous and substantial amounts of fluid and ions. Daily Volumep. HSaliva. Stomach. 15. 00. 1. Providing researchers with access to millions of scientific documents from journals, books, series, protocols and reference works. Brunners Glands duodenum2. Pancreas. 10. 00 1. Bile. 10. 00. 7. 8. Small Intestine. 18. Large Intestine. 20. Physiology Books Pdf' title='Physiology Books Pdf' />Total. Types of glandseditSeveral different types of gland are found in the GI Tract Single cell mucous glands and goblet cells. Pit glands. Invaginations of the epithelia into the submucosa. In the small intestine these are called Crypts of Lieberkuhn. Deep tubular glands. These are found in the stomach the gastric glands, and the upper duodenum Brunners glands. Complex glands, the salivary glands, the pancreas, and the liver. The salivary glands and the pancreas are compound acinous glands. Mechanisms of stimulationeditStimulation occurs due to local effects autonomic stimulation and hormones. Local effectseditThe mechanical presence of food causes stimulation not only locally but also adjacent regions. This may either be a direct effect, or via. Autonomic stimulationeditStimulation of parasympathetic nerves invariably serve to increase secretion. Stimulation of sympathetic nerves may increase some secretions, but usually diminishes blood flow, which will usually decrease overall secretion. HormoneseditSeveral different hormones affect secretions. They will be looked at in the regional review of secretions. Digestive EnzymeseditDigestive enzymes are secreted by glandular cells which will store the enzyme in secretory vesicles until they are ready to be released. These cells are characterised by a robust rough endoplastic reticulum and numerous mitochondria. Passage of materials from the ribosomes, through the endoplasmic reticulum and Golgi body to the secretory vesicles takes about 2. Note the presence of nerve fibers on the basal side of the cell. Water Electrolyte secretionseditGlandular secretions must also secrete water and electrolytes to go along with the organic substances. The following illustration shows the most likely mechanism for this. In its resting state the membrane resting potential is about 3. VNeural stimulation causes an influx of ve chloride ions decreasing resting potential by 1. VSodium ions follow down the electrical gradient. Cell contents become hyper osmotic. Water follows. Intracellular pressure increases. Increased pressure opens ports on apical side of cell flushing water and electrolytes. Micro electrode studies indicate that the whole process lasts about a second Digestive Enzymes of the GI tracteditThe following table shows a summary of the digestive enzymes of the GI tract Location. Enzyme Name. Action. Salivary Glands. Amylase. Lingual Lipase. Starch. Triglycerides limited actionStomach. Pepsin pepsinogenGastric Lipase. Proteins. Triglycerides. Pancreas. Amylase. Bootloader Iso Download. Lipase Colipase. Phospholipase. TrypsinTripsinogenChymotripsinChymotripsinogenStarch. Triglycerides. Phospholipids. Peptides. Peptides. Intestinal Epithelium. Enterokinase. Disaccharidases. Sucrase. Maltase. Lactase. Peptidases. Endopeptidases. Exopeptidases. Aminopeptidase. Carboxypeptidase. Activates Trypsin. Disaccharides. Sucrose. Maltose. Lactose. Peptides. Interior peptide bonds. Terminal peptide bonds. Amide end of of peptide. Cobxyl end of peptide. Note that in both the stomach and the Pancreas the protein digesting enzymes are secreted in non active forms pepsinogen in the stomach and Tripsinogen and Chymotripsinogen in the pancreas. This is to prevent autodigestion. They are then activated in the lumen, in the case of Tripsinogen and Chymotripsinogen these are activated by the small intestine enzyme enterokinase. Digestive Hormones of the Gastrointestinal tracteditNumerous hormones are secreted by the Gastrointestinal system. Here is a summary of the most important hormones secreted by the gut. Hormone. Secreted by TargetsReleasing stimuli. Actions. Gastrin. G cells of Stomach. Histamine secreting and parietal cells of stomach. Peptides in lumen. Increases acid secretion in stomach and gastric motility. Cholecystokinin CCKEndocrine cells of small intestinegall bladder pancreas gastric musclepartially digested proteins and fatty acids in duodenumgallbladder contraction inhibits gastric emptying stimulates secretion of Pancreatic Enzymes. Secretin. Endocrine cells of small intestine. Pancreas stomach. Acid and partially digested proteins and fatty acids in duodenum and small intestine. Stimulates bicarbonate secretion and pepsin release inhibits gastric acid secretion, bile ejection. Motilin. Endocrine cells of upper small intestine. Smooth muscle of Antrum and duodenum. Fasting. Stimulates gastric contractions hunger pangsSecretin is of particular historical interest as it was the first hormone discovered in 1. Mucus Secreting CellseditMucous is a viscous secretion used for protection and lubrication. It consists mainly of Glycoproteins. It is made by mucous cells in the stomach and Goblet cells in the small intestine. Up to 2. 5 of the intestinal epithelial cells are goblet cells. In the mouth about 7. Mucous has the following properties Adherent properties, it sticks well to surfaces. Enough body to prevent contact of most food particles with tissue. Lubricates well has a low resistance to slippage. Strongly resistant to digestive enzymes. Neutralizing properties. As well as a buffer like effect, mucous can also contain large quantities of bicarbonate. Mswmm To Wlmp Converter on this page. Blue staining Goblet cells. Control of secretion is by a variety of neuropeptides in the enteric nervous system parasympathetic innervation and cytokines from the immune system. Transverse section of Villus showing goblet cells. Electrolytes and FluidseditA large portion of the 7 liters is composed of water and ions. The ionic composition varies from region to region. The acini of the salivary glands secrete a sodium and chloride rich secretion, this is then turned to a potassium, bicarbonate rich secretion as it travels down the lumen and ducts of the glands. The Oxyntic cells of the stomach secret Hydrochloric acid. The mucous cells of the stomach secrete a mucous rich in bicarbonates. The pancreatic ducts and ductules secrete a solution rich in bicarbonatethe Crypts of Liberkuhn of the small intestine secrete a solution almost indistinguishable from interstitial fluid. The Salivary glands consist of the parotid, submandibular, and sublingual glands as well as numerous smaller buccal glands secreting both serous and mucoid secretions. The parotid secretions are mainly serous, the buccal glands mucus, and the sublingual and submandibular are a mixture of the two.
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