Multiple myeloma, functional anatomy of the tubular GI tract, secretions, chyme, process of absorption of nutrients, enterohepatic circulation

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Biomedical Science
BMS 460
D.Rao Veeramachaneni

4 October Clinical signs and symptoms of multiple myeloma are a consequence of uncontrolled proliferation of neoplastic plasma cells Bone marrow infiltration with plasma cells → Anemia → Release of cytokines → Anemia → Bone destruction → Fractures → Punched out radiographic bone lesions → Bone pain → Hypercalcemia → urinary stones ↓ IgG → immune deficiency → infection Plasma cell hypersecretion → monoclonal protein → amyloidosis, hyperviscosity, renal failure, Bence Jones proteinuria, electrophoresis The GI tract is subdivided into several functional units by muscular sphincters that regulate the orderly passage of contents from one part of the tract to another Esophagus and anus are voluntary Functional anatomy of the tubular GI tract The mucosal layer is composed of specialized squamous or glandular epithelium that overlies the lamina propria (loose connective tissue and resident chronic inflammatory cells). Underlying the mucosa is a thin muscularis mucosa that separates it from the submucosa composed of adipose tissue, vessels, and nerves. All these structures are surrounded by a muscularis propria (externa) composed of two layers of smooth muscle. The GI tract has an intrinsic nervous system that controls peristalsis (rhythmic contractions that move food and fecal material through the GI tract) with both a submucosal and intermyenteric plexus of nerves and ganglia. Submucosal nerve plexus – Meissner’s Myenteric nerve plexus – Auerbach’s Stimulation of preganglioinic parasympathetic nerve fibers (cholinergic terminals) of the muscularis causes increased motility as well as glandular secretory activity Stimulation of postganglionic sympathetic nerve fibers (adrenergic terminals) of the smooth muscle cells causes decreased motility Epithelial cells in the mucosal lining of GI tract are constantly replace and the turn over is rapid; e.g., the entire epithelium of the SI is replace ~every 5 days Part of Type of epithelium Main cell types of Other distinctive gastrointestinal tract epithelium features Esophagus Stratified squamous Squamous cells Submucosal glands Body/fundus of Glandular – straight Surface mucous cells Lymphoid cells very stomach tubular Neck mucous cells sparse Parietal cells No lymphoid Chief (peptic) cells aggregates Pylorus Glandular – coiled Mucous cells Lymphoid cells very branched tubular Occasional parietal sparse cells No lymphoid aggregates Duodenum Glandular with villi Enterocytes with Brunner’s glands and crypts of microvilli Lieberkuhn Goblet cells Paneth cells Jejunum and ileum Glandular with villi Enterocytes with Peyer’s patches and crypts of microvilli become more Lieberkuhn Goblet cells prominent distally Paneth cells Colon and rectum Glandular – straight Goblet cells Teniae coli Absorptive cells Appendix Glandular – straight Goblet cells Prominent lymphoid crypts Tall columnar cells tissue Anus Glandular – straight Absorptive and Columns of Morgagni Stratified squamous goblet cells Squamous cells 1200 ml water/day; 500-800 g solids/day ingested 1500 ml salivary secretions 2000 ml gastric secretions 500 ml bile 1500 ml pancreatic secretions 1500 ml intestinal secretions (primarily small intestine) 6700 ml absorbed into blood (small intestine) 1400 ml absorbed into blood (large intestine) Feces 100 ml water; 50 g solids excreted Secretions Salivary glands Simple sugars: amylase Stomach Amino acids: HCl, pepsin (pepsinogen activated by HCl) Liver Fatty acids: bile Pancreas Simple sugars: amylase Amino acids: trypsin (trypsinogen activated by enterokinase) Acts on other zymogens, e.g., chymotrypsin Carboxypeptidases Fatty acids: lipase SI mucosa (brush border) Simple sugars: lactase, maltase, sucrase Amino acids: aminopeptidases Chyme and the process of abs
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