DigestiveFunction-Nutrition-Student (1) - Digestive System derived from the\"gut tube in the embryo runs from mouth to anus Alimentary

DigestiveFunction-Nutrition-Student (1) - Digestive System...

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Unformatted text preview: Digestive System derived from the "gut tube" in the embryo, runs from mouth to anus. • Alimentary canal(digestion/absorption)stomach is temporary storage mouth, pharynx,esophagus, stomach, small order of food movement intestine,large intestine.large intestine aka colon, then to rectum & anus • Accessory organs-teeth, tongue,salivary salivary glands have enzymes that breaks down food glands, gall bladder,liver, and pancreas. liver is the largest of the excessory gland in the digestive system pancreas (exocrine function) small intestine: 1. Duodenum 2. Jejunum 3. Ileum *in the oral cavity food is transformed to BOLUS to fit in esophagus Digestive Process food item is ingested and is converted into BOLUS, which is propelled (propulsion) in the esophagus • Ingestion • Propulsion • Mechanical digestion occurs in oral cavity and then in the stomach ("churns things") • Chemical digestion occurs in the intestines, via enzymes • Absorption of nutrients into the cells for ATP, via small intestine • Excretion of Bi-products that are not utilized (absorbed) * Digestive lining protects against corrosive effects of enzymes/acids,abrasions, and pathogens. digestive tract produces Acid, HCl (hydrochloric acid) to break things down buffers are what protects corrosive effects of the acids abrasions (scrapings of gut tube, when food is not chewed properly) pathogens, i.e. E-coli via "e-coli sandwich"--from improper hand washing or salmonella. -Lymphatic Nodules: protect from pathogens, like e-coli organization of the gut tube from innermost to outermost layers: (tube w/i a tube arrangement) Histological Organization Lumen: space in tube • Mucosa • Submucosa • Muscularis externa composed of smooth muscle (most of the time) • Serosaoutermost (by default), alternate is ADVENTITIA (has more CT fibers compared to Serosa) 1 is suppose to be going in one direction (esophagus --> stomach), defies gravity Peristalsis/Segmentation rhythmic/ intermittent (takes turns) • Peristaltic wave-rhythmic contractions of circular and longitudinal muscles; pacesetter cells • Segmentation-churn and fragment digested materials;circular contractions only the circular segments when circular layer of muscle contracts, the diameter of the lumen is reduced (relaxation goes back to where it started). When the longitudinal muscles contract it shortens & lengthens the lumen for bolus to move down the esophagus. *circular and longitudinal actions are peristaltic actions throw-up=EMESIS: same mechanism as peristalsis, but REVERSED! Functional Anatomy of the Digestive System Oral Cavity • Bounded by lips, cheeks, palate, tongue • Vestibule space between the cheeks and gums (used for temporary storage) [chewing tobacco, can cause oral cancer or storage of contraband (things not allowed in jail)] • Hard/soft palate(uvula) hard palate is mainly bone, soft is mainly muscle w/ uvula at terminus leading to gagging reflexes (then emesis) • Tongue manipulate bolus and food. Taste buds: salty bitter sour umami polyphyodonts: endless supply of teeth diphyodont: 3 sets of teeth The Teeth • • • • • **teeth are important for the mechanical digestion of food into BOLUS. Primary(deciduous),permanent dentitions grows in around 5/6 years old Incisors Canines Premolars AKA bicuspids Molars AKA tricuspids 2 Salivary Glands • Saliva: 99% water +buffers, metabolites, enzymes. enzyme: amylase that breaks down amylose (starch) • Saliva cleanses mouth, moistens/dissolves food. ***swallowing= DEGLUTITION The Pharynx (muscles in the palate) • Pharyngeal constrictors-initiates bolus movements • Palatal muscles-raise soft palate & portions raises soft palate to close off nasopharynx (or nasal cavity) of pharyngeal wall • Swallowing process 1. buccal phase: when food is still in oral cavity (voluntary swallowing) 2. esophageal phase: involuntary *goblet cells in stomach act as a buffer The Esophagus Lumen: space in the esophagus • Hollow, muscular tube:25 cm.long,2 cm diameter (long and hallow) esophagus traverses (travels) and enters the diaphragm, via the HIATUS (opening), it ends at the CARDIA (not a true sphincter) • GERD walls of the hiatus mimic the action of a sphincter, results in weakness which leads to... H.I.: GERD- gastro esophageal reflux disease (heart burn) b/c HCl acid in the stomach are hitting the esophagus persistant GERD is known as BARRET'S DISEASE, which can lead to esophageal cancer 3 The Stomach temporary storage • Stomach functions in: storage of ingested food, mechanical breakdown, and chemical digestion(chyme formation). mechanical digestion occurs w/ churning, Mechanical and Chemical digestion causese transformation of the BOLUS to CHYME. • Empty(50ml),full(up to 4L). • Rugae infoldings of the innermost layer of the stomach--MUCOSA, Rugae is only seen on an empty stomach. • Cardia, body, fundus Cardia is the end of the esophagus (as it enters the stomach) Fundus: expansive portion of the stomach • Pylorus, sphincter. walls of the stomach: circular, long., & oblique -has specialized cells--GHRELIN CELLS: responsible for hunger drive/ appetite. • Musculature:circular,longitudinal -Fundus is the target site of bariatric surgeons (gastric bypast) Pylorus is the end of the stomach and leads to a thickening of the muscular externa (Pylorus sphincter--TRUE sphincter b/c a one way valve is created, nothing comes back up!) circular layer reduces longitudal shortens oblique twists Stomach Histology • Gastric pits/glands • Gastric glands have three cell types:(1) parietal-HCL/intrinsic factor;(2) chiefpepsinogen, rennin/gastric lipase(newborns);(3) enteroendocrinegastrin 1. parietal cells produce HCL, and secretes intrinsic factors (increases uptake of Vit. B12 through guttube. 2. chief cells: produces pepsinogen (precursor to pepsin--breaks apart peptide bonds in proteins) -in newborn Rennin (gastric lipase) is produced to break down lipids 3. enteroendocrine (glands) cells secretes gastrin --basis for "enteric brain (butterfly stomach)" Large Intestine • Frames small intestine on three sides and extends from ileocecal valve to anus ileocecal valve is the end of the large intestine, TRUE sphincter(valve) • 1.5m long • Functions:(1) resorption of water/ electrolytes; compaction of feces(2)vitamin absorption(bacterial flora) bacterial flora--E-coli is found in the colon 4 The Small Intestine • • • • • Body’s major digestive organ 6m long, 4cm-2.5 cm diameter Accounts for 90% of nutrient absorption nutrient and water absorption Plicae circulares (found in the mucosa)--circular folds (tightly coiled) function as little speed bumps, as chyme goes through S. intestine, Plicae slows things down and the motility of the chyme is slown down in order to increase absorption Three subdivisions: duodenum, jejunum, tightly coiled in the... ileum ileum (distal ileum) the plicae circulares are more spread out Large Intestine (cont’d) Cecum is the start part of colon,then... • Cecum,vermiform appendix • Colon:haustra,taenia coli, epiploic haustra: pouches taenia coli: ridge of longitudinal smooth muscle in the walls of the colon appendages epiploic appendages: "fatty tags" serve little purpose, allows identification of small intestine vs • Colon regions:Ascending>hepatic colon hepatic (right colon) flexure>transverse>splenic splenic (left colon by the spleen) flexure>descending>sigmoid flexure>sigmoid • Rectum: Anal canal/ columns, internal/external anal sphincter, anal orifice. internal sphincter is composed of smooth muscle (involuntary contractions), b/c in the wall of the rectum (end of colon) external sphincter is skeletal muscle w/ voluntary contractions ailementary canal (guttube The Liver • Largest visceral organ • Functions:metabolic/hematological regulation, bile production. bile is produced by the hepatocytes (liver cells) detoxifier 5 Liver -->lobes --> segments--> functional units (lobules) lobules are hexagonal shape • Lobules(central vein), hepatocytes (liver cells) • Portal triad:hepatic artery branch, portal vein branch, bile duct • Sinusoids(hepatic macrophages) found in the corners of lobules liver has 2 blood supplies: from the hepatic artery (O2 rich) & portal supply from portal vein (CO2) leaky capillaries, hepatic macrophages AKA Kupffer cells to clean the blood (from hepatic art. and portal veins) veins from the gut wall of the intestines, veins carry nutrients drain and go back to the portal vein that gets cleaned out then to the central vein and to the IVC (inferior vena cava --right atrium) Bile ducts collect the bile that is being produced from the hepatocytes bile is stored in the gall bladder and liver produces *bile goes to right and left hepatic ducts to common hepatic duct to gall bladder then to bile duct and dumps into the duodenum Gall Bladder • Stores/modifies bile • Fundus, body, neck • Cystic duct bile emulsifies lipids fundus expands--> body-->narrows to neck cystic duct is where stored bile exits and secretes to the duodenum. enteroendocrine cells (in the intestines): secrete CCK (CHOLECYSTOLKININ)--targets the wall of the gall bladder (smooth muscle) and triggers it to contract to expel bile to duodenum. H.I. CHOLELITHIASIS (gall stones): too large that cannot squeeze through cystic duct. CHOLECYSTECTOMY (removal of gall stones) The Pancreas • Exo/endocrine gland • Head, body, tail • Exocrine product-pancreatic juice (proteases, lipases, carbohydrases, nucleases) nucleases (break down nucleic acid) • Islets of Langerhans islets have alpha (glucagon is secreted), beta (secretes insulin), and delta (secretes somatostatin) cells outside of this is the exocrine, inside is endocrine 6 Nutrition • Nutrient – a substance that promotes normal growth, maintenance, and repair • Major nutrients – carbohydrates, lipids, and proteins • Other nutrients – vitamins and minerals (and technically speaking, water) Carbohydrates • Complex carbohydrates are found in bread, cereal, flour, pasta, nuts, and potatoes • Simple carbohydrates are found in soft drinks, candy, fruit, and ice cream • Glucose is the molecule ultimately used by body cells to make ATP through Cellular respiration • Neurons and RBCs rely almost entirely upon glucose to supply their energy needs • Excess glucose is converted to glycogen or storage polysaccharide, stored in the liver and muscle cells (hepatocytes and myocytes) fat and stored Lipids • The most abundant dietary lipids, triglycerides, are found in both animal and plant foods • Essential fatty acids – found in most vegetables, must be ingested • Dietary fats: – Help the body to absorb vitamins – Are a major energy fuel of hepatocytes and skeletal muscle – Are a component of myelin sheaths and all cell membranes 7 Lipids: Dietary Requirements • Higher for infants and children than for adults • The American Heart Association suggests that: – Fats should represent less than 30% of one’s total caloric intake – Saturated fats should be limited to 10% or less *saturated fats are not good! (usually solids) of one’s total fat intake – Daily cholesterol intake should not exceed 200 mg (cholesterol reading is the total cholesterol count, LDL cholesterols are the bad cholesterol, HDL is good LDL: low density lipoprotein Proteins • Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk products, meat, and fish • Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetables rice and beans (complete protein) Proteins • Proteins supply: – Essential amino acids proteins that the body cannot synthesize (produce, must be attained through diet) – The building blocks for nonessential amino acids 8 Vitamins • Organic compounds needed for growth and good health • They are crucial in helping the body use nutrients and often function as coenzymes • Only vitamins D, K, and B are synthesized (made) in the body; all others must be ingested • Water-soluble vitamins (B-complex & C) will not are absorbed in the gastrointestinal tract do much harm if overdosed must drink water to avoid RENAL CALCULI (stones) increases immune system response (Linus Pauling--overdosing of vit. C.) Vitamins • Fat-soluble vitamins (A, D, E, and K) bind bind to adipose tissue to ingested lipids and are absorbed with their digestion products • Vitamins A, C, and E are considered antioxidants Minerals • Seven minerals are required in moderate amounts – Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium • Dozens are required in trace amounts • Minerals work with nutrients to ensure proper body functioning • Calcium, phosphorus, and magnesium salts harden bone 9 Minerals • Sodium chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function • Uptake and excretion must be balanced to prevent toxic overload Metabolism = anabolism+ catabolism • Metabolism – all chemical reactions necessary to maintain life • Anabolic reactions/catabolic reactions • Cellular respiration Glycogenesis, Glycogenolysis & Gluconeogenesis • Glycogenesis –formation of glycogen when glucose supplies exceeds cellular need occurs when one is HYPOglycemic • Glycogenolysis – breakdown of glycogen in response to low blood glucose [ ] • Gluconeogenesis-formation of glucose from noncarbohydrate molecules 10 ...
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  • Fall '08
  • BRINN
  • Digestive System

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