Digestive System I’m from Chiquita banana & I’m here to say, I’ve got a recipe for you today. You take a banana & you shove it down, You wait a few minutes & it comes out brown! You wait a few minutes & it comes out brown!

net/s92enjog.htm net/s92enjog.htm Let’s Tour The Digestive System!

William Beaumont Father of Gastric Physiology Surgeon’s mate in US Army during War of 1812 Surgeon’s mate in US Army during War of 1812 Later observed musket wound in Alexis St. Martin’s stomach Later observed musket wound in Alexis St. Martin’s stomach Wound would not heal Wound would not heal Beaumont dangled food thru hole using string Beaumont dangled food thru hole using string 1 st person to observe digestion in stomach 1 st person to observe digestion in stomach Conclusions about nature of gastric juice, & observations of chemical digestion Conclusions about nature of gastric juice, & observations of chemical digestion mont/dr_life.htm mont/dr_life.htm mont/dr_life.htm mont/dr_life.htm

Nutritional Requirements All animals oxidize organic molecules in order to provide ATP for life processes All animals oxidize organic molecules in order to provide ATP for life processes Glucose is main fuel, but body may also use lipids & proteins-all under hormonal control Glucose is main fuel, but body may also use lipids & proteins-all under hormonal control Essential nutrients-organism cannot make, must be taken in with food Essential nutrients-organism cannot make, must be taken in with food Include amino acids, fatty acids, vitamins (organic) & minerals (inorganic) Include amino acids, fatty acids, vitamins (organic) & minerals (inorganic) Too few calories=undernourishment Too few calories=undernourishment Too few essential nutrients- malnourishment Too few essential nutrients- malnourishment

Feeding Mechanisms Herbivores, carnivores, omnivores Herbivores, carnivores, omnivores Suspension feeders Suspension feeders Sift from water Sift from water Substrate feeders Substrate feeders Live on or in food source, eat their way through it Live on or in food source, eat their way through it Fluid feeders Fluid feeders Suck nutrients from host body fluid Suck nutrients from host body fluid Bulk feeders Bulk feeders Eat relatively large pieces of food Eat relatively large pieces of food

Stages of Food processing Ingestion-chemical & physical Ingestion-chemical & physical Mouth,teeth Mouth,teeth Digestion-mechanical & chemical Digestion-mechanical & chemical Breakdown food into smaller particles Breakdown food into smaller particles Saliva, gastric juice, accessory glands, teeth, peristalsis Saliva, gastric juice, accessory glands, teeth, peristalsis Absorption-keeping the good stuff Absorption-keeping the good stuff Mainly sm. Intestine, water in colon Mainly sm. Intestine, water in colon Elimination-getting rid of the bad stuff, or excess Elimination-getting rid of the bad stuff, or excess

Intracellular digestion Food broken down in vacuoles, fused w/ lysosomes Food broken down in vacuoles, fused w/ lysosomes Heterotrophic protists & sponges Heterotrophic protists & sponges Extracellular digestion Food broken down outside cells in compartments continuous w/ the outside environment gastrovascular cavities(incomplete)-single openings, function in digestion & distribution Alimentary canals (complete)-2 openings More specialized, better isolation of enzymes, ability to digest more food even if previous food remains undigested

Comparative Anatomy Crops-food storage(stomach) Gizzards-grind & fragment

Mammalian System Breaks down food chemically & physically/mechanically Breaks down food chemically & physically/mechanically Mammalian digestive system is a complete system (alimentary canal) Mammalian digestive system is a complete system (alimentary canal) Food only travels through one way(normally) Food only travels through one way(normally) Has 2 openings to external environment(mouth & anus) Has 2 openings to external environment(mouth & anus) Vulnerable to outside pathogens Vulnerable to outside pathogens Digestive tract is completely isolated from the rest of the body Digestive tract is completely isolated from the rest of the body Digestive enzymes can be isolated Digestive enzymes can be isolated Toxins are kept away from rest of body Toxins are kept away from rest of body Peristalsis Peristalsis Smooth muscle along entire digestive tract contracts to move food Smooth muscle along entire digestive tract contracts to move food

Pathway of Food Oral cavity-mechanical & chemical Oral cavity-mechanical & chemical Mastication-chewing-increases surface area for enzymes Mastication-chewing-increases surface area for enzymes Saliva Saliva Mucin-protects mouth & lubricates Mucin-protects mouth & lubricates Buffers-neutralize acid, prevent tooth decay Buffers-neutralize acid, prevent tooth decay Salivary amylase-hydrolyzes starch & glycogen Salivary amylase-hydrolyzes starch & glycogen Tongue- tastes, shapes into bolus, pushes back Tongue- tastes, shapes into bolus, pushes back Pharynx-intersection of digestive & respiratory systems Pharynx-intersection of digestive & respiratory systems Epiglottis-cartilaginous flap that covers opening to trachea(glottis) during swallowing Epiglottis-cartilaginous flap that covers opening to trachea(glottis) during swallowing Esophagus-chemical digestion continues(salivary amylase) Esophagus-chemical digestion continues(salivary amylase) Top part contains voluntary, striated muscle, bottom has smooth, involuntary Top part contains voluntary, striated muscle, bottom has smooth, involuntary

Pathway of Food Stomach-mechanical & chemical Stomach-mechanical & chemical 3 muscle layers contract to break up food(longitudinal, vertical, diagonal) 3 muscle layers contract to break up food(longitudinal, vertical, diagonal) Cardiac sphincter-between esophagus & stomach Cardiac sphincter-between esophagus & stomach Gastric juice-secreted by epithelial cells Gastric juice-secreted by epithelial cells HCL-disrupts ECM to break up plant & animal tissue, kills bacteria HCL-disrupts ECM to break up plant & animal tissue, kills bacteria Pepsin-protein hydrolysis Pepsin-protein hydrolysis Mucus-protects lining from HCL Mucus-protects lining from HCL End product of stomach process results in a mixture called acid chyme End product of stomach process results in a mixture called acid chyme Cells of stomach lining Cells of stomach lining Mucus cells-mucin & gastrin Mucus cells-mucin & gastrin Chief cells-pepsinogen(inactive) converted to pepsin by HCL Chief cells-pepsinogen(inactive) converted to pepsin by HCL Parietal cells-HCL Parietal cells-HCL Pyloric sphincter-between stomach & small intestine Pyloric sphincter-between stomach & small intestine

ulcer

Pathway of Food Small intestine-21 ft long Small intestine-21 ft long Major site of digestion(duodenum) & absorption (jejunum & ileum) Major site of digestion(duodenum) & absorption (jejunum & ileum) Structure(see fig ) Structure(see fig ) Villi & microvilli increase surface area for absorption Villi & microvilli increase surface area for absorption Capillary & lacteal in each villi Capillary & lacteal in each villi Duodenum-1 st 25cm Duodenum-1 st 25cm Functions in breakdown of lipids, CBH, & proteins-most digestion takes place here Functions in breakdown of lipids, CBH, & proteins-most digestion takes place here Secretes its own enzymes, & also receives enzymes from accessory glands Secretes its own enzymes, & also receives enzymes from accessory glands Jejunum & ileum-function in absorbing nutrients-diffusion & active transport Jejunum & ileum-function in absorbing nutrients-diffusion & active transport All capillaries from small intestine pass into hepatic portal vein & go to liver before anywhere else!! All capillaries from small intestine pass into hepatic portal vein & go to liver before anywhere else!!

Pathway of Food Colon/large intestine Colon/large intestine Ascending, transverse, descending Ascending, transverse, descending Cells absorb water back into body, and produce mucus to lubricate Cells absorb water back into body, and produce mucus to lubricate Contains high amount of bacteria to aid in digestion Contains high amount of bacteria to aid in digestion Appendix-remnant of large cecum in herbivores Appendix-remnant of large cecum in herbivores Rectum-stores feces before elimination Rectum-stores feces before elimination Anus- Anus- 2 sphincter muscles-1 voluntary, 1 involuntary 2 sphincter muscles-1 voluntary, 1 involuntary

Enzymatic Digestion

Accessory Organs Pancreas Pancreas Secretes enzymes into sm. Int., regulates blood sugar Secretes enzymes into sm. Int., regulates blood sugar Gall bladder Gall bladder Stores liver secretions (bile) for fat digestion Stores liver secretions (bile) for fat digestion Secretes into duodenum Secretes into duodenum Liver Liver Produces bile salts, regulates cholesterol, stores fat soluble vitamins, breaks down Hb into bilirubin, regulates blood sugar Produces bile salts, regulates cholesterol, stores fat soluble vitamins, breaks down Hb into bilirubin, regulates blood sugar

Digestive Hormones Gastrin Gastrin Secreted by cells of stomach wall Secreted by cells of stomach wall Stimulates gastric juice Stimulates gastric juice Secretin Secretin Cells of duodenum Cells of duodenum Stimulates pancreas to release bicarbonate Stimulates pancreas to release bicarbonate Cholecystokinin Cholecystokinin Cells of duodenum Cells of duodenum Causes gall bladder to release bile Causes gall bladder to release bile