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Digestive Systems

Pancreas. Digestive Systems. Accessory organs. Functions of digestive system:. Exocrine gland between stomach and small intestine. Produces several digestive enzymes:. trypsin: digests proteins. pancreatic amylase: digests starches. lipase: digests fats. Also acts as endocrine gland.

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Digestive Systems

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  1. Pancreas Digestive Systems • Accessory organs • Functions of digestive system: • Exocrine gland between stomach and small intestine • Produces several digestive enzymes: • trypsin: digests proteins • pancreatic amylase: digests starches • lipase: digests fats • Also acts as endocrine gland • produces hormones to regulate glucose levels in blood (insulin and glucagon)

  2. Digestive Systems • Accessory organs • Functions of digestive system: • Liver • Large exocrine gland lying above stomach • Produces bile that empties into small intestine : • Bile pigments of old red blood cells eliminated in feces • Bile salts break fats into small droplets (=emulsifies) for lipase

  3. Digestive Systems • Accessory organs • Functions of digestive system: • Liver • Liver also removes toxins, poisons and alcohol from blood • Converts toxic ammonia produced by bacteria in large intestine into urea eliminated in urine • Also regulates levels of many substances produced in body (e.g. steroids hormones)

  4. Gall bladder Digestive Systems • Accessory organs • Functions of digestive system: • Exocrine gland that stores and concentrates bile • Empties directly into small intestine

  5. Digestive Systems • Digestion regulated by neural and hormonal signals • Regulation of digestion: • Nervous system stimulates salivary stomach secretions • When food reaches stomach, hormone gastrin released, which in turn causes release of pepsinogen and HCl

  6. Digestive Systems • negative feedback systems • Regulation of digestion: • Protein present in stomach, gastrin released • Gastrin causes release of pepsinogen and HCl • HCl lowers stomach pH and inhibits release of gastrin

  7. Cholecystokinin (CCK) released if fat in chyme, triggers gall balder to release bile • Secretin released in response to low pH of chyme, stimulate pancreas to release bicarbonate Digestive Systems • Small intestine releases two hormones to regulate digestion • Regulation of digestion:

  8. Digestive Systems • Protein diets are easily digested; carnivores have short digestive tracts • Vertebrate digestive systems vary: • Herbivores require long digestive tracts with specialized organs to digest cellulose in plants • 4-chambered stomach (ruminants) • Large cecum

  9. 4-chambered ruminant stomach Digestive Systems • Herbivore digestive systems: • Plant enters 2 chambers were plants partially digested • Rumen acts as fermentation vat where bacteria and protists break down cellulose • Similar symbiotic relationships occur in termites • ‘cud’ regurgitated and rechewed • ‘cud’ enters final two chambers into which gastric juices released

  10. Non-ruminant herbivores • Cecum enlarged and serves as fermentation vat Digestive Systems • Herbivore digestive systems: • Does not allow for reguritation and rechewing • Improve digestion of plants accomplished by eating feces (= coprophagy)

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