The Human Digestive System 1 Major stages of

The Human Digestive System 1

Major stages of digestion: 1. Ingestion (eating) 2. Digestion (breaking food into molecules the body can absorb) 3. Absorption (nutrients absorbed from digestive tract) 4. Elimination (removal of undigested wastes) 2

Digestive organs HERE http: //www. templejc. edu/dept/biology/RHicks/biol 2404 Int/cavities. gif 3

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INVOLUNTARY 8

BLUE = ACCESSORY ORGANS The cecum is a pouch connecting ileum with first part of LI. Ileocecal valve (sphincter) markes beginning of LI. Appendix is connected to cecum. 9 http: //cikgurozaini. blogspot. com/2010/08/human-digestive-system. html

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11 http: //classes. midlandstech. edu/carterp/Courses/bio 211/chap 23. htm

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Nucleic acids are another essential ORGANIC nutrient! Water is another essential inorganic nutrient! 13

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Saliva contains mainly water, mucus, buffers and salivary amylase. Salivary amylase: optimal p. H is 7. 15

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Glottis – vocal cords and space between them The epiglottis is made of elastic cartilage tissue which guards the T R entrance of A glottis C glottis by H E “closing” as A the larynx rises during swallowing so food cannot enter http: //www. faemse. org/downloads/glottis 1. jpg trachea. epiglottis Vocal cords (2 membranes stretched across larynx which vibrate w/ air to produce sound). Closed when holding breath. 20

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Peristalsis (wave-like) Alternating contraction & relaxation of smooth muscles propel materials forward all through the alimentary canal. 22

muscles 23 http: //cikgurozaini. blogspot. com/2010/08/human-digestive-system. html

Sphincters close off top & bottom of stomach. Rugae = deep folds in stomach wall (incr. SA). Layers of smooth muscle continue to churn food. http: //img. webmd. com/dtmcms/live/webmd/consumer_assets/site_images/articles/image_artic le_collections/anatomy_pages/stomach_72. jpg 24

“Gastric Juice” contains mainly water, mucus, HCl and pepsin. Though the stomach is not considered a nutrient-absorption organ, it does in fact absorb small amounts of water, some drugs/medications, glucose & alcohol. 25

1. 2. 3. 4. FOOD ENTERS STOMACH GASTRIN PRODUCTION IS STIMULATED HCL PRODUCTION IS STIMULATED PEPSIN IS ACTIVATED BY HCl (optimal p. H 2 -3) 26

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“Pancreatic Juice” contains mainly water, Na. HCO 3, amylase, nucleases, lipases, proteases. 32

The emulsification process is physical/mechanical, NOT chemical! 33

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We know that the SI is important as the major area of nutrient and water absorption. But let's not forget that it releases enzymes of its own! 37

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Intestinal Lipases also act to break down lipids http: //www. slideshare. net/sciencechris/digestion-366112 41

42 http: //cikgurozaini. blogspot. com/2010/08/human-digestive-system. html

SI – a busy place! PANCREAS -sodium bicarbonate (neutralize chyme – need p. H around 8 -9 now) -proteases (trypsin, chymotrypsin) -carbohydrases (amylase) -lipases -nucleases LIVER -bile (salts – not an enzyme - to emulsify fats) SMALL INTESTINE -proteaseses (peptidases) -carbohydrases (sucrase, lactase, maltase) -nucleases 43

“Intestinal Juice” contains mainly water, mucus, peptidases, maltase/sucrase/lactase, nucleases and lipases. 44

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Microvilli are a/k/a “brush border” 46

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Trypsin and chymotrypsin are proteases released by pancreas Carboxypeptidase, aminopeptidase, dipeptidase – all are peptidases (proteases) released by SI itself 49 http: //classes. midlandstech. edu/carterp/Courses/bio 211/chap 23. htm

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Lacteals A lacteal is a small lymphatic vessel in the lymphatic system (analagous to a capillary in the circ sys). Lymph fluid (similar to plasma – no RBC's but has WBC's Travels in these vessels In SI, cholesterol and triglycerides are packaged into little philic round particles called chylomicrons. These go directly into the lacteal because they are too large to cross into the wall of the capillary. 54

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56 http: //classes. midlandstech. edu/carterp/Courses/bio 211/chap 23. htm

More on lacteals. . . The lacteals from the various villi all converge into larger lymph vessels – eventually a large lymph vessel carries the philic packages to a vein in the shoulder area. Once they are in the circ sys they can travel throughout body. Many will make their way to the liver. Here the cholesterol can be repackaged as LDL's and HDL's. Triglycerides can be repackaged and sent to the adipose (fat) tissue for storage 57

Some will make their way to other body cells where the cholesterol can be used for membrane and triglycerides can be used for production of phospholipids. (or triglycerides can be used for energy – C/R) Lacteals are considered to be part of both the LYMPHATIC and DIGESTIVE systems. 58

Diarrhea – not enough water absorbed Constipation – too much water absorbed. 59

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ULCERS http: //www. riversideonline. com/source/images/image_popup/r 7_ulcers. jpg Heliobacter pylori --> http: //www. bio. davidson. edu/people/sosarafova/Assets/Bio 307/vinardone/page 01. html 66