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Human Health and Physiology Ms. Scott J205

Digestion Part II. Human Health and Physiology Ms. Scott J205. Goals of Digestion. Extract nutrients from food Transform nutrients into useful forms Absorb nutrients and distribute them where they are needed. Quick Review – Functions of the Digestive System .

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Human Health and Physiology Ms. Scott J205

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  1. Digestion Part II Human Health and PhysiologyMs. Scott J205

  2. Goals of Digestion • Extract nutrients from food • Transform nutrients into useful forms • Absorb nutrients and distribute them where they are needed

  3. Quick Review – Functions of the Digestive System • Ingestion: intake of nutrients • Digestion: breakdown of large particles into smaller ones • Absorption: uptake of nutrient molecules • Defecation: elimination of undigested residues

  4. Actions of the Digestive System Motility • Breaks up food • Moves food through the GI tract (Peristalsis) • Mixes with digestive enzymes • Secretion • Release of enzymes and hormones for chemical digestion and regulation • Membrane Transport - Absorption of nutrients from the tissues by the blood and lymph for transport

  5. Stages of Digestion • Mechanical: physical breakdown of food • Chemical: digestive enzymes hydrolyze food particles to break larger molecules into smaller ones • Some nutrients are absorbed with out digestion • Vitamins, minerals, cholesterol, water

  6. Oral Cavity Pharynx Esophagus Stomach Pyloric Sphincter Small Intestine Large Intestine Anatomy of the Digestive System 6.1.4 Liver Gall bladder Pancreas

  7. Teeth Tongue Salivary Glands Liver Gall Bladder Pancreas Accessory Organs

  8. Functions: A. Ingestion: cheeks lips and tongue mobilize food B. Digestion: Mechanical Mastication Chemical 3 salivary glands Amylase Digests some starches and fat Oral Cavity

  9. Motility: pharyngeal constrictors force food down during swallowing Pharynx

  10. Straight muscular tube about 1 foot long Motility: muscular contraction moves food towards stomach What causes heartburn “acid reflux”? www.mywebmd.ca.com Esophagus

  11. Heartburn and the Esophagus Heartburn, “ acid reflux”, is caused by acid and food going from the stomach into the esophagus The diaphragm normally prevents acid reflux, in conjunction with the lower esophageal sphincter. When this fails, the burning sensation felt is known as “heartburn”

  12. Liver, Gall bladder and Pancreas • Liver secretes bile that is active in the small intestine • Bile: aids in fat digestion and absorption • Activates pancreatic enzymes • Synthesized from cholesterol • Bacteria in the small intestine use bilirubin to make your feces brown • Gall bladder stores and concentrates bile • Pancreas produces an alkaline solution rich in bicarbonate and other enzymes that neutralizes the acidity in the chyme.

  13. Functions: Food storage Mechanical digestion Mixing enzymes with food Chemical digestion Secretes HCl HCL provides optimum pH Secretes pepsin for protein digestion When HCl and pepsin form within the stomach lining, why aren’t the cells that line the stomach damaged? 6.1.5 Outline the function of the Stomach Pylorus Rugae Duodenum Lumen Pyloric Sphincter

  14. Rugae- folds in the stomach lining that allow it to expand with more food Folds produce gastric juices that aid in digestion and mucous to create a protective coating on the lining of the stomach How do we vomit? http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion Rugae in the Stomach

  15. Ring of smooth muscle Regulates the passage of material from the stomach into the duodenum http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion Pyloric Sphincter 9/9/2013

  16. http://www.afns.ualberta.ca/bbo/1/ANATOMY/SI1.asp Functions: Completes the digestion of food Most enzymatic hydrolysis of the macromolecules of food Chemical Digestion Intestinal wall secretes enzymes Receives Enzymes from the pancreas Nutrient Absorption Has villi for absorption Motility Peristalsis keeps the mixture of digested and undigested food moving through the intestine 6.1.5 Outline the function of the Small Intestine

  17. Duodenum Chyme Bile from gall bladder and liver is emptied in Receives stomach contents, pancreatic juice and bile Neutralizes stomach acid and pepsin Jejunum Pancreatic enzymes are released Bile take over chemical digestion Ileum Last stage of small intestine What is the main role of the small intestine? What do you think takes place here? Fig 25.22 Small Intestine

  18. Motility smooth muscle contract Digestion chemical enzymes received from the pancreas, liver and gall bladder Nutrient Reabsorption microvilli increase surface area for absorption and has rich blood supply Small Intestine Microvilli

  19. Chemical Digestion – Small Intestine • Pepsin is resistant to the denaturing effect of low pH environment of the stomach. Thinking about the different digestive processes that occur in the small intestine, what adaptation do you think that the digestive enzymes in the that compartment share? • Take 3 minutes to think about this and write your comments down • Take another 3 minutes to discuss with row buddies • Share out

  20. Chemical Digestion Small Intestine • Since enzymes are proteins and proteins are hydrolyzed in the small intestines, the digestive enzymes in that compartment need to be resistant to enzymatic cleavage, other than the cleavage required to activate them.

  21. Need pic of large intestine Functions: Moves Undigested material Mucus and peristalsis Absorbs Water Used a solvent for digestive juices What drives the digestive process? Reabsorbed by osmosis Electrolytes Synthesizes vitamins B &K Transport to the blood Since water is reclaimed for use in the blood, what happens to the undigested food? Produces Feces If the lining of the colon is irritated (viral or bacterial infection), has an over absorption or under absorption of water what do you think would occur? 6.1.5 Outline the function of the Large Intestine

  22. Video Analysis – Reason on This • What would happen to the normal function of the digestive tract if part of one of the following organs was removed of greatly reduced in size ( for example, as a result of a surgery following an accident)? How would a person’s eating habits need to be changed to accommodate reduction in size ?

  23. Mechanism of Absorption • Membrane Transport: • Nutrients pass through membrane surface • The greater the membrane surface area, the greater the amount of nutrients that can be transported • Surface Area • Rugae • Microvilli

  24. Final Destinations of Digestion Products • Starches  bloodstream • Fats  lymph vessels (lacteals) • Proteins  bloodstream

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