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Biology 20

Biology 20. Digestive System. DIGESTIVE SYSTEM. HETEROTROPHIC NUTRITION Unable to manufacture food from inorganic molecules. Depend on autotrophs. AUTOTROPHIC NUTRITION Organisms capable of synthesizing organic molecules from simple inorganic material.

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Biology 20

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  1. Biology 20 Digestive System

  2. DIGESTIVE SYSTEM • HETEROTROPHIC NUTRITION • Unable to manufacture food from inorganic molecules. • Depend on autotrophs. • AUTOTROPHIC NUTRITION • Organisms capable of synthesizing organic molecules from simple inorganic material. • Types: photosynthesizers and chemosynthesizers.

  3. 4 Steps of Heterotrophic Nutrition 1) Ingestion • eating or drinking • Heterotrophs need: • Sugars • Amino Acids • Fatty Acids • Glycerol • Minerals • Vitamins

  4. 4 Steps of Heterotrophic Nutrition 2) Digestion • Breakdown of macromolecules into smaller ones that can be absorbed by the cells • Mechanical -- chewing • Chemical -- digestive enzymes Carbs Monosaccharides Fatty Acids & Glycerol Fats Proteins Amino Acids

  5. 4 Steps of Heterotrophic Nutrition 3) Absorption • Nutrients are absorbed into the blood • Digested monomers • Water • Minerals • Vitamins 4) Egestion • Elimination of undigested material

  6. Organs Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Rectum Glands Salivary Glands Pancreas Liver Gall Bladder Parts

  7. Order of Events The Beginning Mouth Pharynx Esophagus Small Intestine Stomach Large Intestine Rectum The End

  8. Order of Events Mouth Pharynx Esophagus Small Intestine Stomach Large Intestine Rectum

  9. Digestive System • Overview – Labeling of the Digestive system!

  10. Mouth • Hard Palate • hard part of roof of mouth • Soft Palate • back of roof of mouth • Pharynx • chamber in throat where • nasal cavity and mouth meet • esophagus and trachea meet • Mucus Membranes • lubricates walls of mouth for easy passage of food

  11. Mouth • Purpose • Mechanical digestion by teeth and tongue • increases surface area for action by enzymes • Mixes food thoroughly • Chemical digestion by enzymes in saliva • Secretions • Saliva • 1 to 2 liters per day • from 3 pairs of glands in the mouth

  12. Salivary Glands

  13. Mouth • Composition of Saliva • Water • moistens food • Amylase • begins STARCH digestion • Mucin • lubricant • binds food together for easier swallow

  14. Mouth • Control of Salivary Secretions • Mechanical pressure • food in the mouth • Nervous system • Brain thinking of food in the mouth • Signal sent to salivary glands from the brain • Mmmmmmm. Fooooood….

  15. Order of Events Mouth Pharynx Esophagus Small Intestine Stomach Large Intestine Rectum

  16. Pharynx

  17. Pharynx

  18. Pharynx • Throat • Common tube through which both air and food pass • Four openings • Nasal Cavity Mouth Cavity • Trachea Esophagus • Contains a flap of tissue called the EPIGLOTTIS • This prevents food from entering the trachea

  19. Order of Events Mouth Pharynx Esophagus Small Intestine Stomach Large Intestine Rectum

  20. Esophagus • Hollow muscular tube • Connects pharynx to the stomach What makes the food go to the stomach? • Movement of food by peristalsis • rhythmic waves of contraction and relaxation of muscular walls • food is squeezed through esophagus into stomach

  21. Peristalsis

  22. Peristalsis

  23. Esophagus • Hollow muscular tube • Connects pharynx to the stomach What makes the food go to the stomach? • Movement of food by peristalsis • rhythmic waves of contraction and relaxation of muscular walls • food is squeezed through esophagus into stomach • Epiglottis shunt food into esophagus during swallowing

  24. Esophagus • Structure • thick walled and muscular • from pharynx to stomach • walls contain mucus glands which secrete mucin • mucin lubricates food for easy passage

  25. Order of Events Mouth Pharynx Esophagus Small Intestine Stomach Large Intestine Rectum

  26. Stomach • a hollow muscular pouch • located high in the abdominal cavity, just under the diaphragm • The esophagus connects to the stomach by the cardiac sphincter. Heartburn • muscular ring surround esophagus at this point • acts like a valve to open and close the tube • keeps the food from falling out of your stomach when standing on your head.

  27. Stomach Esophagus Cardiac Sphincter

  28. Stomach • FUNCTIONS • temporary storage of food • liquefaction of food • beginning of protein digestion

  29. Secretions -- Gastric Juice • Secreted into the stomach cavity by stomach cells • churning of the stomach mixes juice with food • Contains • Hydrochloric Acid – HCl(aq) • pH of 1-2 • destroys bacteria present in food • liquefies food.

  30. Secretions -- Gastric Juice • Pepsin • an enzyme which begins protein digestion • (proteins broken down into smaller chains) But aren’t the stomach cells made of protein? • Pepsin is produced and secreted in an inactive form called pepsinogen • which is converted into the active form by the low pH. • This protects the cell from self-digestion

  31. Stomach • stomach lined with mucus coating • prevents acid and protein digesting enzymes from damaging wall • when food is liquefied it is called chyme. • squirted into small intestine through the pyloric sphincter

  32. Stomach Esophagus Cardiac Sphincter Pyloric Sphincter

  33. Small Intestine • About 6 meters long • Three sections 1) Duodenum • first 25 cm • digestion 2) Jejunum • next 2 meters • absorption 3) Ileum • next 4 or 5 meters • absorption

  34. Small Intestine • FUNCTION • complete the digestion of food • absorb the nutrients into the circulatory system (blood) • important secretions from the pancreas and the liver.

  35. Secretions -- Pancreatic Fluid • Contains • NaHCO3– sodium bicarbonate • raises pH to 8 • Pancreatic Amylase • an enzyme which continues the digestion of starch into maltose units • Lipase • enzyme digesting lipids into fatty acids & glycerol • Trypsinand Chymotrypsin • enzymes which continue protein digestion • also secreted in inactive forms • activated by alkaline pH

  36. Small Intestine • LIVER and GALLBLADDER • The liver produces bile • brown fluid • bile is stored in the gallbladder • when fats enter the small intestine, the gallbladder contracts and squirts bile into the duodenum

  37. Small Intestine • bile emulsifiesfats • physically breaks them down into smaller drops • Kaboom!!! Blows it up!!! • greater surface area for action by lipase • bile is NOT an enzyme because it does not cause a chemical change in fat.

  38. Small Intestine • All types of foods are acted upon. Amylase Starch Maltose Units Trypsin Amino Acids & Dipeptides Proteins Chymotrypsin Glycerol & Fatty Acids FAT Bile Lipase

  39. Small Intestine • digestion of disaccharides and dipeptides is completed by enzymes produced by the small intestine • sucrase • digests sucrose • maltase • digests maltose • lactase • digests lactose • aminopeptidase • breaks down dipeptides into amino acids

  40. Small Intestine • once all food molecules are at monomer stage, they are ready to be absorbed into the circulatory system • the inside of the S.I. is covered with millions of tiny finger-like projections called villi • each villus is actually covered with millions of microvilli • the villi and microvilli increase surface area for absorbing food molecules into blood.

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