Digestive System Ingests breaks down food and absorbs nutrients Works with circulatory system to deliver nutrients to cells Both chemical breakdown hydrolysis and physical breakdown of material ID: 1043500
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1. 6.2 – Digestive System
2. Digestive SystemIngests, breaks down food, and absorbs nutrientsWorks with circulatory system to deliver nutrients to cellsBoth chemical breakdown (hydrolysis), and physical breakdown of materialA tube ~8m longWaste eliminated through anus
3. Digestive TractOrgans that contain foodMouthEsophagusStomachSmall intestineLarge intestineRectumAnus Accessory OrgansSalivary glandsLiverGall bladderPancreas
4. The Digestive Processbegins with IngestionThe taking in of nutrients
5. DigestionThe breakdown of complex organic molecules into smaller components by enzymes
6. AbsorptionThe transport of digested nutrients to the cells of the body
7. EgestionThe removal of food waste from the body
8.
9. Mouth & Physical digestion Teeth break down food into smaller pieces increases surface area for chemical digestion
10. Mouth & Chemical digestion Idea, smell, or thought of food triggers the salivary glandsSecrete salivaBegins digestion of starches (using amylase)Lubricates mouth & food to aid swallowing
11. Moving Food to the EsophagusTongue forms food into a bolusBolus passes through pharynx, epiglottis closes, and bolus continues to esophagus
12. EpiglottisThe flap of tissue that prevents food from going into the trachea
13. EsophagusTube from the mouth to the stomachFood travels partly by gravity, but mostly by peristalsis
14. PeristalsisWave-like muscular contractions, involving circular and longitudinal muscles
15. esophageal sphincterEntry of bolus into stomach is controlled by the esophageal sphincter, which prevents stomach acid from backing up into esophagus
16. Stomach FunctionJ-shaped, muscularPyloric sphincter controls movement of stomach contents to small intestineFunctions:StorageSome digestionPush food into small intestine
17. Stomach SizeEmpty – 50 mL capacity; can expand to store 2-4 L of food
18. Stomach Structure
19. Digestion in the StomachPhysical & chemical digestionChurning mixes food with gastric juice, creating a thick liquid chymeGastric juiceWater, mucus, salts, hydrochloric acid, enzymespH 1-3 helps kill bacteria
20. Protein DigestionProteins and polypeptides are very large moleculesAn enzyme known as pepsin is produced by peptic cells in the stomachThis enzyme works along with the hydrochloric acid in the stomach to break down the polypeptides into smaller units
21. Why Doesn’t Stomach Digest Itself?3 methods of protection:Does not secrete much gastric juice until food is presentMucus is secreted to protect stomach liningStomach secretes pepsin (a protein-digesting enzyme) that is not activated until it is in the presence of hydrochloric acid
22. Stomach LayersA Acid ChymeB Mucus (with buffering)D Stomach lining producing mucus
23. Absorption in the StomachFew substances are absorbed in stomach (they are not broken down enough yet)Does absorb water, some salts, alcohol, and some medications