Digestive System

1. Digestive System

2. Digestive To assimilate food in bowels

3. The Process of Digestion Digestion: The process of breaking down food into its MOLECULAR and CHEMICAL components so that these nutrient molecules can cross cell membranes to be used for cellular processes.

4. Ingestion-an active voluntary process in which food is placed in the mouth • Propulsion-the movement of food through the digestive tract • Mechanical Digestion-physical fragmentation of food • Chemical Digestion-the process by which large food molecules are broken down into smaller building blocks by enzymes • Absorption- the transfer of food molecules from the digestive tract into the bloodstream • Elimination/Defecation-the elimination of indigestible residues

5. Two Parts • Alimentary Canal • Aliment = nourish • Also called gastrointestinal tract • Mouth • Pharynx • esophagus, • Stomach • Small intestines • Large intestine • anus • Accessory digestive organs (next set of notes!)

6. Digestive System Pathway It can take food from 8 to 48 hours to pass through your digestive tract from mouth to anus! http://health.howstuffworks.com/adam-200086.htm

7. A. Mouth MECHANICAL-chewing CHEMICAL-amylase, an enzyme breaks down carbohydrates 1. Tongue pushes chewed food (bolus) into the throat 2. Epiglottis folds over larynx at entrance of trachea

8. Pig

9. Pig Equine Endoscopy Epiglottis is tongue-like structure

10. Starches and sugars are both carbohydrates… As you chew a cracker enzymes in your saliva (amylase) break down the complex polysaccharide (starch) in the cracker and you begin to notice the sweet taste of sugar. This is an example of a chemical reaction that is a part of your bodies’ metabolism, in which food is converted to usable energy for your cells.

11. B. Pharynx/Esophagus • PERISTALSIS, rhythmic contractions of the smooth muscles pushes food down. • The Cardioesophageal Sphincter, a valve at the end of the esophagus controls bolus entry into stomach

12. C. Stomach 1.Stomach walls contract to churn food (MECHANICAL DIGESTION) 2. Hydrochloric acid and pepsin (enzyme) break down PROTEINS (Chemical Digestion) 3. Creates CHYME (processed food – or what you puke).

15. When full, stomach can hold about 1 gallon of food • Pyloric sphincter (valve) allows flow into the intestines

16. D. Small Intestine 1.Digestion of FATS begins, while carbohydrates and proteins continue. (Chemical Digestion) 2.Nutrient ABSORPTION 3. Small diameter-7 meters long.

17. Has three distinct parts • Duodenum : twelve fingers width long • food from the stomach is mixed with enzymes from the pancreas and bile from the gallbladder. The enzymes and bile help break down food • Jejunum: empty • inside walls absorb the food's nutrients

18. Ileum: twisted intestine • absorbs bile acids, which are returned to the liver to be made into more bile • absorbs vitamin B 12 , which the body uses to make nerve cells and red blood cells • Ileocecal valve – joins small to large intestine

20. e. The small intestine is lined with VILLI, which increase the surface area and absorption rates.

21. Surface of Stomach

22. Surface of Stomach

23. E. Large Intestine • WATER and water-soluble vitamins are absorbed by the large intestine. • Approximately 1.5 meters long-large diameter.

24. F. Anus • Exit/opening for the removal of feces

25. Homework

26. Aliment = nourish or food. Why is the alimentary canal thus named? • Because it nourishes the body by breaking food down in to usable pieces and getting rid of waste

27. Label the following “pieces” of the oral cavity. Hard palete Soft palate teeth epiglottis tongue trachea esophagus

28. Explain how bolus moves from the mouth to the stomach. • The process of peristalsis – alternating waves of contraction and relaxation of esophageal muscles

29. Label the parts of the stomach on the diagram below. fundus esophagus Cardioesophageal sphincter Longitudinal layer Lesser curvature Pyloric sphincter Circular layer duodenum Oblique layer serosa Greatuer curvature Pyloric antrum

30. What happens when the stomach is empty? • It collapses in on itself

31. What happens to food in the stomach? What role do the gastric juices play? • Physical: breakdown of food • Churning, mixing, pummeling • Chemical: continued breakdown of carbohydrates and beginning breakdown of proteins

32. What is the role of the mucus lining of the stomach? • Protects the stomach muscles from being “eaten” by stomach acids

33. Why is the small intestine considered the body’s major digestive organ? • Because chemical digestion really begins here. • Nearly all food absorption occurs in small intestines

34. Why is the small intestine well suited for its function? • Because it has three structures that increase absorptive surface: • Microvilli (finished digestion of proteins and carbohydrates) • Villi - (rich in capillaries) • Circular folds – (increases surface area so there are more villi)

35. What are the villi and why are they important? • Small fingerlike projections which are rich in capillaries allowing for nutrients to pass from the small intestines to the bloodstream

36. Why does the large intestine not have villa? • Because only water and water soluble vitamins are absorbed through the large intestine walls