The Digestive System

1. The Digestive System

2. Case Study • A classmate tells you that he missed 3 classes due to illness. He tells you that he had no health problems until about 2 months ago when he started developing recurring bouts of diarrhea, four times in the past 2 months. Each time, the diarrhea lasted 3 days and then went away. • Since you are in an A&P class, he had no reservations describing that he had semisolid BM’s with some blood after 2 days of diarrhea.

3. During the bouts of diarrhea, he experienced headaches, mild cramps, and abdominal pain on the right side, but no fever, nausea, or vomiting. You notice that your classmate smokes regularly. He also has significant stress from school and work. Your classmate mentions that his mother had an intestinal disorder, but cannot remember the name of the disease. • What could be causing your classmate’s ailments?

4. Fun facts: • Americans eat about 700 million pounds of peanut butter a year. • Americans eat over 2 billions pounds of chocolate each year. • In your lifetime, your digestive system may handle about 50 tons!

5. How important is it to have a well functioning digestive tract?

6. How long does it take food to pass through the digestive system? 30-32 hours

7. The Digestive System is responsible for the physical and chemical breakdown of food so it can be taken into the bloodstream and used by body cells and tissues.

8. What are some organs and structures of the Digestive System?

9. The Digestive System includes the Alimentary canal and Accessory organs

10. Alimentary Canal • A long, muscular tube that begins at the mouth and includes pharynx, esophagus, stomach, small intestine, large intestine, and anus.

11. Accessory Organs • The accessory organs include salivary glands, tongue, teeth, liver, gallbladder, and pancreas

12. Alimentary Canal

13. The Mouth • Receives food as it enters the body • Food is: • Tasted • Broken down physically by the teeth • Lubricated and partially digested by saliva • Swallowed

14. The Teeth • Special structures in the mouth • Break down food physically by chewing and grinding the food, a process called mastication. **

15. The Tongue • Muscular organ • *Contains special receptors called taste buds that allow a person to taste sweet, salt, sour, and bitter sensations • *Also aids with chewing and swallowing of food

16. Hard Palate • Bony structure that forms the roof of the mouth • Separates mouth from nasal cavities

17. Soft Palate • Located behind the hard palate • Separates mouth from the nasopharynx • Uvula • Cone-shaped muscular structure • Hangs from the middle of the soft palate • Prevents food from entering the nasopharynx during swallowing

18. **Salivary Glands** • Three pairs of glands • Parotid, sublingual, and submandibular • Produce a liquid called saliva • Lubricates the mouth during speech and chewing • Moistens food so it can be swallowed easily • Also contains an enzyme called salivary amylase. • Speeds up a chemical reaction • Begins the chemical breakdown of carbohydrates or starches into sugars that can be taken into the body

19. Our saliva glands produce over 2 litresof saliva everyday. That’s an average of 5,500 gallonsevery year.

20. Pharynx (Throat)

21. After food is chewed and mixed with saliva, it is called a **bolus **and it enters the pharynx or throat • The Pharynx carries food from the mouth to the esophagus. • When bolus is swallowed, muscle action causes epiglottis to close over larynx • Prevents bolus from entering respiratory tract • Bolus now enters the esophagus

22. Esophagus

23. Muscular tube dorsal to the trachea • Receives bolus from pharynx and carries it to the stomach • Relies on a rhythmic, wavelike involuntary movement of its muscles, called **peristalsis**to move the food in a forward direction

24. Stomach

25. Stomach • The enlarged part of alimentary canal • Receives food from esophagus • Mucous membrane lining contains folds called rugae. They disappear as stomach fills with food and expands.

26. Rugae

27. The Cardiac Sphincter • Circular muscle between esophagus and stomach • Closes after food enters stomach • Prevents food from going back up into the esophagus

28. The Pyloric Sphincter • Circular muscle between stomach and small intestine • Keeps food in stomach until it is ready to enter small intestine • *Food usually remains in the stomach for about two to four hours

29. Cardiac Sphincter Pyloric Sphincter

30. **Gastric Juices** • Produced by glands in the stomach • Converts food into a semi-fluid material called chyme. • Juices contain hydrochloric acid • Kills bacteria • Facilitates absorption of iron • Juices also contain enzymes • Lipase-begins chemical breakdown of fats • Pepsin-starts protein digestion • Rennin-only present in infants, aids in digestion of milk

31. Small Intestine

32. The Small Intestine is a coiled section of the alimentary canal about 20 feet long and 1 inch in diameter. • Receives food, in form of chyme, from the stomach. • There are three sections of the small intestine.

33. Section 1: Duodenum • The first 9-10 inches of the small intestine. • Bile from the gallbladder and liver and pancreatic juice from pancreas enter this section through ducts or tubes.

34. Bile • Liquid that enters small intestine from liver and gallbladder • Emulsifies, or physically breaks down fats

35. Pancreatic Juice • Liquid that enters small intestine from pancreas • Contains enzymes that complete the process of digestion

36. Section 2: Jejunum • About 8 feet long • Forms the middle section of small intestine

37. Section 3: Ileum • Final 12 feet • Connects with large intestine at the cecum • Circular muscle called ileocecal valve separates ileum and cecum and prevents food from returning to ileum.

39. Two Functions of small intestine: • Completes the process of digestion 2. Absorbs products of digestion into bloodstream for use by body cells

40. Intestinal juices • Produced by small intestine • Contains the enzymes maltase, sucrease, and lactase, which break down sugars into simpler forms • Contain enzymes known as peptidases, which complete digestion of proteins • Contain the enzyme steapsin (lipase) which aids in digestion of fat. *In your workbook pages*

41. Villi • Fingerlike projections that line the wall of small intestine that contain blood capillaries • Allow food to be absorbed or taken into bloodstream • Blood capillaries absorb digested nutrients and carry them to the liver where they are stored or released into general circulation for use by body cells

42. If you flattened out all the villi of the small intestine…..it would cover an entire tennis court!

44. When food has completed its passage through the small intestine only wastes, indigestible materials, and excess water remain

45. Large Intestine

46. Final section of the alimentary canal • About 5 feet long and 2 inches in diameter

47. Functions: • Absorption of water and any remaining nutrients • Storage of indigestible materials before they are eliminated from the body • Transportation of the waste products out of the alimentary canal

48. Sections of large intestine: • Cecum • Colon • Rectum

49. Cecum • First section • Connects with ileum of small intestine • Contains a small projection called the vermiform appendix

50. Colon • Four divisions: • Ascending colon continues up on the right side of the body from cecum to lower part of liver. • Transverse colon extends across the abdomen, below liver and stomach, but above the small intestine • Descending colon extends down left side of body • Sigmoid colon • Connects with descending colon • S-shaped section that joins with rectum