Digestion

1. Digestion

2. What have you eaten today? • Think about the food you have eaten today. • Visualize it going through the various parts of the digestive system as we continue this discussion.

3. Digestion = • the process by which your body breaks down food and the nutrients in food into simpler substances.

4. The blood can then carry these simple substances to cells for use in • growth, • repair, and • maintenance.

5. Digestion involves two processes: • mechanical digestion which involves crushing and churning the food. • chewing • peristalsis • chemical digestion which involves mixing food with powerful acids and enzymes.

6. Enzymes = • a type of protein produced by cells that cause specific chemical reactions to begin. (In other words, they jump start chemical reactions in the body.)

7. Gastrointestinal tract • As food is digested, it passes through a muscular tube leading from the mouth to the anus. This tube is called the gastrointestinal tract. (abbreviation = GI tract) • The gastrointestinal tract is about 25 to 30 feet in length. Each section performs an important function.

8. Absorption • is the process that follows digestion. • is the process by which the body takes nutrients into the body and makes them part of the body.

9. Food enters the GI tract through the mouth.

10. Mastication • The first step in the digestive process is mastication or chewing. • Chewing food well aids digestion because the body can break down small food particles faster than larger particles.

11. Taste Buds • Taste buds are found on the tongue. • Taste buds sense the flavors of foods. • This taste sensation along with the odor of food trigger the production of a solution called saliva.

12. Saliva • Saliva is a mixture of about 99% water plus a few chemicals • One of these chemicals is an enzyme called salivary amylase. • This enzyme, found only in the mouth, helps chemically break down (digest) the starches in foods. (NOTE: Starches are a type of carbohydrate.)

13. Functions of saliva: • Break down starches • Prevent mouth dryness (which would cause food to seem like it has little taste) • Moistens, softens, and dissolves food • Helps cleanse the teeth • Neutralizes mouth acids

14. Bolus • As you chew, the muscles of your mouth and tongue form the food into a small ball called a bolus. • Your tongue moves the bolus to the back of your mouth and you swallow it.

15. Esophagus • As you swallow, food passes from the mouth to the stomach through the esophagus. • The esophagus is about 10 inches long, and connects the mouth and the stomach.

16. Epiglottis • When you swallow food, a flap of skin called the epiglottis closes to keep food from entering the trachea. • The trachea, also called the windpipe, is also a tube in the throat. • Breathing automatically stops when you swallow food to help prevent choking.

17. Peristalsis • A series of squeezing actions by the muscles of the esophagus help move food through the tube. These involuntary actions which happen automatically when food is present are called peristalsis.

18. Stomach • When you eat, the stomach produces gastric juices to prepare for digesting the soon-to-arrive food. • The term “gastric” means stomach. • The gastric juices contain hydrochloric acid, digestive enzymes, and mucus.

19. Chyme • The mixture of gastric juices and chewed and swallowed food combine in the stomach. This mixture is called chyme.

20. Mucosa • The acid in the stomach is very strong. • The stomach wall has a thick lining, called the mucosa. • This thick lining secretes a thick fluid, called mucus, which helps soften and lubricate food. • It also helps protect the stomach from its strong acidic juices.

21. Pepsin • Protein digestion begins in the stomach. • The major gastric enzyme that begins to chemically break down protein is called pepsin.

22. Most people can hold about one quart of food in their stomachs. • 1 quart = 4 cups

23. Food generally remains in the stomach for 2 to 3 hours.

24. Liquids leave the stomach before solids. • Carbohydrates and proteins digest faster than fats.

25. Small intestine • From the stomach the chyme moves to the small intestine. • 95% of digestion takes place in the small intestine.

26. Duodenum = the first section and is about 12 inches long Jejunum = the second section and is about 4 feet long Ileum = the last section and is about 5 feet long. The small intestine is coiled in the abdomen in circular folds.

27. When stretched out the small intestine measures about 20 feet in length and is about 1 inch in diameter.

28. It takes 5-14 hours for food to travel from the mouth through the small intestine. • During this time strong muscular contractions (peristalsis) constantly mix and churn food, aiding in mechanical digestion.

29. Peristalsis moves food through the small intestine.

30. Pancreas • The small intestine needs a less acidic environment than the stomach to perform its work. The pancreas, an elongated gland behind the stomach, helps create the correct acid environment. It secretes bicarbonate, which neutralizes hydrochloric acid that has come from the stomach with the partially digested food.

31. Pancreas • The pancreas also produces digestiveenzymes which aid in the chemical digestion that takes place in the small intestine. These enzymes break down proteins, fats and carbohydrates into their most basic parts so your body can use them.

32. Liver • The liver is also involved in the chemical digestion that happens in the small intestine. This organ is a large gland, which sits above the stomach.

33. Bile • The liver produces a digestive juice called bile which aids in fat digestion. • Bile is responsible for the color of human solid waste.

34. Gallbladder • Bile is stored in a Gallbladder muscular sac called the gallbladder until it is needed for digestive purposes.

35. Large intestine • The small intestine is connected to the largeintestine, which is sometimes called the colon.

36. The large intestine measures about 3 ½ feet in your body or 5 to 6 feet when stretched.

37. Very little digestion occurs in the large intestine. • The main job of the large intestine is to reabsorb water and prepare waste material for elimination as solid waste.

38. Chyme is very liquid when it enters the large intestine. • Chyme usually stays in the colon for one to three days before elimination.

39. While the chyme is in the large intestine, water is absorbed through the walls of the large intestine. • Useful bacterial in the colon work on fiber to break it down further so that it can be eliminated. • Gas is produced as a by-product of the action of the bacteria on fiber. This is called flatulence.

40. The bacteria in the large intestine also work to help manufacture small amounts of some vitamins. • Vitamin K

41. Feces • Solid waste that result from digestion are called feces. • These wastes include mucus, bile pigments, fiber, sloughed off cells from the lining of the large intestine, and water.

42. Rectum • The end of the large intestine is called the rectum. • Feces collect here until they are ready to pass from the body through the anus.

43. Absorption • After being digested in the small intestine, the nutrients in food are ready for passage into the circulatory or lymphatic system. This is called absorption. • Most nutrients pass through the walls of the small intestine.

44. Alcohol and a few other drugs can be absorbed into the blood stream in the stomach. • Alcohol can also be absorbed into the blood stream in the mouth.

45. Villi • The inside surface area of the small intestine is about 600 times larger that it seems it should be. • This is because the wall of the small intestine is pleated with thousands of folds.

46. The folds are covered with villi. • These tiny, fingerlike projections give the lining of the small intestine a velvet like texture. • Each cell of every villus is covered with microvilli, which are like microscopic hairs that help catch nutrient particles.

47. Circulatory system • Once the nutrients are digested and absorbed, the circulatory system carries nutrients and oxygen to individual cells.

48. Metabolism • All the chemical changes that occur as cells produce energy and materials needed to sustain life are known as metabolism.

49. Factors that affect digestion and absorption: • Eating habits: • eating too little, • eating a diet that lacks variety, • not eating enough fiber, • eating too much, • eating too fast, • eating a high fat diet, • eating contaminated food.

50. Additional factors that affect digestion and absorption: • Food allergies • Food intolerance • Emotions • Physical Exercise