1. Ingestion and the Stomach

2. Ingestion and the Stomach It starts when we put the food in our mouths.

3. Ingestion and the Stomach Mouth of a fetal pig.

4. Ingestion and the Stomach Saliva contains the enzyme amylase which begins the chemical digestion of carbohydrates. It also contains mucus to lubricate the food and help taste buds function.

5. Ingestion and the Stomach We have 3 salivary glands.

6. Ingestion and the Stomach

7. Ingestion and the Stomach Saliva enters the mouth via ducts.

8. Ingestion and the Stomach The teeth and tongue crush and grind food into smaller pieces, increasing surface area of food.

9. Ingestion and the Stomach Tearing Grinding Tearing and grinding /Cuspid /Bicuspid Cutting

10. Ingestion and the Stomach

11. Ingestion and the Stomach The tongue has taste buds to taste the food. It also helps with mechanical digestion.

12. Ingestion and the Stomach

13. Ingestion and the Stomach The uvula helps prevent bolus from going down before it is ready in addition to being used to make sounds in some languages. It is also a common cause of snoring.

14. Ingestion and the Stomach The newly formed bolus is swallowed, passing into the esophagus.

15. Ingestion and the Stomach The epiglottis is a flap of cartilage that ensures food does not go into the windpipe. epiglottis

16. The Epiglottis epiglottis

17. The Epiglottis epiglottis

18. The Esophagus The mouth and stomach are connected by the esophagus (oesophagus).

19. The Esophagus The process of moving food down the esophagus is called peristalsis .

20. The Esophagus

21. The Esophagus Lumen Means “ empty space” The esophagus is made up of circular and longitudinal layers of involuntary muscles. The inside is lubricated with mucous membranes.

22. The Esophagus The esophagus has 2 sphincters to control the food going down. Top: upper esophageal sphincter (UES) Bottom: lower esophageal sphincter (LES) or cardiac sphincter or gastroesophageal sphincter

23. The Esophagus A sphincter is a ring of muscle that closes or opens to let substances pass. Most are involuntary. Cardiac Sphincter

24. The Esophagus Acid reflux (heartburn) is caused by incomplete closure of the LES. Gastric juices flow backward.

25. The Esophagus Smoking relaxes the sphincter which may allow acid reflux. An overfull stomach may also be to blame. Irritating foods also cause excess production of stomach acid.

26. The Stomach

27. The Stomach

28. The Stomach Protein digestion starts in the stomach.

29. The Stomach There are 4 regions of the stomach: 1) Cardiac 2) Fundus 3) Pylorus 4) Body

30. The Stomach There are 4 layers of tissue of the stomach: 1) Mucosa 2) Submucosa 3) Muscularis 4) Serosa

31. The Stomach

32. Layers of the Stomach - Mucosa

33. Layers of the Stomach - Mucosa 1) The mucosa secretes gastric juices which contain: - enzymes ( pepsinogen  pepsin ) - hydrochloric acid - mucus It is also frequently replacing cells to repair damage.

34. Layers of the Stomach - Mucosa The gastric juices are secreted from sections called gastric pits (glands) which contain gastric cells .

35. - It is possible for the stomach to digest itself , since it is made from protein . - There are several ways this is prevented. Layers of the Stomach - Mucosa

36. i) Frequent mucus secretion and cell division of the mucosa. Layers of the Stomach - Mucosa

37. Acids readily burn through flesh. Layers of the Stomach - Mucosa

38. ii) Pepsinogen is the inactive enzyme pepsin . It is only activated when it meets HCl in the stomach, to prevent premature digestion of stomach tissue. (Hydrochloric Acid) Layers of the Stomach - Mucosa

39. - If the stomach does digest itself, it is called a stomach ulcer . - The bacteria H. pylori is a common cause of ulcers. Layers of the Stomach - Mucosa

40. Other causes of ulcers include: - Smoking - Weakened mucosal linings (alcohol) - Anti-inflammatory medicines (like aspirin). Layers of the Stomach - Mucosa

41. The inner layer also has folds called rugae which allow the stomach to expand when large amounts of food are ingested. Layers of the Stomach - Mucosa

42. 2) The submucosa contains nerves and circulates blood to the stomach. Layers of the Stomach - Submucosa

43. - It also secretes the hormone gastrin into the blood when food is present. This is what triggers gastric juice secretion by gastric glands. Layers of the Stomach - Submucosa

44. 3) The muscularis controls mechanical digestion of the stomach by churning the contents. Layers of the Stomach - Muscularis

45. There are 3 layers of involuntary muscle that, together, can squeeze and mix in all directions: Layers of the Stomach - Muscularis

46. - longitudinal - circular - oblique Layers of the Stomach - Muscularis

47. Layers of the Stomach - Muscularis Through mechanical and chemical digestion, the food bolus becomes a semi-liquid mixture of food and gastric juice called chyme . Chyme is extremely acidic, with a pH of 2. Heartburn medication (antacids) have high pH's

48. Layers of the Stomach - Muscularis Chyme is extremely acidic, with a pH of 2. Heartburn medication (antacids) are bases (have high pH's) to neutralize the acid.

49. Layers of the Stomach - Serosa

50. Layers of the Stomach - Serosa 4) The serosa is the outer layer of the stomach which lubricates it to reduce friction with other organs. Stomach of a rabbit.

51. The Stomach Once the chyme is sufficiently processed, the pyloric sphincter of the stomach allows food to pass into the small intestine (duodenum).

52. The Stomach The pyloric sphincter is the barrier between the stomach and small intestine.

53. Nausea Vomiting ( emesis ) is the forceful expulsion of stomach contents (chyme is now referred to as vomitus ).

54. Nausea The diaphragm and abdominal muscles work with stomach muscles to cause emesis. The UES and LES open and the epiglottis closes. Mouth

55. Nausea Causes of nausea include: - inner ear conditions - drugs - infections - brain conditions - injury - disease