The digestive system includes organs that ingest, transport, digest, absorb, and eliminate food and waste. Food enters the mouth where it is chewed and the enzymes in saliva begin to break it down. It then moves to the stomach through the esophagus where acids and enzymes further break it down into a liquid called chyme. The chyme then enters the small intestine where most absorption occurs through the intestinal walls into the bloodstream. Undigested waste then moves to the large intestine where water is absorbed before elimination of solid waste from the body.

1. Digestive System

6. Why do we eat??

10. Extracellular digestion

13. Health and Social Issues

17. How many people die from starvation? How widespread a problem is malnutrition?

20. What happens during starvation

32. Body image pressure for females

35. Check out my clavicles!

36. Body image pressure for males

37. The ingestion and absorption of nutritious food is essential for life

38. Digestive system

39. The digestive system includes the organs that ingest food, transport food, digest the food into smaller usable components, absorb the nutrients, and expel the waste products from the body.

40. Defecation

41. The digestive organs collectively make up the gastrointestinal (GI) tract (alimentary canal). The GI tract organs include the oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine.

42. As long as food is in the long hose extending from the mouth to the anus, it is NOT technically in the body . Only when it is absorbed is it in the body.

43. Food is utilized at a cellular level .

44. An example is when you put your finger in the hole of a doughnut. Your finger is NOT in the doughnut. If you image your G.I. tract as an elongated doughnut , then you can see the similarity.

45. The accessory digestive organs do not form the long GI tube, but often develop as outgrowths from and are connected to the GI tract. These accessory organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas

46. Ingestion of food that will cause atherosclerosis.

47. Food must be mechanically and chemically reduced before it can be absorbed across the intestinal wall.

48. Ingestion and mastication

49. Swallowing. Note closure of epiglottis over entrance to larynx

51. Endoscopic view of intestinal secretions that aid in digestion

52. Digestion and absorption

53. Defecation to eliminate feces

54. Mouth receives food, masticates, and instigates swallowing

55. Mouth (oral cavity) is bounded anteriorly by the teeth and lips and posteriorly by the oropharynx. The roof is the hard and soft palates, while the floor contains the tongue and muscles covered with mucosa.

56. The oral cavity has two distinct regions: the vestibule (space between the cheeks or lips and the gums) and the oral cavity proper (region central to the alveolar processes of the mandible and maxillae Oral cavity proper

57. Muscle of cheeks is primarily the buccinator

58. The lips (labia) are formed primarily by the obicularis oris. The gingivae (gums) help support the teeth. The superior and inferior labial frenulum extend from the lips to the gingivae.

59. The hard palate is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bones. Transverse folds assist the tongue in manipulating food. The soft palate is mostly composed of skeletal muscle. The uvula and soft palate rise superiorly during swallowing to close of the nasopharynx. The palatine tonsils monitor ingested food and drink for harmful antigens.

60. Tongue , which is composed of skeletal muscle, assists in mastication, in swallowing, has taste buds, and helps with speech.

61. Lingual frenulum anchors the tongue to the floor of the mouth. Note location of submandibular salivary ducts that can squirt! Lingual

62. Saliva (spit) contains amylase which breaks down starch to maltose. It also contains lysozyme, and antibacterial substance.

64. The parotid salivary glands are the largest salivary glands and are located near the ear, partially overlying the masseter muscle. The parotid duct travels parallel to the zygomatic arch and opens into the vestibule near the second upper molar.

65. Swollen parotid gland in child with viral mumps . This virus can also infect the testes.

66. The submandibular salivary glands are inferior to the body of the mandible. A submandibular duct opens from each gland in the floor of the mouth on the lateral sides of the lingual frenulum. These are the squirters used in “gleeking”!

67. “ Gleeking” with submandibular gland at base of lingual frenulum

68. The sublingual salivary glands are inferior to the tongue. Each sublingual gland extends multiple tiny sublingual ducts that open onto the inferior surface of the oral cavity.

69. The facial nerve (CN VII) innervates the submandibular and sublingual glands The glossopharyngeal nerve (CN IX) innervates the parotid glands

70. Parasympathetic innervation stimulates salivary gland secretion (anticipation of tasty food). Sympathetic stimulation inhibits normal secretion, which is why persons who are frightened experience the sensation of a dry mouth.

71. A tooth has an exposed crown , a constricted neck , and one or more roots that anchor it to the jaw. The roots fit into dental alveoli where they are bound to the surrounding bone by the periodontal ligaments to form a gomphosis joint .

73. Permanent teeth

74. Teeth. The third molar (“wisdom teeth”) are not shown.

75. Permanent teeth found on one quadrant of the mouth : 2 incisors, 1 canine, 2 premolars, 3 molars.

76. Trauma

77. Dental implant post

78. Dental implants are effective, but are very expensive

79. Tooth being mounted on post.

80. Pharynx is the funnel-shaped structure that connects the oral and nasal cavities to the esophagus and trachea.

81. The superior, middle, and inferior pharyngeal constrictors , composed of skeletal muscle aid in swallowing. The vagus nerves (CN X) innervate most of the pharyngeal muscles.

82. Peritoneal

83. Within the abdomen, some organs are completely surrounded by visceral peritoneum (intraperitoneal organs). An example is the stomach.

84. Within the abdomen, some organs lie behind the parietal peritoneum (retroperitoneal organs). An example is the pancreas .

85. Mesenteries are double-layered folds of the peritoneum that support and stabilize intraperitoneal organs.

86. The greater omentum (“fatty apron”) extends from the greater curvature of the stomach and then all the way down to cover most of the small intestine and inferior abdominal organs.

87. Greater omentum flipped back over chest to reveal underlying intestines Note mesentery proper and mesocolon

88. Lesser omentum (omentum = “apron” in Latin) attaches the stomach and upper duodenum to inferior surface of liver.

89. The falciform (“sickle-shaped”) ligament attaches the liver to the inferior portion of the diaphragm and to the anterior abdominal wall.

90. The mucosa (mucous membrane) has absorptive and secretory functions. The submucosa has lymph vessels, blood vessels, mucin-secreting glands, and nerve plexuses.

91. The muscularis typically contains two layers of smooth muscle, which are responsible for peristalsis.

92. The outermost tunic may be either an adventitia (loose connective tissue) or a serosa (visceral peritoneum).

93. Esophagus connects the laryngopharynx to the stomach. It passes through the diaphragm via the esophageal hiatus .

94. The wall of the esophagus contains both skeletal and smooth muscle

95. There are two sphincters associated with the esophagus: superior esophageal sphincter and inferior esophageal sphincter

96. Defective lower sphincter Read the clinical view in text

97. Acid damage to esophagus by acid reflux through defective lower sphincter

98. The J-shaped stomach stores food (the semidigested mass is called chyme), initiates the digestion of proteins, has only minimal absorption, and moves materials on to the small intestine.

99. Stomach

100. Close-up of pyloric sphincter and pyloric orifice

101. Gastric rugae allow stretching of the stomach Note greater and lesser curvatures

102. Close-up of gastric rugae

103. Gastric cells and their secretions

104. Read about peptic ulcers in the clinical view in the text