1. DIGESTIVE SYSTEM

2. I. Introduction A. Organs of the Digestive System 1. Alimentary Canal
mouth to the anus in between is the alimentary canal
24-48 hours

3. Food is digested in the duodenum becomes nutrients, nutrients are absorbed (jejunum and ileum) to the bloodstream

4. 4 major types of organic compounds
1. carbohydrates = monosaccharides
2. lipids (fats) = fatty acids
3. proteins = amino acids
4. nucleic acids = nucleotides

5. 2 types of glands in the Body
1. Endocrine glands = secretes hormones in the body
ex. Thyroid gland = thyroxine hormone
2. Endocrine glands = secretes a chemical substance into a duct (tube)
ex. Salivary glands

6. Salivary Glands

7. Glands
Parotid gland
Submandibular

8. Glands
Sublingual
Submandibular

9. Pharyngeal tonsil
Palatine tonsil

10. Salivary gland

11. Salivary gland

13. Tongue
Taste buds

14. 2. Accessory Exocrine Glands
A. secretes enzymes and other substances into the alimentary canal
1. salivary glands
2. liver (bile)
3. gall bladder
4. pancreas

15. Ingestion = food = digestion = food residues (cellulose) + nutrients = absorption = egestion
4. egestion (defecation)

16. Exocrine glands – parotid, submandibular, sublingual glands

17. Parotid gland – located just in front and below (antero-inferior) the ears * Mumps: viral infection

19. C. Overall Embryological Development of the Digestive System
1. during the 4th week
- the mouth and anus develop, forming a continuous tube (the alimentary canal)
2. during the 5th week
a. the yolk sac constricts off from the mid-gut
b. endodermal buds begin to develop from the alimentary canal, and project into the surrounding mesoderm at certain locations

20. Regions of the Alimentary Canal
A. Divisions: Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine (Colon), Anus
B. Mouth

23. 1. Oral Cavity
A. Lips
(1) superior labial frenulum (“bridle”)
(2) inferior labial frenulum
B. Cheeks
** Buccinator Muscles
C. Gingivas (gums) – consists of the oral mucosa (non-keratinizing epidermis and underlying dermis)

24. Teeth

25. Occlusal surface of the crown = the portion of the crown that contacts opposing teeth
Cusps – the elevations present on the occlusal surface of the crown

27. Root – the inferior portion of the tooth that is embedded in the alveolar process of the maxilla or mandible (which is covered by periosteum, called the periodontal membrane)
Neck – the constricted region between the crown and the root of the tooth

28. Tooth fills into a socket called an alveolar process
Tooth is filled into a socket
In between the teeth and alveolar process is the (dento-alveolar) joint – Gomphosis
Periodontal membrane – around the tooth

29. Crown
i. anatomical crown = the superior portion of the tooth that is covered by enamel
Ii. clinical crown – that portion of the anatomical crown visible above the gingiva

32. A. Incisors – front teeth, one root
i. chisel-shaped teeth used for biting
ii. Crown is chisel-shaped
iii. There is one root

33. B. canines (cuspids) – pointed teeth, very prominent in dogs
i. pointed teeth used for tearing
ii. crown has 1 cusp
iii. there is one root

34. C. Premolars (bicuspids) – 2 cusps in each tooth
i. broad teeth used for grinding
ii. crown has 2 cusps
iii. there is 1 or 2 roots

35. D. Molars (multicuspids) – multiple elevations
i. broad teeth used for grinding and crushing
ii. crown has 3-5 cusps
iii. there is 2-3 roots

38. Permanent Teeth
a. begins to erupt at about 6 years of age
B. dental formula
I, C, P, M = in each quadrant
2, 1, 2, 3 x 4 = 32 teeth
3rd molar is the wisdom tooth
The last 8 set of permanent molars are called wisdom teeth

39. Deciduous (Milk) Teeth
A. begins to erupt about 6 months of age
B. dental formula
I, C, P, M
2, 1, 0, 2 x 4 = 20 teeth

42. Endodontics – dental specialization focusing on the inner tissue of the teeth called the pulp.

44. Sensory neuron for the upper and lower teeth Dentists inject anesthetic into the trigeminal nerve

45. Diseases of the Teeth
A. dental caries (cavities) – holes in the enamel caused by acids produced by bacteria
B. gingivitis
C. (pyorrhea) Periodontitis – infection of the alveolar socket
D. impacted wisdom tooth

48. Periodontitis

49. Tongue = lingual 1. functions: A. mastication
B. deglutition – swallowing
C. speaking = study of languages is linguistics
D. taste buds (chemoreceptors) =
chemoreceptors = sensory receptors sensitive to chemicals

50. Sensory Neurons
Sweet = activated by sugars, chemicals that can also activate sweet receptors are artificial sweeteners
Sour = activated by acids like citric acid (oranges, lemons, grapefruit, plain yogurt)
Salty = salts (NaCl) is a metal and a non-metal
Bitter = aspirin (KCl)
Umami (Savory, meaty, brothy) = activated by amino acids (MSG) – monosodium glutamate = derived from glutamic acid (an amino acid

51. Taste buds tell us whether there are sugar, salts, bitter
Bitter maybe toxic or poisonous
Taste buds inform us what is in our food

52. Three tonsils 1. palatine tonsils (“tonsilitis/tonsilectomy)
2. lingual tonsil
3. pharyngeal tonsil (nasopharynx)

54. Microscopic Anatomy of the GI Tract The GI tract consists of a tube that extends from the mouth to the anus. It has four tissue layers (tunics):

58. Gastroesophageal Junction

60. Histology of The Stomach Wall

61. Histology of the Small Intestine (Duodenum)

62. Intestinal Villus

63. Histology of Selected GI Tract Organs
A. The Pancreas – Gross View

64. The Liver Gross View of the Liver

65. Liver – Microscopic Anatomy

66. Gross Anatomy of the GI Tract

67. The Mouth

69. The Esophagus

70. The Stomach

71. Pharyngeal constrictor muscles

72. Inside tonsils:
Macrophages and Lymphocytes (WBCs) = antibodies (proteins, immunoglobulins) = inactivate foreign agents

74. Salivay gland = parotid gland = largest among the salivery glands below the ear

75. Submandibular Salivary Glands
Located within the lower jaw (mandible)
The duct opens just beside the lingual frenulum

76. Esophagus
1. a 10-inch long muscular tube that extends from the laryngo-pharynx down to the stomach
2. the bolus of food moves down the esophagus by a peristaltic wave of contraction (and by gravity)
Food is ushered down the digestive sytem by peristaltic contractions of circular muscles that proceed downward, forcing the food along in front of them.

78. The vertebral column is the yardstick for locating organs

79. Histological appearance of the alimentary canal:
A. the mucosa
1. epithelial lining
2. lamina propria
3. muscularis mucosa
B. the submucosa
C. the muscularis
D. the serosa

80. The Stomach
1. the stomach is a J-shaped muscular organ located in the left upper quadrant of the abdominal cavity

81. Appendix – right lower quadrant
Liver – biggest organ in the body not counting the skin

82. Gastro-esophageal (Cardiac) sphincter – circular/ring- shaped muscle
Palatine rugae – ridges in the mouth
Sphincters/valves = function is to always allow one-way flow

83. A. gastro-esophageal (“cardiac”) sphincter (valve)
B. fundus of stomach
C. body of stomach
D. pylorus of stomach
E. pyloric-sphincter (valve) – allows what is in the stomach to go into the duodenum and prevent it from going back

84. Greater curvature attach the fatty membrane called greater omentum
Greater omentum – hanging from the stomach which you have to lift up to see the intestine
- protects/cushions the stomach from any blow to the abdomen

85. Functions of the greater omentum
1. cushions underlying viscera
2. protects underlying viscera from the spread of infection
3. stores fat – in part explains belly fat, because the greater omentum is fat

87. Histology of the digestive system

88. Lesser omentum – not as fatty or big, still protective in nature

89. 3 divisions of the stomach
1. body – middle part of the stomach
2. pylorus – last part of the stomach
3. fundus – top part of the stomach
* gastric rugae – prominent folds of the mucosal lining

90. The stomach functions to churn, mix and hold the partially digested food called chyme
A. gastric glands located in the lamina propria of the mucosa, secretes gastric juice
1. HCl (parietal cells) – kills bacteria
2. pepsinogen (chief or principal cells)
a. pepsinogen (inactive) = HCL = pepsin (active) (an enzyme)
* gen (inactive) = no gen (active)
fibrinogen = fibrin
b. protein (polypeptide) = pepsin = short peptide chains
* a peptide is 3 or 4 amino acids each

91. Very little digestion or absorption in the stomach
Main job of the stomach is to hold food as well as churn or grind the food
The walls of the stomach filled with gastric glands that secrete gastric juice

92. Chyme = food that is churned or mixed up
- it is called vomit if it is outside our body
- it is just food mixed with gastric juice
Gastric juice = HCl and pepsinogen

93. Substances normally absorbed in the stomach
1. water
2. monosaccharides – honey (lots of simple sugars or monosaccharides)
3. alcohol – warm feeling in the stomach
4. aspirin – may irritate the wall of the stomach

94. The contents of the stomach are normally emptied within 1-4 hours

95. Disorders associated with the stomach
A. Gastric Irritation
B. Esophagitis (“heartburn”, gastric reflux)
- “GERD” (Gastro-Esophageal Reflux Disease)
* Esophagus is right behind the heart
* Eat a large pizza plus lots of beer at midnight then sleep
C. Gastric Ulcer (Sore)

96. Majority of gastric ulcers were caused by Helicobacter pylori
D. Gastritis – inflammation of the stomach
E. Flatulence (“gas”) – carbonated drinks, swallow air,
- burp or flatulence

97. Gas formed in the stomach comes out of the mouth = belch/burp
Gas formed in the small and large intestine = flatulence
- these are the gases produced by bacteria breaking down food residues in the large intestine

98. F. Cancer of the stomach = surgically remove the whole stomach
- *obese*
G. Pyloric stenosis (Constriction) – congenital condition, common

99. Pyloric stenosis – more common among boys than girls
Boys – 1 in 200 births
Girls – 1 in 1000 births
- if the baby keeps burping out all the milk and the baby is losing weight, you call a pediatrician and they will most likely think pyloric stenosis and do surgery

102. Vomiting (heaves) = valsalva maneuver – tightening of the abdominal muscles to expel something (vomiting, defecate, expel baby)
The gastro-esophageal sphincter does not close effectively unlike the pyloric sphincter in order for vomiting to occur

103. Acid/Peptic Disease
The stomach produces hydrochloric acid, with a pH of about 3
The main purpose of this acidic secretion is to sterilize food as it enters the body

104. In certain situations, this acid can do damage to:
Esophagus
Stomach
Duodenum

105. Acid/Peptic Disease
The stomach produces mucous that lines the stomach and protects the stomach from the acid
Sometimes the stomach does not produce enough of this protective mucous

106. Acid/Peptic Disease
Sometimes the stomach does not produce enough of this protective mucous, this can be caused by: STRESS!

107. If more stomach acid is produced than what the protective mucous lining can handle, the result can be:
- gastritis
- errosions – preulcers
- ulcers (peptic ulcer disease, PUD)

108. Picture of Gastrointestinal Tract

109. Stomach errosion

110. Stomach errosion

111. Acid/Peptic Disease
Sometimes the stomach acid is refluxed into the esophagus
Gastro Esophageal Reflux Disease (GERD)

113. Acid/Peptic Disease
If GERD is severe enough, it can change the lining of the esophagus:
- esophagitis
- errosions
- strictures
- Barrett’s Esophagitis – precancerous

114. Esophageal Stricture

115. Acid/Peptic Disease
Sometimes excess stomach acid production can lead to ulcers of the duodenum as well

117. Gastrointestinal tract (GI tract)
Mouth:
Internal: nonkeratinized stratified squamous epithelium
Middle: buccinator muscles, bone

118. 2. pharynx: skeletal muscle; nonkeratinized stratified squamous epithelium

119. 3. esophagus:
a. nonkeratinized stratified squamous epithelium
b. skeletal (superior); smooth muscle (inferior)

120. 4. esophagus to anal canal Deep to superficial
Mucosa
Epithelium: touches food
Nsse – protection
Simple columnar (stomach/intestines)– secretion/absorption
exocrine cells (mucus)
endocrine cells (hormones)
Lamina propria (conn.)- blood/lymph vessels
Smooth muscle – makes folds

121. Submucosa
Binds mucosa to muscularis
Blood/lymph vessels/neurons

122. Muscularis
Skeletal muscle until middle esophagus (swallowing); external anal sphincter
Smooth muscle
Inner: circular fibers
Outer: longitudinal fibers

123. Serosa: connective and simple squamous epithelium (reduce friction)

124. ACCESSORY ORGANS

125. pancreas Small clusters of glandular epithelial
99%: called acini (exocrine function – secrete pancreatic juice for digestion)
1%: called pancreatic islets (endocrine function)

126. liver Consists of many lobules
Contains epithelial cells called hepatocytes arranged irregularly around a central vein. Capillaries, called sinusoids, are highly present and contain fixed phagocytes (to removed WBCs and RBC, bacteria, etc)

127. gallbladder
Mucosa is simple columnar epithelium