Chapter 15: Digestive Tract

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1

What is composed by the oral cavity, esophagus, stomach, small and large intestines, and anus?

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digestive tract

2

What are the eight functions of the digestive tract?

  1. ingestion of food and liquid
  2. mastication divides solid food
  3. motility moves materials through the tract
  4. secretion of mucus, enzymes, and fluids
  5. hormone release for local control
  6. chemical digestion or enzymatic degradation
  7. absorption of the small molecules and water
  8. elimination of indigestible components
3

What are the four main layers of the GI tract?

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  1. mucosa
  2. submucosa
  3. muscularis
  4. serosa
4

What are the three layers of the mucosa of the GI tract?

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  1. epithelial lining
  2. lamina propria
  3. muscularis mucosae
5

What plexus of autonomic nerves is located in the submucosa of the GI tract?

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submucosal (Meissner) plexus

6

What are the two layers of the muscularis of the GI tract based on the orientation of the smooth muscle fibers?

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  1. inner circular layer
  2. outer longitudinal layer
7

What plexus of autonomic nerves is located in the muscularis of the GI tract?

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myenteric (Auerbach) plexus

8

What do the submucosal plexus and myenteric plexus of the GI tract together comprise?

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enteric nervous system

9

What is the simple squamous epithelium covering the serosa of the GI tract called?

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mesothelium

10

What large fold of adipose connective tissue suspends the intestines and is continuous with the peritoneum?

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mesentery

11

What thick layer of connective tissue surrounds the esophagus instead of the serosa?

adventitia

12

What do the numerous free immune cells and lymphoid nodules in the mucosa and submucosa comprise?

mucosa-associated lymphoid tissue (MALT)

13

What disease is caused by congenital absence of the plexuses of the enteric nervous system?

Hirschsprung disease

14

What disease is caused by infection with the protozoan Trypanosoma cruzi, resulting in injury to the plexuses of the enteric nervous system?

Chagas disease

15

What vesicular or ulcerating lesions of the oral mucosa are caused by HSV-1?

canker sores

16

Where is keratinized squamous epithelium found in the oral cavity?

In the masticatory mucosa on the gingiva (gum) and hard palate.

17

Where is nonkeratinized squamous epithelium found in the oral cavity?

In the lining mucosa over the soft palate, cheeks, the floor of the mouth, and the pharynx.

18

What is the transitional zone between internal mucous surface and the outer skin surface of the lip?

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vermilion zone

19

What is the V-shaped groove separating the anterior papillary and posterior tonsillar areas of the tongue?

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sulcus terminalis

20

What are the four types of lingual papillae?

  1. filiform
  2. fungiform
  3. foliate
  4. vallate
21

Which lingual papillae are very numerous, have an elongated conical shape, and are heavily keratinized?

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filiform papillae

22

Which lingual papillae are less numerous, lightly keratinized, and interspersed?

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fungiform papillae

23

Which lingual papillae consist of several parallel ridges on each side of the tongue?

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foliate papillae

24

Which lingual papillae are the largest, normally aligned just in front of the terminal sulcus?

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vallate papillae

25

What small, serous glands empty into the deep, moatlike groove surrounding each vallate papilla?

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salivary (von Ebner) glands

26

What ovoid structures within the stratified epithelium on the tongue’s surface sample the general chemical composition of ingested material?

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taste buds

27

What three cell types comprise a taste bud?

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  1. gustatory (taste) cells
  2. supportive cells
  3. stem cells
28

What is the small opening at the apical ends of the gustatory cells of a taste bud?

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taste pore

29

How many permanent teeth are found in the normal adult dentition?

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32

30

How many deciduous teeth are found in the normal primary dentition?

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20

31

What is the portion of the tooth exposed above the gingiva called?

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crown

32

What is the portion of the tooth that fits into the bony dental alveolus called?

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root

33

What is the very hard, acellular tissue covering the crown of the tooth?

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enamel

34

What is the bone-like tissue covering the root of the tooth?

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cementum

35

What is the calcified material, surrounding the pulp cavity of the tooth?

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dentin

36

What is the highly vascular and well-innervated tissue in the pumlp cavity and tooth roots?

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dental pulp

37

What is the narrow extension of the pulp cavity into each tooth root?

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root canal

38

What is the opening at the tip of each root where blood vessels, lymphatics, and nerves enter the pulp cavity?

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apical foramen

39

What are the fibrous bundles of collagen fibers inserted into both the cementum and the alveolar bone?

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periodontal ligaments

40

What is the composition of dentin?

It consists of 70% hydroxyapatite, and an organic matrix containing type I collagen and proteoglycans.

41

Which cells lining the pulp cavity secrete predentin that is mineralized into dentin?

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odontoblasts

42

What are the spaces through which odontoblasts extend their long apical processes?

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dentinal tubules

43

What bacterial infection is a frequent cause of pharyngitis and tonsillitis?

Streptococcus pyogenes

44

What viral infection is a frequent cause of leukoplakia on the sides of the tongue?

Epstein-Barr virus

45

What fungal infection causes a white exudate on the tongue’s dorsal surface, oral thrush?

Candida albicans

46

What is the composition of enamel?

It consists of 96% hydroxyapatite with little organic material including few proteins and no collagen.

47

What are the uniform, interlocking columns that comprise enamel?

enamel rods

48

Which cells secrete the matrix for the enamel rods in a developing tooth bud?

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ameloblasts

49

What specialized area of epithelium in the tooth bud are the ameloblasts part of?

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enamel organ

50

What are the apical extensions from each ameloblast contains numerous secretory granules?

ameloblast (or Tomes) process

51

What structural protein of developing enamel guides growth of each elongating enamel rod?

amelogenin

52

What type of disease is caused by inflammation of the gums or tissue surrounding the tooth?

periodontal disease

53

What comprises the structures responsible for maintaining the teeth in the maxilla and mandible?

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periodontium

54

What four components comprise the periodontium?

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  1. cementum
  2. periodontal ligament
  3. alveolar bone
  4. associated gingiva
55

What large, elongated cells function to secrete the bone-like cementum covering the tooth root?

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cementoblasts

56

What are former cementoblasts residing in lacunae in the cementum around the tooth root tip called?

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cementocytes

57

What is the a groove between the enamel and the gingival epithelium surrounding the neck of the tooth?

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gingival sulcus

58

What specialized epithelium is bound to the tooth enamel by means of a cuticle?

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junctional epithelium

59

What is the muscular tube which transports swallowed material from the pharynx to the stomach?

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esophagus

60

What small mucus-secreting glands in the submucosa of the esophagus lubricate and protect the mucosa?

esophageal glands

61

What groups of glands in the mucosa of the esophagus near the stomach secrete additional mucus?

esophageal cardiac glands

62

What condition is caused by reflux of acid from the stomach into the esophagus?

reflux esophagitis (heartburn)

63

What disease is caused by erosion of the esophageal mucosa due to incompetency of the inferior esophageal sphincter?

gastroesophageal reflux disease (GERD)

64

What condition can result from metaplastic changes in the stratified squamous epithelium of the esophageal mucosa due to untreated GERD?

Barrett esophagus

65

How is it that swallowing begins with voluntary muscle action but finishes with involuntary peristalsis?

  1. In the upper third of the esophagus, the muscularis is exclusively skeletal muscle.
  2. The middle third of the esophagus has a combination of skeletal and smooth muscle.
  3. In the lower third of the esophagus, the muscularis is exclusively smooth muscle.
66

What is the viscous mass of ingested food and acidic fluid produced in the stomach?

chyme

67

What enzyme is secreted by the stomach to promote the initial digestion of proteins?

pepsin

68

What autoimmune disease is caused by deficiency of intrinsic factor, leading to inadequate absorption of vitamin B12, and reduced proliferation of erythroblasts?

pernicious anemia

69

What four regions make up the stomach?

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  1. cardia
  2. fundus
  3. body
  4. pylorus
70

What is the narrow transitional zone between the esophagus and the stomach?

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cardia

71

What is the funnel-shaped region of the stomach that opens into the small intestine?

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pylorus

72

What are the longitudinal folds in the mucosa and submucosa of the stomach that allow for expansion?

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rugae

73

What bacterial infection can cause painful erosive lesions of the mucosa in the stomach and intestine?

Helicobacter pylori

74

What are the invaginations on the mucosal surface of the stomach opening to the stomach lumen?

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gastric pits

75

What cells the stomach lumen and gastric pits secrete a viscous mucous layer that protects the mucosa?

surface mucous cells

76

What cells are found in a narrow segment (isthmus) between each gastric pit and the gastric glands?

stem cells

77

What four important cell types are found lining gastric pits and their associated glands?

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  1. mucous neck cells
  2. parietal cells
  3. chief (zymogenic) cells
  4. enteroendocrine cells
78

What cells are found in the necks of gastric glands secreting an acidic fluid containing mucin?

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mucous neck cells

79

What cells, found in the necks and deeper parts of the gastric glands, secrete hydrochloric acid (HCl)?

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parietal (oxyntic) cells

80

What is the deep, circular invagination of the apical plasma membrane on parietal cells called?

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intracellular canaliculus

81

What enzyme, contained in parietal cells, catalyzes the conversion of water and CO2 into HCO3 and H+?

carbonic anhydrase

82

Describe HCl synthesis by parietal cells in four steps.

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  1. carbonic anhydrase catalyzes the conversion of H2O and CO2 into HCO3 and H+
  2. H+ is pumped into the lumen of the gastric gland in exchange for K+
  3. HCO3 is exchanged by antiport at the basal cell domain for Cl
  4. Cl diffuses into the lumen of the gastric gland and combines with H+ to form HCl
83

What glycoprotein secreted by parietal cells is required for uptake of vitamin B12 in the small intestine?

intrinsic factor

84

What polypeptide secreted by enteroendocrine cells stimulates parietal cell secretory activity?

gastrin

85

What cells in the lower regions of the gastric glands have granules containing inactive enzyme pepsinogens?

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chief (zymogenic) cells

86

What are pepsinogens converted to in the acid environment of the stomach, which initiate the hydrolysis of ingested protein in the stomach?

pepsins

87

What enzyme secreted by chief cells of the gastric glands digests many lipids?

gastric lipase

88

What epithelial cells with endocrine or paracrine functions are scattered throughout the gastric mucosa?

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enteroendocrine cells

89

What hormone is secreted enteroendocrine cells in the gastric glands of the fundus?

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serotonin

90

What peptid is secreted enteroendocrine cells in the gastric glands of the pylorus?

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gastrin

91

What part of the endocrine system are enteroendocrine cells considered to be part of?

diffuse neuroendocrine system (DNES)

92

What are serotonin-secreting tumors of enteroendocrine EC cells called?

carcinoids

93

What are the coiled portions of the tubular glands in the cardia and pylorus which secrete mucus?

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cardiac or pyloric glands

94

What are the three layers of the muscularis of the stomach based on the orientation of the smooth muscle fibers?

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  1. outer longitudinal layer
  2. middle circular layer
  3. innermost oblique layer
95

What is the thickening of the middle muscularis layer at the pylorus of the stomach?

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pyloric sphincter

96

Where is the site where the digestive processes are completed and where the nutrients are absorbed?

small intestine

97

The small intestine is approximately 5 m. What are the three segments of the small intestine?

  1. duodenum
  2. jejunum
  3. ileum
98

What tumors of smooth muscle cells are the most common tumor of the stomach and small intestine?

leiomyomas

99

What are the circular or semilunar folds in the mucosa and submucosa of the small intestine?

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plicae circulares

100

What are the short outgrowths projecting from the mucosa into the lumen of the small intestine?

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villi

101

What is the central lymphatic extending into the core of loose connective tissue of each villus called?

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lacteal

102

What disease, characterized by an immune reaction to gluten, causes malabsorption and can lead to damage or destruction of the villi?

celiac disease (sprue)

103

What are the short tubular glands located between the villi of the small intestine?

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intestinal glands or crypts (of Lieberkühn)

104

What are the four main cell types in the mucosa of the small intestine?

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  1. enterocytes
  2. goblet cells
  3. paneth cells
  4. enteroendocrine cells
105

What are the columnar epithelial cells lining the villi which function in absorption?

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enterocytes

106

What is the prominent ordered region of microvilli located at the the apical end of each enterocyte?

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striated (or brush) border

107

Describe the absorption of lipids by enterocytes. (5)

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  1. Ingested fats are emulsified by bile acids to form a suspension of lipid droplets.
  2. Lipids are digested by lipases to produce glycerol, fatty acids, and monoglycerides.
  3. The products diffuse across the membranes and resynthesized as triglyceride.
  4. These triglycerides are packaged in vesicles containing chylomicrons.
  5. Chylomicrons are into the extracellular space, where most enter the lacteals.
108

What are the mucin-secreting cells interspersed among the absorptive enterocytes in the small intestine?

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goblet cells

109

What are the secretory located in the basal portion of the intestinal crypts below the stem cells?

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paneth cells

110

What hydrophobic peptides secreted by paneth cells break down membranes of microorganisms?

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defensins

111

What specialized epithelial cells, located in the ileum overlying the lymphoid follicles of Peyer patches, play an important part in mucosal immunity?

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M (microfold) cells

112

What is the nerve plexus located in the submucosa of the small intestine?

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submucosal (Meissner) nerve plexus

113

What are the branched tubular glands in the proximal part of the duodenum, which secrete alkaline mucus to neutralize chyme entering from the pylorus?

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duodenal (or Brunner) glands,

114

What are the large lymphoid nodule aggregates, located primarily in the ilium, underlying M cells?

Peyer patches

115

What is the nerve plexus located between the layers of the muscularis of the small intestine?

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myenteric (Auerbach) nerve plexus

116

What chronic inflammatory bowel disease occurs most commonly in the ileum or colon, effecting any or all layers of the tract wall?

Crohn disease

117

What portion of the GI tract absorbs water and electrolytes and forms indigestible material into feces?

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large intestine (bowel)

118

What are the five regions of the large intestine?

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  1. cecum
  2. ascending colon
  3. transverse colon
  4. descending colon
  5. rectum
119

What structure in the cecum separates the ileum from the large intestine?

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ileocecal valve

120

What is the blind projection of the cecum containing large aggregates of lymphoid tissue?

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appendix

121

What are large sacs arranged in series, making up the walls of the colon?

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haustra

122

What are the tubular glands lined by goblet and absorptive cells in the large intestine?

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intestinal glands

123

What are the columnar absorptive cells lining the intestinal glands of the large intestine?

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colonocytes

124

What are the three longitudinal bands of smooth muscle within the muscularis of the large intestine?

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teniae coli

125

What adenocarcinoma develops from benign polyps in the mucosal epithelium of the rectum or colon?

colorectal cancer

126

What are three screening tests for colorectal cancer?

  1. sigmoidoscopy
  2. colonoscopy
  3. fecal occult blood
127

What painful disorder is caused by swollen blood vessels in the mucosa or submucosa of the anal canal?

hemorrhoids

128

What is the 3-4 cm long canal located at the distal end of the GI tract?

anal canal

129

What is the transition area where the simple columnar mucosal lining of the rectum is replaced by stratified squamous epithelium of the anal canal?

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rectoanal junction

130

What are the longitudinal fold in the mucosa and submucosa of the anal canal ?

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anal columns

131

What is formed by the circular layer of the muscularis of the anal canal at the entrance to the anus?

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internal anal sphincter

132

What is formed by voluntary skeletal muscle surrounding the anus?

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external anal sphincter

133

What are bulges formed by herniation of the mucosa of the colon between teniae coli?

diverticulosis

134

What is local inflammation of diverticula due to impaction of fecal material?

diverticulitis

135

See summary table.

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