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1

gastroenterology

the study of the digestive tract and the diagnosis and treatment of its disorders

2

digestive system

the organ system that processes food, extracts nutrients from it, and eliminates the residue

3

five stages of digestion

ingestion
digestion
absorption-
compaction
defecation

4

ingestion

selective intake of food

5

digestion

mechanical and chemical breakdown of food into a form usable by the body

6

absorption-

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

7

compaction

absorbing water and consolidating the indigestible residue into feces

8

defecation

elimination of feces

9

mechanical digestion

the physical breakdown of food into smaller particles
–cutting and grinding action of the teeth
–churning action of stomach and small intestines
–exposes more food surface to the action of digestive enzymes

10

chemical digestion

aseries of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues)
–carried out by digestive enzymes produced by salivary glands, stomach, pancreas and small intestine

11

results:

•polysaccharides into monosaccharides
•proteins into amino acids
•fats into monoglycerides and fatty acids
•nucleic acids into nucleotides

12

some nutrients are present in a usable form in ingested food

–absorbed without being digested
–vitamins, free amino acids, minerals, cholesterol, and water

13

digestive system has two anatomical subdivisions

digestive tract
gastrointestinal

14

digestive tract

(alimentary canal)
–30 foot long muscular tube extending from mouth to anus
–mouth, pharynx, esophagus, stomach, small intestine, and large intestine

15

gastrointestinal (GI) tract

is the stomach and intestines

16

accessory organs

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

17

General Anatomy

•digestive tract is open to the environment at both ends
•most material in it has not entered the body tissues
–is considered to be external to the body until it is absorbed by the epithelial cells of the alimentary canal
•in a strict sense, defecated food residue was never in the body

18

basis structural plan

most of the digestive tract follows the basis structural plan with digestive tract wall consisting of the following tissue layers, in order from inner to outer surface

19

basis structural plan

order

•mucosa
–epithelium
–lamina propria
–muscularis mucosae
•submucosa
•muscularis externa
–inner circular layer
–outer longitudinal layer
•serosa
–areolar tissue
–mesothelium

20

mucosa

(mucous membrane) –lines the lumen and consists of:
–inner epithelium
–lamina propria –
–muscularis mucosa
–mucosa-associated lymphatic tissue (MALT) –

21

inner epithelium

•simple columnar in most of digestive tract
•stratified squamous from mouth through esophagus, and in lower anal canal

22

lamina propria

loose connective tissue layer

23

muscularis mucosa

thin layer of smooth muscle
•tenses mucosa creating grooves and ridges that enhance surface area and contact with food
•improves efficiency of digestion and nutrient absorption

24

mucosa-associated lymphatic tissue (MALT)

the mucosa exhibits an abundance of lymphocytes and lymphatic nodules

25

submucosa

thicker layer of loose connective tissue
–contains blood vessels, lymphatic vessels, a nerve plexus, and in some places mucus secreting glands that dump lubricating mucus into the lumen
–MALT extends into the submucosa in some parts of the GI tract

26

muscularis externa

consists of usually two layers of muscle near the outer surface

27

inner circular layer

•in some places, this layer thickens to form valves (sphincters) that regulate the passage of material through the tract

28

outer longitudinal layer

•responsible for the motility that propels food and residue through the tract

29

serosa

composed of a thin layer of areolar tissue topped by simple squamous mesothelium
–begins in the lower 3 to 4 cm of the esophagus
–ends just before the rectum

30

adventitia

a fibrous connective tissue layer that binds and blends the pharynx, most of the esophagus, and the rectum into the adjacent connective tissue of other organs

31

enteric nervous system

a nervous network in the esophagus, stomach, and intestines that regulated digestive tract motility, secretion, and blood flow
–thought to have over 100 million neurons
–more than the spinal cord
–functions completely independently of the central nervous system
•CNS exerts a significant influence on its action

32

composed of two networks of neurons

submucosal (Meissner) plexus
myenteric (Auerbach) plexus

33

submucosal (Meissner) plexus

in submucosa
•controls glandular secretion of mucosa
•controls movements of muscularis mucosae

34

myenteric (Auerbach) plexus

parasympathetic ganglia and nerve fibers between the two layers of the muscularis externa
•controls peristalsis and other contractions of muscularis externa

35

enteric nervous system contains sensory neurons that

monitor tension in gut wall and conditions in lumen

36

mesenteries

connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall
–allows stomach and intestines to undergo strenuous contractions
–allow freedom of movement in the abdominal cavity
–hold abdominal viscera in proper relationship to each other
–prevents the intestines from becoming twisted and tangled by changes in body position and by its own contractions
–provides passage of blood vessels and nerves that supply digestive tract
–contain many lymph nodes and lymphatic vessels

37

parietal peritoneum

a serous membrane that lines the wall of the abdominal cavity
–turns inward along posterior midline
–forms dorsal mesentery –a translucent two-layered membrane extending to the digestive tract
–the two layers of the mesentery separate and pass around opposite sides of the organ forming the serosa
–come together on the far side of the organ and continue as another sheet of tissue –the ventral mesentery
•may hang freely in the abdominal cavity
•may attach to the anterior abdominal wall or other organs

38

lesser omentum

a ventral mesentery that extends from the lesser curvature of the stomach to theliver

39

greater omentum

hangs from the greater curvature of the stomach
–covers the small intestines like an apron
–the inferior margin turns back on itself and passes upward
–forming a deep pouch between its deep and superficial layers
–inner superior margin forms serous membranes around the spleen and transverse colon

40

mesocolon

extension of the mesentery that anchors the colon to the posterior abdominal wall

41

intraperitoneal

when an organ is enclosed by mesentery on both sides
–considered within the peritoneal cavity
–stomach, liver, and other parts of small and large intestine

42

retroperitoneal

when an organ lies against the posterior body wall and is covered by peritoneum on its anterior side only
–considered to be outside the peritoneal cavity
–duodenum, pancreas, and parts of the large intestine

43

motility and secretion of the digestive tract are controlled by

neural, hormonal, and paracrine mechanisms

44

neural control

short (myenteric) reflexes
long (vagovagal) reflexes

45

short (myenteric) reflexes

stretch or chemical stimulation acts through myenteric plexus
•stimulates peristaltic contractions of swallowing

46

long (vagovagal) reflexes

parasympathetic stimulation of digestive motility and secretion

47

hormones

–chemical messengers secreted into bloodstream, and stimulate distant parts of the digestive tract
–gastrin and secretin

48

paracrine secretions

–chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells

49

The Mouth

the mouth is known as the oral, or buccal cavity

50

functions include:

–ingestion (food intake)
–other sensory responses to food –chewing and chemical digestion
–swallowing, speech, and respiration

51

mouth enclosed by

cheeks, lips, palate, and tongue

52

oral fissure

anterior opening between lips

53

fauces

posterior opening to the throat

54

stratified squamous epithelium

lines mouth
–keratinized in areas subject to food abrasion –gums and hard palate
–nonkeratinizedin other areas –floor of mouth, soft palate, and inside of cheek and lips

55

cheeks and lips

–retain food and push it between the teeth for chewing
–essential for articulate speech
–essential for sucking and blowing actions, including suckling by infants
–fleshiness due to subcutaneous fat, buccinator muscle of the cheek, and the orbicularis oris of the lips

56

labial frenulum

median fold that attaches each lip to the gum between the anterior incisors

57

vestibule

the space between cheek or lips and the teeth

58

lips divided into three areas:

cutaneous area

59

cutaneous area

colored like the rest of the face
•has hair follicles and sebaceous glands

60

red (vermillion) area

hairless region where lips meet
•tall dermal papilla that allows blood vessels and nerves to come closer to epidermal surface
•redder and more sensitive than cutaneous area

61

labial mucosa

the inner surface of the lips facing the gums and teeth

62

tongue

muscular, bulky, but remarkably agile and sensitive organ
–manipulates food between teeth while it avoids being bitten
–can extract food particles from the teeth after a meal
–sensitive enough to feel a stray hair in a bite of food

63

nonkeratinized stratified squamous epithelium covers

its surface

64

lingual papillae

bumps and projections on the tongue that are the sites of the taste buds

65

body

anterior two-thirds of the tongue occupies oral cavity

66

root

posterior one-third of the tongue occupies the oropharynx

67

vallate papillae

a V-shaped row of papillae that mark the boundary between the body and root of the tongue

68

terminal sulcus

groove behind the V-shaped vallate papillae

69

lingual frenulum

median fold that attaches the body to the floor of the mouth

70

intrinsic muscles

are contained entirely within the tongue
•produce the subtle tongue movements of speech

71

extrinsic muscles

with origins elsewhere and insertions in the tongue
•produce stronger movements of food manipulation
•genioglossus, hyoglossus, palatoglossus, and styloglossus

72

lingual glands

serous and mucous glands amid the extrinsic muscles
•secrete a portion of the saliva

73

lingual tonsils

contained in the root

74

palate

separates the oral cavity from the nasal cavity
–makes it possible to breathe while chewing food

75

hard (bony) palate

anterior portion that is supported by the palatine processes of the maxillaeand the palatinebones

76

palatine rugae

transverse ridges that help the tongue hold and manipulate food

77

soft palate

posterior with a more spongy texture
–composed of skeletal muscle and glandular tissue
–no bone

78

uvula

conical medial projection visible at the rear of the mouth
–helps retain food in the mouth until one is ready to swallow

79

pair of muscular arches on each side of the oral cavity

–palatoglossal arch –anterior arch
–palatopharyngeal arch –posterior arch
–palatine tonsils are located on the wall between the arches

80

dentition

the teeth

81

masticate food into smaller pieces

–makes food easier to swallow
–exposes more surface area for action of digestive enzymes speeding chemical digestion

82

32 adult teeth –20 deciduous (baby) teeth

–16 in mandible
–16 in maxilla

83

from midline to the rear of each jaw

•2 incisors–chisel-like cutting teeth used to bite off a piece of food
•1 canine–pointed and act to puncture and shred food
•2premolars –broad surface for crushing and grinding
•3 molars–even broader surface for crushing and grinding

84

alveolus

tooth socket in bone

85

gomphosis joint

between tooth and bone

86

periodontal ligament

modified periosteum whose collagen fibers penetrate into the bone on one side and into the tooth on the other
–anchors tooth firmly in alveolus
–allows slight movement under pressure of chewing

87

gingiva (gum)

covers the alveolar bone

88

regions of a tooth

crown
root
neck
gingival sulcus

89

crown

portion above the gum

90

root

the portion below the gum, embedded in alveolar bone

91

neck

the point where crown, root, and gum meet

92

gingival sulcus

space between the tooth and the gum
•hygiene in the sulcus in important to dental health

93

dentin

hard yellowish tissue that makes up most of the tooth

94

enamel

covers crown and neck

95

cementum

covers root
•cementum and dentin are living tissue and can regenerate
•enamel is noncellular secretion formed during development

96

root canal

in the roots leading to pulp cavity in the crown
–nerves and blood vessels

97

apical foramen

pore at the basal end of each root canal

98

occlusion

meeting of the teeth with the mouth closed

99

Deciduous Teeth

20 deciduous teeth (milk teeth or baby teeth)
•teeth develop beneath the gums and erupt in a predictable order
–erupt from 6 to 30 months
–beginning with incisors
–between 6 and 32 years of age, are replaced by 32 permanent teeth

100

(wisdom teeth

third molars (wisdom teeth) erupt from 17 –25
–may be impacted–crowded against neighboring teeth and bone so they cannot erupt

101

Tooth and Gum Disease

the human mouth is home to more than 700 species of microorganisms, especially bacteria

102

plaque

sticky residue on the teeth made up of bacteria and sugars
–calculus –calcified plaque
–bacteria metabolize sugars and release acids that dissolve the minerals of enamel and dentin to form dental caries (cavities

103

root canal therapy

is necessary if cavity reaches pulp

104

calculus

in the gingival sulcus wedges the tooth and gum apart
–allows bacterial invasion of the sulcus
–gingivitis–inflammation of the gums
–periodontal disease –destruction of the supporting bone around the teeth which may result in tooth loss

105

mastication(chewing)

breaks food into smaller pieces to be swallowed and exposes more surface to the action of digestive enzymes

106

mastication

process

–first step in mechanical digestion
–food stimulates oral receptors that trigger an involuntary chewing reflex
–tongue, buccinator, and orbicularis oris manipulate food
–masseter and temporalis elevate the teeth to crush food
–medial and lateral pterygoids, and masseter swing teeth in side-to-side grinding action of molars

107

saliva

–moisten mouth
–begin starch and fat digestion
–cleanse teeth
–inhibit bacterial growth
–dissolves molecules so they can stimulate the taste buds
–moistens food and binds it together into bolus to aid in swallowing

108

Saliva

contents

hypotonic solution of 97.0% to 99.5% water and the following solutes:
–salivary amylase –enzyme that begins starch digestion in the mouth
–lingual lipase –enzyme that is activated by stomach acid and digests fat after the food is swallowed
–mucus–binds and lubricates the mass of food and aids in swallowing
–lysozyme–enzyme that kills bacteria
–immunoglobulin A (IgA) –an antibody that inhibits bacterial growth
–electrolytes-Na+, K+, Cl-, phosphate and bicarbonate

109

saliva

ph

pH of 6.8 to 7.0

110

intrinsic salivary glands

small glands dispersed amid other oral tissues
–lingual glands –in the tongue –produce lingual lipase
–labial glands –inside of the lips
–buccal glands –inside of the cheek
–all secrete saliva at a fairly constant rate

111

extrinsic salivary glands

three pairs connected to oral cavity by ducts
–parotid
–submandibular gland
–sublingual glands –

112

parotid

–located beneath the skin anterior to the earlobe
•mumps is an inflammation and swelling of the parotid gland caused by a virus

113

submandibular gland

–located halfway along the body of the mandible
•its duct empties at the side of the lingual frenulum, near the lower central incisors

114

sublingual glands

–located in the floor of the mouth
•has multiple ducts that empty posterior to the papilla of the submandibular duct

115

Histology of Salivary Glands

•compound tubuloacinar glands
–branched ducts ending in acini
•mucous cells secrete mucus
•serous cells secrete thin fluid rich in amylase and electrolytes
•mixed acinus has both mucous and serous cells

116

Salivation

extrinsic salivary glands secrete about of 1 to 1.5 L of saliva per day

117

cells of acini

filter water and electrolytes from blood and add amylase, mucin, and lysozyme

118

salivary nuclei

in the medulla oblongata and pons respond to signals generated by presence of food
–tactile, pressure, and taste receptors
–salivary nuclei receive input from higher brain centers as well
•odor, sight, thought of food stimulates salivation
–send signals by way of autonomic fibers in the facial and glossopharyngeal nerves to the glands

119

parasympathetics

stimulate the glands to produce an abundance of thin, enzyme-rich saliva

120

sympathetic stimulation

stimulates the glands to produce less, and thicker saliva with more mucus

121

bolus

mass swallowed as a result of saliva binding food particles into a soft, slippery, easily swallowed mass

122

pharynx

a muscular funnel that connects oral cavity to esophagus and allows entrance of air from nasal cavity to larynx
–digestive and respiratory tracts intersect

123

pharyngeal constrictors

(superior, middle, and inferior) -circular muscles that force food downward during swallowing
–when not swallowing, the inferior constrictor remains contracted to exclude air from the esophagus
–this constriction is considered to be the upper esophageal sphincter although it is not an anatomical feature
–disappears at the time of death when the muscles relax, so it is a physiological sphincter, not an anatomical structure

124

esophagus

a straight muscular tube 25-30 cm long
–begins at level between C6 and the cricoid cartilage
–extends from pharynx to cardiac orifice of stomach passing through esophageal hiatus in diaphragm

125

lower esophageal sphincter

food pauses at this point because of this constriction
•prevents stomach contents from regurgitating into the esophagus
•protects esophageal mucosa from erosive effect of the stomach acid

126

heartburn

burning sensation produced by acid reflux into the esophagus

127

esophagus

tissue type

–nonkeratinized stratified squamous epithelium
–esophageal glands in submucosa secrete mucus
–deeply folded into longitudinal ridges when empty
–skeletal muscle in upper one-third, mixture in middle one-third, and only smooth muscle in the bottom one-third
–meets stomach at level of T7
–covered with adventitia

128

swallowing

(deglutition) –a complex action involving over 22 muscles in the mouth, pharynx, and esophagus

129

swallowing center

pair of nuclei in medulla oblongata that coordinates swallowing
•communicates with muscles of the pharynx and esophagus by way of trigeminal, facial, glossopharyngeal, and hypoglossal nerves

130

swallowing occurs in two phases:

buccal phase
pharyngoesophageal phase

131

buccal phase

under voluntary control
•tongue collects food, presses it against the palate forming a bolus, and pushes it posteriorly
•food accumulates in oropharynx in front of the „blade‟ of the epiglottis
•epiglottis tips posteriorly and food bolus slides around it
•bolus enters laryngopharynx and stimulates tactile receptors and activates next phase

132

pharyngoesophageal phase

•three actions prevent food and drink from reentering the mouth or entering the nasal cavity or larynx
–the root of the tongue blocks the oral cavity
–the soft palate rises and blocks the nasopharynx
–the infrahyoid muscles pull the larynx up to meet the epiglottis while laryngeal folds close the airway
•food bolus is driven downward by constriction of the upper, then middle, and finally the lower pharyngeal constrictors
•bolus enters esophagus, stretches it, and stimulates peristalsi

133

peristalsis

wave of muscular contraction that pushes the bolus ahead of it
–an entirely involuntary reflex

134

stomach

a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
–primarily functions as a food storage organ
•internal volume of about 50 mL when empty
•1.0 –1.5 L after a typical meal
•up to 4 L when extremely full and extend nearly as far as the pelvis

135

stomach

function

mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat
–chyme –soupy or pasty mixture of semi-digested food in the stomach
•most digestion occurs after the chyme passes on to the small intestine

136

chyme

soupy or pasty mixture of semi-digested food in the stomach

137

stomach

divided into four regions

cardiac region (cardia)
fundic region (fundus
body (corpus)

138

cardiac region (cardia)

small area within about 3 cm of the cardiac orifice

139

fundic region (fundus

dome-shaped portion superior to esophageal attachment

140

body (corpus)

makes up the greatest part of the stomach

141

pyloric region

narrower pouch at the inferior end
–subdivided into the funnel-like antrum
–and narrower pyloric canal that terminates at pylorus
–pylorus –narrow passage to duodenum

142

pyloric (gastroduodenal) sphincter

regulates the passage of chyme into the duodenum

143

stomach receives:
–parasympathetic fibers from

vagus

144

stomach receives:
sympathetic fibers from

celiac ganglia

145

supplied with blood by branches of the

celiac trunk

146

all blood drained from stomach and intestines enters

hepatic portal circulation and is filtered through liver before returning to heart

147

stomach

simple columnar epithelium covers

mucosa
–apical regions of its surface cells are filled with mucin
–swells with water and becomes mucusafter it is secreted

148

gastric rugae

mucosa and submucosa flat when stomach is full, but form longitudinal wrinkles called gastric rugae when empty

149

muscularis externa

has three layers instead of two
•outer longitudinal, middle circular and inner oblique layers

150

gastric pits

depressions in gastric mucosa
–lined with simple columnar epithelium
–two or three tubular glands open into the bottom of each gastric pit

151

cardiac glands

in cardiac region

152

pyloric glands

in pyloric regions

153

gastric glands

in the rest of the stomach

154

Cells of Gastric Glands

mucous cells


155

mucous cells

secrete mucus
–predominate in cardiac and pyloric glands
–in gastric glands, called mucous neck cells since they are concentrated at the neck of the gland

156

regenerative (stem) cells

found in the base of the pit and in the neck of the gland
–divide rapidly and produce a continual supply of new cells to replace cells that die

157

parietal cells

found mostly in the upper half of the gland
–secrete hydrochloric acid (HCl), intrinsic factor, and a hunger hormone called ghrelin

158

chief cells

most numerous
–secrete gastric lipase and pepsinogen
–dominate lower half of gastric glands
–absent in pyloric and cardiac glands

159

enteroendocrine cells

concentrated in lower end of gland
–secrete hormones and paracrine messengers that regulate digestion

160

gastric juice

2 –3 liters per day produced by the gastric glands
•mainly a mixture of water, hydrochloric acid, and pepsin

161

gastric juice has a high concentration of

hydrochloric acid
–pH as low as 0.8

162

parietal cells produce

HCl and contain carbonic anhydrase (CAH)

163

Functions of Hydrochloric Acid

•activates pepsin and lingual lipase
•breaks up connective tissues and plant cell walls
–helps liquefy food to form chyme
•converts ingested ferric ions (Fe3+) to ferrous ions (Fe2+)
–Fe2+ absorbed and used for hemoglobin synthesis
•contributes to nonspecific disease resistance by destroying most ingested pathogens

164

zymogens

digestive enzymes secreted as inactive proteins
–converted to active enzymes by removing some of their amino acids

165

pepsinogen

zymogen secreted by the chief cells
–hydrochloric acid removes some of its amino acids and forms pepsin that digests proteins
–autocatalytic effect –as some pepsin is formed, it converts more pepsinogen into pepsin

166

pepsin digests dietary proteins into

shorter peptide chains
–protein digestion is completed in the small intestine

167

gastric lipase

produced by chief cells
•gastric lipase and lingual lipase play a minor role in digesting dietary fats
–digests 10% -15% of dietary fats in the stomach
–rest digested in the small intestine

168

intrinsic factor

a glycoprotein secreted by parietal cells
•essential to absorption of vitamin B12 by the small intestine
–binds vitamin B12 and intestinal cells absorb this complex by receptor-mediated endocytosis

169

vitamin B12 is needed to

synthesize hemoglobin
–prevents pernicious anemia

170

indispensable function of the stomach

secretion of intrinsic factor is the only indispensable function of the stomach
–digestion can continue if stomach is removed (gastrectomy), but B12supplements will be needed

171

Chemical Messengers

gastric and pyloric glands have various kinds of enteroendocrine cells that produce as many as 20 chemical messengers
–some are hormones enter blood and stimulate distant cells
–others are paracrine secretions that stimulate neighboring cells
–several are peptides produced in both the digestive tract and the central nervous system –gut-brain peptides

172

Gastric Motility

swallowing center of medulla oblongata signals stomach to relax
•food stretches stomach activating a receptive-relaxation response
–resists stretching briefly, but relaxes to hold more food
•soon stomach shows a rhythm of peristaltic contractions controlled by pacemaker cells in longitudinal layer of muscularis externa

173

allowing only a small amount into the duodenum enables the duodenum to:

•neutralize the stomach acid
•digest nutrients little by little

174

vomiting

the forceful ejection of stomach and intestinal contents (chyme) from the mouth

175

emetic center

in the medulla oblongata integrates multiple muscle actions

176

vomiting is usually preceded by

nausea and retching

177

retching

thoracic expansion and abdominal contraction creates a pressure difference that dilates the esophagus

178

vomiting –occurs when

abdominal contractions and rising thoracic pressure force the upper esophageal sphincter to open
–esophagus and body of the stomach relax
–chyme is driven out of the stomach and mouth by strong abdominal contractionscombined with reverse peristalsis of gastric antrum and duodenum

179

projectile vomiting

sudden vomiting with no prior nausea or retching
–common in infants after feeding

180

chronic vomiting causes:

dangerous fluid, electrolyte, and acid-base imbalances

181

bulimia–

eating disorder in which the tooth enamel becomes eroded by the hydrochloric acid in the chyme

182

most digestion and nearly all absorption occur after

the chyme has passed into the small intestine
•stomach does not absorb any significant amount of nutrients

183

alcoholis absorbed mainly by

small intestine
–intoxicating effects depends partly on how rapidly the stomach is emptied

184

living stomach is protected in three ways from the harsh acidic and enzymatic environment it creates

–mucous coat –
–tight junctions -
–epithelial cell replacement
•breakdown of these protective measures can result in inflammation and peptic ulcer

185

mucous coat

thick, highly alkaline mucus resists action of acid and enzymes

186

tight junctions

between epithelial cells prevent gastric juice from seeping between them and digesting the connective tissue of the lamina propria and beyond

187

epithelial cell replacement

stomach epithelial cells live only 3 to 6 days
•sloughed off into the chyme and digested with the food
•replaced rapidly by cell division in the gastric pits

188

gastritis

inflammation of the stomach can lead to a peptic ulceras pepsin and hydrochloric acid erode the stomach wall
•most ulcers are caused by acid-resistant bacteria, Helicobacter pylori that can be treated with antibiotics and Pepto-Bismol

189

Regulation of Gastric Function

nervous and endocrine systems collaborate

190

gastric activity is divided into three phases:

cephalic phase
gastric phase
intestinal phase
•phases overlap and can occur simultaneously

191

cephalic phase

stomach being controlled by brain

192

gastric phase

stomach controlling itself

193

intestinal phase

stomach being controlled by small