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Bioscience II > GI System Function and Pathology > Flashcards

GI System Function and Pathology Flashcards

1
Q

What are the four layers of the GI tract from innermost to outermost?

A

mucosal layer–>submucosal layer–> muscularis layer–> Serosal layer

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2
Q

What makes up the mucosal layer?

A

epithelium
lamina propria
muscularis mucosae

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3
Q

what does the lamina propria of the mucosal layer contain?

A

connective tissue layer that contains capillaries and lacteals

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4
Q

what is the muscularis mucosae?

A

the muscle layer of the mucosa that helps to increase surface area but NOT motility

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5
Q

what does the submucosal layer contain?

A

it is a connective tissue layer that contains blood vessels, secretory glands and neurons

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6
Q

What are the neurons of the submucosal layer known as?

A

known as Meissner’s plexus; they are mostly post-ganglionic parasympathetic neurons

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7
Q

What does the muscularis layer contain?

A

it has an inner muscle layer that is circular to wrap around tubes and has contractions to narrow the tube
it has an outer muscle layer that is longitudinal and its contractions shorten and increase the diamerter of the tube

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8
Q

What group of neurons does the muscularis layer contain?

A

the myenteric plexus or Auerbach’s plexus

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9
Q

What is the serosal layer similar to?

A

same as the visceral peritoneum

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10
Q

How is absorption limited?

A

by digestion

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11
Q

what can limit digestion?

A

secretion and motility

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12
Q

What initiates chemical digestion in the mouth?

A

salivary enzymes such as beta amylase that can break some CHO bonds

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13
Q

What does saliva contain?

A

water, salts, mucus, some amino acids, IgA, amylase and some salivary lipases

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14
Q

Name the functions of saliva

A

chemical digestion of CHO and, to a lesser extent, lipids
• lubrication of GI tract, aids in bolus formation
• enhances taste - nutrients need to be in solution to interact with taste buds
• keeps mouth and teeth clean

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15
Q

What can stimulate saliva production?

A

parasympathetic stimulation produces copious, watery saliva
• smell, thought, or sight of foods
• sour foods
• local reflexes - act of chewing enhances production

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16
Q

What are the 4 pairs of salivary glands?

A

parotid, sublingual, submaxillary, buccal

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17
Q

What is Sjogrens syndrome?

A

lymphocyte and plasma cell invasion of salivary and lacrimal glands

  • dry mouth (xerostommia) and eyes are the result
  • associated with connective tissue disorders such as rheumatoid arthritis, lupus, scleroderma
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18
Q

Where does the esophagus move food from and to

A

moves bolus of food from the mouth to the stomach via peristalsis

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19
Q

What is the proximal 1/3 of the espohagus made up of?

A

skeletal muscle; the rest is smooth muscle

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20
Q

What transition occurs at the GEJ?

A

at this point there is an abrupt transition from stratified squamous epithelium to the pseudocolumnar
epithelium seen in the stomach

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21
Q

What is also found at the GEJ?

A

the lower esophageal sphincter which functions to allow ingested food into the stomach and prevent movement of gastric contents into the esophagus

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22
Q

Define GERD

A

gastroespohageal reflux disease
heartburn is not the equivalent of reflux, however, heartburn that occurs more than twice per
week is probably reflux

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23
Q

the primary symptoms of GERD

A

usually upper/mid abdomen, can radiate into chest, throat, shoulder, back
- described most often as burning
- pain is typically constant but waxes and wanes
- made worse after eating, especially large meals
- tends to be most severe at night or when individual is reclining
There can also be respiratory symptoms

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24
Q

Treatment for GERD

A 
• stop smoking
• eliminate alcohol consumption
• lose weight
• eat small meals
• wear loose fitting clothing
• avoid recumbency after meals, raise head of the bed
surgical= fundoplication
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25
Q

what causes reflux in children

A

small stomach and esophagus!
• more frequent spontaneous relaxations of LES
usually resolves by age 2
occurs at least once/day in half of infants (0-3 months)

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26
Q

main consequences of GERD

A

pain and mucosal injury do not correlate!

  • esophageal ulceration and stricture (connective tissue narrowing) can occur!
  • Barrett’s esophagus
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27
Q

what is Barrett’s esophagus

A

conversion of esophageal mucosa to intestinal mucosa in response to repeated exposure
to gastric contents!
• occurs in 10-15% of people with long-term GERD, primarily white males over 50 yrs old!
• GERD can result in a cycle of repetitive cell turnover and eventual metaplasia

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28
Q

what type of cancer is Barrett’s esophagus a risk factor for?

A

esophageal cancer

it creates a 30-125x greater risk

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29
Q

typical symptoms of esophageal cancer

A

dysphagia (difficulty swallowing)

weight loss

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30
Q

primary types of esophageal cancer

A

adenocarcinoma

squamous cell carcinoma

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31
Q

Where does Adenocarcinoma most likely occur?

A

distal 1/3 of the esophagus

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32
Q

facts about adenocarcinoma

A

50% of esophageal cancer cases!
• tends to be associated with Barrett’s esophagus!
• more common in white males!

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33
Q

In which population is squamous cell carcinoma more common?

A

more common in African Americans

more closely associated with environmental factors such as alcohol and smoking

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34
Q

Which type of presentation of esophageal cancer has the poorest survival rate?

A

distant lymph node involvement has a 3% survival rate
localized=38%
regional=20%

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35
Q

which type of esophageal cancer has a slightly better prognosis?

A

adenocarcinoma

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36
Q

what separates the esophagus from the stomach?

A

LES

lower esophageal sphincter

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37
Q

What separates the stomach from the duodenum?

A

pyloric sphincter

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38
Q

what are the 4 cell types in the gastric pits of the surface epithelium?

A

mucous neck cells
chief (zygomatic) cells
parietal cells
endocrine cells

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39
Q

what do mucous neck cells secrete?

A

they secrete alkaline mucus that protects the underlying structures from the contents of the stomach

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40
Q

what do chief cells make?

A

they make pepsinogen; precursor(active form) of pepsin

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41
Q

what do parietal cells make?

A

HCl and intrinsic factor

hydrochloric acid has a low pH that kills bacteria in the stomach and denatures ingested proteins to activate pepsin

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42
Q

what is intrinsic factor necessary for?

A

vitamin B12 absorption

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43
Q

what develops from a lack of intrinsic factor/vitamin B12?

A

pernicious anemia

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44
Q

what do endocrine cells secrete?

A

gastrin which increases the strength of gastric peristaltic contractions

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45
Q

what does lamina propria contain?

A

capillaries that provide fluids for secretions and act as nutrient blood supply

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46
Q

what types of cells generate smooth muscle contraction in the stomach?

A

pacemaker cells create a wave of excitation that spreads

basic electrical rhythm generates peristaltic contractions (weak at rest when the stomach is empty)

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47
Q

What area of the GI acts as a feedback of contractions?

A

the duodenum inhibits strength of contractions to ensure complete nutrient absorption

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48
Q

What activities enhance the secretion of pepsinogen and HCl?

A 
presence of proteins
distention of the stomach
parasympathetic stimulation
gastrin
histamine
49
Q

What inhibits pepsinogen and HCl?

A

increased duodenal activity

50
Q

What can stimulate mucus secretion?

A

vagal stimulation and irritation from ingested foods

51
Q

What is acute gastritis?

A

local irritation as a result of exposure to alcohol, aspirin or other NSAIDs, bacterial endotoxins!
- varies in severity!
• can include erosion of mucosa!
- usually self limiting -

52
Q

How is acute gastritis self-limiting?

A

removal of irritant results in regeneration and healing of mucosa over several days!

53
Q

What is chronic gastritis?

A

chronic inflammatory changes that lead to atrophy of glandular epithelium
there are no grossly lesions
leads to increased risk of stomach cancer

54
Q

What is peptic ulcer disease?

A

disruption of the mucosal barrier and exposure of underlying tissue to HCl and pepsin can result in ulceration of epithelium

55
Q

Which type of ulcer is more common at any age?

A

duodenal are 5x more common

men are 3-4 times more likely to have ulcers in either location

56
Q

What type of ulcers is more common in older adults?

A

gastric ulcers have a peak incidence of 55-70 years old

men are 3-4 times more likely to have ulcers in either location

57
Q

What is the most common cause of ulcers?

A

Helicobacter pylori
nearly all duodenal and 70% of gastric ulcers !
• not all people with infection get ulcers!

58
Q

Result of NSAID use and ulcers

A

20% of gastric ulcers and
2-5% of duodenal ulcers are a result of NSAID use
aspirin is the most likely cause

59
Q

symptoms of ulcers

A

worse when the stomach is empty!
• typically described as burning or gnawing!
• occurs in midline of epigastrum, can radiate to chest, back, or right shoulder!
• exacerbating/remitting pattern is common!
• pain is relieved by consumption of food or antacids!

60
Q

treatment of ulcers

A

diagnosis of H. pylori infection is very important!
- antibiotics!
• clarithromycin, metronidazole, amoxicillin, or tetracycline (often 2 in combination)!
- proton pump inhibitors!
- coating agents!
- prostaglandin analogs!
- often used in combinations!

61
Q

How do H2 receptors treat GERD/ulcers?

A

inhibit binding of histamine to H2 receptors, suppress HCl secretion by parietal cells!
• also decrease gastric acid secretion that occurs as a result of stimulation by gastrin and acetylcholine
more effective when combined with proton pump inhibitors

62
Q

How to proton pump inhibitors work in treatment?

A

drug molecules irreversibly bind to H+/K+ ATPase (proton pump) of parietal cells!
- for parietal cell to resume acid secretion, it must synthesize new pumps, a process which
takes about 18 hours
more expensive but more effective than H2 blockers
adverse effect: increased fracture risk with prolonged use

63
Q

How does Pepto-Bismol work?

A

a bismuth that forms a barrier and stimulates bicarbonate and PGE2 secretion, inhibits H. pylori growth

64
Q

risk factors for stomach cancer

A

genetics!
• age - 60s-80s!
• consumption of smoked and preserved foods!
• autoimmune gastritis!
• benign adenomas/polyps!
• H. pylori infection, though most people with infection never develop cancer!

65
Q

what is the most important part of the stomach for digestion and absorption?

A

the duodenum

66
Q

What do the endocrine cells of the small intestine secrete?

A

secretin and CCK (cholecystokinin)

both of these hormones control pancreatic secretions

67
Q

importance of brush border enzymes

A

membrane bound enzymes on the surface of absorptive cells in the small intestine!
- perform final breakdown of consumed nutrients!

68
Q

examples of brush border enzymes

A

disaccharases and peptidases

69
Q

How does sympathetic stimulation of brunner’s glands contribute to duodenal ulcers?

A

Brunner’s glands produce alkaline mucus which can be inhibited by sympathetic stimulation therefore causing inappropriate lowering of the duodenal pH

70
Q

What stimulates the release of CCK?

A

presence of nutrients, specifically fat, in the duodenum

71
Q

What does CCK stimulate?

A

causes the pancreas to produce enzyme-rich secretions that create the gall bladder to contract

72
Q

where is bile stored?

A

in the gall bladder and

is made by the liver

73
Q

What occurs with contraction of the gall bladder?

A

bile salts are released into the duodenum after CCK stimulates the gall bladder

74
Q

Name the 2 types of contractions

A

segmenting contractions produced by BBR

peristalsis

75
Q

What are segmenting contractions?

A

most important when small intestine is moving a meal!
- small segments are alternately contracting and relaxing!
- tend to move contents up and down within small intestine!
- function to mix contents, maximize contact with absorptive cells!
- BER associated with these contractions!
• occur about 12 times/minute in duodenum!
• slow with progression through small intestine, down to 8x/minute in terminal ileum!
• this allows for gradual movement through length of small intestine!

76
Q

When is peristalsis most active?

A

between meals to keep whatever is in the small intestine moving distally

77
Q

What increases secretion and motility?

A

parasympathetic stimulation and distention

78
Q

Which enzymes are responsible for digestion/absorption of protein?

A

gastric, pancreatic and brush border enzymes absorb protein which is actively transported via facilitated diffusion and brought to the liver via portal system

79
Q

Which enzymes control digestion/absorption of CHO?

A

salivary, pancreatic and brush border enzymes

80
Q

Which enzymes control digestion/absorption of fat?

A

pancreatic lipases mainly

81
Q

what type of absorption must occur for water to be absorbed?

A

solute reabsorption needs to occur; water always follows solute

82
Q

What organ regulates absorption of salts?

A

the kidney

83
Q

How are water soluble vitamins (B and C) absorbed?

A

by diffusion or mediated transport

84
Q

Where does the gastro-ileal reflex move contents?

A

from the terminal ileum of the SI to the proximal colon of the large intestine

85
Q

what does the bacteria in the colon do?

A

acts on undigested material such as fiber to produce Vitamin K, small chain fatty acids which are absorbable and intestinal gas

86
Q

what is the major source of motility of the large intestine?

A

haustral churning
haustras are puckers created by the thin longitudinal muscle layer of the large intestine
a major form of motility is mass movement by the gastro-colic reflex

87
Q

Does peristalsis occur in the colon?

A

it is very weak

88
Q

what reflexively stimulates mass movement in the colon?

A

food in the stomach that increases both gastric motility and gastrin production to initiate mass movement by the gastro-colic reflex

89
Q

What stimulates the defecation reflex?

A

stretch of rectal smooth muscle by parasympathetic efferents

cortical acknowledgement must occur to allow relaxation of the external sphincter

90
Q

Define Irritable Bowel Syndrome (IBS)

A

chronic disorder characterized by abdominal pain and altered bowel habits in the absence of pathology!
• as no specific pathology is present, it is usually a diagnosis of exclusion!

91
Q

Who is more likely to have IBS?

A

women are 2-3x more likely

92
Q

symptoms of IBS (irritable bowel syndrome)

A

recurrent abdominal pain at least 3 days/month for 3 months !
- discomfort associated with at least 2 of 3 !
• bowel movements that occur more or less often than usual!
• bowel movements that relieve the discomfort!
• stool that appears less solid and more watery, or harder and more lumpy, than usual!
- other symptoms include nausea, vomiting, bloating, gas, passing mucus, feeling that a
bowel movement is incomplete

93
Q

What are the 4 subtypes of Irritable Bowel Syndrome (IBS)

A

IBS with constipation (IBS-C)!

  • IBS with diarrhea (IBS-D)!
  • mixed IBS (IBS-M)!
  • unsubtyped IBS (IBS-U)!
94
Q

List some of the causes of Irritable Bowel Syndrome (IBS)

A

brain/gut signal problems!
- GI motor dysfunction!
- hypersensitivity - lower pain threshold in response to stretching of bowel!
- contribution of mental health issues - anxiety, depression, panic disorder, post-traumatic
stress!
- bacterial gastroenteritis!
- small intestinal bacterial overgrowth!
- altered levels of neurotransmitters, appear to fluctuate in response to hormone levels!
- genetics!
- food sensitivity!
REMEMBER there is no specific pathology so diagnosis is of exclusion

95
Q

Treatment for IBS

A

lifestyle changes!
• stress management!
• diet - high fiber, increased water intake in patients with constipation!
• avoiding some foods - caffeine, legumes, lactose, and fructose!
- drugs!
• anti-cholinergics for IBS-D!
• anti-diarrheals!
• tricyclic antidepressants - act as visceral analgesics, decrease motility, at doses that
would be sub-therapeutic for treatment of depression!

96
Q

Define Inflammatory Bowel Disease (IBD)

A

inflammation of uncertain origin but with a pattern of

familial occurrence

97
Q

What two conditions make up Inflammatory Bowel Disease (IBD)

A

Ulcerative Colitis and Chron’s Disease

98
Q

Chron’s Disease

A

may involve entire length of GI tract from mouth to anus, but only rarely are more proximal
regions involved
much more common that ileum and cecum are involved
occurs slightly more in females
bimodal distribution of age of onset
cause is unknown

99
Q

What are skip lesions?

A

segmental, discontinuous involvement by a non-specific granulomatous inflammatory
process
appears as patchy inflamed wound that skips over some areas

100
Q

What are some characteristics that are more common in Chron’s?

A

granulomatous inflammation and ulceration that can produce obstruction, stricture, abscesses and FISTULAS
submucosal involvement
skip lesions
primarily ileum is involved

101
Q

symptoms of Chron’s

A 
depends on the location of the lesion
fever!
• diarrhea!
• nausea, vomiting!
• fluid and electrolyte disturbances!
• nutrient absorption can be significantly impaired, leading to weight loss and fatigue!
• abdominal pain!
102
Q

Treatment for Chron’s

A

fiber supplementation
low roughage when there is obstruction
avoid caffeine, high fat foods, alcohol, spicy foods

103
Q

Ulcerative Colitis characteristics that are more common

A

always originates in rectum and may progress proximally
uncertain cause but may exhibit familial pattern
rectal bleeding=more common
colon cancer=more common
ulcerative and exudative type of inflammation
primarily mucosal level of involvement

104
Q

How can intestinal infections occur?

A

can occur as a result of viral or bacterial infection

105
Q

how is viral enterocolitis primarily transmitted?

A

fecal-oral route as a result of poor hygiene
common in children
targets small and large intestine
self-limiting infection

106
Q

bacterial enterocolitis

A 
Clostridium difficile (C-diff) 
also a fecal-oral transmission
107
Q

What is diverticular disease

A

condition in which mucosal layer herniates through muscularis layer, forming a small pouch
they are benign lesions that usually occur in the sigmoid colon

108
Q

What can increase the risk of diverticular disease?

A

poor diet
lack of exercise
poor bowel habits- straining, holding

109
Q

What is diverticulitis?

A

inflammation and/or perforation of diverticulum!

  • contents of colon can enter peritoneum, causing peritonitis!
  • treated with antibiotics and/or surgery!
110
Q

What causes large volume diarrhea?

A

result of infection or magnesium intake

111
Q

What causes small volume diarrhea?

A

occurs in IBD or fecal incontinence

112
Q

Treatment for diarrhea

A

BRAT diet
bananas, rice, applesauce, toast
drugs such as Imodium can reduce motility to promote absorption
this increased time in the color=increased absorption of water

113
Q

differences between primary and secondary constipation

A

primary=something in the GI limiting motility

secondary=other external problems affecting GI such as diet high in Ca2+ or iron, opioids

114
Q

Where are intestinal neoplasms primarily found?

A

in the colon and rectum

115
Q

What are benign lesions known as?

A

polyps that almost half of adults over the age of 60 have

116
Q

What are the risk factors of colorectal cancer

A

increasing age - 90% of cases are diagnosed in individuals over 50!
• personal history of colorectal polyps or cancer!
• personal history of IBD !
• family history of colorectal cancer or adenomatous polyps!
• type 2 diabetes!
• diet - red meat, processed meat increase risk; fruits vegetables, and whole grains
decrease risk!
• physical inactivity!
• obesity!
• smoking!
• heavy alcohol use!
This the most preventable and curable form of cancer

117
Q

Skip lesions are most closely associated with?

A

Chron’s disease

118
Q

intestinal infections are most likely to result in diarrhea by decreasing what?

A

absorptive functions of intestinal epithelial cells

119
Q

Laxatives are used in the management of constipation because….

A

they add bulk to the contents of the colon
lubricate the contents of the colon
soften the contents of the colon

Bioscience II (10 decks)

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