GI System Function and Pathology Flashcards
(119 cards)
1
Q
What are the four layers of the GI tract from innermost to outermost?
A
mucosal layer–>submucosal layer–> muscularis layer–> Serosal layer
2
Q
What makes up the mucosal layer?
A
epithelium
lamina propria
muscularis mucosae
3
Q
what does the lamina propria of the mucosal layer contain?
A
connective tissue layer that contains capillaries and lacteals
4
Q
what is the muscularis mucosae?
A
the muscle layer of the mucosa that helps to increase surface area but NOT motility
5
Q
what does the submucosal layer contain?
A
it is a connective tissue layer that contains blood vessels, secretory glands and neurons
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
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
8
Q
What group of neurons does the muscularis layer contain?
A
the myenteric plexus or Auerbach’s plexus
9
Q
What is the serosal layer similar to?
A
same as the visceral peritoneum
10
Q
How is absorption limited?
A
by digestion
11
Q
what can limit digestion?
A
secretion and motility
12
Q
What initiates chemical digestion in the mouth?
A
salivary enzymes such as beta amylase that can break some CHO bonds
13
Q
What does saliva contain?
A
water, salts, mucus, some amino acids, IgA, amylase and some salivary lipases
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
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
16
Q
What are the 4 pairs of salivary glands?
A
parotid, sublingual, submaxillary, buccal
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
18
Q
Where does the esophagus move food from and to
A
moves bolus of food from the mouth to the stomach via peristalsis
19
Q
What is the proximal 1/3 of the espohagus made up of?
A
skeletal muscle; the rest is smooth muscle
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
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
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
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
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
25
what causes reflux in children
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)
26
main consequences of GERD
pain and mucosal injury do not correlate!
- esophageal ulceration and stricture (connective tissue narrowing) can occur!
- Barrett’s esophagus
27
what is Barrett's esophagus
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
28
what type of cancer is Barrett's esophagus a risk factor for?
esophageal cancer
| it creates a 30-125x greater risk
29
typical symptoms of esophageal cancer
dysphagia (difficulty swallowing)
| weight loss
30
primary types of esophageal cancer
adenocarcinoma
| squamous cell carcinoma
31
Where does Adenocarcinoma most likely occur?
distal 1/3 of the esophagus
32
facts about adenocarcinoma
50% of esophageal cancer cases!
• tends to be associated with Barrett’s esophagus!
• more common in white males!
33
In which population is squamous cell carcinoma more common?
more common in African Americans
| more closely associated with environmental factors such as alcohol and smoking
34
Which type of presentation of esophageal cancer has the poorest survival rate?
distant lymph node involvement has a 3% survival rate
localized=38%
regional=20%
35
which type of esophageal cancer has a slightly better prognosis?
adenocarcinoma
36
what separates the esophagus from the stomach?
LES
| lower esophageal sphincter
37
What separates the stomach from the duodenum?
pyloric sphincter
38
what are the 4 cell types in the gastric pits of the surface epithelium?
mucous neck cells
chief (zygomatic) cells
parietal cells
endocrine cells
39
what do mucous neck cells secrete?
they secrete alkaline mucus that protects the underlying structures from the contents of the stomach
40
what do chief cells make?
they make pepsinogen; precursor(active form) of pepsin
41
what do parietal cells make?
HCl and intrinsic factor
| hydrochloric acid has a low pH that kills bacteria in the stomach and denatures ingested proteins to activate pepsin
42
what is intrinsic factor necessary for?
vitamin B12 absorption
43
what develops from a lack of intrinsic factor/vitamin B12?
pernicious anemia
44
what do endocrine cells secrete?
gastrin which increases the strength of gastric peristaltic contractions
45
what does lamina propria contain?
capillaries that provide fluids for secretions and act as nutrient blood supply
46
what types of cells generate smooth muscle contraction in the stomach?
pacemaker cells create a wave of excitation that spreads
| basic electrical rhythm generates peristaltic contractions (weak at rest when the stomach is empty)
47
What area of the GI acts as a feedback of contractions?
the duodenum inhibits strength of contractions to ensure complete nutrient absorption
48
What activities enhance the secretion of pepsinogen and HCl?
```
presence of proteins
distention of the stomach
parasympathetic stimulation
gastrin
histamine
```
49
What inhibits pepsinogen and HCl?
increased duodenal activity
50
What can stimulate mucus secretion?
vagal stimulation and irritation from ingested foods
51
What is acute gastritis?
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
How is acute gastritis self-limiting?
removal of irritant results in regeneration and healing of mucosa over several days!
53
What is chronic gastritis?
chronic inflammatory changes that lead to atrophy of glandular epithelium
there are no grossly lesions
leads to increased risk of stomach cancer
54
What is peptic ulcer disease?
disruption of the mucosal barrier and exposure of underlying tissue to HCl and pepsin can result in ulceration of epithelium
55
Which type of ulcer is more common at any age?
duodenal are 5x more common
| men are 3-4 times more likely to have ulcers in either location
56
What type of ulcers is more common in older adults?
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
What is the most common cause of ulcers?
Helicobacter pylori
nearly all duodenal and 70% of gastric ulcers !
• not all people with infection get ulcers!
58
Result of NSAID use and ulcers
20% of gastric ulcers and
2-5% of duodenal ulcers are a result of NSAID use
aspirin is the most likely cause
59
symptoms of ulcers
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
treatment of ulcers
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
How do H2 receptors treat GERD/ulcers?
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
How to proton pump inhibitors work in treatment?
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
How does Pepto-Bismol work?
a bismuth that forms a barrier and stimulates bicarbonate and PGE2 secretion, inhibits H. pylori growth
64
risk factors for stomach cancer
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
what is the most important part of the stomach for digestion and absorption?
the duodenum
66
What do the endocrine cells of the small intestine secrete?
secretin and CCK (cholecystokinin)
| both of these hormones control pancreatic secretions
67
importance of brush border enzymes
membrane bound enzymes on the surface of absorptive cells in the small intestine!
- perform final breakdown of consumed nutrients!
68
examples of brush border enzymes
disaccharases and peptidases
69
How does sympathetic stimulation of brunner's glands contribute to duodenal ulcers?
Brunner's glands produce alkaline mucus which can be inhibited by sympathetic stimulation therefore causing inappropriate lowering of the duodenal pH
70
What stimulates the release of CCK?
presence of nutrients, specifically fat, in the duodenum
71
What does CCK stimulate?
causes the pancreas to produce enzyme-rich secretions that create the gall bladder to contract
72
where is bile stored?
in the gall bladder and
| is made by the liver
73
What occurs with contraction of the gall bladder?
bile salts are released into the duodenum after CCK stimulates the gall bladder
74
Name the 2 types of contractions
segmenting contractions produced by BBR
| peristalsis
75
What are segmenting contractions?
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
When is peristalsis most active?
between meals to keep whatever is in the small intestine moving distally
77
What increases secretion and motility?
parasympathetic stimulation and distention
78
Which enzymes are responsible for digestion/absorption of protein?
gastric, pancreatic and brush border enzymes absorb protein which is actively transported via facilitated diffusion and brought to the liver via portal system
79
Which enzymes control digestion/absorption of CHO?
salivary, pancreatic and brush border enzymes
80
Which enzymes control digestion/absorption of fat?
pancreatic lipases mainly
81
what type of absorption must occur for water to be absorbed?
solute reabsorption needs to occur; water always follows solute
82
What organ regulates absorption of salts?
the kidney
83
How are water soluble vitamins (B and C) absorbed?
by diffusion or mediated transport
84
Where does the gastro-ileal reflex move contents?
from the terminal ileum of the SI to the proximal colon of the large intestine
85
what does the bacteria in the colon do?
acts on undigested material such as fiber to produce Vitamin K, small chain fatty acids which are absorbable and intestinal gas
86
what is the major source of motility of the large intestine?
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
Does peristalsis occur in the colon?
it is very weak
88
what reflexively stimulates mass movement in the colon?
food in the stomach that increases both gastric motility and gastrin production to initiate mass movement by the gastro-colic reflex
89
What stimulates the defecation reflex?
stretch of rectal smooth muscle by parasympathetic efferents
| cortical acknowledgement must occur to allow relaxation of the external sphincter
90
Define Irritable Bowel Syndrome (IBS)
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
Who is more likely to have IBS?
women are 2-3x more likely
92
symptoms of IBS (irritable bowel syndrome)
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
What are the 4 subtypes of Irritable Bowel Syndrome (IBS)
IBS with constipation (IBS-C)!
- IBS with diarrhea (IBS-D)!
- mixed IBS (IBS-M)!
- unsubtyped IBS (IBS-U)!
94
List some of the causes of Irritable Bowel Syndrome (IBS)
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
Treatment for IBS
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
Define Inflammatory Bowel Disease (IBD)
inflammation of uncertain origin but with a pattern of
| familial occurrence
97
What two conditions make up Inflammatory Bowel Disease (IBD)
Ulcerative Colitis and Chron's Disease
98
Chron's Disease
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
What are skip lesions?
segmental, discontinuous involvement by a non-specific granulomatous inflammatory
process
appears as patchy inflamed wound that skips over some areas
100
What are some characteristics that are more common in Chron's?
granulomatous inflammation and ulceration that can produce obstruction, stricture, abscesses and FISTULAS
submucosal involvement
skip lesions
primarily ileum is involved
101
symptoms of Chron's
```
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
Treatment for Chron's
fiber supplementation
low roughage when there is obstruction
avoid caffeine, high fat foods, alcohol, spicy foods
103
Ulcerative Colitis characteristics that are more common
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
How can intestinal infections occur?
can occur as a result of viral or bacterial infection
105
how is viral enterocolitis primarily transmitted?
fecal-oral route as a result of poor hygiene
common in children
targets small and large intestine
self-limiting infection
106
bacterial enterocolitis
```
Clostridium difficile (C-diff)
also a fecal-oral transmission
```
107
What is diverticular disease
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
What can increase the risk of diverticular disease?
poor diet
lack of exercise
poor bowel habits- straining, holding
109
What is diverticulitis?
inflammation and/or perforation of diverticulum!
- contents of colon can enter peritoneum, causing peritonitis!
- treated with antibiotics and/or surgery!
110
What causes large volume diarrhea?
result of infection or magnesium intake
111
What causes small volume diarrhea?
occurs in IBD or fecal incontinence
112
Treatment for diarrhea
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
differences between primary and secondary constipation
primary=something in the GI limiting motility
| secondary=other external problems affecting GI such as diet high in Ca2+ or iron, opioids
114
Where are intestinal neoplasms primarily found?
in the colon and rectum
115
What are benign lesions known as?
polyps that almost half of adults over the age of 60 have
116
What are the risk factors of colorectal cancer
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
Skip lesions are most closely associated with?
Chron's disease
118
intestinal infections are most likely to result in diarrhea by decreasing what?
absorptive functions of intestinal epithelial cells
119
Laxatives are used in the management of constipation because....
they add bulk to the contents of the colon
lubricate the contents of the colon
soften the contents of the colon
