GI Disorders Flashcards
Damage to the fifth, ninth, or tenth cranial nerve can cause
paralysis of the swallowing mechanism.
Diseases that can prevent normal swallowing by damaging the swallowing center in the brain stem.
poliomyelitis and encephalitis,
Paralysis of the swallowing muscles causes
can also prevent normal swallowing.
occurs in persons with muscle dystrophy
result of failure of neuromuscular transmission in persons with myasthenia gravis or botulism
When the swallowing mechanism is partially or totally paralyzed, the abnormalities that can occur include
(1) complete abrogation of the swallowing act
(2) failure of the glottis to close
(3) failure of the soft palate and uvula to close the posterior nares
most serious instances of paralysis of the swallowing mechanism occurs when
patients are in a state of deep anesthesia. anesthetic has blocked the reflex mechanism of swallowing.
a con dition in which the lower esophageal sphincter fails to relax during swallowing.Mag
the musculature of the lower esophagus remains spastically contracted and the myenteric plexus has lost its ability to transmit a signal to cause “receptive relaxation” of the gastroesophageal sphinc ter as food approaches this sphincter during swallowing.
Achalasia
Achalasia is caused by
damage in the neural network of the myenteric plexus in the lower two thirds of the esophagus.
often becomes putridly infected during the long periods of esophageal stasis.
as much as 1 liter of food
infection may also cause
ulceration of the esophageal mucosa
leading to severe substernal pain or even rupture and death
Considerable benefit from achalasia/megaesophagus can be achieved by
balloon inflated on the end of a swallowed esophageal tube
Antispasmodic drugs (i.e., drugs that relax smooth muscle
can be acute and severe, with ulcer ative excoriation of the stomach mucosa by the stomach’s own peptic secretions.
gastritis
gastritis often is caused by
chronic bacterial infection of the gastric mucosa
certain ingested irritant substances can be especially damaging to the
protective gastric mucosal barrier —that is, to the mucous glands and to the tight epithelial junctions between the gastric lining cells—
Two of the most common of these substances are
excesses of alcohol or aspirin.
low level of absorption is mainly due to two specific features of the gastric mucosa:
(1) It is lined with highly resistant mucous cells that secrete viscid and adherent mucus, and (2) it has tight junctions between the adjacent epithelial cells.
gastric barrier
other impediments to gastric absorption
highly resistant mucous cells
tight junctions between the adjacent epithelial cells
gastric barrier pathologically is resistant enough
T/F
False. Normally
True or False
In gastritis, the permeability of the barrier is greatly increased.
True
mucosa susceptible to digestion by the peptic digestive enzymes, thus frequently resulting in
gastric ulcer
in some people autoimmunity develops against the gastric mucosa, which also leads eventually to gastric atrophy. Loss of the stomach secretions in gastric atrophy leads to
achlorhydria
pernicious anemia.
when the pH of the gastric secretions fails to decrease below 6.5 after maximal stimulation.
Achlorhydria
When acid is not secreted, pepsin also usually is not secreted.
lack of acid prevents it from functioning because pepsin requires an acid medium for activity.
Hypochlorhydria
Normal gastric secretions contain a gly coprotein called______ secreted by the same pari etal cells that secrete hydrochloric acid
intrinsic factor
combines with vitamin B12 in the stomach and protects it from being digested and destroyed as it passes into the small intestine, binds with receptors on the ileal epithelial surface, which in turn makes it possible for the vitamin B12 to be absorbed.
intrinsic factor
In the absence of intrinsic factor, only about 1/5 of the vitamin B12 is absorbed.
True or False
False. 1/50
excoriated area of stomach or intestinal mucosa caused principally by the digestive action of gastric juice or upper small intestinal secretions.
Peptic Ulcer
peptic ulcers most frequently occur
within a few centimeters of the pylorus.
Lesser curvature of the antral end of the stomach
more rarely, in the lower end of the esophagus
wherever a surgical opening such as a gastrojejunostomy has been made between the stomach and the jejunum of the small intestine
marginal ulcer
The usual cause of peptic ulceration is
imbalance between the rate of secre tion of gastric juice and the degree of protection
(1) the gastroduodenal mucosal barrier and (2) the neu tralization of the gastric acid by duodenal juices
Peptic ulcer protection
lower esophagus - compound mucous glands
mucous neck cells of the gastric glands
deep pyloric glands that secrete mainly mucus
glands of Brunner of the upper duodenum, which secrete a highly alkaline mucus.
areas normally exposed to gastric juice are well supplied with mucous glands
In addition to the mucus protection of the mucosa, the duodenum is protected by the
alkalinity of the small intestinal secretions
pancreatic secretion,
contains large quantities of sodium bicarbonate that neutralize the hydrochloric acid of the gastric juice, thus also inactivating pepsin and preventing digestion of the mucosa.
large amounts of bicarbonate ions are provided in
the secretions of the large Brunner glands in the first few centimeters of the duodenal wall and
2) bile coming from the liver.
two feedback control mechanisms normally ensure that this neutralization of gastric juices is complete
inhibits gastric secretion and peristalsis in the stomach, thereby decreasing the rate of gastric emptying.
acid in the small intestine liberates secretin from the intestinal mucosa. secretion of pancreatic juice contains a high concentration of sodium bicarbon ate,
peptic ulcer can be caused in either of two ways:
excess secretion of acid and pepsin by the gastric mucosa
diminished ability of the gastroduodenal mucosal barrier to protect
the bacterium is capable of penetrating the mucosal barrier by virtue of
its physical capability to burrow through the barrier and by releasing ammonium that liquefies the barrier and stimulates the secretion of hydrochloric acid.
factors that predispose to ulcers include
smoking, presumably because of increased nervous stimulation of the stomach secretory glands
consumption of alcohol, because it tends to break down the mucosal barrier;
consumption of aspirin and other nonsteroidal antiinflammatory drugs that also have a strong propensity for breaking down this barrier.
Treatment of Peptic Ulcers.
antibiotics
acidsuppressant drug, especially ranitidine
cut the two vagus nerves that supply parasympathetic stimulation to the gastric glands.
an antihistaminic agent that blocks the stimulatory effect of histamine on gastric gland histamine2 receptors, thus reducing gastric acid secretion by 70 to 80 percent
ranitidine
Abnormal Digestion of Food in the Small Intestine
failure of the pancreas to secrete pancreatic juice into the small intestine
Lack of pancreatic secretion frequently occurs (3) in
pancreatitis
duct is blocked by a gallstone at the papilla of Vater
head of the pancreas has been removed because of malignancy.
True or False
Loss of pancreatic juice means loss of trypsin, chymotrypsin, carboxypolypeptidase, pancreatic amylase, pancreatic lipase,
True
True or False
Without these enzymes, up to 10 percent of the fat entering the small intestine may not be absorbed, along with one third to one half of the proteins and carbohydrates
60%
trypsinogen accumulates that it over-comes the trypsin inhibitor
gallstone blocks the papilla of Vater, the main secretory duct from the pancreas and the common bile duct are blocked.
trypsin activates still more trypsinogen, as well as
chymotrypsinogen and carboxypolypeptidase,
can occur when large portions of the small intestine have been removed.
Malabsorption
idiopathic sprue,
celiac disease (in children), or
gluten enteropathy,
Nontropical Sprue
In milder forms of the disease, only the microvilli of the absorbing enterocytes on the villi are destroyed
decreasing the absorptive surface area as much as twofold. Nontropical sprue
results in a cure within weeks, especially in children with this disease. Nontropical sprue
Removal of wheat and rye f lour from the diet
this variety of sprue is usually caused by inflammation of the intestinal mucosa resulting from unidentified infec tious agents. in the tropics
tropical sprue
True or False
The fat that appears in the stools is almost entirely in the form of salts of fatty acids rather than undigested fat
demonstrating that the problem is one of digestion, not of absorption
False. problem is one of absorption, not of digestion
In severe cases of sprue, in addition to malabsorption of fats, impaired absorption of
proteins, carbohydrates, calcium, vitamin K, folic acid, and vitamin B12
1) severe nutritional deficiency, which often results in wasting of the body;
2) osteomalacia (i.e., demineralization of the bones because of lack of calcium);
3) inadequate blood coagula tion caused by lack of vitamin K; and
4) macrocytic anemia of the pernicious anemia type, resulting from diminished vitamin B12 and folic acid absorption.
severe cases of sprue
associated with large quantities of dry, hard feces in the descending colon that accumulate because of excess absorption of fluid or insuf f icient fluid intake.
Constipation
Any pathology of the intestines that obstructs movement of intestinal contents, such as______ can cause constipation
tumors,
adhesions that constrict the intestines,
or ulcers
if one does not allow defecation to occur when the defecation reflexes are excited or if one overuses laxa tives to take the place of natural bowel function, the reflexes become progressively less strong over months or years, and the colon becomes
atonic
in the early years of life requires that they learn to control defecation; this control is effected by
inhib iting the natural defecation reflexes
if a person estab lishes regular bowel habits early in life, the development of constipa tion in later life is less likely.
defecating when the gastrocolic and duodenocolic reflexes cause mass move ments in the large intestine,
True or False
Constipation can also result from spasm of a small segment of the sigmoid colon
True
After the constipation has con tinued for several days and excess feces have accumulated above a spastic sigmoid colon,
excessive colonic secretions often then lead to a day or so of diarrhea.
tremendous quantities of fecal matter to accumulate in the colon, causing the colon some times to distend to a diameter of 3 to 4 inches
megacolon, or Hirschsprung’s disease
One cause of megacolon is
lack of or deficiency of ganglion cells in the myenteric plexus in a segment of the sigmoid colon.
sigmoid becomes small and almost spastic while feces accumulate proximal to this area, causing
megacolon in the ascending, transverse, and descending colons.
True or False
As a consequence, neither defecation reflexes nor strong peristaltic motility can occur in this area of the large intestine
True
In usual infectious diarrhea, the infection is most extensive in
the large intestine and the distal end of the ileum.
T his mechanism is important for ridding the intestinal tract of a debilitating infection.
large quantities of fluid are made available for washing the infectious agent toward the anus, and at the same time strong propulsive movements propel this fluid forward.
True or False
cholera toxin directly stimulates excessive secretion of electrolytes and fluid from the crypts of Lieberkühn in the distal ileum and colon
True
loss of fluid and electrolytes can be so debil itating within several days that death can ensue.
The amount can be 10 to 12 liters per day, although the colon can usually reabsorb a maximum of only 6 to 8 liters per day.
basis of therapy in cholera
as rapidly as they are lost, mainly by giving the patient intravenous solu tions along with the use of antibiot ics
excessive stimulation of the parasympathetic nervous system, excites both (1) motility and (2) excess secretion of mucus in the distal colon.
psychogenic emotional diarrhea,
disease in which extensive areas of the walls of the large intestine become inflamed and ulcerated.
mass movements occur much of the day rather than for the usual 10 to 30 minutes.
Ulcerative colitis
Some clinicians believe that ulcerative colitis results from an
allergic or immune destructive effect
from a chronic bacterial infection
strong hereditary tendency for susceptibility
mediated defecation reflex passing from the rectum to the___^^_______ and then back to the descending colon, sigmoid, rectum, and anus.
conus medullaris of the spinal cord
voluntary aid to defecation
increased abdominal pressure and relaxation of the voluntary anal sphincter
because the cord defecation reflex can still occu
a small enema to excite action of this cord reflex, usually given in the morning shortly after a meal, can often cause adequate defecation.
part of the upper tract becomes excessively irritated, overdistended, or even overexcitable.
Vomiting
distention or irritation of the duodenum provides
an especially strong stimulus for vomiting.
sensory signals that initiate vomiting originate mainly from
the pharynx, esophagus, stomach, and upper portions of the small intestines transmitted by both vagal and sympathetic afferent nerve fibers
together are called the “vomiting center.”
multiple distributed nuclei in the brain stem, especially the area postrema,
From here, motor impulses that cause the actual vomiting are transmitted from the vomiting center by way of
the fifth, seventh, ninth, tenth, and twelfth cranial nerves to the upper gastrointestinal tract,
through vagal and sympathetic nerves to the lower tract,
and through spinal nerves to the diaphragm and abdominal muscles.
True or False
Antiperistalsis does not begin as far down in the intestinal tract as the ileum
False. It may.
wave travels backward up the intestine at a rate o
2 to 3 cm/sec;
as these upper portions of the gastrointestinal tract, especially the duodenum, become overly distended,
this distention becomes the exciting factor that initiates the actual vomiting act.
strong intrinsic contractions occur in both the duodenum and the stomach
With partial relaxation of the esophagealstomach sphincter
At the onset of vomiting allowing vomitus to begin moving from the stomach into the esophagus
A. raising of the hyoid bone and larynx to pull the upper esophageal sphincter open
B. a deep breath
C. lifting of the soft palate to close the posterior nares.
D. closing of the glottis to prevent vomitus f low into the lungs, and
Arrange
BADC
building the intragastric pressure to a high level.
downward con traction of the diaphragm along with simultaneous con traction of all the abdominal wall muscles, which squeezes the stomach between the diaphragm and the abdominal muscles
allowing expulsion of the gastric contents upward through the esophagus.
lower esophageal sphincter relaxes completely
results from a squeezing action of the muscles of the abdomen associated with simultane ous contraction of the stomach wall and opening of the esophageal sphincters
vomiting act
vomiting can also be caused by nervous signals arising in areas of the brain. This mechanism is particularly true for a small area called
Destruction of this area blocks this type of vomiting but does not block vomiting resulting from irritative stimuli in the gastrointestinal tract itself
chemoreceptor trigger zone for vomiting, located in the area postrema on the lateral walls of the fourth ventricle.
administration of which drugs can directly stimulate this chemoreceptor trigger zone (located in the area postrema) and initiate vomiting
apomorphine, morphine, and some digitalis
motion stimulates receptors in
from here impulses are transmitted mainly by way of the brain stem vestibular nuclei into the cerebellum, then to the chemoreceptor trigger zone, and finally to the vomiting center
the vestibular labyrinth of the inner ear,
prodrome of vomiting
conscious recognition of subconscious exci tation in an area of the medulla closely associated with or part of the vomiting center
sensation of nausea
sensation of nausea can be caused by
irritative impulses coming from
the gastrointestinal tract, lower brain associated with motion sickness, & cerebral cortex to initiate vomiting.
Vomiting occasionally occurs without the prodromal sensation of nausea, which indicates tha
only certain portions of the vomiting center are associated with the sensation of nausea.
Some common causes of obstruction are
cancer,
fibrotic constriction resulting from ulceration or from peritoneal adhesions,
spasm of a segment of the gut, and
paralysis of a segment of the gut.
True or False
T he abnormal consequences of obstruction does not depend on the point in the gastrointestinal tract that becomes obstructed.
False. Depend
whole-body metabolic alkalosis.
excessive loss of hydrogen ions
fibrotic constriction at the pylorus after peptic ulceration
persistent vomiting depresses bodily nutrition
antiperistaltic reflux from the small intestine causes intestinal juices to flow backward If the obstruction is
beyond the stomach
If the obstruction is near the distal end of the large intestine,
feces can accumulate in the colon for a week or more.
intense feeling of constipa tion,
it finally becomes impossible for additional chyme to move, severe vomiting then occurs
Prolonged obstruction of the large intestine can finally cause
rupture of the intestine or dehydration and
circulatory shock resulting from the severe vomiting.
flatus, can enter the gastrointestinal tract from three sources:
swallowed air,
gases formed in the gut as a result of bacterial action, or
gases that diffuse from the blood into the gastrointestinal tract
Most gases in the stomach are______ expelled by
mixtures of nitrogen and oxygen derived from swallowed air.
belching
In the ________bacterial action generates most of the gases, including especially
large intestine
carbon dioxide, methane, and hydrogen.
known to cause a mild explosion
methane and hydrogen become suitably mixed with oxygen
Use of the electric cautery during sigmoidoscopy
Certain foods are known to cause greater expulsion of flatus through the anus than others
others—beans, cabbage, onion, cauliflower, corn, and certain irritant foods such as vinegar
medium for gasforming bacteria
unabsorbed fermentable types of carbohydrates.
in other instances, excess expulsion of gas results from
irritation of the large intestine, which promotes rapid peristaltic expulsion of gases through the anus before they can be absorbed.
amount of gases entering or forming in the large intestine each day averages______
amount expelled through the anus is usually only about
7 to 10 liters
0.6 liter
The remainder is normally absorbed into the blood through the intestinal mucosa and expelled through the lungs.
