GI Disorders Flashcards by Josh Sap

Damage to the fifth, ninth, or tenth cranial nerve can cause

paralysis of the swallowing mechanism.

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Diseases that can prevent normal swallowing by damaging the swallowing center in the brain stem.

poliomyelitis and encephalitis,

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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

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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

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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.

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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

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Achalasia is caused by

damage in the neural network of the myenteric plexus in the lower two thirds of the esophagus.

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often becomes putridly infected during the long periods of esophageal stasis.

as much as 1 liter of food

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infection may also cause

ulceration of the esophageal mucosa

leading to severe substernal pain or even rupture and death

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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

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can be acute and severe, with ulcer ative excoriation of the stomach mucosa by the stomach’s own peptic secretions.

gastritis

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gastritis often is caused by

chronic bacterial infection of the gastric mucosa

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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—

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Two of the most common of these substances are

excesses of alcohol or aspirin.

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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.

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gastric barrier

other impediments to gastric absorption

highly resistant mucous cells

tight junctions between the adjacent epithelial cells

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gastric barrier pathologically is resistant enough

T/F

False. Normally

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True or False

In gastritis, the permeability of the barrier is greatly increased.

True

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mucosa susceptible to digestion by the peptic digestive enzymes, thus frequently resulting in

gastric ulcer

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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.

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when the pH of the gastric secretions fails to decrease below 6.5 after maximal stimulation.

Achlorhydria

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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

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Normal gastric secretions contain a gly coprotein called______ secreted by the same pari etal cells that secrete hydrochloric acid

intrinsic factor

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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

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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.