Lectures 13 & 14 - GI Pathophysiology I & II Flashcards
What are the 5 clinical manifestations of GI pathophysiologies?
- Anorexia
- Nausea
- Vomiting (emesis)
- Hematemesis
- Melena: tarry or occult
What does anorexia mean?
Loss of appetite
What kind of mechanism is vomiting? Describe it.
Reflex
Vomiting center of the brain regulated by:
- The chemoreceptor trigger zone in the 4th ventricle of the brain in contact with blood and CSF
- Cerebral cortex
What is hematemesis?
Blood in vomit
How to tell where the blood is from in vomit?
Higher in GI: more red
Lower in GI: darker red
What is melena?
Blood in stool
How to tell where the blood is from in stool? What is this called?
Higher in GI: darker red = tarry
Lower in GI: more red
What does occult melena mean?
Blood in stool that is not grossly visible
Definition of diarrhea?
Passage of more than 200g per day of feces
4 types of diarrhea?
- Osmotic
- Secretory
- Inflammatory
- Noninflammatory
Diarrhea consistency?
Depends on origin
Example of secretory diarrhea?
Cholera
What is an inflammatory diarrhea?
Diarrhea with inflammation of the walls of the GIT
2 examples of inflammatory diarrhea?
- Ulcerative colitis
2. Crohn’s disease
Definition of constipation? What to note?
Infrequent passage of stool (precise infrequency not defined as what might be normal for one person might be abnormal for another0
Causes of constipation?
- Could be a primary problem
- Problem association with another disease condition:
- Failure to respond to the urge to defecate
- Inadequate dietary fiber
- Inadequate fluid intake
- Weakness of the abdominal muscles
- Inactivity
- IBS
Why does inactivity cause constipation?
Decreased GIT motility => increased water reabsorption
Functions of upper esophageal sphincter?
- Ensures air breathed in does not enter the GIT
2. Ensures food does not enter the trachea
Functions of lower esophageal sphincter?
- Ensures no regurgitation of gastric contents in the esophagus
- Regulates the flow of food from the esophagus into the stomach
Are esophageal sphincters normally in a tonic state?
YUP
What is the LES made of?
- Circular smooth muscle in the esophageal wall
- Reinforced by esophageal hiatus of the diaphragm
- Oblique muscles of the stomach
What is the UES made of?
Skeletal muscles sling around the esophagus:
1. Cricopharyngeal mucles
+ 3 other skeletal muscles
How does the UES stay closed?
Receives constant autonomic innervation to remain constricted, which stops for relaxation
How does the LES stay closed?
Normally tonically constricted without need for constant innervation, and relaxes when innervated to do so
What is esophageal manometry? How does it work?
Test used to measure the function of the UES and LES: long wire inserted in the esophagus to the stomach
Force transducers are along the wire to measure the force (in mmHg) of the esophagus during swallowing
What is a normal reading using esophageal manometry?
- UES: normal pressure is 100 mmHg/during swallowing the pressure drops to 0 (complete relaxation) and then goes back higher than 100 and then back to normal
- Rest of esophagus: normal pressure is 0 mmHg/pressure goes up as bolus goes down = wave of peristalsis moving the bolus down
- LES: normal pressure is 40 mmHg/during swallowing the pressure drops to 0 (complete relaxation) and then goes back higher than 40 and then back to normal
- Stomach: normal pressure is >0 mmHg
Significance of normal gastric pressure > 0 mmHg?
Without a LES, there would be regurgitation since the pressure in the esophagus IS 0 mmHg
4 pathologies associated with swallowing?
- Dysphagia
- Odnyphagia
- Pyrosis
- Achalasia
What does dysphagia mean? 2 types?
= difficulty swallowing
- Oropharyngeal dysphagia: cannot get the food from the mouth to the esophagus
- Esophageal dysphagia
How many cranial nerves associated with swallowing reflex?
Many
In what patients is dysphagia common? Why?
Stroke victims as cranial nerves are affected
What is odnyphagia? Causes?
Painful swallowing
Causes: infections, cancer, strictures
What is pyrosis?
Heart burn
What is achalasia?
Failure of LES to relax when swallowing
Treatment for prominent cricopharyngeus?
Surgery to de-innervate or remove the muscle
What 2 factors increase relaxation of the LES?
- Gastric distension
2. High fat meals
What 2 factors increase relaxation of the LES?
- Gastric distension
2. High fat meals
Describe the innervation of the LES. Which innervation causes relaxation?
- Vagus nerve
- SNS from the sympathetic chain ganglia in the thorax, which then synapses in the celiac ganglion
- ***Other innervation (interneuron) that is unknown
Describe the manometry reading of a patient with achalasia.
- Loss of normal peristalsis
- LES pressure remains high during swallowing
- High resting tone (=basal pressure) of the LES
Diagnostic tool for achalasia?
Barium swallow with imaging
Effects of long-term achalasia?
- Dilation of the esophagus
- Sigmoid or megaesophagus
- Weight loss and malnutrition
Achalasia treatment? Side effect?
Surgical opening of the LES to remove its muscles
Side effect: GERD
Achalasia cause?
Unknown
What is GERD?
= Gastroesophageal Reflux Disease
- Incompetent LES
- Delayed gastric emptying
- Acid hypersecretion
- Decreased salivation: further worsens the delayed gastric emptying and not enough esophageal protection from gastric contents
Which esophageal sphincter opens for longer during swallowing? Implication?
LES
Implication: gastric reflux is normal to a certain extent
What can cause an incompetent LES? Which is the hardest to treat?
- Weak basal LES pressure
- Inadequate LES response to increased abdominal pressure (should constrict to avoid regurgitation) (e.g. coughing)
- Inadequate LES response to gastric contractions
- ***Transient relaxation of the LES (for unknown reason)
Anatomic abnormality causing GERD?
Hiatal hernia
Pathophysiology of GERD?
Acid refluxes into distal esophagus => disruption of tight junctions => acid reaches intercellular space => cell edema and death => mucosal inflammation
4 symptoms of GERD?
- Reflux involves mucosal injury to the esophagus, hyperemia, and inflammation
- Heartburn:
- 30-60 min after eating
- Made worse by bending at the waist due to increased abdominal pressure
- Most often occurs at night because laying down and because of hormones relaxing the LES - Belching and chest pain
- Respiratory symptoms: wheezing, chronic cough, and hoarseness
4 effects of chronic GERD?
- Persistent reflux: cycle of mucosal damage that causes hyperemia, edema, and erosion of the luminal surface
- Strictures: narrowing of the esophagus due to inflammation causing scarring
- Barrett’s esophagus: normal squamous mucosa becomes metaplastic columnar mucosa (same as stomach epithelial lining) to handle the high acid load
- Increased risk for cancer due to Barrett’s esophagus
What is hyperemia?
An excess of blood in the vessels supplying an organ
Treatments for GERD?
- Conservative measures first: avoidance of positions and conditions that increase GERD:
- Avoid large meals and foods that reduce LES tone (e.g. caffeine, fats, chocolate)
- Avoid smoking and alcohol
- Have meals eaten sitting up
- Avoid bending for long periods of time
- Weight loss - Aggressive treatments:
- Block gastric acid secretion
- Drugs that increase motility
What protects the stomach from its acidity and peptic enzymes? What are these regulated by?
- The gastric mucosal barrier: water-repellent hydrophobic layer with bicarb in the mucus
- High restitution: cell turnover
- High gastric blood flow: washes away gastric acid
=> regulated by prostaglandins
Why is stomach cancer so lethal?
Because the stomach has a great distention ability so tumors go unnoticed for a long time => usually asymptomatic until late in its course