BIOL 2420 Lecture Notes - Lecture 12: Polyethylene Glycol, Intravenous Therapy, Cholera Toxin
26 Apr 2018
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Unit 9 – Lecture 12
Diarrhea Can Cause Dehydration
- A pathological state
o Intestinal secretion of fluid is not balanced by absorption, resulting in watery stools
- Occurs if normal intestinal water absorption mechanisms are disrupted or if there are unabsorbed
osmotically active solutes that “hold” water in the lumen
o Substances that cause osmotic diarrhea include undigested lactose and sorbitol, a sugar
alcohol from plants
o Sorbitol is used as an “artificial” sweetener in some chewing gums and in foods made for
people with diabetes
- Another unabsorbed solute that can cause osmotic diarrhea, intestinal cramping, and gas is
Olestra
o “fake fat” made from vegetable oil and sugar
- clinical settings
o patients who need to have bowels cleaned out before surgery or other procedures are
often given 4 liters of an isotonic solution of polyethylene glycol and electrolytes to drink
▪ polyethylene glycol – cannot be absorbed, making it pass into the colon –
triggering copious diarrhea removing all solid waste from GI tract
- secretory diarrheas
o occur when bacterial toxins (cholera toxin from Vibrio cholerae and Esherichia coli
enterotoxin) enhance colonic Cl- and fluid secretion
o excessive fluid secretion is coupled with increased motility, diarrhea results
o in response to intestinal infection
▪ viewed as adaptive – it helps flush pathogens out of the lumen
▪ also has the potential to cause dehydration if fluid loss is excessive
- WHO estimates that in developing countries 4 million people die from diarrhea each year
o US – diarrhea in children causes about 200,000 hospitalizations per year
▪ Oral replacement fluids for treatment of diarrheal salt and water loss can prevent
morbidity and mortality associated with diarrhea
▪ Oral rehydration solutions usually contain glucose or sucrose as well as Na+, K+,
and Cl-
• Inclusion of a sugar enhances Na+ absorption
▪ If dehydration is severe, intravenous fluid therapy may be necessary
Immune Functions of the GI Tract
- GI tract is the largest immune organ in the body
o Luminal surface is continuously exposed to disease-causing organisms
o Immune cells of the GALT must prevent pathogens from entering the body through
delicate absorptive tissues
- First lines of defense are:
o the enzymes and immunoglobins in saliva
o The highly acidic environment of the stomach
- If pathogens or toxic materials make it into the small intestine
o Sensory receptors and the immune cells of the GALT respond
o Two common responses are
▪ Diarrhea
▪ Vomiting
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Document Summary
Intestinal secretion of fluid is not balanced by absorption, resulting in watery stools. Another unabsorbed solute that can cause osmotic diarrhea, intestinal cramping, and gas is. If dehydration is severe, intravenous fluid therapy may be necessary. Gi tract is the largest immune organ in the body: luminal surface is continuously exposed to disease-causing organisms. Immune cells of the galt must prevent pathogens from entering the body through delicate absorptive tissues. First lines of defense are: the enzymes and immunoglobins in saliva: the highly acidic environment of the stomach. If pathogens or toxic materials make it into the small intestine: sensory receptors and the immune cells of the galt respond, two common responses are, diarrhea, vomiting. Both bacteria cause diarrhea, and salmonella also causes fever and vomiting. During vomiting: respiration is inhibited, epiglottis and soft palate close off the trachea and nasopharynx to prevent the vomitus from being inhaled (aspirated)
