Fluid and Electrolyte DSA

Question 1

• Tight junctions in the SI are _ and tight junctions in the colon are _
• SI thus permits more _ movement than the colon

Answer 1

• Loose, tight
• Paracellular

Question 2

• The fluid absorbed (absorbate) in the intestine is _

Answer 2

• Isoosmotic

Question 3

• What are the main ions absorbed in the jejunum of the SI?
• What transporters are present in the jejunum?
• What is this similar to?

Answer 3

• Na+ and HCO3-
• APICAL
  
  • ​Na+/Sugar or AA cotransporter
  • Na+/H+ exchanger
• BASOLATERAL
  
  • ​Na+/K+ ATPase
  • Sugar or AA transporter
  • HCO3- transporter

Similar to early proximal tubule in the kidney

Question 4

• What are the main ions absorbed in the ileum of the SI?
• What transporters are present in the ileum?

Answer 4

• Na+ and Cl-
• APICAL
  
  • ​Na+/Sugar or AA cotransporter
  • Na+/H+ exchanger
  • HCO3-/Cl- exchanger
• BASOLATERAL
  
  • ​Na+/K+ ATPase
  • Sugar or AA transporter
  • Cl- transporter

Question 5

• In the colon there is net absorption of _ and secretion of _
• Synthesis of Na+ channels is induced by _
• Transporters present?

Answer 5

• Na+ absorption and K+ secretion
• ALDOSTERONE
• APICAL
  
  • ​Na+ channel
  • K+ channel
• BASOLATERAL
  
  • ​Na+/K+ ATPase
  • K+ leak channel

Question 6

• Diarrhea can lead to _ d/t excess secretion of K+ from high flow rate of intestinal fluid

Answer 6

• Hypokalemia

Question 7

• _ channels are present on the BASOLATERAL surface of epithelial cells in intestinal crypts
• _ channels are present on the APICAL surface of epithelial cells in intestinal crypts

Answer 7

• Na+/K+/2Cl-
• Cl-

Question 8

• _ and _ lead to an increased activation of Cl- channels on the apical surface of intestinal crypt cells (which leads to intracellular activation of cAMP)
• What diseases can stimulate this channel?

Answer 8

• ACh and VIP
• Cholera (via adenylyl cyclase and cAMP)

Question 9

• What are the causes of diarrhea?
• What type of acid base disturbance is seen in patients with diarrhea? Why?

Answer 9

• Decreased surface area for absorption, osmotic (presence of non-absorbable solutes in intestinal lumen) or secretory (excessive secretion of intestinal fluid) diarrhea
• Hyperchloremic metabolic acidosis with normal anion gap (Large loss of HCO3- relative to Cl-)

Question 10

• What can lead to a decreased surface area for absorption?

Answer 10

• Infection
• Inflammation

Question 11

• What can cause osmotic diarrhea?

Answer 11

• Lactase deficiency/Enzymatic deficiency that will build up nonabsorbable solute in intestinal lumen (will draw water into lumen with it)

Question 12

• What causes secretory diarrhea?

Answer 12

• E coli or Cholera
• Catalyzes ADP ribosylation
• GTP permanently bound to alpha s subunit -permanent activation of adenylyl cyclase
• Cl- channels on apical membrane kept open (accompanied by secretion of Na+ and H2O)