Salivary Gland Secretion Tonicity -- FA Error??

[Krazykritter]

---

Members do not see this ad.

In GI section -- FA says that "Low flow rate --> hypotonic." "High flow rate --> closer to isotonic."

I think this is backwards according to our ENT unit we had. It would make sense to me that a lower flow rate would give increase time to pump secretory products into the saliva (making it closer to isotonic) whereas a higher flow rate would yield a more hypotonic solution (more H20 & less secretory product).

Can anyone confirm this or clarify what I'm missing here? Thanks.

 

[stargirl50]

I took notes from Costanzo on this, and here is what I wrote:

The saliva starts out isotonic (before any modifications are made in the duct)
-Low flow rate= hypotonic because the ductal cells have more time to pump Na, Cl out (H2O stays)
-High flow rate= closer to isotonic because the fluid spends less time in the lumen of the duct, so less time for ions to be pumped out

Na, Cl are pumped out and K, HCO3 are pumped in by the ductal cells by secondary active transport. More Na, Cl is pumped out than K, HCO3 in.

Hope that helps!

 

[Krazykritter]

That helps a lot. Thanks, stargirl.

Meh, chalk it up to clinicians coming in trying to teach basic science stuff...Good explanation though.