Anyone know an easy description of fish ventialtion?

Question

I have my Biology AS level mock tomorrow, and this is the thing I find most confusing!

Ventilation of the gills
For example- Inspiration;
Mouth Opens, Buccal Cavity drops

Vol. of buccal cavity increases
pressure in buccal cavity decreases

high water pressure outside fish causes water to flow into the buccal cavity
operculum valve is closed

mouth closes, buccal cavity contracts
pressure in buccal cavity increases

water flows down presure gradient into opercular cavity

water starts to flow over gills, in opposite direction of blood (countercurrent flow)


Expiration
opercular cavity contracts, vol. decreases
pressure in opercular cavity increases

water flows over gills to go out of operculum valve

floor of buccal cavity contracts furthermore to increase the pressure

water is forced out

operculum valve opens (mouth closed)



I just find this so confusing!

Answer 1

Fish ventilation? Are you refering to respiration? Please clairify and I'll be glad to help.

EDIT: You have it nailed! No problems at all with what you wrote. Some times it helps to stop and think about how the motion of the operculums cause the increased pressure in the water and the way the buccal cavity expands and contracts to generate additional pressure. Think of the buccal cavity as a ballon with two openings, the mouth and the gill slits. Water comes in the mouth to fill the expanded buccal cavity, the mouth is sealed off. The fish squeezes the buccal cavity to increase water pressure and the opens it's operculums to allow the force of the water to flow over the gills.

Really you have it down better than you might think. I teach Fish Health for Fisheries Sciences and I would pass what you wrote for a brief discription of the process.

MM

Answer 2

A fish tank or pond has natural ventillation.

Answer 3

gills? i don't understand what you mean by fish ventilation!

Answer 4

GILLS