CHAPTER 7THE RESPIRATORY STRUCTURES AND

BREATHING MECHANISMS OF THE FISH

• A bony fish has 4 pairs of gills, supported by a bony arch.• The gills consist of two rows of gill filament numerous gill lamella.• Each gill lamella is folded into gill plate, have thin walls & well supplied with blood capillaries to increase the surface area of the gills.• Characteristics : Bony/Gill arches - To support the filaments. Filaments - Numerous (Increase the surface area for gaseous exchange). Thin Membrane - To ease the gases absorption. Many blood capillaries.

BREATHING MECHANISM OF FISH

Opens its mouth - lower the floor of the mouth - volume of the mouth is increased - the pressure inside the mouth falls below that of the external pressure - water with high concentration of oxygen enter - operculum close.

Floor of the mouth is raise up - gaseous exchange occurs as water flows past the gills - the pressure in the mouth is increased - water then passes out through the operculum operculum then opens.

EXERCISES1. Fishes have a respiratory structure called ……. .

Bony fish have ……. pairs of gills which are protected by the ……. .

2. Each gill consist of ……. which are supported by a ……. . The filaments have a thin wall called ……. .

3. This structural adaptation of the gills :(a)……. membranes to allow the absorption of

respiratory gases into the blood capillaries.(b) Rich of blood ……. for efficient exchange and

transport of respiratory gases.(c)Surrounded by ……. which enable respiratory

gases to be ……. .(d)Large surface area of filaments and lamellae for

efficient ……. exchange.

4. The efficiency of gaseous exchange is further enhanced by the ……. exchange mechanism.

a. The ……. flows over the ....... in one direction.b. The ……. flows in the ……. direction through

blood capillaries in the ……. .c. As the ……. blood enters the blood capillaries, it

……. water with s higher oxygen content.d. Along the blood capillaries, the concentration

……. allows the transfer of oxygen into the blood.e. However, the concentration of CO2 in blood is

……. than in water, makes the CO2 ……. from blood into water.

f. The efficiency of fish gills is further increased by ……. which is by opening & closing the operculum.

INHALATION

• The floor of the ……. is lowered.• At the same time, the ….. cavity is enlarged and the operculum closes.• This lowers the ……. in the buccal cavity.• Water with dissolved oxygen is drawn into the ……. .

EXHALATION

• When the mouth closes, the floor of the buccal cavity is ……. .• Water flows out through the …... and gaseous exchange between the blood capillaries and water occurs.• At the same time, the opercullar cavity becomes ……. .•The pressure in the buccal cavity is higher than the pressure outside.• The higher water pressure forces the operculum to ……. and water flow out through the operculum.

THE END !A VIDEO PRESENTATION BY

AMANDA CHOI &

ISSABELLE PEREIRA