Respiratory System in fish
Fish breathe with gills (except for Dipnoi fish that breathe with lungs). The gills of bony fish are equipped by gill cover called operculum.
Gills are located in the right and left sides of fish head in a gill sack. Gill are flat filaments with pink color and consist of 5-7 filaments (gill filaments). In the surface of gill filaments, there are many blood capillaries that allow gas exchange between blood and water. Each gill is supported by gill arch. In gill arch, there lies gill bony bar (filter). When water enters mouth cavity, operculum
(gill cover) is closed. At that time, the O2 dissolved in water flows through gill filament and diffuses into blood through capillary vessel of gill filament. When the cleavage is closed and operculum is open, the water has contact with the gill filament. The CO2 in blood diffuses into water and comes out of the fish body.
Respiratory system In Bird
Bird respiratory system plays a role in gas exchange, controlling normal temperature of body, and producing sound. Beside lungs, bird respiratory system is equipped with 8-9 air sacks that are necessary to store O2 reserve and ease the body. The diffusion of breathing air in bird only only occurs in lung. Bird breathe through nostril then the air goes into glottis located at pharynx base that connects it with trachea.
During inspiration, the contraction of intercostall muscle causes the O2 rich air to go into lungs that makes ribcage moves toward and chest bone moves downward. Most of the free air will be transferred into air sacks as air reserve. During expiration, intercostal muscle relaxes and ribcage and chest bones go to back to the first position so that the chest cavity becomes narrow and the air pressure inside becomes higher that outside. Consequently, the CO2 rich air comes out from lungs. At the time, the chest cavity becomes narrow; the air from air sacks goes into lungs and O2 is relased from capillary vessel in lungs.