Fish

• What system do fish use for gas exchange?

  a counter-current system
• is there a lower conc of oxygen in water or in air?

  Lower conc of oxygen in water than in air

  SO fish have special adaptions to get enough oxygen
• where does oxygen enter the fish?

  through its mouth
• where does water pass out of the fish?

  through gills
• what is each gill made of ?

  Lots of thin plates called GILL FILAMENTS. ,
• what do lots of gill filaments give?

  a big surface area for gas exchange
• what are the gill filaments covered in?

  lots of tiny structures called LAMELLAE
• what do LAMELLAE do?

  increase surface area
• what do the lamellae have lots of, to speed up diffusion ?

  blood capillaries and a thin surface layer of cells
• describe the counter current system involving blood and water?

  Blood flows through the lamellae in one direction and WATER flows over in the opposite direction. called a counter current system
• what does the counter-current system do?

  maintains a large concentration gradient between the water and blood.
• is the conc of oxygen higher in the water or blood?

  The concentration of oxygen in the water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the bloof