What are the functions of gill filaments and gill lamellae?
Gill filaments take oxygen into blood. They have many lamellae on top to increase surface area.
What occurs in diastole?
Relaxation. Blood returns to atria via pulmonary vein and vena cava. As atria fill, pressure in them rises causing atrioventricular valves to open and semi-lunar valves close, allowing passage of blood into ventricles. Relaxation of ventricular walls causes them to recoil and thus, have lower pressure than atrial
What occurs in atrial systole?
Walls of atria contract, decreasingvolume and increasing pressure. Atrial pressure rises above ventricular so atrioventricular valves open. Blood is forced into ventricles
What occurs in ventricular systole?
Walls of ventriclescontract, decreasing volume and increasing pressure. Ventricular pressure rises above atrial, so atrioventricular valves close and semi-lunar valves open.Blood forced out of heart.