Circulatory Systems - 9.1

• The circulatory system is a system of blood vessels with a pump and valves to ensure a one-way flow of blood.
• Valves are structures which allow a liquid to flow in one direction only.
• Oxygenated blood flows into left side of heart, which is then sent around body. Deoxygenated blood comes back to right side of heart, which is then sent back to lungs to become oxygenated.
• In a double circulatory system, blood passes through the heart twice on one complete circuit of the body.

  In a single circulatory system, blood passes through the heart once in one complete circuit of the body.
• Double circulatory system is made of 2 parts, blood vessels that carry blood to the lungs and back is pulmonary system, and blood vessels that carry blood around the body and back is systemic system.
• When blood flows thru mammals' lungs or fish's gills, it loses blood pressure. In mammals, it is sent to the heart which raises the pressure and sends it around the body. In fish, this low-pressure blood keeps traveling around the body so fish's organs get blood slower than mammal's organs.
• Any tissues that are metabolically very active require oxygen delivered quickly and fast. This is more efficient in mammals than in fish cuz of double circulatory system.