Circulatory ( or cArdiovascular) System Blood Composition Plasma (55%): Fluid portion of blood Red blood cells (44%): Carry oxygen White blood cells: Defend against pathogens Platelets: Cell fragments, form blood clots

Red Blood Cells  Hemoglobin: Iron-containing molecule  Loosely binds O 2 in lungs (high concentration)  Releases O 2 in body tissue (low concentration)  Shape of RBC’s allows them to travel through narrow capillaries more easily

Red Blood Cell Lifespan  Produced in the marrow  Only type of body cell without a nucleus  Old RBC destroyed in liver, spleen  Average lifespan 120 days

Blood Types RBC Marker Proteins A- A protein B- B protein AB- both A and B proteins O – neither A nor B proteins Another marker protein is Rh factor. Rh +: has Rh factor; Rh - : no Rh factor Immune system produces antibodies against foreign antigens (any protein etc. not produced in the body) AB + is the universal receipient O – is the universal donor

Blood Vessels Arteries  Arterioles (thinner arteries)  Capillaries  Venules (thinner veins)  Veins Arteries  Carry blood away from the heart  Most arteries contain oxygenated blood  Blood is under greater pressure (most arteries protected deeper within body)  Thick walled vessels  Muscular walls expand/ contract to help move blood

Capillaries: Site of Gas/Nutrient Exchange  Microscopic blood vessels  Lining is 1 cell thick  Allows oxygen and nutrients to diffuse into body cells  Waste from cells diffuses into blood

Veins  Carry blood back to the heart  Most veins carry deoxygenated blood  Since many veins travel against gravity, equipped with one-way valves to prevent back-ups Artery: Thicker layer of smooth muscle Vein: One way valves

Heart  Mainly cardiac muscle  Cells have numerous mitochondria  Mammalian hearts have 4 chambers 2 Upper Chambers: Atria  Receiving chambers 2 Lower Chambers: Ventricles  Pump blood out of heart  Left and right sides separated by solid wall (septum) to create two pumps

Video on Flow of Blood in the Heart: click once to start video

Video:Blood Flow through the Body

Pathway of Blood Oxygen poor blood returning from body enters right atrium Right atrium  right ventricle  pulmonary artery  lungs  pulmonary vein  left atrium  left ventricle  aorta  arteries  capillaries  veins  vena cavae

Amphibians and reptiles have a 3 chambered heart rather than four chambered heart, which allows mixing of oxygenated and deoxygenated blood. Mammals and birds have a four chambered heart which keeps oxygenated and deoxygenated blood separated and allows for more efficient transport of oxygen. Discuss with your table partner why amphibians (such as frogs) and reptiles (such as crocodiles) do not require as efficient a heart as mammals and birds.

Mammals and birds are warm-blooded (endotherms.) A large expenditure of energy (ATP) is used to keep the body warm. This ATP is provided by cellular respiration, which requires both food and oxygen. Endotherms require a larger amount of both food and oxygen. Amphibians and frogs are cold-blooded (ectotherms). Their body temperature changes with the outside temperature, and they do not require energy for heating.

Heartbeat regulation Region of heart called the sinoatrial node acts as pacemaker, regulating the heart rate through electrical impulses that spread through the heart. Medulla oblongata regulates the pacemaker, speeding or slowing the heart rate as necessary.

Systolic and Diastolic Pressure Systolic pressure is the pressure exerted when the heart beats. Diastolic pressure is the lowest pressure, when your heart relaxes between beats.