Circulatory System U.4 L.5

  • purpose of circulatory : transport gases, nutrient molecules, hormones and wastes, regulate internal temperature, protect against blood loss and diseases

  • components of circ system ⮕

    heart : muscular organ that pumps blood through the body

    blood vessels : system of hollow tubes that blood moves through

    blood : fluid that transports nutrients, oxygen, carbon dioxide, etc..

  • open circ. system : blood flows freely within the body cavity and touches organs and tissues (insects)

  • closed circ. system : blood is contained by vessels, materials must pass through vessel wall to get to organs (humans)

  • requirements of the circ. system ⮕

    oxygen : for cellular respiration

    food nutrients : for energy and to build cellular structures (lipds for cell membrane)

    water : cells are mostly water, have to get rid of wastes

  • BLOOD COMPONENTS ⮕

    • plasma : 55%, mostly water, dissolved molecules and ions, pH balance, plasma proteins (antibodies/blood clotting proteins)

    • red blood cells : 45% hemoglobin carries oxygen, red blood cells are made in the bone marrow, dead cells are broken down by the liver, biconcave disc shaped cells lack maturity, (anemia happens when there is a shortage of hemoglobin, caused by too few RBC or too little hemoglobin, symptoms : headaches, weakness, fatigue)

    • white blood cells : <1%, protect against infection, destroy bacteria/produce antibodies, inside circ. & lymphatic systems

    • platelets : <1% : fragments of cells and function in blood clotting

  • arteries ⮕

    • carry oxygen-rich blood away from the heart at a high pressure towards the body tissues

    • exception : the pulmonary artery carries deoxygenated blood to the lungs

    • thick and elastic walls for high pressure when ventricles contract, buried deep for protection

    • arterioles to capillaries : arteries branch to smaller vessels called arterioles

    • capillaries : 1 cell thick, exchange materials between the blood and tissues, oxygen and CO2 diffuse across the walls of the capillaries

  • vessels ⮕

    • capillaries collect into venules (smaller than veins) and carry blood back to the heart at a low pressure

    • thin walled vessels are larger in diameter than arteries, not as elastic arteries so they rely on muscle contractions to move blood towards the heart

    • valves prevent backflow of blood

  • veins ⮕

    • every few centimeters along a vein allows blood in one direction to flow to the heart