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Chapter 23 Circulation (Structure of blood vessels fits their function (23…

- - - - Pulmonary arteries carry oxygen-poor blood to the lungs. Blood flows back in to the heart through the pulmonary veins, which bring oxygen- rich blood from the lung.
        
        In the systemic circuit, oxygen-rich blood exits the heart via the aorta. The superior vena cava returns oxygen-poor blood to the heart from the upper body, and the inferior vena cava returns oxygen-poor blood from the lower body.
  - - - During diastole of the cardiac cycle, blood flows form the veins into the heart chambers.
        
        During systole, contraction of the atria push blood into the ventricles, and then stronger contractions of the ventricles propel blood into the larger arteries.
        
        Heart valves prevent the backflow of blood. Cardiac output is the amount of blood per minute pumped by a ventricle.
  - - - The AV node relays these signals to the ventricles. An electrocardiogram records the electrical change.
  - - - Cardiovascular disease- disorders of the heart and blood vessels
        
        Stroke is the death of brain tissue due to the lack of oxygen from the rupture or blockage of arteries in the head.
        
        Researchers use randomized studies to determine the best way to treat patients with atherosclerosis of the coronary arteries.
- - - - Capillaries- Consist of only a single layer of epithelial cells wrapped in an extracellular matrix. Also facilitate exchange is their intimate connection with the body's tissues.
        
        Veins- Transport blood from the lungs and other parts of the body to the heart. Velocity and pressure are lower in veins than in arteries
  - - - Pressure is the highest in the arteries. Blood velocity is slowest in the capillaries.
        
        Skeletal muscle contractions and one-way valve keep blood moving through veins to the heart.
  - - - 1.)Blood flows through the capillary bed when its precapillary sphincters are relaxed.
        
        2.) Bypasses the capillary bed when the sphicters are contracted
- - - - Platelets are cell fragments that are involved in the process of blood clotting.
  - - - The production of red blood in the bone marrow is controlled by a negative-feedback mechanism that is sensitive to the amount of oxygen reaching the tissue via blood.
        
        If the tissue are not receiving enough oxygen, the kidney produce erythropoietin (EPO) , a hormone that stimulates the bone marrow to produce more red blood cells.
  - - - Soon a cluster of sticky platelets forms a plug that quickly provides protection against additional blood loss.
        
        Threads of fibrin reinforce the plug, forming a fibrin clot.
  - - - When a stem cell divides, one daughter cell remains a stem cell and the other can take on a specialized function
- - - - Blood passes through the heart of the fish only once in each circuit through the body, an arrangement called single circulation.
        
        Blood pumped from the ventricle travels first to the gill capillaries. Blood pressure drops considerably as blood flows through the narrow gill capillaries. An artery carries the oxygen rich blood from the gills to capillaries in the tissues and organs, form which the blood returns to the atrium of the heart
        
        Land vertebrate have double circulation in which blood is pumped a second time after it loses pressure in the lungs, with a pulmonary (carries blood between he heart and gas exchange tissues in the lung) and a systemic circuit ( carries blood between the heart and the rest of the body).
- - - - The atrium receives blood from the veins and the ventricle pumps blood to the gills via large arteries.
        
        The large arteries branch into arterioles, small vessels that give rise to capillaries. Networks of capillaries called capillary beds infiltrate every organ and tissue in the body.
        
        The capillary converge into venules, which inturn coverage into larger veins that return blood to the heart.
    - - There are three kind of vessels.
        
        Capillaries covey blood between arteries and veins within each tissues.
        
        Veins return blood to the heart
        
        Arteries carry blood away from the heart to body organs and tissues
      - Closed circulatory system- Earthworms, squids, octopuses and vertebrates all have CCS. It is called "closed" because the circulatory fluid, blood, is confined to vessels, keeping blood distinct from the interstitial fluid.
      - Open circulatory system - Many invertebrates have OCS. The system is called "open" because fluid is pumped through open-ended vessels and flows out among the tissues; there is no distinction between the circulatory fluid and interstitial fluid.