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Circulatory System (Blood Flow (Blood starts in the heart and is pumped to…

- - - - pressure blood applies on the walls of the blood vessels
      - drives fluid out of capillaries into the tissues
    - - pulls fluid back into the capillaries
      - also called blood proteins
- - - - circulatory fluid
        
        Hemolymph- interstitial fluid
      - Heart
        
        pumps hemolymph to sinuses
        
        relaxation pulls hemolymph back in
      - Present in arthropods and some molluscs
      - body movement helps circulate hemolymph
      - requires less energy
    - - Circulatory fluid
        
        Blood
      - present in annelids, molluscs and vertebrates
      - Blood is confined in vessels and separate from interstitial fluid
      - Heart
        
        pumps blood to large vessels where chemical exchange occurs between blood and interstitial fluid and interstitial fluid and body cells
  - - - Types
        
        Capillaries
        
        microscopic vessels that infiltrate tissues and allows diffusion of chemicals to occur between circulatory fluid and interstitial fluid
        
        structure
        
        endothelium and basal lamina
        
        very small
        
        thin walls
        
        these structures help promote diffusion of chemicals to organs and tissues
        
        Arteries
        
        Carries Circulatory fluid away from the heart to organs through the body
        
        structure
        
        endothelium and thick layer of smooth cells which allows them to sustain high pressure when blood is pumped through them
        
        constricted or dilated to regulate blood flow
        
        Veins
        
        Carries circulatory fluid towards the heart
        
        structure
        
        endothelium and thin layer of smooth muscle
        
        maintain blood flow in one direction, valves prevent backflow
      - tubes that contain the circulatory fluid and acts like a transport system to the necessary organs and tissues
    - - Closed - Blood
      - Open - hemolymph
    - - pumps circulatory fluid through out the body so chemical exchange can happen wherever needed
- - - - one complete sequence of pumping and filling of the heart
    - - Atrial systole and ventricular diastole - atrial contraction forcing remaining blood into the ventricles emptying the atria
      - Ventricular systole and atrial diastole - ventricular contractions pumps blood into arteries through semilunar valves
      - Atrial and ventricular diastole - relaxation of heart, blood is moved back into the heart from veins into the atria and then ventricles through the atrioventricular valves
  - - - Extrinsically - medulla oblongata sends signals to manipulate heart rate
      - Intrinsically - pacemaker cells in atrioventricular node
    - - electrical signals spread to walls of atria causing them to contract
      - electrical impulses reach the atrioventricular node, delays impulse for 0.1 seconds
      - after delay and atria finished contracting ventricles contract at the same time
      - summary
        
        SA node -> AV node -> heart apex -> ventricles
      - impulses are carried by the purkinje fibers