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Cardiovascular system (Circulatory system (Coronary circulation: blood…

- - - - prevents cusps from everting
  - - - allows blood to flow into pulmonary trunk and aorta
    - - prevents blood form returning to ventricles, blood fills valve cusps, tightly closing the semilunar valves
  - - - Left side of the heart pumps
      - Left ventricle pumps oxygenated blood into aorta
      - Aorta branches into many arteries that travel to organs
      - Arteries branch into many arterioles in tissue
      - Arterioles branch into thin-walled capillaries for exchange of gasses and nutrients
      - Deoxygenated blood begins its return in venules
      - Venules merge into veins and return to right atrium
    - - right side of the heart pumps deoxygenated blood to lungs
      - right ventricle pumps blood to pulmonary trunk
      - Pulmonary trunk branches into pulmonary arteries
      - Pulmonary arteries carry blood to lungs for exchange of gases
      - oxygenated blood returns to heart in pulmonary veins
  - - - Left coronary artery
        
        supplies left atrium and left ventricles via circumflex branch
        
        supplies both ventricles via the anterior interventricular branch
      - Right coronary artery:
        
        supplies right ventricle via marginal branch
        
        supplies both ventricles via posterior interventricular branch
    - - collect waste from cardiac muscles
      - drains into a large sinus on posterior surface of heart called coronary sinus
        
        coronary sinus empties into right atrium
- - - - begins heart activity that spreads to both atria
      - excitation spreads to AV node
    - - divides into bundle branches and purkinje fibers
    - - SA node fires spontaneously 90-100x per minute
      - AV node fire at 40-50x per minute
      - If both nodes are suppressed, then fibers in ventricles by themselves fire only 20-40x per minute
      - artificial pacemaker needed if pace is too slow
      - extra beats forming at other sites are called ectopic pacemakers
        
        caffeine and nicotine increase activity
  - - - voltage difference across sarcolemma
        
        due primarily to potassium
      - Cell is polarized
      - Resting potential of working cardiac muscle is very stable
    - - electrical impulse applied to cell membrane
      - sodium channels opens, so sodium can rush into cell
      - Depolarization= membrane potential is 0 mV
    - - membrane potential remains at 0 mV
      - another channel is opened
        
        slower calcium channel, calcium is greater outside than inside the cell, so diffuse into cell
      - in most myocardial cells influx of calcium is balanced by outflow of potassium
    - - due to sodium rushing in so quickly, membrane potential rises above 0 mV
      - To balance, the coloring enters cell and or potassium leave cell
    - - slow calcium channels are closed but potassium outflow continues
      - Na/K pump restores original ion concentration balance between sodium and potassium
      - intracellular space become negative again and depolarization occurs
  - - - positive ions slowly leak into cell (phase 4)
      - at the same time, decrease in K+ outflow
      - cell depolarizes automatically w/out a preceding stimulus
      - cell reaches threshold potential: AP occurs
- - - - dense irregular connective tissue
      - protects and anchors the heart and prevents overstitching
    - - thin delicate membrane that contains parietal layer (outer), pericardial cavity w/ pericardial fluid, and visceral layer (epicardium)
        
        layers of the heart wall:
        
        Epicardium: visceral layer of serous pericardium
        
        Myocardium: cardiac muscle is the bulk of the heart
        
        carcgam muscle fibers swirl diagonally around the heart in interlacing bundles
        
        Endocardium: chamber lining & valves
  - - - receives blood from superior vena cava, inferior vena cava, and coronary sinus
      - interracial septum partitions the atria
      - tricuspid valve has 3 cusps composed of dense CT covered by endocardium
        
        blood flows through the right ventricle
    - - forms most of anterior surface of heart
      - papillary muscle are cone shaped trabecular carneae
      - chordea tendineae: cords between valve cusps and papillary muscles
      - inter ventricular septum partitions ventricles
      - pulmonary semilunar valve: blood flows into pulmonary trunk
    - - forms most of the base of the heart
      - receives blood from lungs
      - 4 pulmonary veins (2 right and 3 left)
      - Biscupid valve: blood passes through into left ventricle, has two cusps
    - - forms the apex of heart
      - chordae tendineae anchor bicuspid valve to papillary muscles
      - aortic semilunar valve
        
        blood passes through valve into the ascending aorta
        
        just above the valve is the openings to coronary arteries
- - - - greater proportion of elastic fibers which provides expansion as blood is pumped
      - high pressure and its blood color is red
    - - superior vena cava: brings blood from her and thoracic limb
      - inferior vena cava: brings from abdomen and pelvic limb
      - low pressure and the blood color is blue
      - valves are irregular intervals directed back towards heart
    - - thin walled allows gases, nutrients, and waster to pass to and from cells
  - - - this allows for more time for exchange processes to occur