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Cardiovascular (Anatomy (Location and Position of the Heart (Heart is…

- - - - Two Atria
        
        superior chambers that receive blood and send it to the ventricles
      - Two Ventricles
        
        Inferior chambers that pump blood away
  - - - Transports blood from right ventricle
      - Splits into pulmonary arteries
    - - Transports blood from left ventricle to the body
    - - Drain deoxygenated blood into right atrium
    - - Drain oxygenated blood into left atrium
  - - - Sit between atrium and ventricle of each side
      - Right AV valve (tricuspid)
      - Left AV valve (bicuspid or mitral)
    - - Sit at boundary of ventricle and arterial trunk
      - Open to allow blood to flow through the heart; close to prevent backflow
      - Pulmonary semilunar valve: located between right ventricle and pulmonary trunk
      - Aortic semilunar valve: located between left ventricle and the aorta
  - - - Pericardium: three layered fibroserous sac around heart
        
        Fibrous pericardium: outermost covering
        
        Dense irregular connective tissue
        
        Attaches to diaphragm and base of aorta, pulmonary trunk
        
        Anchors heart and prevents its overfilling
        
        Parietal layer of serous pericardium
        
        Simple squamous epithelium and areolar connective tissue
        
        Attaches to fibrous pericardium
        
        Visceral layer of serous pericardium
        
        Simple squamous epithelium and areolar connective tissue
        
        Attaches directly to heart
  - - - separates atria from ventricles
      - Groove extending around circumference of heart
    - - separate left from right ventricles
      - Anterior interventricular sulcus on anterior side
      - Posterior interventricular sulcus on posterior side
      - Extend from coronary sulcus toward heart apex
  - - - visceral layer of serous pericardium
      - Outermost heart layer
      - Simple squamous epithelium and areolar connective tissue
    - - Middle layer of heart wall (thickest)
      - Cardiac muscle tissue that contracts to pump blood
    - - Covers internal surface of heart and external surface of valves
      - Simple squamous epithelium and areolar connective tissue
      - Continuous with lining of blood vessels
  - - - Interatrial septum separates left atrium from right atrium
      - Interventricular septum separates left ventricle from right ventricle
    - - Pectinate muscles: ridges on anterior wall and within auricle
      - Fossa ovalis: oval depression on interatrial septum
        
        Occupies location of fetal foramen ovale—hole that shunted blood from right to left atrium in fetal life
      - Entrances from coronary sinus (carrying blood from heart wall), superior vena cava, and inferior vena cava
      - Exit to right ventricle through right AV valve
    - - Trabeculae carneae: irregular muscular ridges inside ventricle wall
      - Papillary muscles: cone-shaped projections extending from internal ventricle wall (right ventricle typically has 3 of them)
        
        Anchor chordae tendineae
      - Chordae tendineae (tendinous cords): heart strings
        Thin strands of collagen fibers attaching to AV valve
      - Superior exit to pulmonary trunk through pulmonary semilunar valve
    - - Has pectinate muscles in its auricle
      - Entrances from pulmonary veins
      - Exit to left ventricle through left AV valve
    - - Trabeculae carneae on internal wall surface
      - Two papillary muscles anchor chordae tendineae
      - Superior exit to aorta through aortic semilunar valve
  - - - Right coronary artery branches
        
        Right marginal artery
        Supplies right heart border
        
        Posterior interventricular artery
        Supplies posterior left and right ventricle
      - Left coronary artery branches
        
        Circumflex artery
        Supplies left atrium and ventricle
        
        Anterior interventricular artery
        Supplies anterior surface of both ventricles
        Supplies most of interventricular septum
        “Widowmaker” nickname refers to high risk of fatality if occluded
- - - - Organization gives rise to striated appearance under microscope
      - Optimal length (maximum overlap of filaments) is seen when heart is stretched by blood filling the chamber
    - - up to 35% of the volume of a cardiac cell
      - needs massive O2
    - - work cells have a large stable resting membrane potential and display a prolonged action potential with a plateau phase
      - pacemaker cells have smaller unstable resting potentials and spontaneously depolarize, generating the intrinsic electrical activity of the heart
        
        found in the sinoatrial (SA) and atrioventricular (AV) nodes
    - - allows ions to pass through
  - - - Depolarization opens fast voltage gated Na+ channels in the sarcolemma, allowing extracellular Na+ to enter.
        
        Na+ initiates positive feedback cycle that causes the rising phase of the action potential
    - - transmission of the depolarization wave down the T tubules causes the sarcoplasmic reticulum to release Ca2+ into the sarcoplasm
    - - Excitation- contraction coupling occurs as Ca2+ provides the signal for cross bridge activation and couples the depolarization wave to sliding of the myofilaments