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Heart Anatomy (External)

    Heart (Anterior VIew)

     

    Heart Anatomy Anterior View Image 

     

    Heart (Posterior View)

     

    Heart Anatomy Posterior View Image 

     

     
    Main Chambers of the Heart
    • Right Atria:
      • Receives venous (or deoxygenated) blood from the superior and inferior vena cava and the coronary sinus and transfers.
      • Functions to transfer blood thru the tricuspid valve during diastole (ventricular relaxation) into the right ventricle.
    • Left Atria:
      • Receives oxygenated blood from the pulmonary veins and transfers it through the mitral valve during diastole (ventricular relaxation) into the left ventricle.
    • Right Ventricle
      • Receives blood from the right atrium via the tricuspid valve during diastole and is responsible for moving deoxygenated blood to the lungs for oxygenation and CO2 elimination during systole (ventricular contraction).
      • Considered a low pressure system
    • Left Ventricle:
      • Receives blood from the left atrium via the mitral valve during diastole and is responsible for moving oxygenated blood to the systemic vasculature and organs during systole (ventricular contraction).
      • Considered a higher-pressure system compared to the right ventricle.
    Orientation of the Heart
    • Anterior or Sternocostal Surface:
      • Mainly the right ventricle
    • Inferior Border or Diaphragmatic Surface:
      • Mainly the left ventricle and part of the right ventricle
    • Right Border or Pulmonary Surface:
      • Right atrium
    • Left Border or Pulmonary Surface:
      • Left ventricle and creates the cardiac impression in the left lung
    Blood Supply
    • General: 
      • The endocardium and subendocardial tissue receive oxygen and nutrients by diffusion or microvasculature directly from the chambers of the heart. The remainder is supplied by the coronary vasculature, which is primarily embedded in the pericardial fat on the surface of the heart and supplies predominantly the epicardium.
    • Left Coronary Artery:
      • Arises from the proximal aspect of the aortic sinuses, superior to the aortic valve in the ascending aorta.
      • Supplies blood flow to the:
        • Left atrium
        • Left Ventricle (majority of it)
        • Right Ventricle (small portion of it)
        • Interventricular system
    • Right Coronary Artery:
      • Arises from the proximal aspect of the aortic sinuses, superior to the aortic valve in the ascending aorta.
      • Supplies blood flow to the:
        • Right atrium
        • Sinoatrial node (SA node) in about 60% of people
        • AV node in about 80% of people
        • Right border of the heart and ventricle
        • Posterior aspect of the heart
        • Patients who are right coronary artery dominant have a branch off of the right coronary artery that supplies the posterior interventricular branch (or posterior descending artery). 
        • About 67% of patients are right dominant.
    Function of the Heart
    • Diastole:
      • State of the cardiac cycle when the ventricles are being filled with blood.
      • The diastolic blood pressure is a reflection of the amount of recoil in the arterial system (i.e., resting pressure on the blood vessels being applied).  The faster the pulse (heart rate), the shorter the diastolic filling time and less run off of blood into more distal arterial vessels/branches, thereby leading to higher diastolic pressures. 
    • Systole:
      • State of the cardiac cycle when the ventricles are contracting and ejecting blood out of the heart.
      • The systolic blood pressure is a reflection of the maximum pressure achieved by the contraction of the left ventricle.  The heart must generate enough force that it creates more pressure within the ventricle so that blood can move forward to areas of lower pressure (i.e., this is the afterload or resistance to forward flow).
    • Pulse Pressure:
      • The difference between the systolic and diastolic blood pressure.
      • Influenced by changes in aortic regurgitation, stroke volume, and changes in vascular compliance.
    Innervation of the Heart
    • Parasympathetic Nervous System:
      • Primary via the vagus nerve (cranial nerve X)
      • Afferent nerve fibers release acetylcholine on target tissues in the heart and work on the muscarinic-2 (M2) receptors
      • Slows pulse through reductions in SA node activation (negative chronotropy) and slowing of action potential speed through the AV node (negative dromotropy)
      • Reduces the force of contraction of the ventricular myocytes (negative inotropy)
    • Sympathetic Nervous System:
      • Superior paravertebral ganglia release norepinephrine to stimulate the B1 receptor
      • Increases the pulse through reductions in SA node activation (positive chronotropy) and increasing the speed of the action potential through the AV node (positive dromotropy)
      • Increases the force of contraction of the ventricular myocytes (positive inotropy)
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    Editors & Reviewers

    Editor-in-Chief: 

    • Anthony J. Busti, MD, PharmD, FNLA, FAHA
    • Karolina DeAugustinis, MD

    Last Reviewed:  July 2015