A&P Cardiovascular System: The Heart

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lburke2
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139584
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A&P Cardiovascular System: The Heart
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2012-03-05 21:45:22
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Cardiovascular System Heart
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A&P Cardiovascular System: The Heart
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  1. Heart Anatomy (size, location, orientation)
    Size: closed fist weighing 250-350g or 8-10 oz

    Location: mediastinum (medial cavity of thorax)

    Orientation: base = posterior surface & apex = point of anterior surface
  2. Coverings of Heart
    Pericardium and Pericardial cavity
  3. Coverings of Heart - Pericardium:

    Fibrous Pericardium
    Serous Pericardium
    Double walled sac that surrounds and protects the heart

    Fibrous Pericardium: outer fibrous layer which protects heart, anchors to surrounding structures, and prevents the heart from overfilling with blood

    Serous Pericardium: inner layer composed of two layers (parietal and visceral)
  4. Coverings of Heart - Pericardial Cavity
    Contains fluid between the parietal and visceral layers of the serous pericardium which reduces friction between the two layers
  5. Layers of the Heart Wall
    Epicardium, myocardium, endocardium
  6. Layers of Heart Wall: Epicardium
    Visceral layer of serous pericardium, thin transparent layer
  7. Layers of Heart Wall: Myocardium
    Middle layer of cardiac muscle, skeleton of heart
  8. Layers of Heart Wall: Endocardium
    Inner thin layer of endothelium (squamous epithelium)
  9. Chambers and Associated Great Vessels - Makeup
    Four chambers, three sulci, atria, ventricles
  10. Chambers and Associated Great Vessels: Four Chambers
    Atria: two superior receiving chambers divided by interartrial septum

    Ventricles: two inferior discharging chmbers divided by interventricular septum

    Thickness of myocardium of the four chambers varies according to the chamber's function
  11. Chambers and Associated Great Vessels: Three Sulci (grooves)
    Coronary: between atria and ventrices

    Anterior: between ventricles on anterior surface

    Posterior: between ventricles on posterior surface
  12. Chambers and Associated Great Vessels: Atria
    Small thin-walled chambers which return blood to heart

    a. Auricles: external flaps on each atrium that increases their volume

    b. Pectinate Muscles: internal ridges in each atrium composed of bundles of muscle tissue

    c. Fossa Ovalis: shallow depression remnant of an opeing in fetal heart (foramen ovale)

    Blood enters right atrium via superior vena cava, inferior vena cava and coronary sinus

    Blood enters left atrium via four pulmonary veins
  13. Chambers and Associated Great Vessels: Ventricles
    Large thick-walled chambers (left ventricle thickest wall) which pump blood away from heart

    a. Trabeculae Carnea: internal irregular ridges of muscle in each ventricle

    b. Papillary Muscles: cone-like muscles involved in valve function

    Blood leaves right ventricle via pulmonary trunk

    Blood leaves left ventricle via aorta
  14. Pathway of Blood Flow Through the Heart:

    Pulmonary Circuit
    Systematic Circuit
    The heart is a double pump

    Pulmonary Circuit: circulation of blood through the lungs, function of the right side of heart

    Systematic Circuit: circulation of blood throughout the body except the air sacs in the lungs, function of the left side of the heart
  15. Coronary Circulation: Arterial & Venous
    Functional blood supply to heart

    Arterial: left and right coronary arteries

    Venous: cardiac veins and coronary sinus
  16. Heart Valves: Atrioventricular & Semilunar (two each)
    Atrioventricular: tricuspid and bicuspid (mitral)

    Chordae Tendinae: strands of collagen cords which anchor cusps of valve to the papillary muscles

    Semilunar: pulmonary semilunar and aortic semilunar
  17. Cardiac Muscle Cells - Structure
    a. striated

    b. short, fat, branched

    c.one or two large nuclei

    d. interconnected by intercalated discs

    e. large numerous mitochondria

    f. sarcomeres with Z discs, A bands, and I bands

    g. calcium delivering system least elaborate, no triads
  18. Mechanisms and Events of Contraction
    a. 1% of cardiac cells are self-excitable and autorhythmic

    b. all cardiac muscle cells are a single contractile unit which contracts as a unit or not at all

    c. long absolute refractory period which prevents tetanic contractions

    d. sequence of electrical events (ion movements) similar to that in skeletal muscle fibers
  19. Energy Requirements
    Aerobic Respiration: greater dependence on oxygen therefore more mitochondria than skeletal muscle
  20. Electrical Events: Heartbeat
    Not dependent on nervous system but autorhythmic cells
  21. Electrical Events: Conduction System
    Intrinsic Conduction System: noncontractile cardiac cells specialized to initiate and distribute impulses throughout heart

    a. Sinoatrial (SA) node: pacemaker

    b. Atrioventricular (AV) node

    c. Atrioventricular bundle: bundle of His

    d. right and left bundle branches

    e. perkinje fibers
  22. Electricle Events: Innervation
    Extrinsic innervation of heart

    a. Cardioacceleratory center (sympathetic)

    b. Cardioinhibitory center (parasympathetic)
  23. Electrical Events: Electrocardiogram (ECG or EKG)
    Record of electrical changes during each cardiac cycle

    a. P wave: atrial depolarization

    b. QRS complex: onset of ventricular depolarization

    c. T wave: ventricular repolarization

    d. P-Q interval or P-R interval: conduction time from beginning of atrial excitation to beginning of ventricular excitation

    e. S-T segment: time when ventricular contractile fibers are fully depolarized

    f. Q-T interval: beginning of ventricular depolarization through ventricular repolarization
  24. Heart Sounds
    S1 = "lubb" - blood turbulence associated with closing AV valves

    S2 = "dubb" - blood turbulence associated with closing semilunar valves
  25. Mechanical Events: Cardiac Cycle

    (systole and diastole of both atria and ventricles)
    a. Ventricular filling (mid-to-late diastole): ventricular filling and atrial contraction

    b. Ventricle systole (atria in diastole): isovolumetric contraction and ventricular ejection

    c. Isovolumetric relaxation (early diastole)
  26. Cardiac Output
    The amount of blood ejected by the left ventricle into the aorta or right ventricle into the pulmonary trunk per minute

    Product of heart rate (beats per minute) x stroke volume (ml per minute)

    Stroke volume
  27. Cardiac Output: Stroke Volume
    a. amount of blood ejected by a ventricle during systole

    b. end diastolic volume (EDV) - end systolic volume (ESV)

    • c. Regulation of stroke volume
    • i. preload = degree of stretch (Starling's Law)
    • ii. contractility = contractile strength achieved as a given muscle length
    • iii. afterload = pressure that must be overcome for the ventricles to eject blood
  28. Regulation of the Heart Rate: autonomic nervous system regulation
    Cardiovascular center in medulla oblongata

    a. sympathetic impulses increase heart rate and force contraction

    b. parasympathetic impulses decrease heart rate, vagal tone
  29. Regulation of the Heart Rate: chemical regulation
    a. Hormones: epinephrine, norepinephrine, and thyroxine

    b. Ions: Na+, K+, and Ca2+
  30. Regulation of the Heart Rate: factors that influence heart rate
    • Body temperature
    • Age
    • Gender
    • Emotions
    • Exercise
  31. Homeostatic Imbalances: Trachycardia & Bradycardia
    Trachycardia: abnormally fast heart rate ( > 100 beats/min)

    Brachycardia: heart rate slower than 60 beats/min

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