4.19 The Heart

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4.19 The Heart
2010-11-12 02:31:02
Anatomy Chapter Heart

Location and orientation, Structure of the heart, heart valves, pathway of blood, tissue, innervation, blood supply, disorders of the heart, throughout life
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  1. The Heart as a Double Pump
    • The heart is a muscular double pump with two functions:
    • 1. The right side receives oxygen-poor blood from the body tissues and pumps it to the lungs to pick up oxygen and dispel carbon dioxide
    • 2. The left side receives the oxygenated blood returning from the lungs and pumps it throughout the body to supply oxygen and nutrients to the body tissues

    Pulmonary circuit — takes blood to and from the lungs

    Systemic circuit — vessels transport blood to and from body tissues

    Atria — receive blood from the pulmonary and systemic circuits

    Ventricles — the pumping chambers of the heart
  2. Structure of the Heart: Coverings
    The Pericardium is a triple-layered sac that encloses the heart.

    Two primary layers:

    • Fibrous pericardium: outer layer
    • • Strong layer of dense connective tissue; adheres to diaphragm inferiorly; superiorly fused to roots of heart vessels; holds the heart in place and keeps it from overfilling with blood

    • Serous pericardium: a closed sac sandwiched between the fibrous pericardium and the heart
    • Formed from two layers:
    • Parietal layer of the serous pericardium: adheres to the inner surface of the fibrous pericardium
    • Visceral layer of the serous pericardium: or epicardium; lies on the heart and is considered a part of the heart wall

    • - Slit-like space between the parietal and visceral layers of the serous pericardium is called the pericardial cavity
    • Epithelial cells lining the cavity secrete serous fluid that reduces friction between the beating heart and the outer wall of the pericardial sac
  3. Structure of the Heart: Layers of the Heart Wall
    • The wall of the heart has three layers, all richly vascularized
    • Epicardium:
    • • Visceral layer of the serous pericardium; often infiltrated with fat

    • Myocardium: forms the bulk of the heart
    • • Consists of cardiac muscle tissue; contracting layer
    • • Muscle arranged in circular and spiral patterns called bundles that function to squeeze blood through the heart in proper directions

    • Endocardium: sheet of simple squamous epithelium resting on a thin layer of connective tissue
    • • Lines the heart chambers and covers the heart valves
  4. Structure of the Heart: Heart Chambers
    List Overview
    • Right and left atria
    • • Superior chambers

    • Right and left ventricles
    • • Inferior chambers

    • Internal divisions
    • • Interventricular septa (wall between ventricles)
    • • Interatrial septa (wall between atria)

    • External markings
    • • Coronary sulcus: forms a crown by circling the boundary between the atria and ventricles
    • • Anterior interventricular sulcus: marks the anterior position of the interventricular septum between the two ventricles
    • • Posterior interventricular sulcus: separates the two ventricles on the heart's inferior surface.
  5. Heart: Anterior View
  6. Heart: Inferior View
  7. Heart: Frontal Section
  8. Structure of the Heart: Heart Chambers
    Right Atrium
    Forms right border of heart

    Receives deoxygenated blood from systemic circuit via superior vena cava, inferior vena cava, and the coronary sinus

    • Pectinate muscles
    • • Ridges inside anterior of right atrium (separated from smooth posterior atrium by crista terminalis)

    Fossa ovalis

    • •Depression in interatrial septum
    • •Remnant of fetal foramen ovale
  9. Structure of the Heart: Heart Chambers
    Right Ventricle
    • Forms most of the anterior surface of the heart.
    • Receives blood from right atrium through the tricuspid valve

    • Pumps blood into pulmonary circuit via
    • Pulmonary trunk

    • Internal walls of right ventricle
    • Trabeculae carneae: irregular ridges of muscle
    • Papillary muscles: cone-shaped muscles that project superiorly from the walls into the ventricular cavity
    • Chordae tendineae: thin, strong bands that project superiorly from the papillary muscles to the flaps of the tricuspid valve

    • Pulmonary semilunar valve
    • • Located at opening of right ventricle and pulmonary trunk
  10. Structure of the Heart: Heart Chambers
    Left Atrium
    Makes up heart’s posterior surface

    Receives oxygen-rich blood from lungs through two left and two right pulmonary veins

    • Opens into the left ventricle through
    • Mitral valve (left atrioventricular valve)
  11. Structure of the Heart: Heart Chambers
    Left Ventricle
    • Internal walls of left ventricle
    • • Trabeculae carneae
    • • Papillary muscles
    • • Chordae tendineae

    • Pumps blood through systemic circuit via
    • Aortic semilunar valve (aortic valve): located at opening of left ventricle and aorta
  12. Cardiac Muscle Tissue
    Forms a thick layer called myocardium

    • • Striated like skeletal muscle
    • • Contractions pump blood through the heart and into blood vessels
    • Cardiac muscle cells
    • • Short
    • • Branching (networks called fibers)
    • • Have one or two nuclei
    • Cells join at intercalated discs
    • • Complex junctions (transverse fasciae adherens and longitudinal gap junctions help transmit ions and contractile signals to adjacent cells); allows cells in heart to contract simultaneously
    • Intercalated Discs
    • Adjacent sarcolemmas interlock
    • Possess three types of cell junctions
    • • Desmosomes

    • • Fasciae adherans—long desmosome-like junctions
    • • Gap junctions