Histology: Epicardium and Cardiac Muscle Layers
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Questions and Answers

What is the name of the specialized regions in cardiac muscle that have many desmosomes and adherent junctions joining the cells firmly?

  • Endomysium
  • Striations
  • Intercalated discs (correct)
  • Perimysium
  • Which structure surrounds the muscle cells in cardiac muscle and contains a rich capillary network?

  • Perimysium
  • Desmosomes
  • Endomysium (correct)
  • Fibrous skeleton
  • What is the function of sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) in cardiac muscle cells?

  • To transport calcium ions back into the sarcoplasmic reticulum after muscle contraction (correct)
  • To release calcium ions into the cytoplasm during muscle contraction
  • To help generate action potentials for muscle contraction
  • To facilitate the binding of actin and myosin during muscle contraction
  • What is the main function of the fibrous skeleton in specific areas of cardiac muscle?

    <p>To separate bundles and layers of muscle fibers</p> Signup and view all the answers

    Which part of the cardiac muscle cell plays a crucial role in coordinating excitation-contraction coupling by regulating calcium levels?

    <p>Intercalated discs</p> Signup and view all the answers

    Which layer of the heart contains Purkinje fibers specialized for impulse conduction?

    <p>Subendocardial layer</p> Signup and view all the answers

    What type of cells make up the Purkinje fibers in the heart?

    <p>Modified cardiac muscle cells</p> Signup and view all the answers

    Which layer of the heart typically stains paler due to glycogen filling much of the cytoplasm?

    <p>Subendocardial layer</p> Signup and view all the answers

    The mesothelium that lines the pericardial space also covers which layer of the heart?

    <p>Epicardium</p> Signup and view all the answers

    What does the simple mesothelium secrete to prevent friction as the heart beats?

    <p>Lubricant fluid</p> Signup and view all the answers

    Which layer of the heart includes an endothelium and a subendothelial connective tissue?

    <p>Endocardium</p> Signup and view all the answers

    What is the main function of sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) in cardiac muscle relaxation?

    <p>Removal of 80% of Ca2+ from the sarcoplasm</p> Signup and view all the answers

    Which component is responsible for the Ca2+-stimulated release of Ca2+ in cardiac muscle?

    <p>Ryanodine receptors</p> Signup and view all the answers

    What is the function of Na+/K+ ATPase in cardiac muscle?

    <p>Maintaining Na+ concentration gradient for Na+/Ca2+ exchanger</p> Signup and view all the answers

    Which type of channel opens upon the action potential conducted along the sarcolemma and T-tubules in cardiac muscle?

    <p>Voltage-gated Ca2+ channels</p> Signup and view all the answers

    Where is the epicardium located within the cardiac muscle layers?

    <p>External tunic of the heart</p> Signup and view all the answers

    What is responsible for forming cross-bridges and initiating the power stroke in cardiac muscle?

    <p>Ca2+ binding to troponin C</p> Signup and view all the answers

    Study Notes

    Epicardium

    • The epicardium is the visceral layer of the pericardium and is covered by the simple mesothelium.
    • The mesothelial cells secrete a lubricant fluid that prevents friction as the beating heart contacts the parietal pericardium.

    Endocardium

    • The endocardium is the lining layer of the heart, consisting of the endothelium and its supportive subendothelial connective tissue.
    • It has a middle myoelastic layer of smooth muscle cells and connective tissue, and a deeper connective tissue layer of variable thickness called the subendocardial layer.
    • The subendocardial layer in the ventricles contains the conducting (Purkinje) fibers of the heart's impulse conducting network.
    • Purkinje fibers are modified cardiac muscle cells joined by intercalated disks but specialized for impulse conduction rather than contraction.

    Cardiac Muscle Cells

    • Cardiac muscle cells have nuclei, intercalated discs, and striations.
    • Surrounding the muscle cells is a delicate sheath of endomysium with a rich capillary network.
    • A thicker perimysium separates bundles and layers of muscle fibers and forms larger masses of fibrous connective tissue.

    Intercalated Discs

    • Transverse intercalated disc regions have many desmosomes and adherent junctions called fascia adherentes, which join the cells firmly.

    Excitation-Contraction Coupling in Cardiac Muscle

    • Ca2+-stimulated Ca2+ release is the mechanism of excitation-contraction coupling in cardiac muscle.
    • Action potentials conducted along the sarcolemma and T-tubules open voltage-gated Ca2+ channels, leading to Ca2+ release from the SR.
    • Ca2+ binds to troponin C, leading to the formation of cross-bridges and power stroke.

    Cardiac Muscle Relaxation

    • Ca2+ concentration in the cytoplasm is reduced by active transport back into the SR and removal of Ca2+ out of the cell through the plasma membrane.
    • Myocardium relaxes when Ca2+ concentration is reduced.

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    Description

    Test your knowledge on the epicardium being the visceral layer of the pericardium and the different layers of cardiac muscles. This quiz is based on Junquiera's Basic Histology.

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