Anatomy of the Heart: Mediastinum
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Questions and Answers

What is the mediastinum?

  • A broad central partition that separates the two pleural cavities (correct)
  • A part of the heart's vasculature
  • A sac surrounding the heart and roots of great vessels
  • A layer of the pericardium

    • What is the pericardium?

  • A partition that separates the two pleural cavities
  • A fibrous sac surrounding the heart and roots of great vessels
  • A part of the heart's vasculature
  • A fibroserous sac surrounding the heart and roots of great vessels (correct)

    • What is the fibrous pericardium?

  • A part of the heart's vasculature
  • A thin layer of the pericardium that adheres to the heart
  • A layer of the pericardium that lines the inner surface of the fibrous pericardium
  • A tough connective tissue outer layer that defines the boundaries of the middle mediastinum (correct)

    • What is the orientation of the base of the heart?

    <p>Faces posteriorly</p> Signup and view all the answers

    What is the anterior surface of the heart?

    <p>Faces anteriorly and consists mostly of the right ventricle with some of the right atrium</p> Signup and view all the answers

    What is the diaphragmatic surface of the heart?

    <p>The surface on which the heart rests</p> Signup and view all the answers

    What is the posterior portion of the pericardial sac?

    <p>Shows reflections of the serous pericardium</p> Signup and view all the answers

    How many parts does the serous pericardium have?

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

    What is the location of the left atrium in relation to the right atrium?

    <p>Behind the right atrium</p> Signup and view all the answers

    What is the structure that separates the left atrium from the esophagus?

    <p>Fibrous pericardium</p> Signup and view all the answers

    What is the characteristic of the interior of the left atrium?

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

    How many pulmonary veins open into the left atrium?

    <p>4</p> Signup and view all the answers

    Which valve guards the atrioventricular orifice?

    <p>Mitral valve</p> Signup and view all the answers

    How many cusps does the mitral valve have?

    <p>2</p> Signup and view all the answers

    What part of the ventricle is below the aortic orifice?

    <p>Aortic vestibule</p> Signup and view all the answers

    What type of fibers innervate the heart via the cardiac plexuses?

    <p>Sympathetic and parasympathetic fibers</p> Signup and view all the answers

    What is the function of the inferior vena cava?

    <p>To return blood to the heart from the lower half of the body</p> Signup and view all the answers

    What surface of the heart faces the left lung?

    <p>Left pulmonary surface</p> Signup and view all the answers

    What is the purpose of the coronary sinus?

    <p>To drain blood from the heart wall</p> Signup and view all the answers

    What is the function of the coronary sulcus?

    <p>It separates the atria from the ventricles</p> Signup and view all the answers

    What are the projecting ridges in the right ventricle wall known as?

    <p>Trabeculae carneae</p> Signup and view all the answers

    What is the small outpouching of the right atrium?

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

    What vein opens into the upper part of the right atrium?

    <p>Superior vena cava</p> Signup and view all the answers

    What is the function of the papillary muscles?

    <p>To prevent the cusps of the tricuspid valve from bulging into the ventricle</p> Signup and view all the answers

    What are the three cusps of the tricuspid valve?

    <p>Anterior, septal, and inferior</p> Signup and view all the answers

    What is the part of the atrium posterior to the crista terminalis?

    <p>Smooth walled</p> Signup and view all the answers

    What is the purpose of the chordae tendineae?

    <p>To connect the papillary muscles to the tricuspid valve</p> Signup and view all the answers

    What is the groove on the outside of the heart at the junction between the right atrium and the right auricle?

    <p>Sulcus terminalis</p> Signup and view all the answers

    What is the ridge formed by the sulcus terminalis on the inside of the heart?

    <p>Crista terminalis</p> Signup and view all the answers

    What is the shape of the right ventricle near the pulmonary orifice?

    <p>Funnel-shaped</p> Signup and view all the answers

    What is the function of the musculi pectinati?

    <p>It roughens the wall of the atrium</p> Signup and view all the answers

    What is the structure of the pulmonary valve?

    <p>Three semilunar cusps</p> Signup and view all the answers

    Which part of the sympathetic trunks gives rise to the sympathetic supply?

    <p>Cervical and upper thoracic portions</p> Signup and view all the answers

    Which nerve is responsible for the parasympathetic supply?

    <p>Vagus nerve</p> Signup and view all the answers

    Which of the following is NOT a great vessel of the heart?

    <p>Coronary artery</p> Signup and view all the answers

    Where is the apex of the heart located?

    <p>Fifth left intercostal space</p> Signup and view all the answers

    What forms the superior border of the heart?

    <p>Roots of the great blood vessels</p> Signup and view all the answers

    Where is the tricuspid valve located?

    <p>Behind the right half of the sternum</p> Signup and view all the answers

    What is the location of the mitral valve?

    <p>Behind the left half of the sternum</p> Signup and view all the answers

    What is the distance from the midline to the apex beat?

    <p>3.5 inch (9 cm)</p> Signup and view all the answers

    Study Notes

    Location of the Heart

    • The heart is located in the mediastinum, a broad central partition that separates the two pleural cavities.
    • The mediastinum is subdivided into several smaller regions: superior mediastinum, inferior mediastinum (anterior, middle, and posterior).

    Pericardium

    • The pericardium is a fibroserous sac surrounding the heart and the roots of the great vessels.
    • It consists of two components: fibrous pericardium (tough connective tissue outer layer) and serous pericardium (thin, consisting of two parts: parietal layer and visceral layer).
    • The fibrous pericardium defines the boundaries of the middle mediastinum.
    • The serous pericardium lines the inner surface of the fibrous pericardium (parietal layer) and adheres to the heart, forming its outer covering (visceral layer).

    Orientation and Surfaces of the Heart

    • The heart is a pyramid-shaped organ with its apex pointing forward, downward, and to the left.
    • The base of the heart is opposite the apex and faces posteriorly.
    • The heart has four surfaces: anterior (sternocostal), diaphragmatic (inferior), right pulmonary, and left pulmonary.
    • The anterior surface consists mostly of the right ventricle with some of the right atrium on the right and some of the left ventricle on the left.
    • The diaphragmatic surface consists of the left ventricle and a small portion of the right ventricle.

    External Sulci

    • Internal partitions divide the heart into four chambers, producing surface or external grooves referred to as sulci.
    • The coronary sulcus circles the heart, separating the atria from the ventricles.
    • The interventricular sulcus (anterior and posterior) separates the right and left ventricles.

    Right Atrium

    • The right atrium consists of a main cavity and a small outpouching, the auricle.
    • The sulcus terminalis is a vertical groove on the outside of the heart, forming a ridge, the crista terminalis, on the inside.
    • The main part of the atrium is smooth walled, while the part in front of the ridge is roughened or trabeculated by bundles of muscle fibers.

    Openings into the Right Atrium

    • The superior vena cava opens into the upper part of the right atrium without a valve.
    • The inferior vena cava (larger than the superior vena cava) opens into the lower part of the right atrium with a rudimentary, nonfunctioning valve.
    • The coronary sinus opens into the right atrium between the inferior vena cava and the atrioventricular orifice, guarded by a rudimentary, nonfunctioning valve.

    Right Ventricle

    • The walls of the right ventricle are thicker than those of the right atrium, showing internal projecting ridges formed of muscle bundles.
    • The projecting ridges give the ventricular wall a spongelike appearance and are known as trabeculae carneae.
    • The tricuspid valve guards the atrioventricular orifice, consisting of three cusps (anterior, septal, and inferior).
    • The pulmonary valve guards the pulmonary orifice, consisting of three semilunar cusps.

    Left Atrium and Left Ventricle

    • The left atrium is similar to the right atrium, consisting of a main cavity and a left auricle.
    • The left atrium is situated behind the right atrium, forming the greater part of the base or posterior surface of the heart.
    • The four pulmonary veins open into the posterior wall of the left atrium without valves.
    • The left atrioventricular orifice is guarded by the mitral valve, consisting of two cusps (anterior and posterior).
    • The left ventricle communicates with the left atrium through the atrioventricular orifice and with the aorta through the aortic orifice.

    Blood Supply of the Heart

    • The heart is supplied by the coronary arteries, which arise from the aorta.
    • The coronary arteries are divided into two main branches: the right coronary artery and the left coronary artery.

    Nerve Supply of the Heart

    • The heart is innervated by sympathetic and parasympathetic fibers of the autonomic nervous system via the cardiac plexuses.
    • The cardiac plexuses are situated below the arch of the aorta.
    • The sympathetic supply arises from the cervical and upper thoracic portions of the sympathetic trunks.
    • The parasympathetic supply comes from the vagus nerves.

    Great Vessels

    • The great vessels of the heart function to carry blood to and from the heart.
    • The great vessels of the thorax are the pulmonary trunk, aorta, superior vena cava, inferior vena cava, and pulmonary veins.

    Surface Anatomy of the Heart

    • The heart has an apex and four borders: superior, right, left, and inferior.
    • The apex is formed by the left ventricle and corresponds to the apex beat.
    • The surface markings of the heart valves are as follows:
      • The tricuspid valve lies behind the right half of the sternum opposite the fourth intercostal space.
      • The mitral valve lies behind the left half of the sternum opposite the fourth costal cartilage.

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    Description

    Explore the mediastinum, a central partition that separates the two pleural cavities, and learn about its subdivisions, including the superior and inferior mediastinum.

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