• Overview:

  • 4 cardiac chambers

  • 4 valves

  • Great vessels

• Observable by several imaging modalities:   e.g.,ultrasound, computer-aided tomography (CAT-Scan), magnetic resonance imaging (MRI)

Right Atrium: Anatomy and blood entry

• Synonym = right auricle: larger than the left atrium, but with thinner walls (about 2 mm); blood capacity about 60 mls

• Blood enters the right atrium through the:

  •  Superior vena cava (SVC): opens into the upper and back part of the atrium {orifice direction downward and forward, towards the atrioventricular orifice}: no valve associated with the opening

  •  Inferior vena cava (IVC): opens into the lowest part of the atrium, near the atrial septum;{orifice direction upward and backward, towards the atrial septum 

  •  Coronary sinus- opens between the inferior vena cava orifice and the atrioventricular opening  (definition: atrioventricular opening= major communication between atrium and ventricle, tricuspid orifice)

  • Details:

    1. Inferior vena cava ostium: protected by the eustachian valve-- in the adult, it may remain however mostly it is small and sometimes lacking {in the fetus the eustachian valve is important and serves to direct the blood from the inferior vena cava, by way of the foramen ovale, into the left atrium}

    2.  Coronary sinus ostium: protected by the thebesian valve, a semicircular valve, also known as the valve of the coronary sinus

  • Right and Left atria: separated by: 

    1. Interatrial septum (central ovoid component)

    2. Fossa ovalis: Definition = oval depression on the atrial septal wall (foramen ovale in the fetus); Located at the lower part of the septum, above and left of the inferior vena cava orifice

    3. Remnant of the fetal foramen ovale

  • Right atrial outflow tract:

    •  Through the tricuspid valve (blood direction: anteriorly inferiorly-- towards the right ventricular outflow tract)

      • Aperture about 4 cm in diameter {surrounded by fibrous ring and covered by the cardiac lining membrane}; significantly larger then be communication aperture between the left atrium and left ventricle

    •  Tricuspid valve: composition-- three leaflets -- (area 8-11 cm²)

"Right atrioventricular (tricuspid) valve:{anterior aspect after removal of the  anterior wall the right  ventricle)"

Right atrium Anterior cusp of the tricuspid valve Chordae tendineae Trabeculae carneae Interventricular septum Septal cusp of the tricuspid valve Anterior papillary muscle Myocardium of the right ventricle  Reference: Rohen, J.W. and Yokochi, C.,Color Atlas of Anatomy: Photographic Study of the Human Body, third edition, Ikaku-Shoin, New York, Tokyo, p. 240, 1993 Permission Pending

•  Anterior or infundibular cusp (largest) is interposed between the atrioventricular orifice of the conus arteriosus

  • Attached to the crystal supraventricularis

  • Controlled by the anterior papillary muscle

•  Posterior or marginal cusp

•  Medial or septal cusp

•  Tricuspid valve cusp bases are attached to a fibrous ring surrounding the atrioventricular orifice and join each other, forming a continuous annular membrane -- their apices projecting into the ventricular cavity

•  Atrial surfaces: (towards the atrium)--smooth

•  Ventricular surfaces: (towards the ventricle) are irregular and rough surfaces serving as attachment points for some of the tendinous cords making up the chordae tendineae

Right Heart: Anterior aspect -- Anterior wall of right atrium and ventricle removed

Reference: Rohen, J.W. and Yokochi, C.,Color Atlas of Anatomy:  Photographic Study of the Human Body, third edition, Ikaku-Shoin, New York, Tokyo, p. 240, 1993.