Configuration extérieure et intérieure du cœur

General Characteristics and External Anatomy of the Heart

• Definition and Primary Function:

  • The heart is an intra-thoracic, unpaired, mixed muscular, hollow organ characterized by rhythmic contractions.
  • Its essential physiological role is to propel blood through the blood vessels, serving as the central crossroads of the circulatory system.

• Anatomical Location and Position:

  • Situated inside the thoracic cavity between the right and left lungs.
  • Occupies the middle mediastinum of the inferior mediastinal floor (médiastin moyen de l'étage inférieur du médiastin).
  • Rests directly upon the superior surface of the diaphragm.

• Color, Consistency, and Weight:

  • Consistency and Color: Firm texture with a reddish color; its external surface is covered with scattered fatty deposits (amas graisseux).
  • Weight: Increases progressively with age.
  • Average weight in males: $270\,g$.
  • Average weight in females: $260\,g$.

• General Geometry and Axes:

  • Shaped as a triangular pyramid with a posterior base and an antero-left apex.
  • Major Axis: Oriented obliquely forward, to the left, and downward.
  • Base Orientation: Directed backward and to the right.

External Sulci, Faces, Borders, Base, and Apex

• Main External Sulci (Grooves):

  • Sulci define the boundaries of internal cardiac chambers on the heart surface and harbor coronary vessels embedded in adipose tissue.
  • Inter-atrial Sulcus (Sillon inter-atrial): Positioned at the base of the heart, separating the right atrium from the left atrium.
  • Inter-ventricular Sulcus (Sillon inter-ventriculaire): Lies in a vertical plane along the heart's main axis. Divides the anterior face and posterior diaphragmatic face into right and left ventricular regions. It is traversed by inter-ventricular vessels.
  • Atrio-ventricular Sulcus (Coronary Sulcus / Sillon atrio-ventriculaire): Lies in a plane perpendicular to the heart's axis, separating atria from ventricles. Posteriorly, it meets the inter-atrial and posterior inter-ventricular sulci. Divides each face into an anterior (ventricular) segment and a posterior (atrial) segment.

• Faces of the Heart:

  • Anterior Face (Sterno-costal Face):
  • Faces forward and to the right.
  • Ventricular Segment: Contains an arterial (posterior) zone occupied by the aortic and pulmonary artery orifices, and a ventricular zone proper (anterior) divided by the anterior inter-ventricular sulcus into left and right ventricular fields.
  • Atrial Segment: Positioned superior to the arterial zone as a wide gutter-shaped depression, concave anteriorly, housing the aorta and pulmonary artery. The floor corresponds to the inter-atrial septum. Gives rise to the right and left auricles, which feature flattened, irregularly dentated extensions.
  • Inferior Face (Diaphragmatic Face):
  • Slightly convex, sloping downward and forward.
  • Ventricular Segment: Subdivided by the inferior (posterior) inter-ventricular sulcus into a large right field (right ventricle) and a narrow left field (left ventricle).
  • Atrial Segment: Narrow, merging with the broad opening of the inferior vena cava (IVC).
  • Left Lateral Face (Pulmonary Face):
  • Convex top-to-bottom, directed backward and to the left.
  • Subdivided by the left portion of the coronary sulcus into an anterior ventricular segment (lateral aspect of left ventricle) and a narrow posterior atrial segment (corresponding to the left auricle).

• Borders of the Heart:

  • Three borders separate the three faces: one right border and two left borders.
  • Right Border: Positioned between the anterior face and the inferior face.
  • Left Borders: Rounded contours separating the left lateral face from the anterior and inferior faces; categorized into superior and inferior left borders.
  • All borders converge towards the apex.

• Base and Apex:

  • Base: Posterior, facing backward and to the right. Formed exclusively by the atria and divided by the inter-atrial sulcus.
  • Left portion: Receives the openings (ostia) of the four pulmonary veins.
  • Right portion: Features the crista terminalis, which divides the right atrium into a left area (junction zone between the superior vena cava [SVC] and inferior vena cava [IVC]) and a right area.
  • Apex (Sommet / Pointe): Belonging entirely to the left ventricle, forming the extreme tip of the heart.

Radiological Silhouette and Cardiac Arcs

• Cardiac Silhouette Evaluation:

  • Thoracic X-ray analysis measures cardiac size via the cardiothoracic ratio.
  • Normal cardiac ratio: $\le 0.5$.
  • Pathological ratio: $> 0.55$, indicating cardiomegaly.

• Radiological Arcs of the Cardiac Contour:

  • Left Border Arcs:
  • Superior left arc: Formed by the aortic knob / aortic arch (bouton/crosse de l'aorte).
  • Middle left arc: Formed by the trunk of the pulmonary artery and the left auricle.
  • Inferior left arc: Formed by the left ventricle.
  • Right Border Arcs:
  • Superior right arc: Formed by the Superior Vena Cava (SVC / VCS).
  • Inferior right arc: Formed by the right atrium and Inferior Vena Cava (IVC / VCI).

Internal Anatomy and Structural Cavities of the Heart

• Internal Cavities:
  • Divided internally into four distinct chambers: Right Atrium, Right Ventricle, Left Atrium, and Left Ventricle.
  • Right and left chambers are completely partitioned by two septa: the inter-atrial septum and inter-ventricular septum, forming two independent functional units (right heart and left heart).
  • Atria communicate with their corresponding ventricles through atrio-ventricular ostia fitted with valves to prevent backflow during ventricular contraction.
  • The internal muscular wall exhibits prominent ridges termed fleshy columns (colonnes charnues).

Internal Configuration of the Right Heart

• Right Ventricle:

  • Conical shape featuring three walls (anterior, inferior, internal), one base, and one apex.
  • Walls:
  • Anterior wall corresponds to the sterno-costal face.
  • Inferior wall corresponds to the diaphragmatic face.
  • Internal wall corresponds to the inter-ventricular septum.
  • Types of Fleshy Columns (Colonnes Charnues):
  • 1st Order (Papillary Muscles / Piliers du Cœur): Conical muscular projections attached by their base to the ventricular wall; their apex projects tendinous cords (cordages tendineux) attaching to the edges and parietal surface of atrio-ventricular valve leaflets.
  • 2nd Order: Attached to ventricular walls at both ends, with a free central bridge.
  • 3rd Order: Entirely attached along their full length to the ventricular wall surface.
  • Base Orifices:
  • Right Atrio-Ventricular Orifice: Circular opening ($110\text{--}120\,mm$ in circumference) equipped with the tricuspid valve apparatus. Shaped like a funnel with 3 leaflets: anterior, inferior, and internal (septal). Each leaflet connects to tendinous cords arising from 1st-order papillary muscles.
  • Pulmonary Arterial Orifice: Circular opening of the pulmonary trunk, equipped with 3 semilunar (sigmoid) valves: 1 anterior valve and 2 posterior valves (right and left).

• Right Atrium:

  • Irregularly cubic shape with six walls:
  • Anterior Wall: Contains the right atrio-ventricular orifice.
  • External Wall: Features 3rd-order fleshy columns; the right auricle opens via a broad orifice situated superior to the right atrio-ventricular ostium at the anterior-external wall junction.
  • Posterior Wall: Features Lower's tubercle (tubercule de Lower), located between the openings of the two venae cavae.
  • Internal Wall: Formed by the inter-atrial septum; contains the fossa ovalis (fosse ovale), a rounded depression encircled by the prominent annulus of Vieussens (anneau de Vieussens), representing the closed embryonic ductus arteriosus / foramen ovale remnant.
  • Superior Wall: Contains the orifice of the Superior Vena Cava (SVC), which lacks valves (avalvulaire).
  • Inferior Wall: Houses two orifices: the Inferior Vena Cava (IVC) orifice guarded by the Eustachian valve (valvule d'Eustachi), and the coronary sinus orifice guarded by the Thebesian valve (valvule de Thébesius).

Internal Configuration of the Left Heart

• Left Ventricle:

  • Conical shape featuring two walls (internal and external), one base, and one apex.
  • Walls: Both walls display fleshy columns. The right (internal) wall forms the inter-ventricular septum, and the left (external) wall corresponds to the left lateral face of the heart.
  • Base Orifices:
  • Left Atrio-Ventricular Orifice: Circular opening ($90\text{--}110\,mm$ in circumference) equipped with the funnel-shaped mitral valve apparatus, consisting of 2 leaflets: large/anterior/right leaflet and small/posterior/left leaflet.
  • Aortic Arterial Orifice: Valvular apparatus containing 3 semilunar (sigmoid) valves: 2 anterior valves (right and left) and 1 posterior valve.

• Left Atrium:

  • Features six walls:
  • External (Lateral) Wall: Contains the opening of the left auricle.
  • Internal (Medial) Wall: Formed by the inter-atrial septum, showing the remnant of Botal's foramen.
  • Superior and Inferior Walls: Form the upper and lower boundaries.
  • Posterior Wall: Contains the 4 openings (orifices) of the pulmonary veins.
  • Anterior Wall: Opens into the left atrio-ventricular (mitral) orifice.

Clinical Auscultation Sites and Functional Conclusion

• Stethacoustic Projections (Clinical Auscultation Sites):

  • Pulmonary Focus: Located in the 2nd left intercostal space.
  • Aortic Focus: Located in the 2nd right intercostal space (symmetrical to the pulmonary focus).
  • Tricuspid Focus: Located at the base of the xiphoid process.
  • Mitral Focus: Located in the 5th left intercostal space along the mid-clavicular line (ligne médio-claviculaire).

• Functional Summary:

  • The heart functions as the central pump of the circulatory network.
  • Partitioned completely by the inter-atrial and inter-ventricular septa into two distinct physiological divisions:
  • Right Heart: Manages oxygen-poor (deoxygenated) blood circulating to the pulmonary network.
  • Left Heart: Manages oxygen-rich (oxygenated) blood circulating to the systemic network.