External Features of Heart by Dr. Rajitha Vanga

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#heartgrossfeatures #heartanatomy #specimendemonstration
• The heart is a hollow muscular organ situated in the mediastinum of the thoracic cavity, enclosed in the pericardium.
• It is somewhat pyramidal in shape and placed obliquely behind the sternum and adjoining parts of costal cartilages so that one-third of the heart is to the right of median plane and two-third of the heart is to the left of the median plane.
• The heart consists of four chambers—right atrium and right ventricle, and left atrium and left ventricle. On the surface the atria are separated from the ventricles by the atrioventricular groove (also called coronary sulcus) and ventricles from each other by interventricular grooves.
External features
Externally heart presents
• The apex of the heart is a conical area formed by left ventricle. It is directed to the left. It lies at the level of the 5th left intercostal space, 3.5 inches (9 cm) from the midline and just medial to the midclavicular line.

• The base (or posterior surface) of the heart is formed by two atria, mainly by the left atrium (2/3rd by left and 1/3rd by right atria). It lies opposite to the apex. It is located in front of the middle four thoracic vertebrae (T5–T8) in the lying-down position and descends one vertebra in the erect posture (T6–T9). The base is separated from vertebral column by the oblique pericardial sinus, esophagus, and aorta.

• The heart has the four borders: Upper, right, lower (inferior) and left.
 Upper border of the heart is slightly oblique and atrial (mainly the left atrium). Ascending aorta and the pulmonary trunk pass anterior to it (obscuring it) and at its right extremity, the superior vena cava enters the right atrium.
 Right border of the heart corresponds to the right atrium and is slightly convex to the right. It extends from the right side of the opening of superior vena cava (SVC) to that of inferior vena cava (IVC) and separates the base from the sternocostal surface.
 Inferior border of the heart (acute margin) is sharp, thin and nearly horizontal. It extends from the opening of IVC to the apex and is formed partly by right atrium, mainly by the right ventricle, with a small contribution from the left ventricle near the apex. The inferior border separates the sternocostal(anterior) surface from the diaphragmatic (inferior) surface.
 Left border of the heart (obtuse margin) separates the sternocostal and left surfaces. It descends obliquely, convex to the left, from the left atrial appendage to the cardiac apex. It is round and mainly formed by the left ventricle and partly the left atrial appendage.

• The heart has three surfaces: Sternocostal (anterior), and left surface, diaphragmatic (inferior)
 Anterior (sternocostal) surface is formed mostly by right ventricle and right auricle and partly by left ventricle and left auricle. Anterior interventricular groove is evident on this surface which separates right and left ventricle. The left atrium is hidden on the front by the ascending aorta and pulmonary trunk.
 Left surface is formed mainly by the left ventricle and partly by the left atrium and auricle. It is directed upwards, backwards, and to the left.
 Diaphragmatic surface is flat and rests on the central tendon of the diaphragm. It is formed mainly by the left ventricle (2/3) and partly right ventricle (1/3) which are separated from each other by the posterior interventricular groove.
#heart #thoraxanatomy #externalfeaturesheart

• Grooves/sulci
 Coronary (atrioventricular) sulcus is present on the external surface of the heart, in a circumferential manner around the heart, marks the division between the atria and the ventricles.
o Coronary sulcus is divided into anterior and posterior parts. The right half of anterior part is large and lodges right coronary artery.
o Contents: Right side- Right coronary artery, Small cardiac vein, Left side- Left coronary artery, Circumflex artery, Great cardiac vein, Coronary sinus.
 The crux is the point at which the interventricular and interatrial sulci cross the coronary sulcus.
 Anterior interventricular sulcus is between right and left ventricles; marks the interventricular septum anteriorly,
Contents: Left anterior descending (anterior interventricular) artery, Great cardiac vein
 Posterior interventricular sulcus -Demarcates the posterior interventricular septum.
Contents: Posterior interior interventricular artery, Middle cardiac vein