External Features of Heart | Heart Surface Anatomy

External Features of Heart:
The heart presents the below external features:

• Apex,
• Base,
• Three surfaces: Stern costal, diaphragmatic, and left.
• Three borders: Right, left, and inferior.

The Apex of the Heart:
It includes-

• It is a conical area formed by the left ventricle.
• It is directed, forward and to the left in the 5th intercostal space.
• Location: It lies in the 5th intercostal space, about 9cm from the midline and slightly below and medial to the left nipple.

The Base of the Heart:
It includes-

• The base (or posterior surface) of the heart is the most fixed part of the heart.
• It is formed by two atria: Two-thirds by the left atrium and one-third by the right atrium.
• The great veins enter the base of the heart- four pulmonary veins enter the left atrium, and superior and inferior venae cavae enter the right atrium.

The Surface of the Heart:
The surface of the heart has explained the below:

1. Sternocostal (or anterior) Surface:
It includes-

• It is formed mainly by the right atrium and right ventricle which are separated from each other by the anterior part of the atrioventricular groove.
• It is also partly formed by the left auricle and left ventricle.

2. Diaphragmatic (or inferior) surface:
It includes-

• This surface is flat and faces downward and backward.
• It is formed by the left ventricle (two-thirds) and right ventricle (one-third) which are separated from each other by the posterior interventricular groove.

3. Left Surface:
It includes-

• It is directed upward, backward, and to the left.
• It is formed mainly by the left ventricle and partly by the left atrium and left auricle.

Borders of the heart have explained in the following:

1. Right Border:
It includes-

• Rounded and convex, formed only by the right atrium.
• It extends from the right side of the opening of the superior vena cava to that of the inferior vena cava.
• The right border separates the base from the stern coastal surface.

2. Left Border:
It includes-

• It is formed mainly by the left ventricle and partly by the left auricle.
• It extends from the left auricle to the apex of the heart.
• It separates the stern coastal surface from the left surface.

3. Inferior Border:
It includes-

• It is nearly horizontal and extends from the opening of the inferior vena cava to the apex of the heart.
• It separates the stern coastal surface from the diaphragmatic surface.