Orientation and Superficial Anatomy of Heart
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1. The heart lies slightly to left of midline.
The base
of the heart is formed mainly by the left atrium, and,
to a small extent, by the back part of the right
atrium. The apex
is the inferior rounded tip. |
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2. The heart at oblique angle to longitudinal axis.
Because of
this tilt, the apex points obliquely toward the left.
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This tilt in
the orientation of the heart also causes the horizontal
and vertical borders of the heart to be as follows:
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1. The superior border is formed by
the base. |
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2. The right border is formed by the
right atrium. |
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3. The inferior border is formed by
the inferior wall of the right ventricle. |
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4. The left border is formed by the
left ventricle and a small portion of the left
atrium. |
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3. The heart rotated slightly toward left.
Because of
this rotation:
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The
surface of the heart underneath the sternum and
the ribs on the left side, the sternocostal
surface, is that of the right atrium and
ventricle. |
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The
surface of the heart that rests on the diaphragm,
which curves directly behind the heart, is
called the
diaphragmatic surface, and
is formed by the
posterior walls of the right and left ventricles |
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The atria have thin
muscular walls that are distended as they receive blood. When
contracted, the anterior walls form flaps that are called
auricles. A deep groove between the atria and ventricles is
called the coronary sulcus. The boundary between the
right and left ventricles is indicated externally by a shallow
groove on the anterior surface, the anterior interventricular
sulcus, and the posterior surface, the posterior
interventricular sulcus.
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