When the pericardium is opened anteriorly during surgery, a finger placed in the transverse sinus separates arteries from veins. A hand placed under the apex of the heart and moved superiorly slips into the oblique sinus.
The pericardium is supplied by branches from the internal thoracic, pericardiacophrenic, musculophrenic, and inferior phrenic arteries, and the thoracic aorta.
Veins from the pericardium enter the azygos system of veins and the internal thoracic and superior phrenic veins.
Nerves supplying the pericardium arise from the vagus nerve [X], the sympathetic trunks, and the phrenic nerves.
It is important to note that the source of somatic sensation (pain) from the parietal pericardium is carried by somatic afferent fibers in the phrenic nerves. For this reason, “pain” related to a pericardial problem may be referred to the supraclavicular region of the shoulder or lateral neck area dermatomes for spinal cord segments
C3, C4, and C5.
The general shape and orientation of the heart are that of a pyramid that has fallen over and is resting on one of its sides. Placed in the thoracic cavity, the apex of this pyramid projects forward, downward, and to the left, whereas the base is opposite the apex and faces in a posterior direction (Fig. 3.63). The sides of the pyramid consist of: a diaphragmatic (inferior) surface on which the pyramid rests, an anterior (sternocostal) surface oriented anteriorly, a right pulmonary surface, and a left pulmonary surface.
The base of the heart is quadrilateral and directed posteriorly. It consists of: the left atrium, a small portion of the right atrium, and the proximal parts of the great veins (superior and inferior venae cavae and the pulmonary veins) (Fig. 3.64).
Because the great veins enter the base of the heart, with the pulmonary veins entering the right and left sides of the left atrium and the superior and inferior venae cavae at the upper and lower ends of the right atrium, the base of the heart is fixed posteriorly to the pericardial wall, opposite the bodies of vertebrae TV to TVIII (TVI to TIX when standing). The esophagus lies immediately posterior to the base.
From the base the heart projects forward, downward, and to the left, ending in the apex. The apex of the heart is formed by the inferolateral part of the left ventricle (Fig. 3.65) and is positioned deep to the left fifth intercostal space, 8 to 9 cm from the midsternal line.
Surfaces of the heart
The anterior surface faces anteriorly and consists mostly of the right ventricle, with some of the right atrium on the right and some of the left ventricle on the left (Fig. 3.65).
The heart in the anatomical position rests on the diaphragmatic surface, which consists of the left ventricle and a small portion of the right ventricle separated by the posterior interventricular groove (Fig. 3.66). This surface faces inferiorly, rests on the diaphragm, is separated from the base of the heart by the coronary sinus, and extends from the base to the apex of the heart.
The left pulmonary surface faces the left lung, is broad and convex, and consists of the left ventricle and a portion of the left atrium (Fig. 3.66).
The right pulmonary surface faces the right lung, is broad and convex, and consists of the right atrium (Fig. 3.66).
Some general descriptions of cardiac orientation refer to right, left, inferior (acute), and obtuse margins:
The right and left margins are the same as the right and left pulmonary surfaces of the heart.
The inferior margin is defined as the sharp edge between the anterior and diaphragmatic surfaces of the heart (Figs 3.63 and 3.65)—it is formed mostly by the right ventricle and a small portion of the left ventricle near the apex.