QS Study

The pericardium is a conical fibro-serous sac which encloses the heart and the root of the great vessels except for inferior vena cava. It is the membrane enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane.

Pericardial sinuses

It refers to the wall at the back of the pericardial sac. It is ventrally bound by a pericardial membrane within which lies the heart.

Types: There are two types of pericardial sinuses:

  1. Transverse sinus &
  2. Oblique sinus.

Transverse sinus

The epicardium at the roots of the great vessels is arranged in the form of two tubes and the passage between the two tubes is known as the transverse sinus. It is the transverse communication between the left and right parts of the pericardial space proper behind the two outflow arteries of the heart. It is a passage between the posterior and the superior reflections of the serous pericardium.

The arterial tube encloses the ascending aorta & the pulmonary trunk.

The venous tube encloses the vena cava & pulmonary veins.

The sinus is bounded:

  • Anteriorly: By the ascending aorta & pulmonary trunk.
  • Posteriorly: By the superior vena cava & the left atrium.
  • On each side: It opens into the general pericardial cavity.

Oblique sinus

It is a narrow gap behind the heart. It is the small concavity in the pericardial cavity which is situated behind the base of the heart. It is laterally bound by the pericardial reflections on the inferior vena cava and the pulmonary veins.

Features:

(a) It is bounded:

  • Anteriorly: By the left atrium.
  • Posteriorly: By the parietal pericardium.
  • On each side: By the reflections of the pericardium.
  • Below: It opens into the rest of the pericardial cavity.

(b) The sinus permits pulsations of the left atrium to take place freely.

Functions –

(1) It prevents overdistension of heart.

(2) It friction of heart.

(3) It maintains the position of the heart.

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