Visceral serous pericardium, at great vessel roots, arranged into 2 tube-like sheaths:

• Arterial tube — encloses ascending aorta + pulmonary trunk
• Venous tube — encloses SVC, IVC, 4 pulmonary veins

Reflection creates 2 sinuses between parietal + visceral layers.

Transverse Sinus

Definition: Horizontal passage behind arterial tube (ascending aorta + pulmonary trunk), in front of venous tube (SVC + superior pulmonary veins)

Communication: Each side communicates with general pericardial cavity

Relations:

Oblique Sinus

Definition: Recess behind base of heart (behind left atrium); enclosed by ‘J-shaped’ visceral pericardial sheath around 6 veins (2 venae cavae + 4 pulmonary veins)

Development: From absorption of 4 pulmonary veins into left atrium; akin to lesser sac (behind stomach)

Function: Permits left atrial distension during pulmonary venous return

Boundaries:

Applied Anatomy

Transverse sinus — cardiac surgery

• After opening pericardium anteriorly, finger passed through transverse sinus posterior to aorta/pulmonary trunk
• Temporary ligature around aorta + pulmonary trunk; heart-lung machine tubes inserted before tightening

Pericarditis / Cardiac Tamponade

• Pericarditis → pericardial effusion → compresses thin-walled atria → impaired diastolic filling → ↓cardiac output = tamponade
• Pericarditis = terminal event in uraemia

Pericardiocentesis

Pericardial Friction Rub

• Roughened parietal + visceral layers → friction, palpable + audible

Nerve supply: Fibrous pericardium + parietal serous layer = phrenic nerves (somatic, pain-sensitive). Visceral serous layer = sympathetic + vagal (autonomic, pain-insensitive). Pericarditis pain originates from parietal pericardium.

The visceral layer of the serous pericardium, at the roots of the great vessels of the heart, is arranged into two tube-like sheaths:

• The arterial tube — encloses the ascending aorta and pulmonary trunk (the arterial end of the heart tube)
• The venous tube — encloses the superior and inferior venae cavae and the four pulmonary veins (the venous end of the heart tube)

The reflection of the visceral pericardium around these great vessels creates two sinuses (recesses) between the parietal and visceral layers of serous pericardium:

1. Transverse sinus of the pericardium
2. Oblique sinus of the pericardium

---

Transverse Sinus of Pericardium

Definition

The transverse sinus is a horizontal passage lying behind the arterial tube (ascending aorta and pulmonary trunk) and in front of the venous tube (superior vena cava and superior pulmonary veins).

Communication

On each side, the transverse sinus communicates with the general pericardial cavity.

Relations

---

Oblique Sinus of Pericardium

Definition

The oblique sinus is a recess of serous pericardium behind the base of the heart (actually behind the left atrium). It is enclosed by a ‘J-shaped’ sheath of visceral pericardium that encloses six veins — the 2 venae cavae and 4 pulmonary veins.

Developmental Basis

The oblique sinus develops as a result of the absorption of the four pulmonary veins into the left atrium. It is akin to the lesser sac (omental bursa) which lies behind the stomach.

Function

The oblique sinus permits the distension of the left atrium during the return of oxygenated blood from the lungs.

Boundaries

---

Applied Anatomy

Surgical Significance of the Transverse Sinus

During cardiac surgery, after the pericardial sac is opened anteriorly, a finger is passed through the transverse sinus of the pericardium, posterior to the aorta and pulmonary trunk. A temporary ligature is passed through the transverse sinus around the aorta and pulmonary trunk, and the tubes of the heart-lung machine are inserted into these vessels before the ligature is tightened.

Pericarditis and Cardiac Tamponade

Inflammation of the serous pericardium (pericarditis) causes accumulation of serous fluid in the pericardial cavity — termed pericardial effusion. Excessive accumulation compresses the thin-walled atria and interferes with diastolic filling of the heart, reducing cardiac output. This condition is clinically termed cardiac tamponade.

Pericarditis is the terminal event in uraemia.

Pericardiocentesis

Excessive pericardial fluid can be aspirated from the pericardial cavity by two routes:

Pericardial Friction Rub

Roughening of the parietal and visceral layers of serous pericardium by inflammatory exudate causes friction between the two layers — termed pericardial friction rub — which can be felt on palpation and heard through a stethoscope.

Nerve supply note: The fibrous pericardium and parietal layer of serous pericardium are supplied by phrenic nerves (somatic) — sensitive to pain. The visceral layer of serous pericardium is supplied by sympathetic and vagal fibres (autonomic) — insensitive to pain. Hence the pain of pericarditis originates from the parietal pericardium.

Diagram Placeholder

Diagram content will be added later.

• Placeholder 1
• Placeholder 2
• Placeholder 3

Previous Year Questions

1. Placeholder question
2. Placeholder question
3. Placeholder question
4. Placeholder question
5. Placeholder question