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Structure

Venae cavae

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The superior vena cava (SVC) drains the head, neck, upper limbs and thorax, and the inferior vena cava (IVC) drains the lower limbs, pelvis and abdomen. Both open into the right atrium.

Terminologia Anatomica (Latin): Vena cava superior / Vena cava inferior · Open in the 3D atlas

Location

The SVC (about 7 cm) forms behind the right first costal cartilage from the two brachiocephalic veins, descends in the right side of the superior and middle mediastinum and enters the right atrium at the level of the third costal cartilage. The IVC forms at L5 from the common iliac veins, ascends to the right of the aorta, passes through the diaphragm at T8 and enters the atrium almost at once.

Structure

The SVC has no valves and receives the azygos arch posteriorly before entering the pericardium. The IVC receives lumbar, right gonadal, renal, right suprarenal, inferior phrenic and hepatic veins (left gonadal and left suprarenal drain to the left renal vein). The walls are thin, with sparse smooth muscle.

Blood supply

The walls receive small vasa vasorum from neighbouring arteries (bronchial and pericardial branches for the SVC; lumbar and renal branches for the IVC); the thin media is mainly nourished from the lumen.

Innervation

Sympathetic perivascular fibres control venous tone, which is the main determinant of venous capacitance and preload. The right phrenic nerve passes beside the SVC and pericardium.

Function

Return systemic venous blood to the right heart. Venous return to the IVC is aided by the skeletal muscle pump, respiratory movements and venous valves in the limb veins.

Clinical correlations

SVC obstruction, most often from mediastinal malignancy or thrombosis around a catheter, causes facial and arm swelling and distended chest wall veins. Inferior vena cava filters, caval compression by the gravid uterus in the supine position, and caval extension of renal tumour are other clinical contexts. Persistent left SVC (about 0.5%) usually drains to the coronary sinus.

Common exam points

  • SVC formed by the brachiocephalic veins behind the right 1st costal cartilage; IVC formed at L5.
  • IVC pierces the diaphragm at T8 (caval opening), with the right phrenic nerve branches.
  • Azygos vein drains into the SVC and provides a collateral route between SVC and IVC.
  • Left gonadal and left suprarenal veins drain into the left renal vein; right ones drain directly into the IVC.
  • Persistent left SVC drains to the coronary sinus; IVC anomalies include azygos continuation and duplication.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

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