I am reading about ligamentum arteriosum which connects the left pulmonary artery and descending aorta. But I am seeing that if any figure shows left brachiochephalic vein it does not show left pulmonary artery (and vice versa). Are they both the same?

  • $\begingroup$ Veins are not the same as arteries. A non-capillary blood vessel is either one or the other, not both. $\endgroup$ – MattDMo Jun 26 '15 at 14:41
  • $\begingroup$ Please include references for those figures or add those figures to your question. Plus, as MattDMo said, veins cannot be simultaneously labelled as arteries. I guess the figures are intended to show veins and arteries separately (and not in the same picture). In any case that cannot be verified unless you show us the figures. $\endgroup$ – WYSIWYG Jun 26 '15 at 14:51
  • $\begingroup$ They are structurally and functionally distinct. The left brachiocephalic vein joins the superior vena cava which returns deoxygenated blood to the right side of the heart. Deoxygenated blood is pumped OUT of the right heart and travels to the left lung via the left pulmonary artery. The two don't always appear in the same image because many anatomical images remove structures that aren't the area of focus for clarity. However a quick google image search reveals several pictures that illustrate the distinct positions of both. $\endgroup$ – InactionPotential Jun 26 '15 at 15:09

No, they are not the same. The left brachiocephalic vein receives de-oxygenated blood from the left subclavian vein (draining the left arm) and the left internal jugular vein (draining the brain and parts of the face). The brachiocephalic vein then joins with the superior vena cava which flows into the right atrium.

The left pulmonary artery carries the deoxygenated blood that has just passed through the right atrium and ventricle, through the pulmonary trunk to the left lung for oxygenation.

In the foetal circulation, the ductus arteroisus (before it closes into the ligamentum arteriosum) allows blood to bypass the lungs, which are not oxygenated in the uterus!

Please see this diagram (which shows the foetal circulation including PDA for you). The left brachiocephalic vein is circled in yellow, whilst the left pulmonary artery is circled in green.

Diagram showing left pulmonary artery and left brachiocephalic vein

Image from public domain edition of Gray's.

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