What is the purpose of leaving behind the back wall of the left atrium of the patient’s heart?

answer:

A heart transplant replaces the patient's heart with a donor heart. Doctors remove the patient's heart by transecting the aorta, the main pulmonary artery and the superior and inferior vena cavae, and dividing the left atrium, leaving the back wall of the left atrium with the pulmonary vein openings in place.

Explanation:

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a- all cells come from pre-existing cells

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.