Nursing Entrance Exam

to develop pressure sufficient to push blood through the large systemic circuit, whereas the right ventricle needs to pump blood, at lower pressure, only about 15 cm (6 in.) to and from the lungs. The internal organization of the left ventricle generally resembles that of the right ventricle except for the absence of a moderator band. The aortic valve prevents the backflow of blood into the left ventricle once the blood has left the heart and is in the systemic circuit. From the ascending aorta, blood flows through the aortic arch and into the descending aorta. The ligamentum arteriosum connects the aortic arch to the pulmonary trunk, and is a fibrous band that is a remnant of a fetal blood vessel that once linked the pulmonary and systemic circuits in order to bypass the lungs prior to birth.

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