Human Biology, 14 Edition

Published by McGraw-Hill Education
ISBN 10: 1-25924-574-8
ISBN 13: 978-1-25924-574-9

Chapter 18 - Assess - Page 409: 7



Work Step by Step

The fetal heart may start beating as early as the middle of the third week of pregnancy; however, radiological evidence may not be obtainable until about Day 40 of embryogenesis.
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