名市大医学部２年コミュのHuman Biology [chapter 17]

Chapter 17の解答例です。

[目下の問題点]
17.4 特になし。
17.7 ほとんど本文中の文章そのまま。長すぎ？

17.4 What are the three primary germ layers. and what body structures come from each germ layer?
　　The three primary germ layers emerge as tissue layers by the time gastrulation is complete, and consist of ectoderm, mesoderm, and endoderm.
　　Ectoderm, the outer layer, forms epidermis of skin, epithelial lining of oral cavity and rectum, and nervous system.
　　Mesoderm, the middle layer, forms skeleton, muscular system, dermis of skin, cardiovascular system, urinary system, reproductive system, and outer layers of respiratory and digestive systems.
　　Endoderm, the inner layer, forms epithelial lining of digestive tract and respiratory tract, associated glands of these systems, and spithelial lining of urinary bladder.

17.7 Explain how blood ciculates to and from the placenta and the fetus. How is blood shunted away from the lungs?
　　Blood within the fetal aorta travels to its various branches, including the iliac arteries, which connect to the umbilical arteries carrying O2-poor blood to the placenta. The umbilical vein carries blood rich in nutrients and O2 away from the placenta to the fetus. The umbilical vein enters the liver and then joins the venous duct, which merges with the inferior vena cava.
　　To shunt away from the lungs, there are two structures unique to the fetus: oval opening and arterial duct. Blood mixed at the venous duct enters the heart and is shunted to the left atrium through the oval opening. The left ventricle pumps this blood into the aorta. O2-poor blood that enters the right atrium is pumped into the pulmonary trunk, but it joins the aorta by way of the arterial duct. Therefore, all blood entering the right atrium by-passes the lungs.