Page 84 - كتاب تمريض نسا الاكتروني

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Introduction

Throughout the fetal stage of development, the maternal blood supplies the fetus

with O2 and nutrients and carries away its wastes. These substances diffuse between the

maternal and fetal blood through the placental membrane. They are carried to and from

the fetal body by the umbilical blood vessels.

The development of the cardiovascular system

- Begins to develop toward the end of the third week.

- Heart starts to beat at the beginning of the fourth week.

- The critical period of heart development is from 20 day To day 50 after fertilization.

- Many critical events occur during cardiac development, and any deviation from this

normal pattern can cause congenital heart defects, if development of heart does not

occur properly.

- However, we will concern ourselves with the events surrounding the circulatory

changes at birth.

Three shunts in the fetal circulation

1- Ducts arteriosus
- protects lung against circulatory overload.

- allows the right ventricle to strengthen

- pulmonary vascular resistance, low pulmonary blood flow.

- carries mostly med oxygen saturated blood.

2- Ductus venosus

- fetal blood vessel connecting the umbilical vein to the IVC.

- blood flow regulate via sphincter

- carries mostly high oxygenated blood.

3- foremen oval

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