NVCC Bio 212

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Human Development and AgingChapter 29The Fetal
Circulation
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Lecture Overview and Objectives

• Why does the fetus need a different circulatory
  pattern from the newborn?
• What are the anatomical differences in the fetal
  vs. the newborn circulation?
• How do these anatomical differences better meet
  the physiological needs of the fetus?
• When and how does the fetal circulation change
  after birth?

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Overview of Fetal Circulation
Breathing and eating/digestion are carried out by
the mother for the fetus. Gases and nutrients
are exchanged with the fetus through the placenta.

• Besides the umbilical vessels, the major
  differences in fetal circulation arise because
• The fetal lungs are collapsed since the fetus is
  not breathing air
• There is nothing to digest or process since the
  fetus is not eating

Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Pathway of Blood Through Mature Heart
Figure from Saladin, Anatomy Physiology,
McGraw Hill, 2007
Systemic circulation
Pulmonary circulation
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Modifications in Fetal Pulmonary Circulation
Figure from Martini, Ober, Visual Anatomy
Physiology, Pearson Science, 2012
1. Foramen ovale allows blood returning to
right atrium to bypass right ventricle and pass
directly into left atrium (then to lt. ventricle,
then aorta)
2. Ductus arteriosus allows blood from right
ventricle and pulmonary trunk to bypass the
pulmonary arteries and pass directly into the
aorta
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Modifications in Fetal Digestive Circulation
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Figure from Shier et. al., Holes Human Anatomy
Physiology, McGraw-Hill, 2010
1. Ductus venosus allows about 50 of blood
returning to fetus through the umbilical vein to
bypass the liver and empty directly into the
inferior vena cava (then back to rt. atrium of
heart)
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Changes in Fetal Circulation After Birth
Foramen Ovale -gt Fossa ovalis Ductus Arteriosus
-gt Ligamentum arteriosum Ductus Venosus -gt
Ligamentum venosum Umbilical vein -gt Ligamentum
teres Umbilical arteries -gt Medial umbilical
ligaments (and superior vesical arteries to
urinary bladder)
Figure adapted from Tortora, Principles of
Anatomy Physiology, Wiley Press, 2002
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Summary

• Fetal circulation differs from the postpartum
  circulation to accommodate the interaction of the
  fetus and mother through the placenta.
• There are four bypasses (shunts) in the fetus for
  this purpose
• 1) Placental Circulation - 2 umbilical arteries
  and 1 vein
• 2) Ductus Arteriosus
• 3) Foramen Ovale
• 4) Ductus Venosus - Major bypass of the
  liver
• Subsequent to the newborns first breath and
  clamping of the umbilical cord, these bypasses
  within the fetal circulation are eliminated to
  adjust to life outside the uterus.

Bypass of pulmonary circulation
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Summary of Fetal Circulatory Changes
Structure Anatomy/Location Function Associated System (Shunt) in Fetus What happens after birth
Umbilical Arteries (2 arteries) Arise from fetal internal iliac arteries and enter umbilical cord Bring deoxygenated, nutrient-poor blood to placenta Placental Vessels close and become medial umbilical ligaments superior vesical arteries
Umbilical Vein (1 vein) Arises from placenta and enters the ductus venosus (see below) Brings oxygenated, nutrient-rich blood from placenta to fetus Placental Vessel closes and becomes the ligamentum teres
Foramen Ovale Oval flap of tissue in interatrial septum Bypass of right ventricle blood flows from right atrium directly to left atrium Respiratory Flap closes and becomes fossa ovalis
Ductus Arteriosus Vessel connecting pulmonary trunk and aorta Allows most blood from right vetnicle to bypass the pulmonary circulation Respiratory Vessel closes and becomes ligamentum arteriosum
Ductus Venosus Vessel connecting umbilical vein directly to inferior vena cava Allows about 50 of O2/nutrient-rich blood to bypass liver Digestive Vessel closes and becomes ligamentum venosum
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Presentation Supporting Materials Are Available
Online
The slides for this presentation, as well as
supplementary materials to support this topic,
are available online at http//www.gserianne.com
/science/FetalCirculationCCM/ You may email
questions to gerianne_at_optonline.net Thank
you!
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Figure from Shier et. al., Holes Human Anatomy
Physiology, McGraw-Hill, 2010
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Figure from Shier et. al., Holes Human Anatomy
Physiology, McGraw-Hill, 2010
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Congenital Cardiovascular Problems
Right-to-left shunt
Left-to-right shunt -gt Pulmonary hypertension,
pulmonary edema, and cardiac enlargement
(Congenital Present at Birth)
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001
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Congenital Cardiovascular Problems
Figure from Martini, Anatomy Physiology,
Prentice Hall, 2001