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Human Development and Aging Chapter 29 The Fetal Circulation

Human Development and Aging Chapter 29 The Fetal Circulation. 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?

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Human Development and Aging Chapter 29 The Fetal Circulation

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  1. Human Development and AgingChapter 29The Fetal Circulation

  2. 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?

  3. 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

  4. Pathway of Blood Through Mature Heart Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007 Systemic circulation Pulmonary circulation

  5. Modifications in Fetal Pulmonary Circulation 1 2 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

  6. Modifications in Fetal Digestive Circulation 1 Figure from: Shier et. al., Hole’s 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)

  7. Changes in Fetal Circulation After Birth Foramen Ovale -> Fossa ovalis Ductus Arteriosus -> Ligamentum arteriosum Ductus Venosus -> Ligamentum venosum Umbilical vein -> Ligamentum teres Umbilical arteries -> Medial umbilical ligaments (and superior vesical arteries to urinary bladder) Figure adapted from: Tortora, Principles of Anatomy & Physiology, Wiley Press, 2002

  8. 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 newborn’s 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

  9. Summary of Fetal Circulatory Changes

  10. 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@optonline.net ** Thank you! **

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