Fetal Circulation and Placenta Overview

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Questions and Answers

What is the main function of the placenta?

Nutrient and waste exchange between fetal and maternal blood.

How many umbilical arteries carry blood from the fetus to the placenta?

Two

What is the primary reason why fetal lungs are non-functional before birth?

  • They lack sufficient blood supply.
  • They are surrounded by amniotic fluid.
  • They are not yet able to exchange gases. (correct)
  • They are too small.

The ductus venosus allows most of the blood to bypass the ______.

<p>liver</p> Signup and view all the answers

The ductus arteriosus connects the pulmonary trunk to the aorta, allowing blood to bypass the lungs.

<p>True (A)</p> Signup and view all the answers

Which of these structures is NOT a remnant of fetal circulation after birth?

<p>Hepatic portal vein (D)</p> Signup and view all the answers

What happens to the umbilical arteries after birth?

<p>They transform into the medial umbilical ligaments.</p> Signup and view all the answers

Flashcards

Fetal Circulation

The unique circulatory system in a fetus, designed to support development before birth.

Placenta

Organ in the uterus that allows nutrient and waste exchange between fetal and maternal blood.

Umbilical Cord

Structure connecting the fetus to the placenta, carrying blood.

Umbilical Arteries

Two vessels carrying deoxygenated blood from the fetus to the placenta.

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Umbilical Vein

Vessel carrying oxygenated blood from the placenta to the fetus.

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Ductus Venosus

Fetal vessel bypassing the liver, carrying oxygenated blood to the inferior vena cava instead of directly through the liver.

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Foramen Ovale

A specialized opening connecting the right atrium to the left atrium diverting blood from the right side of the heart to the left side.

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Ductus Arteriosus

Fetal bypass for blood from the pulmonary trunk to the aorta, bypassing the non-functional lungs.

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Postnatal Circulation

Circulatory system after birth, activating the lungs & other organs previously non-functional.

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Medial Umbilical Ligaments

Structures formed from the umbilical arteries after birth.

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Ligamentum Teres

The umbilical vein after birth.

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Ligamentum Venosum

The ductus venosus after birth.

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Fossa Ovalis

The remnant of the foramen ovale after birth.

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Ligamentum Arteriosum

The ductus arteriosus after birth.

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Study Notes

Fetal Circulation

  • Fetal circulatory system uniquely designed for development
  • Essential nutrients from mother
  • Different from postnatal circulation
    • Lungs, kidneys, and gut non-functional at birth

Placenta

  • Nutrient and waste exchange via placenta
  • Placenta develops in mother's uterus, connects to fetus via umbilical cord
  • Blood flows from fetus to placenta via two umbilical arteries
  • Fetal blood receives oxygen and nutrients
  • Carbon dioxide and waste removed from fetal blood

Fetal Blood Flow

  • Oxygen-rich blood returns to fetus via single umbilical vein
  • Umbilical vein joins hepatic portal vein
  • One branch of umbilical vein to liver, other (ductus venosus) bypasses liver
  • Empties into inferior vena cava
  • Deoxygenated blood from fetus's lower body mixes with oxygenated blood (from ductus venosus)
  • Mixed blood enters right atrium

Heart Function

  • Deoxygenated blood from upper body enters right atrium via superior vena cava
  • 1/3 blood from right atrium flows through foramen ovale to left atrium (joining systemic circulation)
  • Remaining blood in right atrium goes to right ventricle, pumped into pulmonary trunk
  • Small amount of blood reaches fetal lungs (non-functional before birth)
  • Most blood bypasses lungs via ductus arteriosus (connects pulmonary trunk)

Postnatal Changes

  • Lungs, kidneys, and gut begin functioning
  • Umbilical vessels no longer needed
  • Umbilical arteries become medial umbilical ligaments
  • Umbilical vein becomes ligamentum teres
  • Ductus venosus becomes ligamentum venosum
  • Foramen ovale closes, forming fossa ovalis
  • Ductus arteriosus closes, forming ligamentum arteriosum
  • Oxygenated blood circulates through fetal body via systemic circulation, providing tissues with oxygen

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