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INTERNATIONAL UNIVERSITY
Fetal circulation
Dr. Sam Nang
• All of the respiratory, excretory,
and nutritional needs of the fetus
are provided for by diffusion across
the placenta ...
Objective :
• Describe the fetal circulation
to and from the placenta.
• Describe the structure and
function of the forame...
• The circulation of blood through
a fetus is by necessity different
from blood circulation in a
newborn .
• Respiration, ...
• The capillary exchange between
the maternal and fetal
circulation occurs within the
placenta .
• This remarkable structu...
• The umbilical cord is the
connection between the placenta
and the fetal umbilicus.
• It includes one umbilical vein and
...
• Oxygenated and nutrient
rich blood flows through the
umbilical vein toward the
inferior surface of the liver.
• At this ...
• One branch merges with the
portal vein, while the other
branch, called the ductus
venosus , enters the inferior
vena cav...
• Thus, oxygenated blood is
mixed with venous blood
returning from the lower
extremities of the fetus before it
enters the...
• The inferior vena cava
empties into the right atrium
of the fetal heart.
• Most of the blood passes from
the right atriu...
• Here, it mixes with a small
quantity of blood returning
through the pulmonary
circulation.
• The blood then passes in to...
• Some blood entering the right
atrium passes into the right
ventricle and out of the heart via
the pulmonary trunk.
• Sin...
• Most of the blood in the pulmonary
trunk passes through the ductus
arteriosus into the aortic arch,
where it mixes with ...
• Notice that, in the fetus,
oxygen-rich blood is
transported by the inferior
vena cava to the heart, and
via the foramen ...
• Important changes occur in
the cardiovascular system at
birth.
• The foramen ovale, ductus
arteriosus, ductus venosus,
a...
• The foramen ovale abruptly
close with the first breath of
air because the reduced
pressure in the right side of
the hear...
• This reduction in pressure occurs
because the vascular resistance to
blood flow in the pulmonary
circulation falls far b...
• The constriction of the
ductus arteriosus occurs
gradually over a period of
about 6 weeks after birth as
the vascular sm...
• The remaining structure of the
ductus arteriosus gradually
atrophies and becomes
nonfunctional as a blood vessel.
• Tran...
THE END
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
L11 fetal circulation
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L11 fetal circulation

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Transcript of "L11 fetal circulation"

  1. 1. INTERNATIONAL UNIVERSITY Fetal circulation Dr. Sam Nang
  2. 2. • All of the respiratory, excretory, and nutritional needs of the fetus are provided for by diffusion across the placenta instead of by the fetal lungs, kidneys, and gastrointestinal tract. • Fetal circulation is adaptive to these conditions.
  3. 3. Objective : • Describe the fetal circulation to and from the placenta. • Describe the structure and function of the foramen ovale, ductus venosus, and ductus arteriosus.
  4. 4. • The circulation of blood through a fetus is by necessity different from blood circulation in a newborn . • Respiration, the procurement of nutrients, and the elimination of metabolic wastes occur through the maternal blood instead of through the organs of the fetus.
  5. 5. • The capillary exchange between the maternal and fetal circulation occurs within the placenta . • This remarkable structure, which includes maternal and fetal capillary beds, is discharged following delivery as the afterbirth.
  6. 6. • The umbilical cord is the connection between the placenta and the fetal umbilicus. • It includes one umbilical vein and two umbilical arteries, surrounded by a gelatinous substance.
  7. 7. • Oxygenated and nutrient rich blood flows through the umbilical vein toward the inferior surface of the liver. • At this point, the umbilical vein divides into two branches.
  8. 8. • One branch merges with the portal vein, while the other branch, called the ductus venosus , enters the inferior vena cava.
  9. 9. • Thus, oxygenated blood is mixed with venous blood returning from the lower extremities of the fetus before it enters the heart. • The umbilical vein is the only vessel of the fetus that carries fully oxygenated blood.
  10. 10. • The inferior vena cava empties into the right atrium of the fetal heart. • Most of the blood passes from the right atrium into the left atrium through the foramen ovale, an opening between the two atria.
  11. 11. • Here, it mixes with a small quantity of blood returning through the pulmonary circulation. • The blood then passes in to the left ventricle, from which it is pumped into the aorta and through the body of the fetus.
  12. 12. • Some blood entering the right atrium passes into the right ventricle and out of the heart via the pulmonary trunk. • Since the lungs of the fetus are not functional, only a small portion of blood continues through the pulmonary circulation (the resistance to blood flow is very high in the collapsed fetal lungs).
  13. 13. • Most of the blood in the pulmonary trunk passes through the ductus arteriosus into the aortic arch, where it mixes with blood coming from the left ventricle. • Blood is returned to the placenta by the two umbilical arteries that arise from the internal iliac arteries.
  14. 14. • Notice that, in the fetus, oxygen-rich blood is transported by the inferior vena cava to the heart, and via the foramen ovale and ductus arteriosus to the systemic circulation.
  15. 15. • Important changes occur in the cardiovascular system at birth. • The foramen ovale, ductus arteriosus, ductus venosus, and the umbilical vessels are no longer necessary.
  16. 16. • The foramen ovale abruptly close with the first breath of air because the reduced pressure in the right side of the heart causes a flap to cover the opening.
  17. 17. • This reduction in pressure occurs because the vascular resistance to blood flow in the pulmonary circulation falls far below that of the systemic circulation when the lungs fill with air. • The pressure in the inferior vena cava and right atrium falls as a result of the loss of the placental circulation.
  18. 18. • The constriction of the ductus arteriosus occurs gradually over a period of about 6 weeks after birth as the vascular smooth muscle fibers constrict in response to the higher oxygen concentration in the postnatal blood.
  19. 19. • The remaining structure of the ductus arteriosus gradually atrophies and becomes nonfunctional as a blood vessel. • Transformation of the unique fetal cardiovascular system is summarized in table 16.6.
  20. 20. THE END
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