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|    Message 11,087 of 12,782    |
|    Attila to wHDvK.514398$wIO9.179106@fx12.iad    |
|    Re: An embryo is not a "baby" or a "chil    |
|    01 Jul 22 14:06:39    |
      [continued from previous message]              :closure of the ductus arteriosus and foramen ovale, but some       :minor adjustments continue for 1-2 months, until the adult       :phase begins.       :       :Fetal circulatory adaptions that disappear at birth....       :       :Umbilical vein...Carries oxygenated blood from placenta to       :fetus       :       :Ductus venosus...Conducts about half the blood from the       :umbilical vein directly to the inferior vena cava, thus       :bypassing the liver       :       :Foramen Ovale...Conveys large proportion of blood entering -       :the right atrium from the inferior vena cava, through the       :atrial septum and into the left atrium, thus bypassing the       :lungs       :       :Ductus Arteriosus...Conducts some blood from the pulmonary       :artery to the aorta, thus bypassing the lungs       :       :Umbilical arteries...Carry blood from the internal iliac       :arteries to the placenta for reoxygenation       :       :Immediately following birth, the umbilical vessels       :constrict. The arteries close first, and if the umbilical       :cord is not clamped or severed for a minute or so, blood       :continues to flow from the placenta to the newborn through       :the umbilical vein, adding to the newborn's blood volume.       :       :The proximal portions of the umbilical arteries persist in       :the adult as the superior vesical arteries that supply blood       :to the urinary bladder. The more distal portions become       :solid cords (lateral umbilical ligaments.) The umbilical       :vein becomes the cordlike ligamentum teres that extends from       :the umbilicus to the liver in an adult. Similarly, the       :ductus venosus constricts shortly after birth and is       :represented in the adult as a fibrous cord (ligamentum       :venosum), which is superficially embedded in the wall of the       :liver.       :       :So, to summarize, the hemodynamics of the immediate newborn       :and term fetus differ in these major ways, and many more       :minor ones...ALL abruptly changing at the moment of birth:       :(1) arterial and venous blood no longer mix in the atria;       :(2)the vena cava now carries only deoxygenated blood into       :the right atrium, where it goes into the right ventricle,       :and then is pumped to the pulmonary arteries, and finally to       :the pulmonary capillary bed , and ; (3) the aorta now       :carries only oxygenated blood from the left heart via the       :pulmonary veins for distribution to the rest of the body.       :The 'pipework' is still mostly there, but what enormous       :changes have taken place in a few short seconds!       :       :So, I'd appreciate if we didn't say that the immediate       :newborn and term fetus are almost identical, because they       :just aren't. The digestive changes alone would be ten times       :the length of this very basic circulatory primer, and the       :respiratory chemistry changes at the instant of birth could       :fill a book.       :       :cut here 8<================================================       :       :He listed as sources:       :       : _Gray's Anatomy_ 15th Edition; 1995       :       :_Human Anatomy and Physiology_, Second Edition, John W. Hole       :jr. 1988 Wm C. Brown Co.       :       :_Current Obstetric and Gynecologic Diagnosis and Treatment_       :8th Ed, DeCherney, Pernoll 1994       :       :       :Posted by Pat Winstanley |
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