The ductus venosus and the mechanism of its closure.

Meyer, W. W.; Lind, John

doi:10.1136/adc.41.220.597

Cited by 107 publications

(59 citation statements)

References 12 publications

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“…There is, however, conflicting evidence from previous studies about the structure of the ductus venosus, especially with regard to the presence of a sphincter at the ductus venosus inlet [9][10][11][12][13][14][15][16][17] .…”

Section: Introductionmentioning

confidence: 72%

“…Chako and Reynolds 12 based their study on three fetuses at 12, 24 and 40 weeks' gestation, and described a 6 -8-cell-layer thickness of smooth muscle cells forming the 'contractile elements of a sphincter'. Despite several corroborating 15,16 . There may be a number of reasons for this disparity between previous studies.…”

Section: Discussionmentioning

confidence: 99%

“…The use of immunohistochemical methods in the present study provides an objective interpretation of the components at the ductus venosus inlet and demonstrates the absence of a sphincter at this level. Previous investigators either failed to describe the staining techniques [9][10][11] or used less specific staining methods, which may account for the conflicting findings regarding the existence of a sphincter [12][13][14][15] .…”

Section: Discussionmentioning

confidence: 99%

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The human ductus venosus between 13 and 17 weeks of gestation: histological and morphometric studies

Mavrides

Moscoso

Carvalho

et al. 2002

Ultrasound in Obstet & Gyne

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Section: Introductionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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The human ductus venosus between 13 and 17 weeks of gestation: histological and morphometric studies

Mavrides

Moscoso

Carvalho

et al. 2002

Ultrasound in Obstet & Gyne

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“…The physiologic processes that contribute to the reduction of shunt flow are unknown at the present time, but Meyer and Lind (12) have suggested that a decreased pressure in the portal sinus leads to a passive collapse of the vessel. This distending pressure has not been measured directly but the portal pressure of the sheep fetus has been reported (S), and it is not substantially different from the pressures that were recorded in the present study with Ito 2-day-old lambs (about 6 mm Hg).…”

Section: Discussionmentioning

confidence: 99%

Time Course of Closure of the Ductus Venosus in the Newborn Lamb

Zink

Petten

1980

Pediatric Research

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SummaryThe present study was designed to obtain quantitative data on the extent of portocaval shunting and the time course of closure of the ductus venosus in newborn lambs. Experiments were canducted on eight newborn lambs prepared with chronic portal catheters. The time course of the postnatal closure of the ductus venosus was determined by following the distribution of radiolabelled microspheres injected into the lamb's portal vein 24,48,%, and 168 hr after birth. The fraction of the portal blood flow which bypassed the liver was highly variable. In some animals, the ductus venosus was almost completely closed when the first microspheres were injected 24 hr after birth. In others, almost 40% of the portal blood flow bypassed the hepatic circulation at this time. On average, only 77% of the portal blood flow was directed to the liver in the 1-day lambs. In most cases, closure had occurred by 48 hr after birth, but some animals continued to divert a significant fraction of the portal flow away from the hepatic circulation. SpeculationAt birth, the umbilical perfusion of the liver ceases and the hepatic circulation shifts to a much greater reliance on its portal blood flow. Patency of the ductus venosus during the 1st wk after birth may divert a sizeable fraction of the portal blood flow away from the liver and reduce the hepatic blood flow to levels which limit oxygen exchange and the development of metabolic functions in the postnatal period.The liver blood supply is greatly affected by the collapse of the placental circulation at birth. In utero, umbilical venous blood provides the liver with 80% of its blood flow (17) and almost all of its oxygen supply (5). The portal venous blood is poorly oxygenated and distributed primarily to the right side of the organ (5, 14). Because there is a negligible flow through the hepatic artery (10, 17), the loss of the hepatic umbilical flow at birth removes the main source of oxygen and begins a difficult period of transition as the liver circulation shifts to a much greater reliance on its portal inflow.Measurements of portal blood flow obtained in the immediate postnatal period indicate that it is not much greater than the equivalent flow in the fetus (2). However, it must now perfuse a mass of tissue five times greater than the prenatal distribution (17). During this time continued patency of the ductus venosus may further compromise the hepatic circulation by operating as a portocaval shunt. In human infants, as well as sheep and dogs, it is known that this vessel remains partly open after birth (1 1, 14) but the time course of its closure and the fraction of the portal flow it diverts are unknown. The present study was designed to obtain quantitative data on the extent of portocaval shunting and the time course of closure of the ductus venosus in newborn lambs. MATERIALS AND METHODStional ages that ranged from 144-148 days and none experienced complications during labor. All lambs were healthy, energetic, and nursing freely from the ewe.The portal vein catheter was im...

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“…It has been assumed that the rich nervous supply surrounding 30 seconds the ductus venosus is required for an activation of a sphincter function (8). Might it be, however, that some of the nerve tissue Fig.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Fetal Breathing: A Pilot Study

Enhörning

1993

Pediatr Res

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ABSTRACT. Fetal breathing occurs sporadically and is inhibited during periods of hypoxemia, when blood, returning from the placenta, is mainly taking the shortcut through the ductus venosus. The hypothesis tested is that this inhibition might be caused by an expansion of the ductus venosus. Such expansion is pronounced during fetal life but ceases to occur after birth. Regular breathing of newborn lambs was recorded, and it was noted how the breathing was affected when blood, with the aid of a roller pump, was infused from the umbilical arteries into the umbilical veins. Nine lambs were examined, and for a maximal period of 2 min blood was infused into the umbilical veins at a rate of 50-150 mL/min. During 12 infusions, breathing temporarily came to a complete stop; in 30 cases, respiration was only partially inhibited, and in five cases, it was not affected. It is concluded that a very clear breathing inhibition may be obtained with an infusion of blood into the umbilical vein. It is speculated that expansion of the ductus venosus may trigger the inhibition and that the reason the effect varies may have to do with the fact that blood entering the body through the umbilical veins may predominantly take one of two routes: the ductus venosus or the hepatic vessels. (Pediatr Res 34: 834436,1993) Real-time ultrasonic scanners have made it possible to observe the breathing motions of human fetuses for long periods of time. The breathing is noted to be intermittent and during the last 10 wk of human pregnancy occurs only during about one third of a 24-h observation period (1). Because intrauterine breathing requires as much as 15-30% of the total oxygen supply (2) and will do nothing to augment it, it would be beneficial if it were to be interrupted during periods of inadequate oxygen delivery from the placenta.Periods of fetal hypoxia cause a release of catecholamines and a redistribution of cardiac output, so that vital organs such as heart, brain, and placenta receive a greater proportion of ejected blood and blood returning from the placenta takes the shortcut through the ductus venosus (3-5). A total obstruction of fetal breathing has been observed during fetal hypoxia (6) and thus coincides with the redistribution of blood flow.After birth, the situation changes abruptly in that breathing becomes absolutely necessary for gas exchange, and it would be beneficial for the newborn if hypoxia stimulated respiration. Evolution has seemingly resulted in the most functional response to hypoxia: hypoxia inhibits breathing in the fetus but acts as a stimulus in the neonate. Possibly, this difference in response is due to a mechanism causing an inhibition of breathing that is strongly expressed by the fetus but not by the newborn.It is hypothesized that during fetal life breathing is inhibited as long as there is a flow of blood through the ductus venosus. By causing an active expansion of the ductus, the blood might stimulate baroreceptors in the wall of the vessel. When, after birth, blood is no longer flowing through...

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The ductus venosus and the mechanism of its closure.

Cited by 107 publications

References 12 publications

The human ductus venosus between 13 and 17 weeks of gestation: histological and morphometric studies

The human ductus venosus between 13 and 17 weeks of gestation: histological and morphometric studies

Time Course of Closure of the Ductus Venosus in the Newborn Lamb

Inhibition of Fetal Breathing: A Pilot Study

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