29:
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392:, can obstruct the airways and also deactivate the newborn's surfactant. The inflammation that also results from the inhalation of meconium also causes airway constriction, resulting in poor ventilation of the alveoli and inadequate oxygenation of the pulmonary capillary beds. With a lack of oxygen entering the lungs, pulmonary vascular resistance will remain high and the newborn's blood will no longer be oxygenated, preventing fetal shunt closure.
246:
357:
Lastly, due to the decreased pulmonary vascular resistance, the pressure of the pulmonary artery will fall until it is lower than the pressure of the aorta. Since blood flows from high to low pressure systems, the direction of blood flow across the ductus arteriosus reverses. As the oxygen-rich blood
348:
With decreased resistance in the lungs, there will be increased blood flow to the lungs from the right ventricle of the heart through the pulmonary arteries, establishing the newborn's pulmonary circulation. With each of the newborn's breaths, blood perfuses the pulmonary capillary beds and undergoes
353:
and returning to the heart. Thus, as more blood flows through the pulmonary circulation, there will be a higher volume of blood returning to the left atrium from the lungs. The increased venous return will elevate the pressure of the left atrium until it exceeds the pressure of the right atrium. The
336:
First, the ductus venosus was previously kept open by the blood flow from the umbilical vein. The reduced blood flow through the umbilical vein at birth will collapse and close the ductus venosus. Hence, the IVC will only carry deoxygenated blood from the infant's organs and lower extremities.
317:
has lower pressure than the pulmonary artery, most of the blood flows across the ductus arteriosus away from the lungs. Once the blood goes through the ductus arteriosus, it mixes with the blood from the aorta. This results in mixed blood oxygen saturation that supplies most of the structures of the
395:
In both cases of infant respiratory distress syndrome and meconium aspiration syndrome, fetal shunts will remain open due to the high pulmonary vascular resistance until appropriate measures, such as administration of surfactant or mechanical ventilation, are taken to help the infant breathe on its
366:
where the mitral valve is shut. The removal of the placenta, a source of prostaglandin, is another mechanism by which the ductus arteriosus closes at birth. Within the next 2 to 3 weeks, the constriction results in decreased blood flow to the structure which induces the death of the tissue to keep
370:
As a result of these changes, postnatal circulation will direct deoxygenated blood from the inferior and superior vena cava to the right heart, from which the blood will flow to the lungs via the pulmonary circulation. Blood will be oxygenated in the lungs and return to the left heart, which will
232:
is shifted to the left, meaning that it is able to absorb oxygen at lower concentrations than adult hemoglobin. This enables fetal hemoglobin to absorb oxygen from adult hemoglobin in the placenta, where the oxygen pressure is lower than at the lungs. Around 6 months of age after birth, the gamma
300:
into the left ventricle and will be pumped through the aorta into the body. The shunting of oxygenated blood from right to left atrium will supply blood high in oxygen and nutrient content to the upper extremities, including the critically important brain. Some of the blood moves from the aorta
308:
Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle. This blood consists of oxygenated placental blood and deoxygenated blood returning from the fetal circulation. This blood is pumped into the
379:
compound that allows alveoli to remain open by overcoming the surface tension of water. The resulting difficulty in lung expansion prevents the necessary reduction in pulmonary vascular resistance for the infant to make the normal cardiopulmonary transition, resulting in
313:. At the pulmonary artery, it is met with high pulmonary vascular resistance as a result of collapsed lungs and pulmonary capillaries. In the fetus, there is a special connection between the pulmonary artery and the aorta, called the ductus arteriosus. Because the
93:. A major difference between the fetal circulation and postnatal circulation is that the lungs are not used during the fetal stage resulting in the presence of shunts to move oxygenated blood and nutrients from the placenta to the fetal tissue. At birth, the start of
332:
As the umbilical vessels are obliterated and the infant starts breathing at birth, the source of oxygen changes from the placenta to the lungs. This major trigger will facilitate the transformation from fetal to postnatal circulation in many ways.
374:
In certain cases, the transition from fetal to postnatal circulation may not occur as described above due to complications leading to persistently high pulmonary vascular resistance. Preterm infants are born without fully mature lungs lacking the
358:
from the aorta flows across the ductus arteriosus to the pulmonary artery, the ductus arteriosus will constrict in response to the high oxygen content of the blood. While oxygen serves as a vasoconstrictor of the ductus arteriosus,
199:
The placenta functions as the exchange site of nutrients and wastes between the maternal and fetal circulation. Water, glucose, amino acids, vitamins, and inorganic salts freely diffuse across the placenta along with oxygen. Two
261:
or the liver. When oxygenated blood enters the IVC, it moves in parallel with deoxygenated blood from the fetal systemic veins, establishing a bilaminar blood flow as it enters the right atrium.
204:
carry deoxygenated blood and waste from the fetus to the placenta where waste is exchanged for oxygen and nutrients. The oxygenated blood will then return to the fetus from the placenta via the
1397:
1107:
Monfredini, C., Cavallin, F., Villani, P. E., Paterlini, G., Allais, B., & Trevisanuto, D. (2021). Meconium aspiration syndrome: A narrative review. Children, 8(3), 230.
296:
helps direct the oxygenated blood into the foramen ovale, an opening between the right and left atrium. As the blood flows through the left atrium, it will move through the
33:
The fetal circulatory system includes three shunts to divert blood from undeveloped and partially functioning organs, as well as blood supply to and from the placenta.
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to the umbilical arteries, and re-enters the placenta, where carbon dioxide and other waste products from the fetus are taken up and enter the maternal circulation.
565:, it is ca 50 mmHg. It falls to 30 mmHg in the capillaries in the villi. Subsequently, the pressure is 20 mm Hg in the umbilical vein, returning to the heart.
237:. This new hemoglobin structure is known as hemoglobin A, composed of two alpha and two beta chains (2α2β). Hemoglobin A is the predominant form found in adults.
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The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation, and increases to ca 45 mmHg at 40 weeks of gestation. The fetal
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and maintain proper circulation to important fetal tissue. In the fetal stage, the lungs fill with fluid and collapse because the fetus is within the
540:, which, together with the difference in partial pressure of oxygen, allows a diffusion of oxygen from the mother's circulatory system to the fetus.
577:. Adapted to the weight of the fetus, this corresponds to 115 mL/min/kg at 20 weeks and 64 mL/min/kg at 40 weeks. It corresponds to 17% of the
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It is the fetal heart and not the mother's heart that builds up the fetal blood pressure to drive its blood through the fetal circulation.
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own. If the problem is not corrected, the infant will undergo hypoxia, acidosis, and other serious complications, such as seizures.
345:, which further dilates the blood vessels within the lungs. Together, these forces will decrease the pulmonary vascular resistance.
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and the severance of the umbilical cord prompt various changes that quickly transform fetal circulation into postnatal circulation.
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enhances the fetus' ability to draw oxygen from the placenta. This is facilitated by the hemoglobin molecule that made up of two
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remains high during the fetal stage to prevent blood flow into the lungs. As oxygenated blood arrives at the right atrium, the
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Struijk, P. C.; Mathews, V. J.; Loupas, T.; Stewart, P. A.; Clark, E. B.; Steegers, E. A. P.; Wladimiroff, J. W. (2008).
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Speer, C. P. (2011). Neonatal respiratory distress syndrome: an inflammatory disease?. Neonatology, 99(4), 316-319
833:
Bellotti, Maria; Pennati, Giancarlo; De
Gasperi, Camilla; Battaglia, Frederick C.; Ferrazzi, Enrico (2000-09-01).
835:"Role of ductus venosus in distribution of umbilical blood flow in human fetuses during second half of pregnancy"
363:
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with oxygen. The increased oxygen content will dilate the pulmonary capillaries and also trigger the release of
888:
Vu, Eric L.; Quiñónez, Zoel A. (2019-12-05), Adler, Adam C.; Chandrakantan, Arvind; Litman, Ronald S. (eds.),
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Oxygenated blood from the placenta is carried to the fetus by the umbilical vein, which will drain into the
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pump oxygen-rich blood out through the aorta to supply the rest of the body via the systemic circulation.
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603:. On the other hand, there is no neural vascular regulation, and catecholamines have only little effect.
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The blood flow through the umbilical cord is approximately 35 mL/min at 20 weeks, and 240 mL/min at 40
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384:. In addition, occasionally during birth, infants may inhale remnants of their fecal matter known as
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Intracardiac pressure remains identical between the right and left ventricles of the human fetus.
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can keep the ductus arteriosus open to maintain blood flow to the lower extremities in cases of
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and the placenta is providing the oxygen it needs to grow. With the lung collapsed, pulmonary
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difference in pressure between these two chambers of the heart will close the foramen ovale.
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Hemoglobin is a structure found within the red blood cells that binds to and carries oxygen.
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is ca 20 mmHg at 20 weeks of gestation, increasing to ca 30 mmHg at 40 weeks of gestation.
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8:
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987:"Molecular and mechanical factors contributing to ductus arteriosus patency and closure"
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Crockett, Stacey L.; Berger, Courtney D.; Shelton, Elaine L.; Reese, Jeff (2018-11-23).
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388:, preventing adequate breathing. The presence of meconium within the lungs, known as
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659:"Comprehensive Perinatal & Pediatric Respiratory Care | R2 Digital Library"
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1036:"Molecular Mechanisms for Regulating Postnatal Ductus Arteriosus Closure"
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The blood pressure decreases when passing through the placenta. In the
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Philosophical
Transactions of the Royal Society B: Biological Sciences
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Second, as the infant breathes, the lungs will expand and fill the
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Kiserud, Torvid; Acharya, Ganesh (2004). "The fetal circulation".
940:"Regulation of the Pulmonary Circulation in the Fetus and Newborn"
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American
Journal of Physiology. Heart and Circulatory Physiology
1255:"Blood pressure estimation in the human fetal descending aorta"
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Remnants of the fetal circulation can be found in the adult.
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896:(1 ed.), Cambridge University Press, pp. 264–268,
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of the fetus at 10 weeks, and 33% at 20 weeks of gestation.
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1154:"Fetal hemoglobin during infancy and in sickle cell adults"
778:"Hemoglobin research and the origins of molecular medicine"
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Marty, Makenna; Kerndt, Connor C.; Lui, Forshing (2022),
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Hung, Yu-Chi; Yeh, Jwu-Lai; Hsu, Jong-Hau (2018-06-25).
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portions of the fetal left and right umbilical arteries
536:(HbF) has a higher affinity for oxygen than does adult
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intra-hepatic portion of the fetal left umbilical vein
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Burton, Graham J.; Fowden, Abigail L. (2015-03-05).
1193:Johnson P, Maxwell DJ, Tynan MJ, Allan LD (2000).
532:The core concept behind fetal circulation is that
272:. It also contains two additional structures, the
211:
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1152:Edoh D, Antwi-Bosaiko C, Amuzu D (March 2006).
729:"The placenta: a multifaceted, transient organ"
703:, Treasure Island (FL): StatPearls Publishing,
635:of an embryo of 8 weeks with visible heartbeat.
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1303:"Fetal and maternal blood circulation systems"
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249:Diagram of the human fetal circulatory system.
85:, umbilical blood vessels encapsulated by the
77:is different before and after birth. The
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938:Gao, Yuansheng; Raj, J. Usha (October 2010).
349:oxygenation before exiting the lungs via the
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1195:"Intracardiac pressures in the human fetus"
1040:International Journal of Molecular Sciences
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1122:(Lippincott 2004). Retrieved 2007-03-04.
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1540:Protein signalling in heart development
1259:Ultrasound in Obstetrics and Gynecology
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1131:University of Michigan Medical School,
103:This article is part of a series on the
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1133:Fetal Circulation and Changes at Birth
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494:portions of the fetal left and right
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1772:Embryology of cardiovascular system
264:The fetal heart contains two upper
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1641:Vascular remodelling in the embryo
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367:the structure permanently closed.
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851:10.1152/ajpheart.2000.279.3.H1256
776:Schechter, Alan N. (2008-11-15).
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466:("round ligament of the liver")
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697:"Embryology, Fetal Circulation"
364:hypoplastic left heart syndrome
328:Adaptation to extrauterine life
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1119:Board Review Series Embryology
1116:Dudek, Ronald and Fix, James.
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212:Oxygenation transport in fetus
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390:meconium aspiration syndrome
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1507:Primary interatrial foramen
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890:"Transitional Circulation"
620:Neonatal heart circulation
454:portion of the fetal left
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991:Congenital Heart Disease
462:ligamentum teres hepatis
255:inferior vena cava (IVC)
1602:Posterior cardinal vein
1535:Aorticopulmonary septum
1158:African Health Sciences
1142:. Retrieved 2007-03-04.
579:combined cardiac output
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506:internal iliac arteries
303:internal iliac arteries
1597:Anterior cardinal vein
1487:Atrioventricular canal
745:10.1098/rstb.2014.0066
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57:Anatomical terminology
1607:Common cardinal veins
1211:10.1136/heart.84.1.59
944:Physiological Reviews
443:ligamentum arteriosum
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89:, heart and systemic
1477:Endocardial cushions
1053:10.3390/ijms19071861
1443:Primitive ventricle
1406:Development of the
563:arteria umbilicalis
520:umbilical ligaments
290:vascular resistance
130:Reproductive system
81:is composed of the
1751:Vitelline arteries
1715:Inferior vena cava
1482:Septum intermedium
1433:Truncus arteriosus
1408:circulatory system
1339:Prenatal Diagnosis
1138:2007-05-27 at the
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496:umbilical arteries
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150:Circulatory system
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1695:Fetal circulation
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1462:Chamber formation
1003:10.1111/chd.12714
911:978-1-108-66873-6
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1618:
1617:Lymph vessels
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1598:
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1574:Aortic arches
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1517:Foramen ovale
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1453:Sinus venosus
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1438:Bulbus cordis
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1425:Tubular heart
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1265:(5): 673–81.
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110:organ systems
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91:blood vessels
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45:Gives rise to
42:
37:
30:
25:
20:
1694:
1569:Dorsal aorta
1342:
1338:
1311:. Retrieved
1307:the original
1297:
1262:
1258:
1205:(1): 59–63.
1202:
1198:
1188:
1164:(1): 51–54.
1161:
1157:
1147:
1127:
1117:
1112:
1043:
1039:
1029:
997:(1): 15–20.
994:
990:
980:
947:
943:
933:
923:, retrieved
893:
883:
842:
838:
828:
785:
781:
771:
736:
732:
722:
712:, retrieved
700:
666:. Retrieved
662:
601:vasodilation
597:nitric oxide
583:
572:
560:
553:
550:
547:
531:
482:
474:
460:
441:
434:
427:fossa ovalis
425:
418:
403:
394:
373:
369:
356:
347:
343:nitric oxide
335:
331:
307:
301:through the
298:mitral valve
286:amniotic sac
263:
257:through the
252:
241:Before birth
228:(2α2γ). Its
226:gamma chains
215:
198:
149:
78:
72:
1046:(7): 1861.
589:prostanoids
322:After birth
235:beta chains
1625:Lymph sacs
1579:Aortic sac
925:2022-09-12
714:2022-09-12
701:StatPearls
668:2022-09-12
641:References
585:Endothelin
538:hemoglobin
528:Physiology
377:surfactant
270:ventricles
1219:0007-0769
1062:1422-0067
964:0031-9333
920:243702991
859:0363-6135
802:0006-4971
413:Develops
95:breathing
1766:Category
1742:yolk sac
1685:Placenta
1680:Yolk sac
1561:Arteries
1367:25040285
1359:15614842
1313:June 29,
1289:23575926
1281:18816497
1237:10862590
1180:16615829
1136:Archived
1080:29941785
1021:30468303
972:20959617
875:25412093
867:10993792
820:18988877
763:25602070
709:30725834
492:proximal
386:meconium
276:and the
224:and two
195:Placenta
83:placenta
1670:Chorion
1553:Vessels
1493:Atrial
1228:1729389
1171:1831961
1071:6073350
1012:6393200
811:2581994
754:4305167
599:causes
508:
504:of the
498:
452:hepatic
339:alveoli
39:Details
1365:
1357:
1287:
1279:
1235:
1225:
1217:
1178:
1168:
1078:
1068:
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1019:
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918:
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873:
865:
857:
818:
808:
800:
761:
751:
707:
591:cause
514:distal
450:extra-
410:Fetal
1731:Aorta
1719:Heart
1634:Other
1589:Veins
1528:Other
1416:Heart
1363:S2CID
1285:S2CID
1199:Heart
916:S2CID
871:S2CID
782:Blood
315:aorta
282:lungs
266:atria
222:alpha
61:[
1355:PMID
1315:2011
1277:PMID
1233:PMID
1215:ISSN
1176:PMID
1076:PMID
1058:ISSN
1017:PMID
968:PMID
960:ISSN
906:ISBN
863:PMID
855:ISSN
816:PMID
798:ISSN
759:PMID
705:PMID
587:and
569:Flow
1347:doi
1267:doi
1223:PMC
1207:doi
1166:PMC
1066:PMC
1048:doi
1007:PMC
999:doi
952:doi
898:doi
847:doi
843:279
806:PMC
790:doi
786:112
749:PMC
741:doi
737:370
1768::
1744::
1733:→
1729:→
1725:→
1721:→
1717:→
1713:→
1709:→
1705::
1361:.
1353:.
1343:24
1341:.
1323:^
1283:.
1275:.
1263:32
1261:.
1257:.
1245:^
1231:.
1221:.
1213:.
1203:84
1201:.
1197:.
1174:.
1160:.
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1100:^
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1064:.
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1042:.
1038:.
1015:.
1005:.
995:14
993:.
989:.
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958:.
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861:.
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473:(
178:e
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65:]
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