Placenta - Cord
Embryology - 26 Apr 2024 Expand to Translate |
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Introduction
The placenta (Greek, plakuos = flat cake) named on the basis of this organs appearance. The placental cord (umbilical cord) is the connecting region between the functional placenta and the embryo/fetal umbilical region. The human cord varies greatly in overall length increasing to about 60 to 70 cm at term. This extraembryonic structure contains the placental blood vessels and allantois.
There are essentially 3 separate aortic/venous circulatory systems: umbilical, systemic and vitelline. The umbilical system is lost at birth, the vitelline contributes to the portal system and the systemic (embryonic) is extensively remodelled to fom the the cardiovascular system.
Some Recent Findings
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More recent papers |
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More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Placental Cord <pubmed limit=5>Placental Cord</pubmed> |
Hofbauer Cells
Hofbauer Cells (red asterisks)[3] |
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Historic Embryology - Hofbauer Cells | ||
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Chapter 14. Hofbauer Cells in Normal and Pathologic Conceptuses Contributions to Embryology Carnegie Institution No.56 (1921)
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Wharton's Jelly
Placental cord cross-section showing Wharton's Jelly |
First described and named after Thomas Wharton (1614–1673) an English physician and anatomist.
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Placental Cord Histology
Human placental cord (3.5 month) cross-section.
Persistent Right Umbilical Vein
A fairly rare anomaly, a study of 15,237 obstetric ultrasound examinations performed after 15 weeks' gestation identified only 33 cases of persistent right umbilical vein.[4] Some studies have identified associated fetal anomalies with this condition.[5]
Cord Length
The following are lengths and classifications at term.
- Normal range - 50 to 60 cm.
- Short cord - less than 35 cm.
- Long cords - over 70 cm can be associated with wrapping around the fetus and other abnormalities.[6]
Cord Coiling
A recent review of the published literature on cord coiling[7] states: "Previous studies that draw a link between abnormal cord coiling and clinical outcome are generally too small and/or selective to allow meaningful conclusions or applicability to low-risk populations."
The following suggested associations[8] should therefore be reconsidered.
- Hypocoiling - associated with increased incidence of fetal demise, intrapartum fetal heart rate decelerations, operative delivery for fetal distress, anatomic-karyotypic abnormalities and chorio-amnionitis.
- Hypercoiling - associated with increased incidence of fetal growth restriction, intrapartum fetal heart rate decelerations, vascular thrombosis and cord stenosis.
Placental Cord Ultrasound
There are a number of analyses that can be made by ultrasound scanning of the fetal placental cord. Some detected abnormalities (blood vessel number, blood flow[9]) have been associated with adverse developmental outcomes.
- Quantification of cord length, diameter, structural abnormalities.
- Quantification of placental blood vessel number and size.
- Quantification of uterine artery blood flow (doppler analysis).
Ultrasound image of transverse scan through the cord show the method of estimation of the cross-sectional area.
Cord Abnormalities
Cord Vessel Number
Cord Knotting
There are few abnormalities associated with umbilical cord development, other that abnormally short or long cords, which in most cases do not cause difficulties.
In some cases though, long cords can wrap around limbs or the fetus neck, which can then restrict blood flow or lead to tissue or nerve damage, and therefore effect develoment.
Cord knotting can also occur (1%) in most cases these knots have no effect, in some cases of severe knotting this can prevents the passage of placental blood.
Umbilical Cord Torsion
Rare umbilical cord torsion, even without knot formation can also affect placental blood flow, even leading to fetal demise.[10]
Cord Length
References
Reviews
Articles
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May 2010 search "Placental Cord Development]" All (650) Review (91) Free Full Text (119)
Search Pubmed: Placental Cord | Umbilical Cord | Placental Cord Development | Umbilical Cord Development | Hofbauer cells
Additional Images
see all online Placental materials
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Cite this page: Hill, M.A. (2024, April 26) Embryology Placenta - Cord. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Placenta_-_Cord
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G