ASA Meeting 2013 - Placenta: Difference between revisions

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:'''Links:''' [http://www.a-s-a.com.au/asa2013-sydney Conference Homepage] | [http://www.a-s-a.com.au|Australian Sonographers Association] | [[Placenta Development]] |  [[Main Page|Embryology]]
:'''Links:''' [http://www.a-s-a.com.au/asa2013-sydney Conference Homepage] | [http://www.a-s-a.com.au|Australian Sonographers Association] | [[Placenta Development]] |  [[Main Page|Embryology]]


''Draft Page - notice removed when complete.''
==Introduction==
This page will be updated and contain the final conference presentation.


==Abstract==
==Abstract==
[[Image:Mark Hill.jpg‎|thumb|Dr Mark Hill]]
[[File:Spiegel1626_table07.jpg|thumb|''De formato foetu liber singularis'' (1626) by Adriaan van den Spiegel (1578-1625)]]


Sonographic analysis of the placenta and uterus and their associated blood flow are key diagnostic prenatal assessments in human development. This review will provide an overview of the basic biology of the placentation process and key events in the developmental timeline. This talk should be of value to those wanting a better understanding of the process of human haemochorial placentation.  
Sonographic analysis of the placenta and uterus and their associated blood flow are key diagnostic prenatal assessments in human development. This review will provide an overview of the basic biology of the placentation process and key events in the developmental timeline. This talk should be of value to those wanting a better understanding of the process of human haemochorial placentation.  
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The full presentation and additional information/resources/links is available online (http://embryology.med.unsw.edu.au/embryology/index.php?title=ASA_Meeting_2013_-_Placenta).
The full presentation and additional information/resources/links is available online (http://php.med.unsw.edu.au/embryology/index.php?title=ASA_Meeting_2013_-_Placenta).
----
==Introduction==
[[Image:Mark Hill.jpg‎|thumb|left|Dr Mark Hill]]
[[File:Twitter_icon.jpg|link=https://twitter.com/MarkHill_UNSW|thumb|right|120px|@MarkHill_UNSW]]
[[File:Acps-logo.png|right|link=http://www.acps.unsw.edu.au]]
This talk is intended to provide a broad introduction to placentation and its associated vascular development. This is such an interesting, and both clinically and diagnostically relevant topic in sonography.
 
 
 
My talk will go through a time-course of development from earliest implantation through to the term placenta, specifically related to vascular development. Given that this process takes about 9 months, I will pick some key events in my 20 minute talk. 
 
 
I have designed this online resource for ongoing "self-directed" learning after the conference.
 


As always, I welcome feedback and questions from my readers and encourage you to contact me with any potential educational materials that you would like to share.


[[File:Spiegel1626_table07.jpg|600px]]


Historic drawing of Fetus and Placenta


Table 7 ''De formato foetu liber singularis'' (1626) by Adriaan van den Spiegel (1578-1625)
--[[User:Z8600021|Mark Hill]] 09:14, 10 May 2013 (EST)


==Embryo GA Week 4 (Week 2)==
==Embryo GA Week 4 (Week 2)==
{|
{|
| width=300px|<mediaplayer width='250' height='260' image="http://embryology.med.unsw.edu.au/embryology/images/a/a9/Week2_001_icon.jpg">File:Week2_001.mp4</mediaplayer>
| width=300px|<html5media height="520" width="360">File:Week2_001.mp4</html5media>
| [[File:Week2_001_icon.jpg|200px|right]]
| [[File:Week2_001_icon.jpg|200px|right]]
This animation shows the process of implantation, occurring during week 2 of development in humans.
This animation shows the process of implantation, occurring during week 2 of development in humans.
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|-
|-
| width=260px|<mediaplayer width='220' height='260' image="http://embryology.med.unsw.edu.au/embryology/images/0/08/Chorion_001_icon.jpg">File:Chorion 001.mp4</mediaplayer>
| width=260px|<html5media height="260" width="220">File:Chorion 001.mp4</html5media>
 
| [[File:Chorion 001 icon.jpg|200px|right]] Animation shows the events following implantation and focuses on changes in the the spaces surrounding the embryonic disc, the extraembryonic coelom.  
| [[File:Chorion 001 icon.jpg|200px|right]] Animation shows the events following implantation and focuses on changes in the the spaces surrounding the embryonic disc, the extraembryonic coelom.  


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:'''Links:''' [[Media:Chorion_001.mp4|MP4 version]] | [[Media:Chorion_001.mov|Quicktime version]] | [[Implantation Movie]] | [[Week 2]] | [[Movies]]
:'''Links:''' [[Media:Chorion_001.mp4|MP4 version]] | [[Implantation Movie]] | [[Week 2]] | [[Movies]]
|-
|}
 
{{Gray fetal membrane cartoons}}
 
[[File:Gray0032.jpg|400px]] [[File:Stage7_bf53.jpg|400px]]
 
==Embryo GA Week 5 (Week 3)==
 
{|
|-
! Week 2 ({{GA}} 4)
! Week 3 ({{GA}} 5)
! Week 4 ({{GA}} 6)
|-
| [[File:Gray0036.jpg|250px]]
| [[File:Gray0037.jpg|250px]]
| [[File:Gray0031.jpg|250px]]
|-
| Primary villi
| Secondary villi
| Tertiary villi
|-
| first stage of chorionic villi development, trophoblastic shell cells (syncitiotrophoblasts and cytotrophoblasts) form finger-like extensions into maternal decidua.
| second stage of chorionic villi development, extraembryonic mesoderm grows into villi, covers entire surface of chorionic sac. Basal region will form chorionic plate.
| third stage of chorionic villi development, mesenchyme differentiates into blood vessels and cells, forms arteriocapillary network, fuse with placental vessels, developing in connecting stalk.
|-
|
| valign="bottom"|{{Week 3 movie}}
| valign="bottom"|{{Amnion movie}}
|}
{| class="wikitable collapsible collapsed"
! Placental Classification
|-
|-
| [[File:Haemomonochorial human placenta EM01.jpg|thumb|300px|Haemomonochorial human placenta (electron micrograph)]]
Classification of placenta is on the basis of histological (microscopic) structural organization and layers between fetal and maternal circulation.
Three main groups:
# '''Haemochorial''' - placenta where the chorion comes in direct contact with maternal blood (human).
# '''Endotheliochorial''' - maternal endometrial blood vessels are bare to their endothelium and these comes in contact with the chorion ([[Dog Development|dogs]], [[Cat Development|cats]]).
# '''Epitheliochorial''' - maternal epithelium of the uterus comes in contact with the chorion, considered as primitive ([[Pig Development|pigs]], [[Bovine Development|cows]]).
The presence of these three differing types of placenta have also been used to describe the pattern mammalian evolution.
|}
|}


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==Villi Development==
==Villi Development==
{|
{|
! First Trimester
! Third Trimester
|-
| [[File:Placental_villi_2.jpg|400px]]
| [[File:Placental_villi_4.jpg|400px]]
|}
{|
|-
! Secondary Villi
! Tertiary Villi
|-
| [[File:Placenta_anchoring_villi.jpg|400px]]
| [[File:Placenta_anchoring_villi.jpg|400px]]
| [[File:Placental_villi_6.jpg|400px]]
| [[File:Placental_villi_6.jpg|400px]]
|}
|}


==Placenta Vasculature - MRI and CT==
[[File:Human_placental_villi_cartoon_01.jpg|800px]]
Term placenta viewed from the fetal side.<ref><pubmed>20226038</pubmed>| [http://www.biomedcentral.com/1472-6793/10/3 BMC Physiol.]</ref>
 
==Maternal Blood Vessels==
'''Uterine and Placental Vasculature in Non-pregnant, Pregnant and immediate Post-partum State'''
 
[[File:Uterine_and_placental_vasculature.jpg]]
 
 
Diagrammatic representation of uterine and placental vasculature (red shading = arterial; blue shading = venous) in the non-pregnant, pregnant and immediate post-partum state.
 
{| class="wikitable collapsible collapsed"
! More figure information &nbsp;
|-
|
* Normal pregnancy is characterized by the formation of large arterio-venous shunts that persist in the immediate post-partum period.
* Extravillous cytotrophoblast invasion in normal pregnancy (diamonds) extends beyond the decidua into the inner myometrium resulting in the formation of funnels at the discharging tips of the spiral arteries.
* Pregnancies complicated by severe preeclampsia are characterized by minimal arterio-venous shunts, and thus narrower uterine arteries. Contrast with severe preeclampsia.
|}
 
{| class="wikitable collapsible collapsed"
! Maternal Decidua chances
|-
|
===Fibrinoid===
Exist as 2 forms of extracellular matrix:
# Fibrin-type fibrinoid is a maternal blood-clot product which replaces degenerative syncytiotrophoblast
# Matrix-type fibrinoid is secreted by invasive extravillous trophoblast cells.
 
Fibrinoid layer (Nitabuch's layer) is thought to act to prevent excessively deep implantation.
 
===Decidualization===
 
Process of endometrial stromal cells (fibroblast-like) change in morphology (polygonal cells) and protein expression and secretion (specific decidual proteins: prolactin, insulin-like growth factor binding protein-1, tissue factor, interleukin-15, and VEGF).
# Estrogen and progesterone - receptive phase, luminal and glandular epithelial cells change in preparation for blastocyst adplantation.
# Human Chorionic gonadotropin - luminal epithelium endoreplication leading to epithelial plaque formation.
# Human Chorionic gonadotropin - trophoblast invasion and decidualization of human stromal fibroblasts.
 
===Artery Dilatation===
 
Due to extravillous trophoblast cells invading uterine wall and maternal spiral arteries replacing both smooth muscle with fibrinoid material and part of vessel endothelium. There is also a proliferation of maternal blood vessels.
 
===Other changes===
* Endoreplication - rounds of nuclear DNA replication without intervening cell or nuclear division (mitosis).
* Cytokines - of maternal origin also act on placental development.
* Natural Killer (NK) cells - 30% of all the decidual cells towards the end of the first trimester of pregnancy. These lymphocytes are present in the maternal decidua in large numbers (70%, normal circulating blood lymphocytes 15%) close to the extravillous trophoblast cells. Have a cytolytic potential against virus-infected and tumor-transformed cells.
 
===Preeclampsia ===
 
* '''Preeclampsia''' - describes maternal high blood pressure and protein in the urine after the 20th week (GA) late 2nd or 3rd trimester of pregnancy. This may be due to factors from the placenta.
* '''Eclampsia''' - seizures (convulsions) in a pregnant woman that are not related to a preexisting brain condition.
|}
 
==Placental Cord==
 
===Histology===
[[File:Placental_cord_vessels_01.jpg|thumb|300px|Cord cross-section]]
<gallery>
File:Placental_vein.jpg|Placental vein
File:Placental_artery.jpg|Placental artery
File:Allantois.jpg|Placental allantois
File:Placental cord cross-section.jpg|Placental cord cross-section
</gallery>
===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.
 
===Ultrasound===
[[File:Placental_cord_ultrasound_03.jpg]]
 
Ultrasound image of transverse scan through the cord show the method of estimation of the cross-sectional area.
 
{| class="wikitable collapsible collapsed"
! Vessel Anomalies
|-
|
===Persistent Right Umbilical Vein===
A study of 15,237 obstetric ultrasound examinations performed after 15 weeks' gestation identified only 33 cases of persistent right umbilical vein.
 
<pubmed>7970470</pubmed>
 
===One artery and one vein===
[[File:Placental cord ultrasound 02.jpg|400px]]
 
===Intra-abdominal umbilical vein varix===
 
A focal dilatation of the fetal intra-abdominal portion of the placental vein.
|}
 
 
{| class="wikitable collapsible collapsed"
! Cord Coiling and Knotting
|-
| [[File:Placenta- umbilical cord torsion.jpg|thumb|Umbilical cord torsion]]
===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.
===Cord Knotting===
[[File:Placental cord knot.png|thumb|Placental cord true knot]]
 
Cord knotting can occur (1%) in most cases these knots have no effect, in some cases of severe knotting this can prevents the passage of placental blood.
 
===Cord Torsion===
 
Rare umbilical cord torsion, even without knot formation can also affect placental blood flow, even leading to fetal demise.
 
|}
 
==Exchange==
{|
| [[File:Placenta_oxygen_exchange_levels.jpg]]
| [[File:Placenta_spiral_artery_conversion.jpg]]
|}
{| class="wikitable collapsible collapsed"
! Crossing the placenta &nbsp;
|-
|
* oxygen, carbon dioxide, carbon monoxide
* '''nutrients'''
** water, glucose, vitamins
** electrolytes
* '''waste products'''
** urea, uric acid, bilirubin.
* '''hormones'''
** mainly steroid, protein hormones poorly transported.
** maternal thyroid hormone can slowly cross.
** fetal insulin can impact on maternal diabetes.  
* '''maternal antibodies'''
** maternal IgG antibodies are transferred from about week 13 (GA) across the placenta
** from the maternal lacunae syncytiotrophoblast cell endosomes bind IgG through neonatal Fc receptors.
* '''drugs and their metabolites'''
** pre-existing maternal conditions
** illegal drugs (fetal drug addiction)
* '''infectious agents'''
** cytomegalovirus, rubella, measles, malaria, listeria, microorganisms
|}
 
==Term Placenta==
 
===Maternal and Fetal Side===
[[File:Placenta term anatomy 01.jpg|800px]]
 
===Placenta Vasculature - MRI and CT===
Term placenta viewed from the fetal side.{{#pmid:20226038|PMID20226038}}


[[File:Human placenta vascular 01.jpg|800px]]


{|
{|
|-
| [[File:Human_placenta_vascular_MRI_02.jpg|400px]]
| [[File:Human_placenta_vascular_CT_01.jpg|400px]]
|-
| width=400px|'''Magnetic Resonance Angiography''' (MRA)
| width=400px|'''Magnetic Resonance Angiography''' (MRA)
| width=400px|'''Computed Tomography Angiography''' (CTA)
| width=400px|'''Computed Tomography Angiography''' (CTA)
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|}
|}


===Placenta Measurements===
[[File:Placental volume graph.jpg|thumb|300px|Term Placenta Measurements]]
Morphometric indices at term of placental composition, villous capillarization and the mean cross-sectional areas of peripheral villi and capillaries.
{|
|-bgcolor="CEDFF2"
| width="150px"|'''Variable'''
| width="100px"|'''Unit'''
| width="100px"|'''Placenta'''
|-
|Intervillous space
| mL
| 213
|-bgcolor="F5FAFF"
| Stem villi
| mL
| 71.4
|-
| Peripheral villi
| mL
| 326
|-bgcolor="F5FAFF"
| Trophoblast
| mL
| 95.5
|-
| Stroma
| mL
| 184
|-bgcolor="F5FAFF"
| Fetal capillaries
| mL
| 46.9
|-
| Non-parenchyma
| mL
| 41.5
|-bgcolor="F5FAFF"
| Peripheral villi
| km
| 89.2
|-
| Fetal capillaries
| km
| 310
|-bgcolor="F5FAFF"
| TS area villi
| µm<sup>2</sup>
| 3700
|-
| TS area capillary
| µm<sup>2</sup>
| 150
|-bgcolor="F5FAFF"
| Capillaries
| mL mL<sup>-1</sup>
| 0.147
|-
| Length ratio
| km km<sup>-1</sup>
| 3.6
|-bgcolor="F5FAFF"
|}
Data from a study sample of 15 normal placenta, mean placental volume, 652 ml.{{#pmid:18328557|PMID18328557}}{{#pmid:19141109|PMID19141109}}
{| class="wikitable collapsible collapsed"
! Measurement methodology
|-
|
* Microscopical fields on stained sections were selected by systematic uniform random sampling and analysed stereologically to estimate the volumes of placental compartments and total lengths of villi and fetal capillaries.
* Mean cross-sectional areas of peripheral villi and capillaries, together with measures of villous capillarization (capillary volume densities and capillary : villus length ratios), were derived from global volumes and lengths.
|}
==Abnormalities==
===Hydatidiform Mole===
[[File:Hydatidiform mole.jpg|400px]]
Hydatidiform Mole
When only the conceptus trophoblast layers proliferates and not the embryoblast, no embryo develops, this is called a "hydatidiform mole" (HM), which is due to the continuing presence of the trophoblastic layer, this abnormal conceptus can also implant in the uterus.
{| class="wikitable collapsible collapsed"
! More information
|-
|
The trophoblast cells will secrete human chorionic gonadotropin (hCG), as in a normal pregnancy, and may appear maternally and by pregnancy test to be "normal". Prenatal diagnosis by ultrasound analysis demonstrates the absence of a embryo.
There are several forms of hydatidiform mole: partial mole, complete mole and persistent gestational trophoblastic tumor. Many of these tumours arise from a haploid sperm fertilizing an egg without a female pronucleus (the alternative form, an embryo without sperm contribution, is called parthenogenesis). The tumour has a "grape-like" placental appearance without enclosed embryo formation. Following a first molar pregnancy, there is approximately a 1% risk of a second molar pregnancy.
* The incidence of hydatidiform mole varies between ethnic groups, and typically occurs in 1 in every 1500 pregnancies.
* All hydatidiform mole cases are sporadic, except for extremely rare familial cases.
:'''Links:''' [[Abnormal Development - Hydatidiform Mole|Hydatidiform Mole]] | [[Week_2#Week_2_Abnormalities|Week 2 - Abnormalities]]
|}
{|
! Velamentous Cord Insertion of the Placenta
|-
| [[File:Placenta_velamentous_cord_02.jpg|400px]]
| The placental cord inserts into the chorion laeve (placental membranes) away from the edge of the placenta.{{#pmid:23243528|PMID23243528}}
The placental vessels are therefore unprotected by Wharton's jelly where they traverse the membranes before they come together into the umbilical cord.
This can cause hemorrhage if the vessels are damaged when the membranes are ruptured prior to birth. The condition is more common in monozygotic twins (15%) and triplets.
|}
===Implantation Abnormalities===
[[File:Placenta_abnormalities.jpg|600px|]]
[[File:Placenta previa and increta 02.jpg]]
'''Placenta previa and increta'''
{| class="wikitable collapsible collapsed"
! Implantation abnormalities
|-
|
* '''Placenta Accreta''' - abnormal adherence, with absence of decidua basalis. The incidence of placenta accreta also significantly increases in women with previous cesarean section compared to those without a prior surgical delivery.
* '''Placenta Increta''' - occurs when the placenta attaches deep into the uterine wall and penetrates into the uterine muscle, but does not penetrate the uterine serosa. Placenta increta accounts for approximately 15-17% of all cases.
* '''Placenta Percreta''' - placental villi penetrate myometrium and through to uterine serosa.
* '''Placenta Previa''' - In this placenatal abnormality, the placenta overlies internal os of uterus, essentially covering the birth canal. This condition occurs in approximately 1 in 200 to 250 pregnancies. In the third trimester and at term, abnormal bleeding can require cesarian delivery and can also lead to Abruptio Placenta. Ultrasound screening programs during 1st and early 2nd trimester pregnancies now include placental localization. Diagnosis can also be made by transvaginal ultrasound.
* '''Vasa Previa''' - (vasa praevia) placental abnormality where the fetal vessels lie within the membranes close too or crossing the inner cervical os (opening).
* '''Abruptio Placenta''' - a retroplacental blood clot formation, abnormal haemorrhage prior to delivery.
* '''Chronic Intervillositis''' - (massive chronicintervillositis, chronic histiocytic intervillositis) Rare placental abnormality and pathology defined by inflammatory placental lesions, mainly in the intervillous space (IVS), with a maternal infiltrate of mononuclear cells (monocytes, lymphocytes, histiocytes) and intervillous fibrinoid deposition.
|}
==Online Placenta Links==
{{Placenta Links}}
:{{Historic Placenta}}


==References==
==References==


<references/>
<references/>
===Books===
* Wang Y, Zhao S. '''Vascular Biology of the Placenta.''' San Rafael (CA): Morgan & Claypool Life Sciences; 2010. Available from: http://www.ncbi.nlm.nih.gov/books/NBK53247





Latest revision as of 18:17, 11 April 2018

Placenta Embryology and Circulation

Australian Sonographers Association (ASA) Annual Conference 2013

Educate Innovate Celebrate

May 17 to 19 May 2013
ASA meeting2013 logo.jpg



Links: Conference Homepage | Sonographers Association | Placenta Development | Embryology


Abstract

De formato foetu liber singularis (1626) by Adriaan van den Spiegel (1578-1625)

Sonographic analysis of the placenta and uterus and their associated blood flow are key diagnostic prenatal assessments in human development. This review will provide an overview of the basic biology of the placentation process and key events in the developmental timeline. This talk should be of value to those wanting a better understanding of the process of human haemochorial placentation.


Placentation begins at the implantation site in the second week of development (GA week 4) with conceptus trophoblast cells invading the maternal endometrial epithelium and stroma. From that time on the process of placentation involves complex interactions between maternal uterine and fetal tissues. While there are many animal models of this process, none currently exactly match that seen in humans.


Maternally, these changes include modification of the maternal vascular, endocrine and immune response. Fetally, an entire organ is grown from extra-embryonic tissue that has many functions outside of acting as a simple exchange tissue. The main maternal vascular changes include increased vascularity and trophoblast modification of spiral arteries. The fetal vascular bed consists of large cord vessels and an exponentially growing capillary bed consisting of kilometres of villous capillaries. Identification of cord vessel number, size and blood flow, are important indices of normal fetal development. Furthermore extensive remodeled of the capillary bed occurs throughout development, with some villi morphologies influencing the efficiency of diffusional gas exchange. Clinically, abnormalities of placentation site, placental development, function and blood flow can have both maternal and fetal ramifications.


The full presentation and additional information/resources/links is available online (http://php.med.unsw.edu.au/embryology/index.php?title=ASA_Meeting_2013_-_Placenta).

Introduction

Dr Mark Hill
@MarkHill_UNSW
Acps-logo.png

This talk is intended to provide a broad introduction to placentation and its associated vascular development. This is such an interesting, and both clinically and diagnostically relevant topic in sonography.


My talk will go through a time-course of development from earliest implantation through to the term placenta, specifically related to vascular development. Given that this process takes about 9 months, I will pick some key events in my 20 minute talk.


I have designed this online resource for ongoing "self-directed" learning after the conference.


As always, I welcome feedback and questions from my readers and encourage you to contact me with any potential educational materials that you would like to share.


--Mark Hill 09:14, 10 May 2013 (EST)

Embryo GA Week 4 (Week 2)

<html5media height="520" width="360">File:Week2_001.mp4</html5media>
Week2 001 icon.jpg

This animation shows the process of implantation, occurring during week 2 of development in humans.

The beginning of the animation shows adplantation to the the uterus lining (endometrium epithelium). The hatched blastocyst with a flat outer layer of trophoblast cells (green), the inner cell mass which has formed into the bilaminar embryo (epiblast and hypoblast) and the large fluid-filled space (blastocoel).

  • green cells - trophoblast layer of the conceptus
  • blue cells - epiblast layer of the bilaminar embryo
  • yellow cells - hypoblast layer of the bilaminar embryo
  • white cells - uterine endometrium epithelium
  • red - maternal blood vessel


Implantation Movie Links: MP4 version | Week 2 Chorionic Cavity Movie | Implantation | Week 2 | Trophoblast | Human Chorionic Gonadotropin | Placenta Development | Movies
<html5media height="260" width="220">File:Chorion 001.mp4</html5media>
Chorion 001 icon.jpg
Animation shows the events following implantation and focuses on changes in the the spaces surrounding the embryonic disc, the extraembryonic coelom.

The blastoceol cavity is converted into two separate spaces: the yolk sac and the chorionic cavity.

The third space lies above the epiblast layer of the embryonic disc, the amniotic cavity.


  • white cells - (left) endometrial gland (right) endometrial epithelium
  • blue - epiblast layer (forming ectoderm and amniotic cavity lining)
  • yellow - hypoblast layer (replaced with endoderm during gastrulation)
  • red cells - extraembryonic mesoderm layer
  • green - trophoblast layers (cytotrophoblast and syncitiotrophoblast)
  • red spaces - blood-filled spaces, maternal lacunae


Links: MP4 version | Implantation Movie | Week 2 | Movies


Early embryo membrane development cartoons: Image 24 | Image 25 | Image 26 | Image 27 | Image 28

Gray0032.jpg Stage7 bf53.jpg

Embryo GA Week 5 (Week 3)

Week 2 (GA 4) Week 3 (GA 5) Week 4 (GA 6)
Gray0036.jpg Gray0037.jpg Gray0031.jpg
Primary villi Secondary villi Tertiary villi
first stage of chorionic villi development, trophoblastic shell cells (syncitiotrophoblasts and cytotrophoblasts) form finger-like extensions into maternal decidua. second stage of chorionic villi development, extraembryonic mesoderm grows into villi, covers entire surface of chorionic sac. Basal region will form chorionic plate. third stage of chorionic villi development, mesenchyme differentiates into blood vessels and cells, forms arteriocapillary network, fuse with placental vessels, developing in connecting stalk.
Week3 folding icon.jpg
 ‎‎Week 3
Page | Play
Amnion 001 icon.jpg
 ‎‎Amniotic Cavity
Page | Play

Embryo GA Week 7 (Week 5)

Stage13 bf4.jpg

Embryo Links: Embryo and Placenta | Embryo | Embryo (label) | Embryo (animated) | Embryo (animated large) | Head region | Head region (label) | Body region | Body region (label) | Carnegie stage 13
Stage 13 Links: Week 4 | Week 5 | Somitogenesis | Placodes | Head | Movies | Lecture - Early Vascular | Lecture - Gastrointestinal | Lecture - Head Development | Science Practical - Gastrointestinal | Science Practical - Head | Carnegie Embryos | Category:Carnegie Stage 13 | Next Stage 14
  Historic Papers: 1905 Embryo 148 | 1926 Precervical Sinus | 1945 | 1955

Embryo GA Week 9 (Week 7)

Placental membranes.jpg

Stage18 bf10.jpg Stage18 bf11.jpg
Embryo in gestational sac Embryo open sac
Stage18 bf12.jpg Stage18 bf13.jpg
Embryo with placentation (ectopic) Embryo in amniotic sac

Villi Development

First Trimester Third Trimester
Placental villi 2.jpg Placental villi 4.jpg
Secondary Villi Tertiary Villi
Placenta anchoring villi.jpg Placental villi 6.jpg

Human placental villi cartoon 01.jpg

Maternal Blood Vessels

Uterine and Placental Vasculature in Non-pregnant, Pregnant and immediate Post-partum State

Uterine and placental vasculature.jpg


Diagrammatic representation of uterine and placental vasculature (red shading = arterial; blue shading = venous) in the non-pregnant, pregnant and immediate post-partum state.

Placental Cord

Histology

Cord cross-section

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.

Ultrasound

Placental cord ultrasound 03.jpg

Ultrasound image of transverse scan through the cord show the method of estimation of the cross-sectional area.


Exchange

Placenta oxygen exchange levels.jpg Placenta spiral artery conversion.jpg

Term Placenta

Maternal and Fetal Side

Placenta term anatomy 01.jpg

Placenta Vasculature - MRI and CT

Term placenta viewed from the fetal side.[1]


Human placenta vascular MRI 02.jpg Human placenta vascular CT 01.jpg
Magnetic Resonance Angiography (MRA) Computed Tomography Angiography (CTA)
Legend
  • CA - chorionic artery
  • PSA - primary stem artery
  • SSA - secondary stem artery
  • TSA - tertiary stem artery

Placenta Measurements

Term Placenta Measurements

Morphometric indices at term of placental composition, villous capillarization and the mean cross-sectional areas of peripheral villi and capillaries.

Variable Unit Placenta
Intervillous space mL 213
Stem villi mL 71.4
Peripheral villi mL 326
Trophoblast mL 95.5
Stroma mL 184
Fetal capillaries mL 46.9
Non-parenchyma mL 41.5
Peripheral villi km 89.2
Fetal capillaries km 310
TS area villi µm2 3700
TS area capillary µm2 150
Capillaries mL mL-1 0.147
Length ratio km km-1 3.6

Data from a study sample of 15 normal placenta, mean placental volume, 652 ml.[2][3]

Abnormalities

Hydatidiform Mole

Hydatidiform mole.jpg

Hydatidiform Mole

When only the conceptus trophoblast layers proliferates and not the embryoblast, no embryo develops, this is called a "hydatidiform mole" (HM), which is due to the continuing presence of the trophoblastic layer, this abnormal conceptus can also implant in the uterus.

Velamentous Cord Insertion of the Placenta
Placenta velamentous cord 02.jpg The placental cord inserts into the chorion laeve (placental membranes) away from the edge of the placenta.[4]

The placental vessels are therefore unprotected by Wharton's jelly where they traverse the membranes before they come together into the umbilical cord.

This can cause hemorrhage if the vessels are damaged when the membranes are ruptured prior to birth. The condition is more common in monozygotic twins (15%) and triplets.

Implantation Abnormalities

Placenta abnormalities.jpg

Placenta previa and increta 02.jpg

Placenta previa and increta

Online Placenta Links

Placenta Links: placenta | Lecture - Placenta | Lecture Movie | Practical - Placenta | implantation | placental villi | trophoblast | maternal decidua | uterus | endocrine placenta | placental cord | placental membranes | placenta abnormalities | ectopic pregnancy | Stage 13 | Stage 22 | placenta histology | placenta vascular | blood vessel | cord stem cells | 2013 Meeting Presentation | Placenta Terms | Category:Placenta
Historic Embryology - Placenta 
1883 Embryonic Membranes | 1907 Development Atlas | 1909 | 1910 Textbook | 1917 Textbook | 1921 Textbook | 1921 Foetal Membranes |1921 human | 1921 Pig implantation | 1922 Single placental artery | 1923 Placenta Review | 1939 umbilical cord | 1943 human and monkey | 1944 chorionic villus and decidua parietalis | 1946 placenta ageing | 1960 first trimester placenta | 1960 monkey | 1972 Placental circulation | Historic Disclaimer


Historic Embryology - Placenta 
1883 Embryonic Membranes | 1907 Development Atlas | 1909 | 1910 Textbook | 1917 Textbook | 1921 Textbook | 1921 Foetal Membranes |1921 human | 1921 Pig implantation | 1922 Single placental artery | 1923 Placenta Review | 1939 umbilical cord | 1943 human and monkey | 1944 chorionic villus and decidua parietalis | 1946 placenta ageing | 1960 monkey | 1972 Placental circulation | Historic Disclaimer

References

  1. Rasmussen AS, Lauridsen H, Laustsen C, Jensen BG, Pedersen SF, Uhrenholt L, Boel LW, Uldbjerg N, Wang T & Pedersen M. (2010). High-resolution ex vivo magnetic resonance angiography: a feasibility study on biological and medical tissues. BMC Physiol. , 10, 3. PMID: 20226038 DOI.
  2. Mayhew TM, Jenkins H, Todd B & Clifton VL. (2008). Maternal asthma and placental morphometry: effects of severity, treatment and fetal sex. Placenta , 29, 366-73. PMID: 18328557 DOI.
  3. Mayhew TM. (2009). A stereological perspective on placental morphology in normal and complicated pregnancies. J. Anat. , 215, 77-90. PMID: 19141109 DOI.
  4. Rocha J, Carvalho J, Costa F, Meireles I & do Carmo O. (2012). Velamentous cord insertion in a singleton pregnancy: an obscure cause of emergency cesarean-a case report. Case Rep Obstet Gynecol , 2012, 308206. PMID: 23243528 DOI.


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Cite this page: Hill, M.A. (2024, March 28) Embryology ASA Meeting 2013 - Placenta. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/ASA_Meeting_2013_-_Placenta

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G