2010 Lecture 3: Difference between revisions

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==Lecture Archive==
:Lecture Archive: [[2009_Lecture_3|2009 Lecture]] | [http://embryology.med.unsw.edu.au/Science/ANAT2341lecture03.htm 2008 Lecture]
[[2009_Lecture_3|2009 Lecture]] | [http://embryology.med.unsw.edu.au/Science/ANAT2341lecture03.htm 2008 Lecture]


==Lecture Overview==
[[Image:Week1_summary.jpg|thumb|Week 1 Human Development Overview]]
[[File:Inner_cell_mass_cartoon.jpg|thumb|Inner cell mass]]
* Week 1-2 of human development
* Fertilization options - In vitro fertilization
* Zygote, Morula, Blastocyst
* Cell layers - Trophoblast, Syncytiotrophoblast, Cytotrophoblast, Embryoblast
* Implantation - Normal, Ectopic, Uterine changes, Blastocyst implantation changes
==Fertilization Options==
* Natural sex
* Artificial insemination of mother with father's sperm, with mother with donor sperm, with egg and sperm donors, using surrogate mother
* In vitro fertilization (IVF)  using egg and sperm of parents
** Intra-Cytoplasmic Sperm Injection (ICSI), frozen embryos, pre-implantation Genetic Diagnosis (PGD), egg donor, sperm donor, egg and sperm donor, surrogate using parents' egg and sperm, surrogate and egg donor, surrogate and sperm donor, surrogate using her egg and sperm from baby's father, surrogate using egg and sperm donors
== Week 1 - Formation of Zygote ==
[http://embryology.med.unsw.edu.au/Movies/week1/pronuclear_fusion.mov Pronuclear Fusion] | [http://embryology.med.unsw.edu.au/Movies/week1/genome.htm Movie Parental Genomes]
* male and female pronuclei, 2 nuclei approach each other and nuclear membranes break down
* DNA replicates, first mitotic division
* sperm contributes centriole which organizes mitotic spindle
'''Conceptus''' - term refers to all material derived from this fertilized zygote and includes both the embryo and the non-embryonic tissues (placenta, fetal membranes).
==Cleavage of Zygote==
[http://embryology.med.unsw.edu.au/Movies/week1/earlydiv.htm Early Cell Division Movie] | [http://embryology.med.unsw.edu.au/Movies/week1/week1.mov Cell Cleavage]
* cleavage of zygote forms 2 blastomeres and is cleavage with no cytoplasm synthesis
** special "embryonic" cell cycle S phases and M phases alternate without any intervening G1 or G2 phases (MSMSMSMS, adult MG1SG2) therefore individual cell volume decreases
* cell division is initially synchronous, then asynchronously
** slow- centre cells, larger fast- peripheral cells
== Morula ==
[http://embryology.med.unsw.edu.au/Movies/week1/earlydiv.htm Early Cell Division Movie] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=hmg.figgrp.928 Figure 8.19. Changes in DNA methylation during mammalian development]
* about '''day 4''' is a solid ball of 16-20 cells with peripheral cells flattened against zona pellucida
* compaction occurs forming a cavity and leading to the next blastocyst stage
==Blastocyst==
[[Image:CSt3.jpg|thumb|300px|Hatching Blastocyst]]
* about '''day 5''' have 2 identifiable cell types and a fluid-filled cavity (blastoceol)
** '''trophoblast layer''' - peripheral flattened cells, forms the placenta and placental membranes
** '''inner cell mass''' - embryoblast, mass of rounder cells located on one wall of the blastocoel, forms entire embryo
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3927 Figure 21-69. The blastula]
'''Blastula Cell Communication''' - two forms of cellular junctions
* gap junctions, allow electrically couple cells of epithelium surrounding a fluid-filled cavity
* tight junctions, close to outer surface create a seal, isolates interior of embryo from external medium
'''Blastocyst Hatching''' - zona pellucida lost, ZP has sperm entry site, and entire ZP broken down by uterine secretions and possibly blastula secretions.
'''Uterine Glands''' - secretions required for blastocyst motility and nutrition
== Week 2 - Implantation ==
[http://embryology.med.unsw.edu.au/Movies/week2/week2.mov Movie - Implantation]
The second week of human development is concerned with the process of implantation and the differentiation of the blastocyst into early embryonic and placental forming structures.
*  implantation commences about '''day 6 to 7'''
* '''Adplantation''' - begins with initial adhesion to the uterine epithelium
** blastocyst then slows in motility, "rolls" on surface, aligns with the inner cell mass closest to the epithelium and stops
* '''Implantation''' - migration of the blastocyst into the uterine epithelium, process complete by about '''day 9'''
* '''coagulation plug''' - left where the blastocyst has entered the uterine wall '''day 12'''
'''Normal Implantation Sites''' - in uterine wall superior, posterior, lateral
===Abnormal Implantation===
[[Image:Tubal pregnancy.gif|thumb|Ectopic tubal pregnancy]]
[http://embryology.med.unsw.edu.au/Notes/week2_2.htm Ectopic Pregnancy] | [http://embryology.med.unsw.edu.au/Movies/usoundab/Ectopic1.htm Movie - Ectopic pregnancy ultrasound]
Abnormal implantation sites or Ectopic Pregnancy occurs if implantation is in uterine tube or outside the uterus.
* sites - external surface of uterus, ovary, bowel, gastrointestinal tract, mesentry, peritoneal wall
* If not spontaneous then, embryo has to be removed surgically
'''Tubal pregnancy''' - 94% of ectopic pregnancies
* if uterine epithelium is damaged (scarring, pelvic inflammatory disease)
* if zona pellucida is lost too early, allows premature tubal implantation
* embryo may develop through early stages, can erode through the uterine horn and reattach within the peritoneal cavity
== Uterus ==
<gallery>
Image:Uterus proliferative phase.jpg|Uterus proliferative phase
Image:Uterine gland proliferative phase.jpg|Uterine gland proliferative phase
Image:Uterus secretory phase.jpg|Uterus secretory phase
Image:Uterine gland secretory phase.jpg|Uterine gland secretory phase
</gallery>
* Endometrium - 3 layers in secretory phase of menstrual cycle: compact, spongy, basal
* Myometrium - muscular layer outside endometrium, contracts in parturition
* Perimetrium - tunica serosa of the uterus continuous with the peritoneal wall
===Endometrial Layers===
* Compact - implantation occurs in this layer, dense stromal cells, uterine gland necks, capillaries of spiral arteries
* Spongy - swollen stromal cells, uterine gland bodies, spiral arteries
* Basal - not lost during menstruation or childbirth, own blood supply
===Decidual Reaction===
* occurs initially at site of implantation and includes both cellular and matrix changes
* reaction spreads throughout entire uterus, not at cervix
*  deposition of fibrinoid and glycogen and epithelial plaque formation (at anchoring villi)
* presence of decidual cells are indicative of pregnancy
Cervix - at mouth of uterus, secretes mucus (CMP), forms a plug/barrier, mechanical and antibacterial
Vascular - increased number of blood vessels
===Decidua===
The endometrium becomes the decidua and forms 3 distinct anatomical regions (at approx 3 weeks)
* Decidua Basalis at implantation site
* Decidua Capsularis enclosing the conceptus
* Decidua Parietalis the remainder of uterus
** Decidua  Capsularis and Parietalis fuse eventually fuse and uterine cavity is lost by 12 weeks
=== Uterus Abnormalities ===
'''Endometriosis''' endometrial tissue located in other regions of the uterus or other tissues. This misplaced tissue develops into growths or lesions which respond to the menstrual cycle hormonal changes in the same way that the tissue of the uterine lining does; each month the tissue builds up, breaks down, and sheds. [http://embryology.med.unsw.edu.au/wwwhuman/mcycle/Mcycle.htm#Endometriosis Endometriosis]
== Bilaminar Embryo ==
[http://embryology.med.unsw.edu.au/Movies/week2/chorcav.mov Week 2 Bilaminar Embryo]
[[Image:Pregnancy test.gif|thumb|Pregnancy Test Kit]][[Image:Ovary_corpus_luteum.jpg|thumb|Ovary corpus luteum]]
* about '''day 8 to 9'''
The outer trophoblast and inner embryoblast layers now both differentiate to form two distinct cellular layers. The trophoblast layer forms the syncitotrophoblast and cytotrophoblast layers. The embryoblast (inner cell mass) forms the epiblast and hypoblast layers. This early stage of embryo development is referred to as the bilaminar embryo.
===Syncitiotrophoblasts===
* secrete proteolytic enzymes, enzymes break down extracellular matrix around cells
* Allow passage of blastocyst into endometrial wall, totally surround the blastocyst
* generate spaces that fill with maternal blood- lacunae
* secrete Human Chorionic Gonadotropin (hCG), hormone, maintains decidua and Corpus Luteum, basis of pregnancy diagnostic test, present in urine is diagnostic of pregnancy
** Later in development placenta will secrete hCG
'''MH''' - more information in lecture 4 and laboratory.
===Human Chorionic Gonadotropin===
* levels peak at 8 to 10 weeks of pregnancy, then decline and are lower for rest of pregnancy
:0-1 week: 0-50 mIU/ml 

:1-2 weeks: 40-300 mIU/ml
:3-4 weeks: 500-6,000 mIU/ml
:1-2 months: 5,000-200,000 mIU/ml
:2-3 months: 10,000-100,000 mIU/ml
:2nd trimester: 3,000-50,000 mIU/ml
:3rd trimester: 1,000-50,000 mIU/ml
Non-pregnant females: <5.0 mIU/ml
Postmenopausal females: <9.5 mIU/ml
== Twinning ==
Twinning can be due to two separate fertilization events (dizygotic twins) or as an abnormality of a single fertilization (monozygotic twins) event during the early weeks of development. [http://embryology.med.unsw.edu.au/Defect/twin.htm Twinning]
* In '''dizygotic twinning''' the genetic material is different and implantation and placentation is also different.
* In '''monozygotic twinning''' the genetic material is initially identical and degree of twinning will depend upon the timing (early to late) from separate fetal membranes and placenta to conjoined twins.
** morula stage (diamniotic dichorionic), early blastocyst (diamniotic monochorionic), late blastocyst to bilaminar (monoamniotic monochorionic), bilaminar to trilaminar embryo (conjoined)
* Monozygotic twins are a unique research resource for comparing environmental effects on development and health.
* Congenital abnormality statistics for twins is generally increased in various conditions.
'''MH''' - twinning will be covered in more detail in this weeks laboratory.
==Week 1 Human Development Overview==
[[Image:Week1_summary.jpg|400|Week 1 Human Development Overview]]
==Movies==
{| border='0px'
|-
| [[File:Follicle 001 icon.jpg|90px|link=Development_Animation_-_Ovulation]]
| [[File:Fertilization 002 icon.jpg|90px|link=Development_Animation_-_Fertilization]]
| [[File:Pronuclear_fusion 001 icon.jpg|90px|link=Development_Animation_-_Pronuclear_Fusion]]
| [[File:Week1 001 icon.jpg|90px|link=Development_Animation_-_Week_1]]
|-
| [[Development_Animation_-_Ovulation|Ovulation]]
| [[Development_Animation_-_Fertilization|Fertilization]]
| [[Development_Animation_-_Pronuclear_Fusion|Pronuclear Fusion]]
| [[Development_Animation_-_Week_1|Week 1]]
|-
|}
==UNSW Embryology Links==
* '''Week 1 and 2 Slides''' [http://embryology.med.unsw.edu.au/Science/ANAT2341lecture03.htm Lecture 3 2008] | [http://embryology.med.unsw.edu.au/pdf/ANAT2341L3Week1s1.pdf Lecture 3 2008 Slides]
* '''Week 1 and 2 Movies''' [http://embryology.med.unsw.edu.au/Movies/week1.htm Week 1 Movies] | [http://embryology.med.unsw.edu.au/Movies/week1/pronuclear_fusion.mov Pronuclear Fusion] | [http://embryology.med.unsw.edu.au/Movies/week1/earlydiv.htm Early Cell Division Movie] | [http://embryology.med.unsw.edu.au/Movies/week1/week1.mov Cell Cleavage] | [http://embryology.med.unsw.edu.au/Movies/week2/week2.mov Implantation] | [http://embryology.med.unsw.edu.au/Movies/week2/chorcav.mov Week 2 Bilaminar Embryo] | [http://embryology.med.unsw.edu.au/Movies/usoundab/Ectopic1.htm Movie - Ectopic Pregnancy Ultrasound 1]  | [http://embryology.med.unsw.edu.au/Movies/usoundab/Ectopic1.htm Movie - Ectopic Pregnancy Ultrasound 2] | [http://embryology.med.unsw.edu.au/Movies/week2/chorcav.mov Chorionic cavity]
* '''Week 1 and 2 Notes''' [http://embryology.med.unsw.edu.au/Notes/week1_3.htm Gamete Formation] | [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Oogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_3d.htm Corpus Luteum] | [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_3c.htm Capacitation] | [http://embryology.med.unsw.edu.au/Notes/week1_4.htm Cell division] | [http://embryology.med.unsw.edu.au/Notes/week1_4a.htm Mitosis] | [http://embryology.med.unsw.edu.au/Notes/week1_4b.htm Meiosis] | [http://embryology.med.unsw.edu.au/Notes/week1_5.htm Fertilization] | [http://embryology.med.unsw.edu.au/Notes/week1_5a.htm In Vivo Fertilization] | [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm In Vitro Fertilization] | [http://embryology.med.unsw.edu.au/Notes/week1_6.htm Zygote] | [http://embryology.med.unsw.edu.au/Notes/week1_6.htm#Parental Genomes Parental Genome Organization] | [http://embryology.med.unsw.edu.au/Notes/week1_12.htm Chromosome Location] | [http://embryology.med.unsw.edu.au/Notes/week1_7.htm Blastocyst] | [http://embryology.med.unsw.edu.au/Defect/twin.htm Twinning] | [http://embryology.med.unsw.edu.au/Notes/week2_2.htm Ectopic Pregnancy] | [http://embryology.med.unsw.edu.au/Notes/week1_8.htm Male sex determination] | [http://embryology.med.unsw.edu.au/Notes/week1_9.htm X inactivation] | [http://embryology.med.unsw.edu.au/Notes/week1_10.htm Cloning Issues] | [http://embryology.med.unsw.edu.au/Notes/week1_11.htm Molecular] | [http://embryology.med.unsw.edu.au/Notes/week1_link.htm WWW Links] | [http://embryology.med.unsw.edu.au/Defect/page7.htm Prenatal Diagnosis]
'''Internet Links'''
* [http://www.twins.org.au/index.php?page=31 Australian Twin Registry]
== Glossary Links ==
[[A|A]]  | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] |  [[Numbers|Numbers]]
== References ==
===Textbooks===
* '''The Developing Human: Clinically Oriented Embryology''' (8th Edition) by Keith L. Moore and T.V.N Persaud - Chapter 2
* '''Larsen’s Human Embryology''' by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West -  Chapter 2
===Online Textbooks===
* '''Developmental Biology''' by Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000 [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=dbio.figgrp.2615 Figure 11.22. The cleavage of a single mouse embryo in vitro] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=dbio.figgrp.2618 Figure 11.25. Mouse blastocyst hatching from the zona pellucida] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=implantation&rid=dbio.figgrp.2612 Figure 11.20. Development of a human embryo from fertilization to implantation] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=blastocyst&rid=dbio.figgrp.2617 Figure 11.24. Implantation of the mammalian blastocyst into the uterus]
* '''Molecular Biology of the Cell''' 4th ed. Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002 -  [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.section.3738 Fertilization] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3955 Figure 21-84. Scanning electron micrographs of the early mouse embryo] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3927 Figure 21-69. The blastula]
* '''Molecular Cell Biology''' by Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E. New York: W. H. Freeman & Co.; c1999 Chapter 13. Regulation of the Eukaryotic Cell Cycle
* '''The Cell - A Molecular Approach''' by Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000  [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2492 Figure 14.37. Meiosis of vertebrate oocytes]
* '''HSTAT''' - [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=hstat6.section.1395#1396 In Vitro Fertilization As A Medical Treatment For Male or Female Infertility]
* '''Human Molecular Genetics 2''' Strachan, Tom and Read, Andrew P. New York and London: Garland Science; c1999 [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=morula&rid=hmg.figgrp.928 Figure 8.19. Changes in DNA methylation during mammalian development]
===Search ===
* '''Bookshelf'''  [http://www.ncbi.nlm.nih.gov/sites/entrez?db=Books&cmd=search&term=blastocyst blastocyst] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=Books&cmd=search&term=morula morula] |  [http://www.ncbi.nlm.nih.gov/sites/entrez?db=Books&cmd=search&term=implantation implantation] | [http://www.ncbi.nlm.nih.gov/sites/entrez?db=Books&cmd=search&term=ectopic_pregnancy ectopic pregnancy]
* '''Pubmed''' [http://www.ncbi.nlm.nih.gov/sites/gquery?itool=toolbar&cmd=search&term=blastocyst blastocyst] | [http://www.ncbi.nlm.nih.gov/sites/gquery?itool=toolbar&cmd=search&term=implantation implantation] | [http://www.ncbi.nlm.nih.gov/sites/gquery?itool=toolbar&cmd=search&term=ectopic_pregnancy ectopic pregnancy] |


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Revision as of 11:42, 30 July 2010

Week 1 and 2

Lecture Notice - Mark Hill
This online lecture page will contain the content required when attending the lecture. Currently this page is only a template and will be updated before the lecture (this notice removed when completed). Final lecture pages can also be printed out using the "printable version" lefthand menu.

Introduction

Following fertilization the first week is a series of rapid cell divisions, still contained within the zona pellucida, and still floating and being propelled within the uterine tube towards the uterine body. At the end of the first week and within the second week the process of implantation and early differentiation of cells that will form the embryo and the placenta.

File:Week1_001 icon.jpg</wikiflv> This animation shows the first week of human development following fertilization.


(More? Development Animation - Week 1)

Lecture Archive: 2009 Lecture | 2008 Lecture


Lecture Overview

Week 1 Human Development Overview
Inner cell mass
  • Week 1-2 of human development
  • Fertilization options - In vitro fertilization
  • Zygote, Morula, Blastocyst
  • Cell layers - Trophoblast, Syncytiotrophoblast, Cytotrophoblast, Embryoblast
  • Implantation - Normal, Ectopic, Uterine changes, Blastocyst implantation changes

Fertilization Options

  • Natural sex
  • Artificial insemination of mother with father's sperm, with mother with donor sperm, with egg and sperm donors, using surrogate mother
  • In vitro fertilization (IVF) using egg and sperm of parents
    • Intra-Cytoplasmic Sperm Injection (ICSI), frozen embryos, pre-implantation Genetic Diagnosis (PGD), egg donor, sperm donor, egg and sperm donor, surrogate using parents' egg and sperm, surrogate and egg donor, surrogate and sperm donor, surrogate using her egg and sperm from baby's father, surrogate using egg and sperm donors

Week 1 - Formation of Zygote

Pronuclear Fusion | Movie Parental Genomes

  • male and female pronuclei, 2 nuclei approach each other and nuclear membranes break down
  • DNA replicates, first mitotic division
  • sperm contributes centriole which organizes mitotic spindle

Conceptus - term refers to all material derived from this fertilized zygote and includes both the embryo and the non-embryonic tissues (placenta, fetal membranes).

Cleavage of Zygote

Early Cell Division Movie | Cell Cleavage

  • cleavage of zygote forms 2 blastomeres and is cleavage with no cytoplasm synthesis
    • special "embryonic" cell cycle S phases and M phases alternate without any intervening G1 or G2 phases (MSMSMSMS, adult MG1SG2) therefore individual cell volume decreases
  • cell division is initially synchronous, then asynchronously
    • slow- centre cells, larger fast- peripheral cells

Morula

Early Cell Division Movie | Figure 8.19. Changes in DNA methylation during mammalian development

  • about day 4 is a solid ball of 16-20 cells with peripheral cells flattened against zona pellucida
  • compaction occurs forming a cavity and leading to the next blastocyst stage

Blastocyst

Hatching Blastocyst
  • about day 5 have 2 identifiable cell types and a fluid-filled cavity (blastoceol)
    • trophoblast layer - peripheral flattened cells, forms the placenta and placental membranes
    • inner cell mass - embryoblast, mass of rounder cells located on one wall of the blastocoel, forms entire embryo

Figure 21-69. The blastula Blastula Cell Communication - two forms of cellular junctions

  • gap junctions, allow electrically couple cells of epithelium surrounding a fluid-filled cavity
  • tight junctions, close to outer surface create a seal, isolates interior of embryo from external medium

Blastocyst Hatching - zona pellucida lost, ZP has sperm entry site, and entire ZP broken down by uterine secretions and possibly blastula secretions. Uterine Glands - secretions required for blastocyst motility and nutrition


Week 2 - Implantation

Movie - Implantation The second week of human development is concerned with the process of implantation and the differentiation of the blastocyst into early embryonic and placental forming structures.

  • implantation commences about day 6 to 7
  • Adplantation - begins with initial adhesion to the uterine epithelium
    • blastocyst then slows in motility, "rolls" on surface, aligns with the inner cell mass closest to the epithelium and stops
  • Implantation - migration of the blastocyst into the uterine epithelium, process complete by about day 9
  • coagulation plug - left where the blastocyst has entered the uterine wall day 12

Normal Implantation Sites - in uterine wall superior, posterior, lateral

Abnormal Implantation

Ectopic tubal pregnancy

Ectopic Pregnancy | Movie - Ectopic pregnancy ultrasound

Abnormal implantation sites or Ectopic Pregnancy occurs if implantation is in uterine tube or outside the uterus.

  • sites - external surface of uterus, ovary, bowel, gastrointestinal tract, mesentry, peritoneal wall
  • If not spontaneous then, embryo has to be removed surgically

Tubal pregnancy - 94% of ectopic pregnancies

  • if uterine epithelium is damaged (scarring, pelvic inflammatory disease)
  • if zona pellucida is lost too early, allows premature tubal implantation
  • embryo may develop through early stages, can erode through the uterine horn and reattach within the peritoneal cavity

Uterus

  • Uterus proliferative phase

    Uterus proliferative phase

  • Uterine gland proliferative phase

    Uterine gland proliferative phase

  • Uterus secretory phase

    Uterus secretory phase

  • Uterine gland secretory phase

    Uterine gland secretory phase

  • Endometrium - 3 layers in secretory phase of menstrual cycle: compact, spongy, basal
  • Myometrium - muscular layer outside endometrium, contracts in parturition
  • Perimetrium - tunica serosa of the uterus continuous with the peritoneal wall

Endometrial Layers

  • Compact - implantation occurs in this layer, dense stromal cells, uterine gland necks, capillaries of spiral arteries
  • Spongy - swollen stromal cells, uterine gland bodies, spiral arteries
  • Basal - not lost during menstruation or childbirth, own blood supply

Decidual Reaction

  • occurs initially at site of implantation and includes both cellular and matrix changes
  • reaction spreads throughout entire uterus, not at cervix
  • deposition of fibrinoid and glycogen and epithelial plaque formation (at anchoring villi)
  • presence of decidual cells are indicative of pregnancy

Cervix - at mouth of uterus, secretes mucus (CMP), forms a plug/barrier, mechanical and antibacterial Vascular - increased number of blood vessels

Decidua

The endometrium becomes the decidua and forms 3 distinct anatomical regions (at approx 3 weeks)

  • Decidua Basalis at implantation site
  • Decidua Capsularis enclosing the conceptus
  • Decidua Parietalis the remainder of uterus
    • Decidua Capsularis and Parietalis fuse eventually fuse and uterine cavity is lost by 12 weeks

Uterus Abnormalities

Endometriosis endometrial tissue located in other regions of the uterus or other tissues. This misplaced tissue develops into growths or lesions which respond to the menstrual cycle hormonal changes in the same way that the tissue of the uterine lining does; each month the tissue builds up, breaks down, and sheds. Endometriosis

Bilaminar Embryo

Week 2 Bilaminar Embryo

Pregnancy Test Kit
Ovary corpus luteum
  • about day 8 to 9

The outer trophoblast and inner embryoblast layers now both differentiate to form two distinct cellular layers. The trophoblast layer forms the syncitotrophoblast and cytotrophoblast layers. The embryoblast (inner cell mass) forms the epiblast and hypoblast layers. This early stage of embryo development is referred to as the bilaminar embryo.

Syncitiotrophoblasts

  • secrete proteolytic enzymes, enzymes break down extracellular matrix around cells
  • Allow passage of blastocyst into endometrial wall, totally surround the blastocyst
  • generate spaces that fill with maternal blood- lacunae
  • secrete Human Chorionic Gonadotropin (hCG), hormone, maintains decidua and Corpus Luteum, basis of pregnancy diagnostic test, present in urine is diagnostic of pregnancy
    • Later in development placenta will secrete hCG

MH - more information in lecture 4 and laboratory.

Human Chorionic Gonadotropin

  • levels peak at 8 to 10 weeks of pregnancy, then decline and are lower for rest of pregnancy
0-1 week: 0-50 mIU/ml 

1-2 weeks: 40-300 mIU/ml
3-4 weeks: 500-6,000 mIU/ml
1-2 months: 5,000-200,000 mIU/ml
2-3 months: 10,000-100,000 mIU/ml
2nd trimester: 3,000-50,000 mIU/ml
3rd trimester: 1,000-50,000 mIU/ml

Non-pregnant females: <5.0 mIU/ml Postmenopausal females: <9.5 mIU/ml

Twinning

Twinning can be due to two separate fertilization events (dizygotic twins) or as an abnormality of a single fertilization (monozygotic twins) event during the early weeks of development. Twinning

  • In dizygotic twinning the genetic material is different and implantation and placentation is also different.
  • In monozygotic twinning the genetic material is initially identical and degree of twinning will depend upon the timing (early to late) from separate fetal membranes and placenta to conjoined twins.
    • morula stage (diamniotic dichorionic), early blastocyst (diamniotic monochorionic), late blastocyst to bilaminar (monoamniotic monochorionic), bilaminar to trilaminar embryo (conjoined)
  • Monozygotic twins are a unique research resource for comparing environmental effects on development and health.
  • Congenital abnormality statistics for twins is generally increased in various conditions.

MH - twinning will be covered in more detail in this weeks laboratory.

Week 1 Human Development Overview

Week 1 Human Development Overview

Movies

Follicle 001 icon.jpg Fertilization 002 icon.jpg Pronuclear fusion 001 icon.jpg Week1 001 icon.jpg
Ovulation Fertilization Pronuclear Fusion Week 1

UNSW Embryology Links

Internet Links

Glossary Links

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers

References

Textbooks

  • The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Chapter 2
  • Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 2

Online Textbooks

Search

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Course Content 2010

Embryology Introduction | Cell Division/Fertilization | Lab 1 | Week 1&2 Development | Week 3 Development | Lab 2 | Mesoderm Development | Ectoderm, Early Neural, Neural Crest | Lab 3 | Early Vascular Development | Placenta | Lab 4 | Endoderm, Early Gastrointestinal | Respiratory Development | Lab 5 | Head Development | Neural Crest Development | Lab 6 | Musculoskeletal Development | Limb Development | Lab 7 | Kidney | Genital | Lab 8 | Sensory | Stem Cells | Stem Cells | Endocrine | Lab 10 | Late Vascular Development | Integumentary | Lab 11 | Birth, Postnatal | Revision | Lab 12 | Lecture Audio | Course Timetable

Cite this page: Hill, M.A. (2024, April 16) Embryology 2010 Lecture 3. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_Lecture_3

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
Retrieved from ‘https://embryology.med.unsw.edu.au/embryology/index.php?title=2010_Lecture_3&oldid=29052’
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