4: Fertilization and Early Development of the Embryo
- Page ID
- 91824
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\( \newcommand{\dsum}{\displaystyle\sum\limits} \)
\( \newcommand{\dint}{\displaystyle\int\limits} \)
\( \newcommand{\dlim}{\displaystyle\lim\limits} \)
\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)
( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\id}{\mathrm{id}}\)
\( \newcommand{\Span}{\mathrm{span}}\)
\( \newcommand{\kernel}{\mathrm{null}\,}\)
\( \newcommand{\range}{\mathrm{range}\,}\)
\( \newcommand{\RealPart}{\mathrm{Re}}\)
\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)
\( \newcommand{\Argument}{\mathrm{Arg}}\)
\( \newcommand{\norm}[1]{\| #1 \|}\)
\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)
\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)
\( \newcommand{\vectorA}[1]{\vec{#1}} % arrow\)
\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}} % arrow\)
\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\( \newcommand{\vectorC}[1]{\textbf{#1}} \)
\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)
\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)
\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)
\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)
\(\newcommand{\longvect}{\overrightarrow}\)
\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)
\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Author: Judy Thorn, Ph.D.
In approximately nine months, a single cell—a fertilized egg—develops into a fully formed infant consisting of trillions of cells with myriad specialized functions. The dramatic changes of fertilization, embryonic development, and fetal development are followed by remarkable adaptations of the newborn to life outside the womb. An offspring’s normal development depends on the appropriate synthesis of structural and functional proteins. This, in turn, is governed by the genetic material inherited from the egg and sperm, as well as environmental factors (Betts et al., Open Stax A&P second edition, 1.3.23, 28.1). This chapter addresses the biological and physiological processes associated with pregnancy, including fertilization, zygote formation, implantation, embryo formation, and maintaining pregnancy. It also covers contraception, infertility, and fetal genetic testing.
The content of this chapter is appropriate for, or easily adapted for the following audiences:
By the end of this chapter, you should be able to
- List and explain the steps involved in fertilization.
- Describe the obstacles that sperm must overcome to reach an oocyte.
- Explain capacitation and its importance in fertilization.
- Summarize the events that occur as a sperm fertilizes an oocyte.
- Sketch the stages of early development from the zygote to hatching.
- Describe cleavage and justify why cleavage is an essential step in early development.
- Correlate embryonic stage with its position in the female reproductive tract.
- Identify the cells required for the embryo to successfully implant and describe the consequences resulting from implantation in the wrong location.
- Match the extra-embryonic membranes with their function and location relative to the developing embryo.
- Describe how the placenta is formed and how it supports the developing embryo.
- Propose a treatment plan for treatment for a couple with infertility.
- List contraceptive options and explain how each works to prevent pregnancy.
Chapter 3 Bibliography
American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 88, “Invasive prenatal testing for aneuploidy”. Obstet Gynecol. 110, No. 6(Dec 2007):1459-67. doi: 10.1097/01.AOG.0000291570.63450.44 PMID: 18055749
American College of Obstetricians and Gynecologists (ACOG). "Routine tests in pregnancy", FAQ 133 (2024). Available from ACOG
American Society for Reproductive Medicine (ASRM). "Defining infertility." Fact Sheet, Reproductive Facts.org. (2014). Available from Reproductive Facts
American Society for Reproductive Medicine (ASRM). “Optimizing Natural fertility.” Reproductive Facts.org. (2017). Available from Reproductive Facts
American Urological Association (AUA). “Diagnosis and Treatment of Infertility in Men: AUA/ASRM Guideline (2020).” AUA Guidelines (Oct 2020). Available from AUA
Betts, J. Gordon, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix. Anatomy and Physiology. (2013). Open Stax, 2013 This work is distributed under a CC BY 4.0 license. Available from Open Stax.
Caughey, Aaron B, Linda M Hopkins, and Mary E Norton. “Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss” Obstet Gynecol. 108, No. 3 Pt 1(Sept 2006):612-6. doi: 10.1097/01.AOG.0000232512.46869.fc. PMID: 16946222
Chandra, Anjani, and Casey E. Copen. “Infertility and impaired fecundity in the United States, 1982–2010: Data From the National Survey of Family Growth.” National Health Statistics Reports No. 67 (Aug 14, 2013). Freely available from the Centers for Disease Control and Prevention
Daniilidis A, H Karydas, V Zournatzi, T Tantanasis, C Giannoulis, J Tzafettas. “A four-year retrospective study of amniocentesis: one centre experience”. Hippokratia. 12, No. 2(Apr 2008):113-5. Open Access article available from PMID: 18923654; PMCID: PMC2464303
Driscoll Deborah A and Susan Gross. “Clinical practice. Prenatal screening for aneuploidy”. N Engl J Med. 360, No. 24(Jun 11, 2009):2556-62. doi: 10.1056/NEJMcp0900134. PMID: 19516035
Ehrich, Mathias, Cosmin Deciu, Tricia Zwiefelhofer, John A Tynan, Lelsey Cagasan, et al. “Noninvasive detection of fetal trisomy 21 by sequencing of DNA in maternal blood: a study in a clinical setting.” Am J Obstet Gynecol 204, No 3(Mar 2011):205.e1-11. doi: 10.1016/j.ajog.2010.12.060. Epub 2011 Feb 18. PMID: 21310373
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). "Infertility and Fertility." (2017). Available from NICHD
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). "How do health care providers diagnose Down syndrome?" (Nov 2023). Available from NICHD
Evans Mark I and Ronald J Wapner. “Invasive prenatal diagnostic procedures 2005”. Semin Perinatol 29, No 4(Aug 2005):215-8. doi: 10.1053/j.semperi.2005.06.004. PMID: 16104671.
Gnoth C, D Godehardt, E Godehardt, P Frank-Herrmann, and G Freundl. “Time to pregnancy: results of the German prospective study and impact on the management of infertility”. Hum Reprod 18, No 9(Sep 2003):1959-66. doi: 10.1093/humrep/deg366. PMID: 12923157
Houser M, Kandalaft N, Khati NJ. Ectopic pregnancy: a resident’s guide to imaging findings and diagnostic pitfalls. Emerg Radiol 2022; 29(1): 161–172
Mio, Yasuyuki, Kyoko Iwata, Keitaro Yumoto, Yoshiteru Kai, Haruka C. Sargant, Chizuru Mizoguchi, Minako Ueda, Yuka Tsuchie, Akifumi Imajo, Yumiko Iba, and Kyoko Nishikori. "Possible mechanism of polyspermy block in human oocytes observed by time-lapse cinematography." J Assist Reprod Genet 29 No. 9 (Sept 2012):951-6. doi: 10.1007/s10815-012-9815-x. Epub 2012 Jun 14. PMID: 22695746; PMCID: PMC3463667
MedlinePlus [Internet], National Library of Medicine. "Infertility." In MedlinePlus Health Topics - Infertility. (ND) Available from MedlinePlus
National Human Genome Research Institute. (2010). “About Down Syndrome.” (June 2017). Available from Genome.gov
PDQ Adult Treatment Editorial Board. “Gestational Trophoblastic Disease Treatment (PDQ®): Health Professional Version.” PDQ Cancer Information Summaries (Oct 20, 2022) PMID: 26389414
Peddi, . "A Review of Cordocentesis: Percutaneous Umbilical Cord Blood Sampling." Cureus 13, No. 7 (July 16, 2021):e16423. This article distributed under the terms of the CC-BY 4.0 license. doi: 10.7759/cureus.16423 PMID: 34422463; PMCID: PMC8369974.
Practice Committee of the American Society for Reproductive Medicine and the Practice Committee of the Society for Reproductive Endocrinology and Infertility. “Optimizing natural fertility: a committee opinion.” Fertil Steril 100, No 3 (Sept 2013):631-637. doi.org/10.1016/j.fertnstert.2013.07.011
Reproductive Health Access Project. "Your Birth Control Choices". ND. This work is distributed under a CC BY 4.0 license. Available from Reproductive Health Access Project.
"Screening for Fetal Chromosomal Abnormalities: ACOG Practice Bulletin Summary, Number 226." Obstet Gynecol 136, No. 4 (Oct 2020):859-867. doi: 10.1097/AOG.0000000000004107 PMID: 32976375
Simmons-Duffin, Selena, L A Johnson and Meredith Rizzo. (Apr 12, 2023). “A visual guide to the surprising science of how pregnancy begins.” National Public Radio Shots Health News (Apr 12, 2023). Availalbe from NPR.org.
Steele M W and W R Breg Jr. “Chromosome analysis of human amniotic-fluid cells.” Lancet 1, No 7434 (Feb 19, 1996):383-5. doi: 10.1016/s0140-6736(66)91387-0. PMID: 4159775
Testing.com. "Maternal serum screening, second trimester." (Nov. 2021) Freely available from Testing.com
Tjio J. H., Levan A. The chromosome number of man. Hereditas 1956;42:1–6??? newer: Tjio J H. “The chromosome number of man.” Am J Obstet Gynecol. 130, No 6 (Mar 15, 1978):723-4. doi: 10.1016/0002-9378(78)90337-x. PMID: 345813
Wong C C, K E Loewke, N L Bossert, B Behr, C J De Jonge, T M Baer, and R A Pera. "Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage." Nat Biotechnol (Oct 2010). Licensee: Mark A Hill License Date: Oct 06, 2010 License Number: 2523401420894