Difference between revisions of "Lecture - Fertilization"

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== Introduction ==
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{{Header}}
This lecture will introduce the key concepts of biology cell division and cellular sexual development. Cell division and fertilisation will also be explored further in the Wednesday laboratory.
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==Introduction==
 +
[[File:Frazer002 bw600.jpg|thumb|300px|alt=historic drawing of human oocyte and spermatozoa|Historic drawing of human oocyte and spermatozoa]]
  
{| border='0px'
 
|-
 
| [[File:Mitosis 01 icon.jpg|120px|link=Quicktime Movie_-_Mitosis_1]]
 
|-bgcolor="a3bfb1"
 
|  ‎‎'''Mitosis'''
 
|-bgcolor="F5FFFA"
 
| [[Quicktime Movie_-_Mitosis_1|Quicktime]] | [[Movie_-_Mitosis 1|Flash]]
 
|}
 
  
{|
+
This lecture will cover male and female gametogenesis and fertilisation.
| <wikiflv height= width="320" height="260" autostart="true" repeat="true">Pronuclear_fusion_001.flv|File:Pronuclear_fusion 001 icon.jpg</wikiflv>
+
 
| This animation shows the maternal (egg) and paternal (sperm) gamete pronuclei coming together following fertilization to form the first diploid cell, the '''zygote'''.
+
IN development 1 embryonic cell (zygote) will produce about 10<sup>13</sup> (100,000,000,000,000) cells in the adult at any one time (over time with cell death and ongoing replacement this is substantially more).
  
 +
This is where the first embryonic cell begins! Fertilization is the fusion of haploid gametes, egg (oocyte) and sperm (spermatozoa), to form the diploid zygote. Note though there can be subtle differences in the fertilization process which occurs naturally within the body or through reproductive technologies outside the body, the overall product in both cases is a diplod zygote.
  
(More? [[Development Animation - Pronuclear Fusion]])
 
  
:{{Template:Cell Division Links}}
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{| class="wikitable mw-collapsible mw-collapsed"
{|
+
! 2016 Lecture Video Recording &nbsp;
| [[File:Podcast_icon.jpg|link=ANAT2341_Embryology_2012_Lecture_Recordings]]
+
|-
| '''Lectopia Lecture Audio'''
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| This 2016 lecture video recording is similar in content to the current 2018 lecture and is available to help understand this online content.
  
 +
<html5media height="600" width="800">File:2016ANAT2341-Lecture-Fertilization.mp4</html5media>
  
 +
Click to play new window - [[Media:2016ANAT2341-Lecture-Fertilization.mp4|'''2016 Lecture Video''']] (54.46 MB)
 
|}
 
|}
  
 +
{| class="wikitable mw-collapsible mw-collapsed"
 +
! Some Recent Research &nbsp;
 +
|-
 +
|
 +
* From Meiosis to Mitosis: The Astonishing Flexibility of Cell Division Mechanisms in Early Mammalian Development (2016){{#pmid:27475851|PMID27475851}} "The egg can be arrested in the prophase of meiosis I for decades, and when it is activated, the spindle is assembled de novo. This spindle must function with the highest of fidelity and yet its assembly is unusually achieved in the absence of conventional centrosomes and with minimal influence of chromatin. Moreover, its dramatic asymmetric positioning is achieved through remarkable properties of the actin cytoskeleton to ensure elimination of the polar bodies. The second meiotic arrest marks a uniquely prolonged metaphase eventually interrupted by egg activation at fertilization to complete meiosis and mark a period of preparation of the male and female pronuclear genomes not only for their entry into the mitotic cleavage divisions but also for the imminent prospect of their zygotic expression."
 +
* Meiosis Podcast Biosights [http://jcb.rupress.org/content/200/5/567/suppl/DC2 18 March 2013 - Breaking egg symmetry]
 +
* [http://jcb.rupress.org/content/205/6/754.2.full JCB 16 June 16 2014 How sperm get into the zona]
 
|}
 
|}
  
==Objectives==
+
Lecture Archive: [[Media:2016ANAT2341-Lecture-Fertilization.mp4|2016 Video]] | [[Media:Lecture 2016 - Fertilization - Embryology.pdf|2016 PDF]] | [https://embryology.med.unsw.edu.au/embryology/index.php?title=Lecture_-_Fertilization&oldid=238099 2015] | [[Media:2015ANAT2341 Lecture 2 - Fertilization.pdf|2015 PDF]] | [[Media:ANAT2341 Lecture 2 - 2014 Fertilization.pdf|2014 PDF]] | [[Media:ANAT2341_Lecture_1_-_Beverdam_-_Fertilization.pdf|2013]] | [http://embryology.med.unsw.edu.au/embryology/index.php?title=Lecture_-_Fertilization&oldid=96435 2012] | [http://embryology.med.unsw.edu.au/embryology/index.php?title=Lecture_-_Fertilization&oldid=60496 2011] | [[2010_Lecture_2|2010]] | [[2009_Lecture_2|2009]]
[[File:Cell division - 3 types.jpg|thumb|Cell division - 3 types]]
+
 
# Identify the key features of cell division.
+
==Lecture Objectives==
# Identify the stages and differences between mitosis and meiosis.
+
# Broad understanding of reproductive cycles.
# Understand the differences in male and female gamete meiosis.
+
# Understand the key features of gametogenesis.
# Understanding of gamete fusion during fertilization.
+
# Understand the differences in male and female gametogenesis.
 +
# Brief understanding of the differences between mitosis and meiosis.
 +
# Understanding of the events in fertilization.
  
 +
<gallery>
 +
File:Seminiferous tubule cartoon.jpg|Male - spermatogenesis
 +
File:Human ovary follicle development.jpg|Female - oogenesis
 +
</gallery>
  
==References==
+
==Lecture Resources==
===The Developing Human: Clinically oriented embryology===
+
{| class="wikitable mw-collapsible mw-collapsed"
{|
+
! Movies  &nbsp;
 +
|-
 +
| valign="bottom"|{{2016Lecture-Gametogenesis-Fertilization}}
 +
| valign="bottom"|{{Meiosis movie 1}}
 +
| valign="bottom"|{{Rabbit_ovulation_movie}}
 +
| valign="bottom"|{{Ovulation movie}}
 +
| valign="bottom"|{{Bovine oocyte movie 1}}
 +
| valign="bottom"|{{Spermatozoa movie}}
 +
| valign="bottom"|{{Spermatozoa motility movie}}
 
|-
 
|-
| [[File:The Developing Human, 9th edn.jpg|120px]]
+
| valign="bottom"|{{Human fertilization movie 1}}
| Keith L. Moore, T.V.N. Persaud, Mark G. Torchia. (2011). <i>The Developing Human: clinically oriented embryology</i> (9<sup>th</sup> ed.). Philadelphia: Saunders. Description: xix, 540 p. p. : ill., ports. Publisher: Philadelphia, PA : Saunders/Elsevier, c2013. ISBN: 9781437720020 (pbk.) NLM Unique ID: 101561564
+
| valign="bottom"|{{Human fertilization movie 2}}
 
+
| valign="bottom"|{{Fertilization movie 1}}
The following chapter links only work with a UNSW connection.
+
| valign="bottom"|{{Pronuclear Fusion movie}}
* [http://er.library.unsw.edu.au/er/cgi-bin/eraccess.cgi?url=http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-1-4377-2002-0..00001-1&isbn=978-1-4377-2002-0&uniqId=330028653-2#4-u1.0-B978-1-4377-2002-0..00001-1 Chapter 1 - Introduction to the Developing Human]
+
| valign="bottom"|{{Polar body movie 1}}
 
+
| valign="bottom"|{{Mitochondria movie 1}}
* [http://er.library.unsw.edu.au/er/cgi-bin/eraccess.cgi?url=http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-1-4377-2002-0..00002-3&isbn=978-1-4377-2002-0&uniqId=330028653-2#4-u1.0-B978-1-4377-2002-0..00002-3 Chapter 2 – First Week of Human Development]
 
 
|}
 
|}
  
===Larsen's human embryology===
+
{| class="wikitable mw-collapsible mw-collapsed"
{| border='0px'
+
! colspan=2|References  &nbsp;
 +
|-
 +
| {{MPT2015cover_citation}}
 +
| The following chapter links only work with a UNSW connection.
 +
* [http://ebookcentral.proquest.com.wwwproxy1.library.unsw.edu.au/lib/unsw/reader.action?docID=2074364&ppg=34 First Week of Human Development]
 +
|-
 +
| {{SBBFP2015cover_citation}}
 +
| The following chapter links only work with a UNSW connection.
 +
* [http://ebookcentral.proquest.com.wwwproxy1.library.unsw.edu.au/lib/unsw/reader.action?docID=2074524&ppg=32 Gametogenesis, Fertilization, and First Week]
 
|-
 
|-
| [[File:Larsen's human embryology 4th edn.jpg|90px]]
+
| {{Embryo logocitation}}
| '''Citation:''' Larsen's human embryology 4th ed. Schoenwolf, Gary C; Larsen, William J, (William James). Philadelphia, PA : Elsevier/Churchill Livingstone, c2009.
 
 
 
The following chapter links only work with a UNSW connection.
 
* [http://www.mdconsult.com/books/linkTo?type=bookPage&isbn=978-0-443-06811-9&eid=4-u1.0-B978-0-443-06811-9..10001-6 Chapter 1 - Gametogenesis, Fertilization, and First Week]
 
|}
 
 
 
===UNSW Embryology===
 
{|
 
| [[File:Logo.png|90px]]
 
| Hill, M.A. (2011) <i>UNSW Embryology</i> (11<sup>th</sup> ed.). Sydney:UNSW.
 
*  [[Menstrual Cycle|Menstrual Cycle]] | [[Oocyte]] | [[Spermatozoa]] | [[Cell Division - Meiosis|Meiosis]] | [[Cell Division - Mitosis|Mitosis]] | [[Week 1]]
 
|}
 
 
 
 
 
==Cell Cycle==
 
{|
 
| [[Image:Cell_cycle1.jpg|300px]]
 
 
 
The Cell Cycle
 
 
|  
 
|  
 
+
* {{Cell Division Links}}
* Cell Division (M phase, shown in red) is only a brief moment in the functional life (interphase; G1, S, G2 phases) of most eukaryotic cells.
+
* {{Menstrual cycle}} | {{oocyte}} | {{Zona pellucida}} | {{spermatozoa}} | {{Meiosis}} | {{Fertilization}} | {{Mitosis}} | [[Week 1]]
* Some cells cease cell division throughout life and are said to be in G0 phase.
 
* The eukaryotic cell cycle is regulated by 2 protein families known as cyclins and cyclin-dependent kinases.
 
* Cyclin protein levels within the cell nucleus change at different phases.
 
 
|}
 
|}
  
==Cell Division==
+
==Human Reproductive Cycle==
Development is 1 embryonic cell producing about 100,000,000,000,000 cells in the adult at any one time (over time with cell death and ongoing replacement this is substantially more).
 
  
[[Image:Historic_1882_mitosis_drawing.jpg|thumb|Historic drawing of mitosis]]
+
Sexual reproduction in most species is regulated by regular endocrine changes, or cycles, in the female. These cycles begin postnatally, function for variable times and can then decrease or cease entirely.
* [http://www.nature.com/celldivision/milestones/index.html Cell Division Milestones], Recent Nobel Prizes
 
  
'''Features Two Mechanical Processes'''  
+
* Human reproduction is regulated in females by the [[Menstrual Cycle|'''menstrual cycle''']], a regular cyclic hormonal change which coordinate changes in the ovary and internal reproductive tract. This cycle commences at puberty and ends at menopause.
* Mitosis - microtubule based segregation of chromosomes and formation of 2 nuclei
+
* Non-primates (rats, mice, horses, pig) reproduction is regulated in females by the [[Estrous_Cycle|'''estrous cycle''']] (British spelling, oestrous).
* Cytokinesis - microfilament based splitting of the cell cytoplasmic contents as a whole into 2 daughter cells
 
  
'''Features Two Types'''
+
{|
* Mitosis - occurs in all cells, producing genetically identical progeny.
+
! Female
* Meiosis - occurs only in germ cells (sperm=spermatozoa and egg=oocyte), producing genetically different progeny.
+
! Male
** progeny = daughter cells, offspring
 
 
 
===Cell Changes===
 
 
 
* Nucleus
 
** Chromosome condensation
 
** Nuclear envelope breakdown
 
 
 
* Cytoplasm
 
** Cytoskeleton reorganization
 
** Spindle formation (microtubule, MT) Contractile ring (microfilament, MF)
 
** Organelle redistribution
 
 
 
==Mitosis==
 
{| border='0px'
 
 
|-
 
|-
| [[File:Mitosis 01 icon.jpg|200px|link=Quicktime Movie_-_Mitosis_1]]
+
|
|-bgcolor="a3bfb1"
+
* [[Menstrual Cycle]] a regular cycle of reproduction (28 days)
| &nbsp;‎‎'''Mitosis'''
+
* begins at puberty, release of 1 egg (oocyte) every cycle
|-bgcolor="F5FFFA"
+
* Endocrine controlled (HPG axis) '''H'''ypothalamus - '''P'''ituitary - '''G'''onad
| [[Quicktime Movie_-_Mitosis_1|Quicktime]] | [[Movie_-_Mitosis 1|Flash]]
+
|
 +
* continuous production of sperm (spermatozoa)
 +
* begins at puberty, release millions of spermatozoa
 +
* Endocrine controlled (HPG axis) '''H'''ypothalamus - '''P'''ituitary - '''G'''onad
 
|}
 
|}
  
Mitosis Movie<ref><pubmed>12105179</pubmed></ref> See also [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5500 MCB Movie - The stages of mitosis and cytokinesis in an animal cell]
+
[[File:XXhpgaxis.jpg|300px]] [[File:Menstrual_cycle.png|500px]]
  
* Based on light microscopy of living cells light and electron microscopy of fixed and stained cells
 
* 5 Phases - prophase, prometaphase, metaphase, anaphase, and telophase
 
* Cytokinesis 6th stage overlaps the end of mitosis
 
  
Note that DNA duplication has occurred earlier in the S Phase of the cell cycle.
+
==Gametogenesis==
 +
The term "gametogenesis" describes the process of development of the haploid germ cells.
  
 +
{{Meiosis}} in the gonad (ovary or testis) produces the female and male haploid gametes, {{oocyte}} (egg) and {{spermatozoa}} (sperm).
  
===Prophase ===
+
Meiosis time course and final gamete number differs between female and male.
* Chromosome DNA has been earlier duplicated (S Phase)
 
* Chromosomes begin condensing
 
* Chromosome pairs (chromatids) held together at centromere
 
* Microtubules disassemble
 
* Mitotic spindle begins to form
 
* Prophase ends when nuclear envelope breaks down
 
  
===Prometaphase===
 
  
* Microtubules now enter nuclear region
+
===Male - Spermatogenesis===
* Nuclear envelope forms vesicles around mitotic spindle
+
[[File:Human-spermatozoa EM01.jpg|600px]]
* Kinetochores form on centromere attach to some MTs of spindle
 
* Prometaphase ends when chromosomes move to metaphase plate
 
  
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5509 MCB Movie - Centromeric attachment of microtubules]
+
Human spermatozoa (electron microscope)
  
===Metaphase===
+
[[File:Mouse-_spermatozoa_EM_and_diagram.jpg|600px]]
[[Image:Mitosis_-_Metaphase.jpg]]
 
[[Image:Mitosis_fl.jpg|thumb|Metaphase fluorescent image of Mitotic spindle and Chromosomes]]
 
* Kinetochore MTs align chromosomes in one midpoint plane
 
* Metaphase ends when sister kinetochores separate
 
  
===Anaphase===
+
Mouse spermatozoa (electron microscope)
* Separation of sister Kinetochores
 
* shortening of Kinetochore microtubules pulls chromosome to spindle pole
 
* Anaphase ends as nuclear envelope (membrane) begins to reform
 
  
===Telophase===
+
The testes have two functions.
 +
# produce the male gametes or '''spermatozoa'''
 +
# produce male sexual hormone, '''testosterone''' (internal and external genitalia, sex characteristics)
 +
<gallery>
 +
File:Historic-testis.jpg|Historic testis drawing
 +
File:Testis_histology_006.jpg|Child Seminiferous tubule
 +
File:Seminiferous-tubule-HEx40.jpg|Adult Seminiferous tubule
 +
File:Testis_histology_2.jpg|Seminiferous tubule cross-section and supporting cells
 +
File:Human-spermatozoa.jpg|Human spermatozoa
 +
File:Spermatozoa histology 003.jpg|Human Spermatozoa
 +
</gallery>
  
* Chromosomes arrive at spindle poles
+
Human spermatozoa take about '''48 days''' from entering meiosis until morphologically mature spermatozoa.
* Kinetochore MTs lost
+
{|
* Condensed chromosomes begin expanding
+
|
** Continues through cytokinesis
+
* '''Spermatogonia''' - are the diploid first cells of spermatogenesis
 +
* '''Primary spermatocytes''' - large, enter the prophase of the first meiotic division
 +
* '''Secondary spermatocytes'''  - small, complete the second meiotic division
 +
* '''Spermatid''' - immature spermatozoa
 +
* '''Spermatozoa''' - differentiated gamete
  
===Cytokinesis===
+
::'''Spermatozoa development:''' [[P#primordial germ cell|primordial germ cell]] -  [[S#spermatogonia|spermatogonia]] - [[P#primary spermatocyte|primary spermatocyte]] - [[S#secondary spermatocyte|secondary spermatocytes]] - [[S#spermatid|spermatid]] - [[S#spermatozoa|spermatozoa]]
* Division of cytoplasmic contents
 
* Contractile ring forms at midpoint under membrane
 
* Microfilament ring Contracts forming cleavage furrow
 
* Eventually fully divides cytoplasm
 
  
=== Cell Organelles ===
+
'''Sertoli cells''' (support cells)
  
* Mitochondria - Divide independently of cell mitosis, distributed into daughter cells
+
'''Interstitial cells''' or Leydig cells (produce hormone)
* Peroxisomes - localise at spindle poles
+
| [[File:Seminiferous tubule cartoon.jpg|600px]]
* Endoplasmic Reticulum - associated with the nuclear envelope vesicles.
+
|}
* Golgi Apparatus- Golgi stack undergoes a continuous fragmentation process, fragments are distributed into daughter cells, then reassembled into new Golgi stacks
 
  
==Meiosis==  
+
===Female - Oogenesis===
[[File:Mitosis and meiosis.jpg|800px]]
+
The ovaries have two functions.
 +
# produce the female gametes or '''oocytes'''
 +
# produce female hormones, [[E#estrogen|estrogen]] and [[P#progesterone|progesterone]] (secondary sex characteristics, menstrual cycle)
 +
<gallery>
 +
File:Infant_ovary.jpg|infant ovary
 +
File:Ovary5x.gif|overview of ovary
 +
File:Ovary10x.jpg|three stages of follicle development
 +
File:Ova41he.jpg|primary follicle
 +
File:Ova20he.jpg|tertiary follicle
 +
</gallery>
  
Meiosis Germ cell division (haploid)
+
In an adult human female the development of a primordial follicle containing an oocyte to a preovulatory follicle takes in excess of '''120 days'''.
* Reductive division
+
{|
* Generates haploid gametes (egg, sperm)
+
| [[File:Human_ovary_follicle_development.jpg|600px]]
* Each genetically distinct from parent
 
  
* Genetic recombination (prophase 1)
+
Human Follicle Development
** Exchanges portions of chromosomes maternal/paternal homologous pairs
+
| [[File:Human ovulation 01.jpg|300px|]]
* Independent assortment of paternal chromosomes (meiosis 1)
 
  
Homologous chromosomes pairing unique to meiosis
+
Human Ovulation
 +
|}
 +
Human ovary follicle development
  
* Each chromosome duplicated and exists as attached sister chromatids before pairing occurs
+
::'''Ovarian Follicle Stages:''' [[P#primordial follicle|primordial follicle]] - [[P#primary_follicle|primary follicle]] - [[S#secondary_follicle|secondary follicle]] - [[T#tertiary_follicle|tertiary follicle]] - [[P#preovulatory_follicle|preovulatory follicle]]
* Genetic Recombination shown by chromosomes part red and part black
 
** chromosome pairing in meiosis involves crossing-over between homologous chromosomes
 
  
'''Meiosis I and II'''
 
* Meiosis I separates the pairs of homologous chromosomes, reduces the cell from diploid to haploid.
 
* Meiosis II separates each chromosome into two chromatids (chromosome behavior in meiosis II is like that of mitosis).
 
  
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2486 Figure 14.32. Comparison of meiosis and mitosis]
+
'''Follicle cells''' (support cells) '''Theca cells''' (produce hormone)
  
===Prophase I===
+
{| class="wikitable mw-collapsible mw-collapsed"
* The homologous chromosomes pair and exchange DNA to form recombinant chromosomes.
+
! colspan=2|Ovulation Movie  &nbsp;
* Prophase I is divided into five phases:
+
|-
** '''Leptotene''' - chromosomes start to condense.
+
| <html5media height="300" width="370">File:Follicle_001.mp4</html5media>
** '''Zygotene''' - homologous chromosomes become closely associated (synapsis) to form pairs of chromosomes consisting of four chromatids (tetrads).
 
** '''Pachytene''' - crossing over between pairs of homologous chromosomes to form chiasmata (form between two nonsister chromatids at points where they have crossed over)
 
** '''Diplotene''' - homologous chromosomes begin to separate but remain attached by chiasmata.
 
** '''Diakinesis''' - homologous chromosomes continue to separate, and chiasmata move to the ends of the chromosomes.
 
  
===Prometaphase I===
+
[[Media:Follicle_001.mp4|'''Click Here''' to play on mobile device]]
* Spindle apparatus formed, and chromosomes attached to spindle fibres by kinetochores.
+
| <html5media height="270" width="320">File:Ovulation 001.mp4</html5media>
  
===Metaphase I===
+
[[Media:Ovulation 001.mp4|'''Click Here''' to play on mobile device]]
* Homologous pairs of chromosomes (bivalents) arranged as a double row along the metaphase plate. The arrangement of the paired chromosomes with respect to the poles of the spindle apparatus is random along the metaphase plate. (This is a source of genetic variation through random assortment, as the paternal and maternal chromosomes in a homologous pair are similar but not identical. The number of possible arrangements is 2n, where n is the number of chromosomes in a haploid set. Human beings have 23 different chromosomes, so the number of possible combinations is 223, which is over 8 million.)
+
|}
===Anaphase I===
 
The homologous chromosomes in each bivalent are separated and move to the opposite poles of the cell.
 
  
===Telophase I===
+
==Meiosis Differences==
The chromosomes become diffuse and the nuclear membrane reforms.
+
{| class="wikitable mw-collapsible mw-collapsed"
 +
! Types of Cell Division &nbsp;
 +
|-
 +
|  [[File:Cell division - 3 types.jpg|500px]]
  
===Cytokinesis I===
+
There are 3 types of cell division that can occur.
* Cellular cytoplasmic division to form two new cells, followed by Meiosis II.
+
# Binary fission - occurs in prokaryotes.
 +
# Mitosis - occurs in all eukaryotic cells.
 +
# Meiosis - occurs only in sex cell development.
 +
|}
 +
===Male Meiosis===
 +
{|
 +
|
 +
* Meiosis initiated continuously in a mitotically dividing stem cell population
 +
* 4 gametes produced / meiosis
 +
* Meiosis completed in days or weeks
 +
* Meiosis and differentiation proceed continuously without cell cycle arrest
 +
* Differentiation of gamete occurs while haploid after meiosis ends
 +
* Sex chromosomes excluded from recombination and transcription during first meiotic prophase
  
===Prophase II===
+
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3734 MBoC - Figure 20-27. The stages of spermatogenesis]
* Chromosomes begin to condense, nuclear membrane breaks down and spindle forms.
+
| [[File:Male gametogenesis.jpg|300px|alt=Male gametogenesis cartoon]]
  
===Metaphase II===
+
Male gametogenesis
* Spindle fibres attach to chromosomes, chromosomes align in cell centre.
+
|}
  
===Anaphase II===
+
===Female Meiosis===
* Chromosomes separate and move to the opposite poles of the cell.
+
{|
 
+
|
===Telophase II===
 
* Chromosomes reach spindle pole ends and the nuclear membrane reforms.
 
 
 
===Cytokinesis===
 
Cellular cytoplasmic division to form new cells.
 
 
 
===Comparison of Meiosis/Mitosis===
 
[http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis McGraw-Hill Animation comparing Mitosis and Meiosis]
 
[[Image:Mitosis_meiosis1.jpg|thumb|Comparison of Mitosis and Meiosis]]
 
* After DNA replication 2 nuclear (and cell) divisions required to produce haploid gametes
 
* Each diploid cell in meiosis produces 4 haploid cells (sperm) 1 haploid cell (egg)
 
* Each diploid cell mitosis produces 2 diploid cells
 
 
 
==Meiosis Differences==
 
===Female - Oogenesis===
 
[[File:Female gametogenesis.jpg|thumb|Female gametogenesis]]
 
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2492 The Cell - Figure 14.37. Meiosis of vertebrate oocytes]
 
 
* Meiosis initiated once in a finite population of cells  
 
* Meiosis initiated once in a finite population of cells  
 
* 1 gamete produced / meiosis  
 
* 1 gamete produced / meiosis  
Line 253: Line 227:
 
* All chromosomes exhibit equivalent transcription and recombination during meiotic prophase
 
* All chromosomes exhibit equivalent transcription and recombination during meiotic prophase
  
===Male - Spermatogenesis===
+
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2492 The Cell - Figure 14.37. Meiosis of vertebrate oocytes]
[[File:Male gametogenesis.jpg|thumb|Male gametogenesis]]
+
| [[File:Female gametogenesis.jpg|300px|alt=Female gametogenesis cartoon]]
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3734 MBoC - Figure 20-27. The stages of spermatogenesis]
+
 
* Meiosis initiated continuously in a mitotically dividing stem cell population
+
Female gametogenesis
* 4 gametes produced / meiosis
+
|}
* Meiosis completed in days or weeks
 
* Meiosis and differentiation proceed continuously without cell cycle arrest
 
* Differentiation of gamete occurs while haploid after meiosis ends
 
* Sex chromosomes excluded from recombination and transcription during first meiotic prophase
 
  
 
===Polar Bodies===
 
===Polar Bodies===
[[Image:Early zygote.jpg|thumb|Early zygote showing polar bodies]]
+
{|
 +
|
 
* In female gametogenesis only a single (1) haploid egg is produced from meiosis. In male gametogenesis four (4) haploid sperm are produced from meiosis. So what happens to all the extra DNA in producing this single egg?
 
* In female gametogenesis only a single (1) haploid egg is produced from meiosis. In male gametogenesis four (4) haploid sperm are produced from meiosis. So what happens to all the extra DNA in producing this single egg?
** In Meiosis 1 the "extra" DNA is excluded to the periphery as a 1st polar body, which encloses the extra DNA.
+
** Meiosis 1 the "extra" DNA is excluded to the periphery as a '''1st polar body''', which encloses the extra DNA.
** In Meiosis 2 the "extra" DNA is once again excluded as a 2nd polar body. The first polar body may also under go meiosis 2 producing a 3rd polar body.
+
** Meiosis 2 the "extra" DNA is once again excluded as a '''2nd polar body'''. The first polar body may also under go meiosis 2 producing a '''3rd polar body'''.
 
* These polar bodies are not gametes.  
 
* These polar bodies are not gametes.  
* Polar bodies appear to have no other function other than to dispose of the extra DNA in oogenesis.
+
** Polar bodies have no other function other than to dispose of the extra DNA in oogenesis.  
** Recent research in mice suggest that the position of oocyte polar body may influence fertilization site.
+
** Though recent research in mice suggest that oocyte polar body position may influence fertilization site.
 +
| [[File:Early zygote labelled.jpg|300px]]
 +
 
 +
Early zygote showing polar bodies
 +
|}
 +
 
 +
{| class="wikitable mw-collapsible mw-collapsed"
 +
! Meiosis Polar Body Movie &nbsp;
 +
|-
 +
| <html5media height="400" width="800">File:Oocyte_Meiosis_01.mp4</html5media>
 +
 
 +
[[Media:Oocyte_Meiosis_01.mp4|'''Click Here''' to play on mobile device]]
 +
 
 +
This movie shows labelled DNA (blue) of the mouse oocyte in meiosis 1 segregating DNA to the first polar body. The fluorescence image shows labelled actin (green) that lies directly under the plasma membrane of the oocyte and polar body.
 +
 
 +
{{Meiosis movie 1}}
 +
|}
  
 
== Fertilization ==
 
== Fertilization ==
[[File:Mark Hill icon.jpg]] Gamete formation, menstrual cycle and fertilization will also be covered in this week's Laboratory. We may not complete all content shown below within the lecture.
 
  
Fertilization is the complete process resulting in the fusion of haploid gametes, egg and sperm, to form the diploid zygote. The recent development of aided fertilization is described as in vitro fertilization (in vitro = "in glass", outside the body, IVF). Clinically, all these aided fertilization techniques are grouped as Assisted Reproductive Technologies or ART.
+
Gamete formation, menstrual cycle and fertilisation will also be covered in detail in this week's Laboratory. Fertilization is the complete process resulting in the fusion of haploid gametes, egg and sperm, to form the diploid zygote. The recent development of aided fertilization is described as in vitro fertilization (in vitro = "in glass", outside the body, IVF). Clinically, all these aided fertilization techniques are grouped as Assisted Reproductive Technologies or ART.
 +
 
 +
* Oogenesis - 1 gamete produced/meiosis + 3 polar bodies, meiosis is slow, 1 egg produced and released at ovulation
 +
* Spermatogenesis -  4 gametes produced/meiosis, meiosis is fast, 200-600 million sperm released at ejaculation
 +
 
 +
{| class="wikitable mw-collapsible mw-collapsed"
 +
! Fertilization Movies &nbsp;
 +
|-
 +
| colspan=4|<html5media height="500" width="640">File:Human fertilization 01.mp4</html5media>
 +
 
 +
[[Media:Human fertilization 01.mp4|'''Click Here''' to play on mobile device]]
 +
|-
 +
| valign="bottom"|{{Fertilization movie 1}}
 +
| valign="bottom"|{{Human fertilization movie 1}}
 +
| valign="bottom"|{{Human fertilization movie 2}}
 +
| valign="bottom"|{{Fertilization movie 2}}
 +
|}
 +
===Fertilization Site===
 +
[[File:Human_uterine_tube_ciliated_epithelium_SEM.jpg|thumb|300px|Human uterine tube ciliated epithelium]]
 +
* Fertilization resulting in embryo development usually occurs in first 1/3 of uterine tube (oviduct, Fallopian tube)
 +
* The majority of fertilized oocytes do not go on to form an embryo
 +
* Fertilization can also occur outside uterine tube associated with {{Assisted Reproductive Technology}} (IVF, GIFT, ZIFT...) and [[E#ectopic pregnancy|ectopic pregnancy]] 
 +
* Oocyte ovulation - release from the ovary with associated cells, into peritoneal cavity, uterine tube fimbria then into uterine tube (oviduct, uterine horn, fallopian tube) and epithelial cilia mediated movement.
 +
* Spermatozoa ejaculation - deposited in vagina, movement of tail to "swim" in uterine secretions through cervix, uterine body and into uterine tube, have approximately 24-48h to fertilize oocyte.
  
===Fertilization Preparation===
+
Prior to the fertilization process commencing both the gametes complete of a number of biological processes.
Prior to the fertilization process commencing both the gametes oocyte (egg) and spermatozoa (sperm) require completion of a number of biological processes.
 
  
 
* '''Oocyte Meiosis''' - completes Meiosis 1 and commences Meiosis 2 (arrests at Metaphase II).
 
* '''Oocyte Meiosis''' - completes Meiosis 1 and commences Meiosis 2 (arrests at Metaphase II).
 
* '''Spermatozoa Capacitation''' - following release (ejaculation) and mixing with other glandular secretions, activates motility and acrosome preparation.
 
* '''Spermatozoa Capacitation''' - following release (ejaculation) and mixing with other glandular secretions, activates motility and acrosome preparation.
* '''Migration''' - both Oocyte and Spermatozoa.
+
* '''Migration''' - both oocyte and spermatozoa.
**  oocyte ovulation and release with associated cells,  from ovary into fimbria then into uterine tube (oviduct, uterine horn, fallopian tube) and epithelial cilia mediated movement.
+
 
** spermatozoa ejaculation, deposited in vagina, movement of tail to "swim" in uterine secretions through cervix, uterine body and into uterine tube, have approximately 24-48h to fertilize oocyte.
 
 
[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=endocrin&part=A972&rendertype=box&id=A1230 Endocrinology - Diagram of the comparative anatomy of the male and female reproductive tracts]
 
[http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=endocrin&part=A972&rendertype=box&id=A1230 Endocrinology - Diagram of the comparative anatomy of the male and female reproductive tracts]
  
===Oogenesis===
+
{| class="wikitable mw-collapsible mw-collapsed"
[[Oocyte_Development|Oocyte Development (Oogenesis)]]  
+
! Gamete Movement Movies &nbsp;
[[Image:Ovary5x.gif|thumb|Histology of the Ovary]]
+
|-
[[Image:Ova41he.jpg|thumb|Preantral Follicle]]
+
| Oocyte Motility
[[Image:ova20he.jpg|thumb|Antral Follicle and Oocyte]]
+
 
 +
<html5media height="500" width="640">File:Bovine uterine tube oocyte transport 1.mp4</html5media>
 +
 
 +
[[Media:Bovine uterine tube oocyte transport 1.mp4|'''Click Here''' to play on mobile device]] | [[Bovine_Oocyte_Transport_Movie|More information]]
 +
|-
 +
| Spermatozoa Motility
 +
 
 +
<html5media height="520" width="512">File:Spermatozoa_motility_01.mp4</html5media>
 +
 
 +
[[Media:Spermatozoa_motility_01.mp4|'''Click Here''' to play on mobile device]] | [[Human_Spermatozoa_Motility_Movie|More information]]
 +
|}
 +
 
 +
===Fertilization - Male===
 +
[[File:Human-spermatozoa.jpg|thumb|Human spermatozoa (light microscope)]]
 +
[[Spermatozoa Development|Spermatozoa]]: Ejaculation - Capacitation - Spermatozoa motility - Chemotaxis - Binding to zona pellucida - Acrosome reaction - Membrane fusion
  
* Process of oogonia mature into oocytes (ova, ovum, egg)
+
'''Ejaculation'''
* all oogonia form primary oocytes before birth, therefore a maturation of preexisting cells in the female gonad, ovary
+
* about 3.5 ml, containing 200 - 600 million spermatozoa
[[Image:Oocytenumber.jpg|300px]]
+
* by volume less than 10 % spermatozoa
* humans usually only 1 ovum released every menstrual cycle (IVF- superovulation)  
+
* accessory glands contribute majority of volume (60 % seminal vesicle, 10 % bulbourethral, 30 % prostate)
* oocyte and its surrounding cells = follicle
 
* primary -> secondary -> ovulation releases
 
  
Ovary- Histology - whole transverse section (cortex, medulla)  
+
'''Male Infertility'''
 +
* Oligospermia (Low Sperm Count) - less than 20 million sperm after 72 hour abstinence from sex
 +
* Azoospermia (Absent Sperm) - blockage of duct network
 +
* Immotile Cilia Syndrome - lack of sperm motility
  
====Menstrual Cycle====
+
'''Capacitation'''
 +
* spermatozoa activation process - removal of glycoprotein coat and seminal proteins and alteration of sperm mitochondria
  
* Primary Oocyte - arrested at early Meiosis 1
+
'''Spermatozoa motility'''
** diploid: 22 chromosome pairs + 1 pair X chromosomes (46, XX)
+
* tail of spermatozoa provide movement by microtubules
** autosomes and sex chromosome
+
* energy for this movement is provided by mitochondria in tail initial segment
  
* Oogenesis- pre-antral then antral follicle (Graafian follicle is mature antral follicle released)
+
'''Chemotaxis'''
* Secondary oocyte  
+
* oocyte cumulus cells release '''progesterone''' (may also be other oocyte and follicular fluid factors)
** 1 Day before ovulation completes (stim by LH) Meiosis 1
 
** haploid: 22 chromosomes + 1 X chromosome (23, X)
 
** nondisjunction- abnormal chromosome segregation
 
** begins Meiosis 2 and arrests at metaphase
 
** note no interphase replication of DNA, only fertilization will complete Meiosis 2
 
  
====Ovulation (HPG Axis)====
+
'''Spermatozoa Binding'''
[[Image:XXhpgaxis.gif|300px|HPG Axis]]
+
* Zona pellucida protein ZP3 acts as receptor for spermatozoa binding (species specific)
* Hypothalmus releases gonadotropin releasing hormone (GRH, luteinizing hormone–releasing hormone, LHRH) -> Pituitary releases follicle stimulating hormone (FSH) and lutenizing hormone (LH) -> ovary follicle development and ovulation.
 
** release of the secondary oocyte and formation of corpus luteum
 
** secondary oocyte encased in zona pellucida and corona radiata
 
* Ovulation associated with follicle rupture and ampulla movement.
 
  
====Zona Pellucida====
+
[[File:Model of gamete recognition zona pellucida.jpg|500px]]
[http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.figgrp.3722 MBoC - Figure 20-21. The zona pellucida]
 
* glycoprotein shell ZP1, ZP2, ZP3
 
* mechanical protection of egg
 
* involved in the fertilization process
 
* sperm binding
 
* adhesion of sperm to egg
 
* acrosome reaction
 
** releases enzymes to locally breakdown
 
* block of polyspermy
 
** altered to prevent more than 1 sperm penetrating
 
** may also have a role in development of the blastocyst
 
  
====Corona Radiata====
+
Acrosome Reaction
* granulosa cells and extracellular matrix
+
* exocytosis of acrosome contents (calcium mediated) [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3741 MBoC - Figure 20-31. The acrosome reaction that occurs when a mammalian sperm fertilizes an egg]
* protective and nutritional role for cells during transport
+
* enzymes to digest the zona pellucida
* cells are also lost during transport along oviduct
+
* exposes sperm surface proteins to bind ZP2
  
===Gamete formation- Spermatogenesis===
+
Membrane fusion
[[Spermatozoa Development|Spermatozoa Development (Spermatogenesis)]]
+
* between spermatozoa and oocyte cell membranes, allows sperm nuclei passage into egg cytoplasm
* process of spermatagonia mature into spermatazoa (sperm)
+
* membrane fusion also initiates oocyte processes to block polyspermy
* continuously throughout life occurs in the seminiferous tubules in the male gonad- testis (plural testes)
 
* at puberty spermatagonia activate and proliferate (mitosis)
 
* primary spermatocyte -> secondary spermatocyte-> spermatid->sperm  
 
* Seminiferous Tubule is site of maturation involving meiosis and spermiogenesis
 
  
* Spermatogenesis- Meiosis  
+
===Fertilization - Oocyte===
* meiosis is reductive cell division
+
[[Oocyte Development|Oocyte]]: Membrane depolarization - Cortical reaction - Meiosis 2 completion
** 1 spermatagonia (diploid) 46, XY (also written 44+XY) = 4 sperm (haploid); 23, X    23, X  23, Y  23, Y
+
[[File:Human_MII_oocyte_02.jpg|thumb|300px|alt=Human MII oocyte cortical granules|Human MII oocyte cortical granules]]
 +
Membrane Depolarization
 +
* caused by spermatozoa membrane fusion, acts as primary block to polyspermy (fertilisation by more than one spermatozoa)
  
====Spermiogenesis====
+
Cortical Reaction
* morphological (shape) change from round spermatids to elongated sperm
 
* loose cytoplasm
 
* Transform golgi apparatus into acrosome (in head)
 
* Organize microtubules for motility (in tail, flagellum)
 
* Segregate mitochondria for energy (in tail)
 
  
====Ejaculate====
+
* Inositol triphosphate (IP3) pathway elevates intracellular calcium, exocytosis of cortical granules
+
* enzyme alters ZP2 so it will no longer bind sperm plasma membrane
* By volume <10 % sperm and accessory glands contribute majority of volume (60 % seminal vesicle, 10 % bulbourethral, 30 % prostate)
+
* [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3743 MBoC - Figure 20-32. How the cortical reaction in a mouse egg is thought to prevent additional sperm from entering the egg]
* 3.5 ml, 200-600 million sperm
 
* Capacitation is the removal of glycoprotein coat and seminal proteins and alteration of sperm mitochondria
 
* Infertility can be due to Oligospermia, Azoospermia, Immotile Cilia Syndrome
 
** Oligospermia (Low Sperm Count) - less than 20 million sperm after 72 hour abstinence from sex
 
** Azoospermia (Absent Sperm) - blockage of duct network
 
** Immotile Cilia Syndrome - lack of sperm motility
 
  
===Fertilization Site===
+
Meiosis 2
* Fertilization usually occurs in first 1/3 of oviduct
+
* completion of 2nd meiotic division
* Fertilization can also occur outside oviduct, associated with In Vitro Fertilization (IVF, GIFT, ZIFT...) and ectopic pregnancy 
+
* forms second polar body (third polar body may be formed by meiotic division of the first polar body)  
* The majority of fertilized eggs do not go on to form an embryo
 
  
Fertilization - Spermatozoa
 
* '''Sperm Binding''' - zona pellucida protein ZP3 acts as receptor for sperm
 
* '''Acrosome Reaction''' - exyocytosis of acrosome contents (Calcium mediated) [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3741 MBoC - Figure 20-31. The acrosome reaction that occurs when a mammalian sperm fertilizes an egg]
 
** enzymes to digest the zona pellucida
 
** exposes sperm surface proteins to bind ZP2
 
* '''Membrane Fusion''' - between sperm and egg, allows sperm nuclei passage into egg cytoplasm
 
  
Fertilization- Oocyte
+
===Formation of the Zygote===
* '''Membrane Depolarization''' - caused by sperm membrane fusion, primary block to polyspermy
+
{|
* '''Cortical Reaction''' - IP3 pathway elevates intracellular Calcium, exocytosis of cortical granules [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3743 MBoC - Figure 20-32. How the cortical reaction in a mouse egg is thought to prevent additional sperm from entering the egg]
+
! Early Zygotes
** enzyme alters ZP3 so it will no longer bind sperm plasma membrane
+
|-
* '''Meiosis 2''' - completion of 2nd meiotic division
+
| [[File:Early_zygote_labelled.jpg|320px|alt=Image of early human zygote]]
** forms second polar body (a third polar body may be formed by meiotic division of the first polar body)
+
| [[File:Mouse_zygote_pronuclei_01.jpg|300px|alt=Image of early mouse zygote]]
 +
|-
 +
| Human Zygote
 +
| Mouse Zygote
 +
|}
  
====Formation of the Zygote====
 
[[Image:Early zygote.jpg|thumb|Early human zygote showing Pronuclei]]
 
 
* Pronuclei - Male and Female haploid nuclei approach each other and nuclear membranes break down  
 
* Pronuclei - Male and Female haploid nuclei approach each other and nuclear membranes break down  
 
* chromosomal pairing, DNA replicates, first mitotic division  
 
* chromosomal pairing, DNA replicates, first mitotic division  
Line 397: Line 382:
 
* Oocyte contributes - mitochondria (maternally inherited)
 
* Oocyte contributes - mitochondria (maternally inherited)
  
====Sex Determination====  
+
===Sex Determination===
 
* based upon whether an X or Y carrying sperm has fertilized the egg, should be 1.0 sex ratio.  
 
* based upon whether an X or Y carrying sperm has fertilized the egg, should be 1.0 sex ratio.  
 
* actually 1.05, 105 males for every 100 females, some studies show more males 2+ days after ovulation.
 
* actually 1.05, 105 males for every 100 females, some studies show more males 2+ days after ovulation.
Line 411: Line 396:
  
 
==Abnormalities==
 
==Abnormalities==
[[Image:Trisomy21arrow.gif]][[Image:trisomy21female.jpg|300px]][[Image:trisomy21male.jpg|300px]]
+
[[File:Trisomy21arrow.gif]][[File:trisomy21female.jpg|300px]][[File:trisomy21male.jpg|300px]]
  
 
* The most common chromosome abnormality is '''aneuploidy''', the gain or loss of whole chromosomes.  
 
* The most common chromosome abnormality is '''aneuploidy''', the gain or loss of whole chromosomes.  
 
* Caused by '''meiotic nondisjunction''', the failure of chromosomes to correctly separate homologues during meiosis I or sister chromatids during meiosis II.
 
* Caused by '''meiotic nondisjunction''', the failure of chromosomes to correctly separate homologues during meiosis I or sister chromatids during meiosis II.
* Down Syndrome - caused by an extra copy of chromosome 21. [[Trisomy 21|Abnormal Development - Trisomy 21 (Down Syndrome)]]
+
* Down Syndrome - caused by an extra copy of chromosome 21. {{Trisomy 21}} (Down Syndrome)[[Genetic_risk_maternal_age|Maternal Age]]
  
 
* '''Chromosomal translocations''' occur when there is an inappropriate exchange of chromosomal material. [http://visualsonline.cancer.gov/retrieve.cfm?imageid=7153&dpi=72&fileformat=jpg Philadelphia chromosome]
 
* '''Chromosomal translocations''' occur when there is an inappropriate exchange of chromosomal material. [http://visualsonline.cancer.gov/retrieve.cfm?imageid=7153&dpi=72&fileformat=jpg Philadelphia chromosome]
 
* Philadelphia chromosome - piece of Chr9 exchanged with Chr22 Generates truncated abl, overstimulates cell production, leads to chronic myelogenous leukemia
 
* Philadelphia chromosome - piece of Chr9 exchanged with Chr22 Generates truncated abl, overstimulates cell production, leads to chronic myelogenous leukemia
 +
 +
[[File:Hydatidiform mole.jpg|300px|link=Abnormal Development - Hydatidiform Mole|Hydatidiform Mole]]
 +
 +
[[Abnormal Development - Hydatidiform Mole|Hydatidiform Mole]]
 +
 +
* '''Complete Mole''' - Only paternal chromosomes (no oocyte nucleus contribution)
 +
* '''Partial Mole''' - 3 sets of chromosomes ( (triploidy) instead of the usual 2 (2 spermatozoa contribution)
 +
  
 
==UNSW Embryology Links==
 
==UNSW Embryology Links==
* {{Template:Cell Division Links}} | [[2010_Lecture_2|Lecture 2 2010]]
+
* {{spermatozoa}} {{oocyte}} {{fertilization}} {{Trisomy 21}} (Down Syndrome)
* [[Trisomy 21|Trisomy 21 (Down Syndrome)]]
+
 
* [[Fertilization]] |
+
 
* [http://php.med.unsw.edu.au/cellbiology/index.php?title=2011_Lecture_16 ANAT3231 Cell Division]
+
{{Cell Division Links}}
  
 
== References ==
 
== References ==
 
<references/>
 
<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 1
 
  
 
===Online Textbooks===
 
===Online Textbooks===
Line 437: Line 426:
 
* '''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 - IV. Internal Organization of the Cell Chapter 17. The Cell Cycle and Programmed Cell Death [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.chapter.3167 Programmed Cell Death] |  [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.section.3169 An Overview of the Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.figgrp.3168 Figure 17-1.  The cell cycle] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.section.3738 Fertilization]
 
* '''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 - IV. Internal Organization of the Cell Chapter 17. The Cell Cycle and Programmed Cell Death [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.chapter.3167 Programmed Cell Death] |  [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.section.3169 An Overview of the Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mboc4.figgrp.3168 Figure 17-1.  The cell cycle] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mboc4.section.3738 Fertilization]
 
* '''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  [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.chapter.3432 Regulation of the Eukaryotic Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.section.3463 Overview of the Cell Cycle and Its Control] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.figgrp.3467 Figure 13-2.  Current model for regulation of the eukaryotic cell cycle] | '''Movies''' [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5522 Proposed alternative mechanisms for chromosome congression.] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5509 Centromeric attachment of microtubules.] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5500 The stages of mitosis and cytokinesis in an animal cell.]
 
* '''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  [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.chapter.3432 Regulation of the Eukaryotic Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.section.3463 Overview of the Cell Cycle and Its Control] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=mcb.figgrp.3467 Figure 13-2.  Current model for regulation of the eukaryotic cell cycle] | '''Movies''' [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5522 Proposed alternative mechanisms for chromosome congression.] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5509 Centromeric attachment of microtubules.] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=mcb.figgrp.5500 The stages of mitosis and cytokinesis in an animal cell.]
 
 
* '''The Cell - A Molecular Approach''' by Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000-  IV. Cell Regulation  Chapter 14. The Cell Cycle [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=cooper.section.2433 The Eukaryotic Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=cooper.figgrp.2435 Figure 14.1.  Phases of the cell cycle] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2486 Figure 14.32. Comparison of meiosis and mitosis] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2492 Figure 14.37. Meiosis of vertebrate oocytes]
 
* '''The Cell - A Molecular Approach''' by Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000-  IV. Cell Regulation  Chapter 14. The Cell Cycle [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=cooper.section.2433 The Eukaryotic Cell Cycle] | [http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?db=Books&rid=cooper.figgrp.2435 Figure 14.1.  Phases of the cell cycle] | [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?&rid=cooper.figgrp.2486 Figure 14.32. Comparison of meiosis and mitosis] | [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]
 
* '''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]
  
 +
* MBoC [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mboc4.figgrp.3716 MBoC - Figure 20-18. Influence of Sry on gonad development]
 +
* Endocrinology [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=endocrin&part=A972&rendertype=box&id=A1230 Endocrinology - Comparative anatomy of male and female reproductive tracts]
 
===Search ===
 
===Search ===
  
Line 449: Line 439:
 
====Reviews====
 
====Reviews====
  
* Cell cycle studies based upon quantitative image analysis. Stacey DW, Hitomi M. Cytometry A. 2008 Apr;73(4):270-8. Review. [http://www.ncbi.nlm.nih.gov/pubmed/18163464 PMID: 18163464]
+
<pubmed>18163464</pubmed>
* Analysis of cell cycle phases and progression in cultured mammalian cells. Schorl C, Sedivy JM. Methods. 2007 Feb;41(2):143-50. Review. [http://www.ncbi.nlm.nih.gov/pubmed/17189856 PMID: 17189856]
+
<pubmed>17189856</pubmed>
 +
 
 +
 
 +
==Terms==
 +
 
 +
{{Spermatozoa Terms}}
  
====Articles====
 
  
 
== External Links ==
 
== External Links ==
 +
{{External Links}}
  
*  JCB - Movie Collection [http://jcb.rupress.org/misc/annotatedvideo.shtml#Mitosis Mitosis] | [http://jcb.rupress.org/misc/annotatedvideo.shtml#Cytokinesis Cytokinesis]
 
* '''2008'''  ANAT3231 Lecture PDF lecture14-15 [http://cellbiology.med.unsw.edu.au/units/pdf/08L14-15s1.pdf 1 slide/page (view)] | [http://cellbiology.med.unsw.edu.au/units/pdf/08L14-15s4.pdf 4 slides/page (print)] | [http://cellbiology.med.unsw.edu.au/units/pdf/08L14-15s6.pdf 6 slides/page (print)] | [http://cellbiology.med.unsw.edu.au/units/pdf/08L14-15txt.pdf text (print)]
 
 
*  McGraw-Hill [http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis Animation comparing Mitosis and Meiosis]
 
*  McGraw-Hill [http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120074/bio17.swf::Comparison%20of%20Meiosis%20and%20Mitosis Animation comparing Mitosis and Meiosis]
 
* Salmon Lab [http://www.bio.unc.edu/faculty/salmon/lab/moviesmitosis.html Mitosis Movies]
 
* Salmon Lab [http://www.bio.unc.edu/faculty/salmon/lab/moviesmitosis.html Mitosis Movies]
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[[Category:Human Embryo]] [[Category:Week 1]] [[Category:Fertilization]] [[Category:Oocyte]] [[Category:Spermatozoa]]
 
[[Category:Human Embryo]] [[Category:Week 1]] [[Category:Fertilization]] [[Category:Oocyte]] [[Category:Spermatozoa]]
 
 
[[Category:In Vitro Fertilization]] [[Category:Assisted Reproductive Technology]]
 
[[Category:In Vitro Fertilization]] [[Category:Assisted Reproductive Technology]]

Latest revision as of 16:40, 17 September 2019

Embryology - 18 Oct 2019    Facebook link Pinterest link Twitter link  Expand to Translate  
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Introduction

historic drawing of human oocyte and spermatozoa
Historic drawing of human oocyte and spermatozoa


This lecture will cover male and female gametogenesis and fertilisation.

IN development 1 embryonic cell (zygote) will produce about 1013 (100,000,000,000,000) cells in the adult at any one time (over time with cell death and ongoing replacement this is substantially more).

This is where the first embryonic cell begins! Fertilization is the fusion of haploid gametes, egg (oocyte) and sperm (spermatozoa), to form the diploid zygote. Note though there can be subtle differences in the fertilization process which occurs naturally within the body or through reproductive technologies outside the body, the overall product in both cases is a diplod zygote.


2016 Lecture Video Recording  
This 2016 lecture video recording is similar in content to the current 2018 lecture and is available to help understand this online content.

Click to play new window - 2016 Lecture Video (54.46 MB)

Some Recent Research  
  • From Meiosis to Mitosis: The Astonishing Flexibility of Cell Division Mechanisms in Early Mammalian Development (2016)[1] "The egg can be arrested in the prophase of meiosis I for decades, and when it is activated, the spindle is assembled de novo. This spindle must function with the highest of fidelity and yet its assembly is unusually achieved in the absence of conventional centrosomes and with minimal influence of chromatin. Moreover, its dramatic asymmetric positioning is achieved through remarkable properties of the actin cytoskeleton to ensure elimination of the polar bodies. The second meiotic arrest marks a uniquely prolonged metaphase eventually interrupted by egg activation at fertilization to complete meiosis and mark a period of preparation of the male and female pronuclear genomes not only for their entry into the mitotic cleavage divisions but also for the imminent prospect of their zygotic expression."
  • Meiosis Podcast Biosights 18 March 2013 - Breaking egg symmetry
  • JCB 16 June 16 2014 How sperm get into the zona

Lecture Archive: 2016 Video | 2016 PDF | 2015 | 2015 PDF | 2014 PDF | 2013 | 2012 | 2011 | 2010 | 2009

Lecture Objectives

  1. Broad understanding of reproductive cycles.
  2. Understand the key features of gametogenesis.
  3. Understand the differences in male and female gametogenesis.
  4. Brief understanding of the differences between mitosis and meiosis.
  5. Understanding of the events in fertilization.

Lecture Resources

Movies  
2016LectureGamete-icon.jpg
 ‎‎Fertilization
Page | Play
Oocyte Meiosis 01 icon.jpg
 ‎‎Oocyte Meiosis
Page | Play
Rabbit-ovulation.jpg
 ‎‎Ovulation
Page | Play | Audio
Follicle 001 icon.jpg
 ‎‎Ovulation
Page | Play
Bovine uterine tube oocyte transport 1.jpg
 ‎‎Oocyte Transport
Page | Play
Spermatozoa animation icon.jpg
 ‎‎Spermatozoa
Page | Play
Spermatozoa motility icon 01.jpg
 ‎‎Spermatozoa Motility
Page | Play
Human fertilization 1 icon.jpg
 ‎‎Fertilisation to
4 Blastomere
Page | Play
Human fertilization 2 icon.jpg
 ‎‎Fertilization
Page | Play
Fertilization 002 icon.jpg
 ‎‎Fertilization
Page | Play
Pronuclear fusion 001 icon.jpg
 ‎‎Pronuclear Fusion
Page | Play
DNA bead-induced ectopic polar body-icon.jpg
 ‎‎Ectopic Polar Body
Page | Play
Mouse spermatozoa mito movie icon.jpg
 ‎‎Male Mitochondria
Page | Play
References  
Textbook cover Larsen's human embryology 5th edn.
Moore, K.L., Persaud, T.V.N. & Torchia, M.G. (2015). The developing human: clinically oriented embryology (10th ed.). Philadelphia: Saunders.
The following chapter links only work with a UNSW connection.
Textbook cover Larsen's human embryology 5th edn.
Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., Francis-West, P.H. & Philippa H. (2015). Larsen's human embryology (5th ed.). New York; Edinburgh: Churchill Livingstone.
The following chapter links only work with a UNSW connection.
UNSW Embryology logo
Hill, M.A. (2019). UNSW Embryology (19th ed.) Retrieved October 18, 2019, from https://embryology.med.unsw.edu.au
Cell Division Links: meiosis | mitosis | Lecture - Cell Division and Fertilization | spermatozoa | oocyte | fertilization | zygote | Genetics

Human Reproductive Cycle

Sexual reproduction in most species is regulated by regular endocrine changes, or cycles, in the female. These cycles begin postnatally, function for variable times and can then decrease or cease entirely.

  • Human reproduction is regulated in females by the menstrual cycle, a regular cyclic hormonal change which coordinate changes in the ovary and internal reproductive tract. This cycle commences at puberty and ends at menopause.
  • Non-primates (rats, mice, horses, pig) reproduction is regulated in females by the estrous cycle (British spelling, oestrous).
Female Male
  • Menstrual Cycle a regular cycle of reproduction (28 days)
  • begins at puberty, release of 1 egg (oocyte) every cycle
  • Endocrine controlled (HPG axis) Hypothalamus - Pituitary - Gonad
  • continuous production of sperm (spermatozoa)
  • begins at puberty, release millions of spermatozoa
  • Endocrine controlled (HPG axis) Hypothalamus - Pituitary - Gonad

XXhpgaxis.jpg Menstrual cycle.png


Gametogenesis

The term "gametogenesis" describes the process of development of the haploid germ cells.

meiosis in the gonad (ovary or testis) produces the female and male haploid gametes, oocyte (egg) and spermatozoa (sperm).

Meiosis time course and final gamete number differs between female and male.


Male - Spermatogenesis

Human-spermatozoa EM01.jpg

Human spermatozoa (electron microscope)

Mouse- spermatozoa EM and diagram.jpg

Mouse spermatozoa (electron microscope)

The testes have two functions.

  1. produce the male gametes or spermatozoa
  2. produce male sexual hormone, testosterone (internal and external genitalia, sex characteristics)

Human spermatozoa take about 48 days from entering meiosis until morphologically mature spermatozoa.

  • Spermatogonia - are the diploid first cells of spermatogenesis
  • Primary spermatocytes - large, enter the prophase of the first meiotic division
  • Secondary spermatocytes - small, complete the second meiotic division
  • Spermatid - immature spermatozoa
  • Spermatozoa - differentiated gamete
Spermatozoa development: primordial germ cell - spermatogonia - primary spermatocyte - secondary spermatocytes - spermatid - spermatozoa

Sertoli cells (support cells)

Interstitial cells or Leydig cells (produce hormone)

Seminiferous tubule cartoon.jpg

Female - Oogenesis

The ovaries have two functions.

  1. produce the female gametes or oocytes
  2. produce female hormones, estrogen and progesterone (secondary sex characteristics, menstrual cycle)

In an adult human female the development of a primordial follicle containing an oocyte to a preovulatory follicle takes in excess of 120 days.

Human ovary follicle development.jpg

Human Follicle Development

Human ovulation 01.jpg

Human Ovulation

Human ovary follicle development

Ovarian Follicle Stages: primordial follicle - primary follicle - secondary follicle - tertiary follicle - preovulatory follicle


Follicle cells (support cells) Theca cells (produce hormone)

Ovulation Movie  

Click Here to play on mobile device

Click Here to play on mobile device

Meiosis Differences

Types of Cell Division  
Cell division - 3 types.jpg

There are 3 types of cell division that can occur.

  1. Binary fission - occurs in prokaryotes.
  2. Mitosis - occurs in all eukaryotic cells.
  3. Meiosis - occurs only in sex cell development.

Male Meiosis

  • Meiosis initiated continuously in a mitotically dividing stem cell population
  • 4 gametes produced / meiosis
  • Meiosis completed in days or weeks
  • Meiosis and differentiation proceed continuously without cell cycle arrest
  • Differentiation of gamete occurs while haploid after meiosis ends
  • Sex chromosomes excluded from recombination and transcription during first meiotic prophase

MBoC - Figure 20-27. The stages of spermatogenesis

Male gametogenesis cartoon

Male gametogenesis

Female Meiosis

  • Meiosis initiated once in a finite population of cells
  • 1 gamete produced / meiosis
  • Completion of meiosis delayed for months or years
  • Meiosis arrested at 1st meiotic prophase and reinitiated in a smaller population of cells
  • Differentiation of gamete occurs while diploid in first meiotic prophase
  • All chromosomes exhibit equivalent transcription and recombination during meiotic prophase

The Cell - Figure 14.37. Meiosis of vertebrate oocytes

Female gametogenesis cartoon

Female gametogenesis

Polar Bodies

  • In female gametogenesis only a single (1) haploid egg is produced from meiosis. In male gametogenesis four (4) haploid sperm are produced from meiosis. So what happens to all the extra DNA in producing this single egg?
    • Meiosis 1 the "extra" DNA is excluded to the periphery as a 1st polar body, which encloses the extra DNA.
    • Meiosis 2 the "extra" DNA is once again excluded as a 2nd polar body. The first polar body may also under go meiosis 2 producing a 3rd polar body.
  • These polar bodies are not gametes.
    • Polar bodies have no other function other than to dispose of the extra DNA in oogenesis.
    • Though recent research in mice suggest that oocyte polar body position may influence fertilization site.
Early zygote labelled.jpg

Early zygote showing polar bodies

Meiosis Polar Body Movie  

Click Here to play on mobile device

This movie shows labelled DNA (blue) of the mouse oocyte in meiosis 1 segregating DNA to the first polar body. The fluorescence image shows labelled actin (green) that lies directly under the plasma membrane of the oocyte and polar body.

Oocyte Meiosis 01 icon.jpg
 ‎‎Oocyte Meiosis
Page | Play

Fertilization

Gamete formation, menstrual cycle and fertilisation will also be covered in detail in this week's Laboratory. Fertilization is the complete process resulting in the fusion of haploid gametes, egg and sperm, to form the diploid zygote. The recent development of aided fertilization is described as in vitro fertilization (in vitro = "in glass", outside the body, IVF). Clinically, all these aided fertilization techniques are grouped as Assisted Reproductive Technologies or ART.

  • Oogenesis - 1 gamete produced/meiosis + 3 polar bodies, meiosis is slow, 1 egg produced and released at ovulation
  • Spermatogenesis - 4 gametes produced/meiosis, meiosis is fast, 200-600 million sperm released at ejaculation
Fertilization Movies  

Click Here to play on mobile device

Fertilization 002 icon.jpg
 ‎‎Fertilization
Page | Play
Human fertilization 1 icon.jpg
 ‎‎Fertilisation to
4 Blastomere
Page | Play
Human fertilization 2 icon.jpg
 ‎‎Fertilization
Page | Play
Fertilization 001 icon.jpg
 ‎‎Mouse Fertilisation
Page | Play

Fertilization Site

Human uterine tube ciliated epithelium
  • Fertilization resulting in embryo development usually occurs in first 1/3 of uterine tube (oviduct, Fallopian tube)
  • The majority of fertilized oocytes do not go on to form an embryo
  • Fertilization can also occur outside uterine tube associated with Assisted Reproductive Technology (IVF, GIFT, ZIFT...) and ectopic pregnancy
  • Oocyte ovulation - release from the ovary with associated cells, into peritoneal cavity, uterine tube fimbria then into uterine tube (oviduct, uterine horn, fallopian tube) and epithelial cilia mediated movement.
  • Spermatozoa ejaculation - deposited in vagina, movement of tail to "swim" in uterine secretions through cervix, uterine body and into uterine tube, have approximately 24-48h to fertilize oocyte.

Prior to the fertilization process commencing both the gametes complete of a number of biological processes.

  • Oocyte Meiosis - completes Meiosis 1 and commences Meiosis 2 (arrests at Metaphase II).
  • Spermatozoa Capacitation - following release (ejaculation) and mixing with other glandular secretions, activates motility and acrosome preparation.
  • Migration - both oocyte and spermatozoa.

Endocrinology - Diagram of the comparative anatomy of the male and female reproductive tracts

Gamete Movement Movies  
Oocyte Motility

Click Here to play on mobile device | More information

Spermatozoa Motility

Click Here to play on mobile device | More information

Fertilization - Male

Human spermatozoa (light microscope)

Spermatozoa: Ejaculation - Capacitation - Spermatozoa motility - Chemotaxis - Binding to zona pellucida - Acrosome reaction - Membrane fusion

Ejaculation

  • about 3.5 ml, containing 200 - 600 million spermatozoa
  • by volume less than 10 % spermatozoa
  • accessory glands contribute majority of volume (60 % seminal vesicle, 10 % bulbourethral, 30 % prostate)

Male Infertility

  • Oligospermia (Low Sperm Count) - less than 20 million sperm after 72 hour abstinence from sex
  • Azoospermia (Absent Sperm) - blockage of duct network
  • Immotile Cilia Syndrome - lack of sperm motility

Capacitation

  • spermatozoa activation process - removal of glycoprotein coat and seminal proteins and alteration of sperm mitochondria

Spermatozoa motility

  • tail of spermatozoa provide movement by microtubules
  • energy for this movement is provided by mitochondria in tail initial segment

Chemotaxis

  • oocyte cumulus cells release progesterone (may also be other oocyte and follicular fluid factors)

Spermatozoa Binding

  • Zona pellucida protein ZP3 acts as receptor for spermatozoa binding (species specific)

Model of gamete recognition zona pellucida.jpg

Acrosome Reaction

Membrane fusion

  • between spermatozoa and oocyte cell membranes, allows sperm nuclei passage into egg cytoplasm
  • membrane fusion also initiates oocyte processes to block polyspermy

Fertilization - Oocyte

Oocyte: Membrane depolarization - Cortical reaction - Meiosis 2 completion

Human MII oocyte cortical granules
Human MII oocyte cortical granules

Membrane Depolarization

  • caused by spermatozoa membrane fusion, acts as primary block to polyspermy (fertilisation by more than one spermatozoa)

Cortical Reaction

Meiosis 2

  • completion of 2nd meiotic division
  • forms second polar body (third polar body may be formed by meiotic division of the first polar body)


Formation of the Zygote

Early Zygotes
Image of early human zygote Image of early mouse zygote
Human Zygote Mouse Zygote
  • Pronuclei - Male and Female haploid nuclei approach each other and nuclear membranes break down
  • chromosomal pairing, DNA replicates, first mitotic division
  • Sperm contributes - centriole which organizes mitotic spindle
  • Oocyte contributes - mitochondria (maternally inherited)

Sex Determination

  • based upon whether an X or Y carrying sperm has fertilized the egg, should be 1.0 sex ratio.
  • actually 1.05, 105 males for every 100 females, some studies show more males 2+ days after ovulation.
  • cell totipotent (equivalent to a stem cell, can form any tissue of the body)

Men - Y Chromosome

  • Y Chromosome carries Sry gene, protein product activates pathway for male gonad (covered in genital development)

Women - X Chromosome

  • Gene dosage, one X chromosome in each female embryo cell has to be inactivated
  • process is apparently random and therefore 50% of cells have father's X, 50% have mother's X
  • Note that because men only have 1 X chromosome, if abnormal, this leads to X-linked diseases more common in male that female where bothe X's need to be abnormal.

Abnormalities

Trisomy21arrow.gifTrisomy21female.jpgTrisomy21male.jpg

  • The most common chromosome abnormality is aneuploidy, the gain or loss of whole chromosomes.
  • Caused by meiotic nondisjunction, the failure of chromosomes to correctly separate homologues during meiosis I or sister chromatids during meiosis II.
  • Down Syndrome - caused by an extra copy of chromosome 21. Trisomy 21 (Down Syndrome)Maternal Age
  • Chromosomal translocations occur when there is an inappropriate exchange of chromosomal material. Philadelphia chromosome
  • Philadelphia chromosome - piece of Chr9 exchanged with Chr22 Generates truncated abl, overstimulates cell production, leads to chronic myelogenous leukemia

Hydatidiform Mole

Hydatidiform Mole

  • Complete Mole - Only paternal chromosomes (no oocyte nucleus contribution)
  • Partial Mole - 3 sets of chromosomes ( (triploidy) instead of the usual 2 (2 spermatozoa contribution)


UNSW Embryology Links


Cell Division Links: meiosis | mitosis | Lecture - Cell Division and Fertilization | spermatozoa | oocyte | fertilization | zygote | Genetics

References

  1. Bury L, Coelho PA & Glover DM. (2016). From Meiosis to Mitosis: The Astonishing Flexibility of Cell Division Mechanisms in Early Mammalian Development. Curr. Top. Dev. Biol. , 120, 125-71. PMID: 27475851 DOI.

Online Textbooks

Search

Reviews

<pubmed>18163464</pubmed> <pubmed>17189856</pubmed>


Terms

Spermatozoa Development

Note there are additional glossaries associated with genital, spermatozoa, oocyte and renal.

Spermatozoon
  • acroplaxome - structure forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome. The sub-acrosomal layer located in the developing spermatozoa head perinuclear region, located between the inner acrosomal membrane and the nuclear envelope. The other part of the perinuclear region is the post-acrosomal sheath (PAS) at the post-acrosomal region.
  • acrosome - Cap-shaped cellular structure formed from the golgi apparatus and contains enzymes to dissolve the oocyte (egg) zona pellucida for fertilisation.
  • acrosome compaction - Acrosome reshaping process in final stages of spermatogenesis (spermatid to spermatozoa).
  • acrosome reaction - Chemical change within the spermatozoa following binding to the zona pellucida, only acrosome reacted spermatozoa have an ability to fuse with oocytes.
  • annulus - Cytoskeletal (septin) structure located between the midpiece and principal piece regions of the tail, thought to form a diffusion barrier between these two domains. PMID 20042538
  • asthenozoospermia - (asthenospermia) Term for reduced sperm motility and can be the cause of male infertility.
  • axoneme - (axonema) The basic structure in cilia and eukaryotic flagella and in the spermatozoa tail, consisting of parallel microtubules in a characteristic "9 + 2" pattern. This pattern describes 9 outer microtubule doublets (pairs) surrounding 2 central singlet microtubules, in humans 50 μm long. The motor protein dynenin move the outer microtubules with respect to the central pair, bending the cilia and generating motility. Note that prokaryotic bacteria have a similar process (flagellum) that uses an entirely different mechanism for motility.
  • capacitation - term describing the process by which spermaozoa become capable of fertilizing an oocyte, requires membrane changes, removal of surface glycoproteins and increased motility.
  • caput - proximal head of the epididymis, epithelium with stereocilia, involved in absorbing fluid to concentrate spermatozoa. Underlying smooth muscle aids movement. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • CatSper - cationic (Ca2+) channel of spermatozoa, progesterone activated involved in hyperactivation, acrosome reaction, and possibly chemotaxis.
  • cauda - distal tail of the epididymis, region with a thin epithelium and the greatest quantity of smooth muscle. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • centriole - a microtubule organising centre. First required for axoneme formation (distal centriole) that is lost and a second for pronuclei formation (proximal) following fertilisation. Rodents loose both and only have maternal centrioles.
  • connecting piece - linkage between the spermatozoa head and the midpiece of the tail. PMID 22767409
  • corpus - elongated body of the epididymis, This has an intermediate thickness of epithelium and thicker smooth muscle layer than caput. Epididymis three main parts : caput (head), corpus (body), cauda (tail).
  • cytoplasmic bridges - Transient cytoplasm connections between spermatids arising from one spermatogonium due to incomplete cytokinesis.
  • diploid - (Greek, di = double + ploion = vessel) Having two sets of chromosomes, the normal state for all cells other than the gametes.
  • end piece - Last portion of the spermatozoa tail region.
  • epididymis - testis tubular structure connecting the efferent ducts to the ductus deferent and functions for the storage and maturation of spermatozoa. Epididymis three main parts : caput (head), corpus (body), cauda (tail). PMID27307387
  • fibrous sheath - cytoskeletal structure surrounding the axoneme and outer dense fibers, defining the extent of the principal piece region.
  • haploid - (Greek, haploos = single) Having a single set of chromosomes as in mature germ/sex cells (oocyte, spermatozoa) following reductive cell division by meiosis. Normally cells are diploid, containing 2 sets of chromosomes.
  • interstitial cell - (Leydig cell) Male gonad (testis) cell which secrete the androgen testosterone, beginning in the fetus.
  • interstitium - testis developmental region (space between testis cords) that generates Leydig cells and other less well characterized cell types.
  • Johnsen score - a clinical score (1-10) for assessing spermatogenesis in a human testicular biopsy. Named after the author of the original article. PMID 5527187
  • Leydig cell - (interstitial cell) Male gonad (testis) cell that secrete the androgen testosterone, beginning in the fetus. Fetal Leydig cells develop from coelomic epithelium and undifferentiated perivascular cells in the gonad–mesonephros border region. Adult Leydig cells appear after birth from stem/progenitor cells among peritubular and peri-vascular cells. Leydig cells were first histologically identified in 1850 by Franz von Leydig (1821 - 1908) a German scientist.
  • meiosis - The cell division that occurs only in production of germ cells where there is a reduction in the number of chromosomes (diploid to haploid) which is the basis of sexual reproduction. All other non-germ cells in the body divide by mitosis.
  • midpiece - (middle piece) spermatozoa tail initial segment of axoneme surrounded outer dense fibres then by mitochondria. Next in the tail is the principal piece then finally the end piece.
  • mitosis - The normal division of all cells, except germ cells, where chromosome number is maintained (diploid). In germ cell division (oocyte, spermatozoa) meiosis is a modified form of this division resulting in reduction in genetic content (haploid). Mitosis, division of the nucleus, is followed by cytokinesis the division of the cell cytoplasm and the cytoplasmic contents. cytokinesis overlaps with telophase.
  • outer dense fibres - (ODF, outer dense fibers) cytoskeletal structures that surround the axoneme in the middle piece and principal piece of the spermatozoa tail.
  • primary spermatocyte - arranged in the seminiferous tubule wall deep (luminal) to the spermatogonia. These large cells enter the prophase of the first meiotic division. (More? meiosis)
  • principal piece - Spermatozoa tail segment containing the plasma membrane calcium channels (CatSper1 and CatSper2) required for hyperactivation of motility. Region is partially separated from the midpiece by a barrier called the annulus.
  • sertoli cells - (sustentacular cell) These cells are the spermatozoa supporting cells, nutritional and mechanical, as well as forming a blood-testis barrier. The cell cytoplasm spans all layers of the seminiferous tubule. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist.
  • sperm annulus - (Jensen's ring; Latin, annulus = ring) A region of the mammalian sperm flagellum connecting the midpiece and the principal piece. The annulus is a septin-based structure formed from SEPT1, 4, 6, 7 and 12. Septins are polymerizing GTPases that can act as a scaffold forming hetero-oligomeric filaments required for cytokinesis and other cell cycle roles.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The final process of change in cell shape is also called spermiogenesis.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The maturation process of the already haploid spermatazoa into the mature sperm shape and organization. This process involves reorganization of cellular organelles (endoplasmic reticulum, golgi apparatus, mitochondria), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation).
  • spermatogonia - The cells located in the seminiferous tubule adjacent to the basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.
  • spermatozoa head - Following spermiogenesis, the first region of the spermatozoa containing the haploid nucleus and acrosome. In humans, it is a flattened structure (5 µm long by 3 µm wide) with the posterior part of nuclear membrane forming the basal plate region. The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and spermatozoa tail).
  • spermatozoa neck - Following spermiogenesis, the second region of the spermatozoa attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. In humans, it forms a short structure (1 µm). The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and tail).
  • spermatozoa tail - Following spermiogenesis, the third region of the spermatozoa that has a head, neck and tail). The tail is also divided into 3 structural regions a middle piece, a principal piece and an end piece. In humans: the middle piece (5 µm long) is formed by axonema and dense fibres surrounded by mitochondria; the principal piece (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops; the final end piece (5 µm long) has an axonema surrounded by small amount of cytoplasm and plasma membrane.
  • spermatogonial stem cells - (SSCs) The spermatagonia cells located beside the seminiferous tubule basal membrane that either divide and separate to renew the stem cell population, or they divide and stay together as a pair (|Apr spermatogonia) connected by an intercellular cytoplasmic bridge to differentiate and eventually form spermatazoa.
  • spermatozoon - singular form of of spermatozoa.
  • sperm protein 56 - A component of the spermatozoa acrosomal matrix released to the sperm surface during capacitation.
  • teratospermia - Clinical term for a spermatozoa with abnormal morphology (small, large, defects in the head, tail, and/or mid-piece) present in the semen or ejaculate.
  • testis cords - developmental structure that give rise to the adult seminiferous tubules, the other developmental region is the interstitium.
  • vasectomy - Clinical term for ligation of the scrotal portion of the ductus deferens.

See also: Spermatozoa Terms collapse table

Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Endocrine | Gastrointestinal | Genital | Genetic | Head | Hearing | Heart | Immune | Integumentary | Neonatal | Neural | Oocyte | Palate | Placenta | Radiation | Renal | Respiratory | Spermatozoa | Statistics | Tooth | Ultrasound | Vision | Historic | Drugs | Glossary


External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.



 2018 ANAT2341 - Timetable | Course Outline | Moodle | Tutorial 1 | Tutorial 2 | Tutorial 3

Labs: 1 Preimplantation and Implantation | 2 Reproductive Technology Revolution | 3 Group Projects | 4 GM manipulation mouse embryos | 5 Early chicken eggs | 6 Female reproductive tract | 7 Skin regeneration | 8 Vertebral development | 9 Organogenesis Lab | 10 Cardiac development | 11 Group projects | 12 Stem Cell Journal Club

Lectures: 1 Introduction | 2 Fertilization | 3 Week 1/2 | 4 Week 3 | 5 Ectoderm | 6 Placenta | 7 Mesoderm | 8 Endoderm | 9 Research Technology | 10 Cardiovascular | 11 Respiratory | 12 Neural crest | 13 Head | 14 Musculoskeletal | 15 Limb | 16 Renal | 17 Genital | 18 Endocrine | 19 Sensory | 20 Fetal | 21 Integumentary | 22 Birth | 23 Stem cells | 24 Revision

 Student Projects: Group Projects Information Project 1 | Project 3 | Project 4 | Project 5 | 2018 Test Student | Copyright

Cite this page: Hill, M.A. (2019, October 18) Embryology Lecture - Fertilization. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Lecture_-_Fertilization

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© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G