Difference between revisions of "BGDA Practical 3 - Week 3 Summary"

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{{BGDALab3}}
  
 
==Introduction==
 
==Introduction==
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The timeline at the bottom of this page should give you a better perspective of the sequence of early developmental events. You would not be expected to know exact days (as they are only approximate anyway) it is more important to get the weeks and sequence right.
 
The timeline at the bottom of this page should give you a better perspective of the sequence of early developmental events. You would not be expected to know exact days (as they are only approximate anyway) it is more important to get the weeks and sequence right.
 +
 +
 +
{{Carnegie_stage_table_1}}
  
 
==Stage 7==
 
==Stage 7==
 
[[File:Stage7-sem2.jpg|240px|left]]
 
[[File:Stage7-sem2.jpg|240px|left]]
 
===Facts===
 
===Facts===
Human embryonic stage 7 occurs during week 3 between 15 to 17 days.  
+
[[Carnegie stage 7|Human embryonic stage 7]] occurs during week 3 between 15 to 17 days.  
  
 
The embryo is now 0.4 mm diameter in size.
 
The embryo is now 0.4 mm diameter in size.
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===Events===
 
===Events===
 
+
{|
Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.
+
Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.
  
 
Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.
 
Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.
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The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract.
 
The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract.
 +
| {{SlideStage7bf5}}
 +
|}
  
 
== Carnegie Stage 8 ==
 
== Carnegie Stage 8 ==
 
[[Image:Stage8 SEM1.jpg|240px|left]]  
 
[[Image:Stage8 SEM1.jpg|240px|left]]  
 
===Facts===
 
===Facts===
Human embryonic stage 8 occurs during week 3 between 17 to 19 days.
+
[[Carnegie stage 8|Human embryonic stage 8]] occurs during week 3 between 17 to 19 days.
  
 
The embryo is now 1.0 - 1.5 mm in size.
 
The embryo is now 1.0 - 1.5 mm in size.
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[[Carnegie stage 8]]
 
[[Carnegie stage 8]]
 +
  
 
== Carnegie Stage 9 ==
 
== Carnegie Stage 9 ==
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[[File:Stage9_sem4c.jpg|left]]
 
[[File:Stage9_sem4c.jpg|left]]
 
===Facts===
 
===Facts===
Human embryonic stage 9 occurs during week 3 between 19 to 21 days.  
+
[[Carnegie stage 9|Human embryonic stage 9]] occurs during week 3 between 19 to 21 days.  
  
 
The embryo is now 1.5 to 2.5 mm in size and somites have begun to form and number between  1 to 3 somite pairs during this stage.  
 
The embryo is now 1.5 to 2.5 mm in size and somites have begun to form and number between  1 to 3 somite pairs during this stage.  
  
 
The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images.
 
The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images.
 +
 +
[[File:Stage9 sem1.jpg|600px]]
  
 
===Events===
 
===Events===
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'''Endoderm''' - Notochordal plate still visible which will form the notochord. Endoderm is still widely open to the yolk sac and germ cells form part of this layer. Extra-embryonic mesoderm on the yolk sac surface begins to form "blood islands".
 
'''Endoderm''' - Notochordal plate still visible which will form the notochord. Endoderm is still widely open to the yolk sac and germ cells form part of this layer. Extra-embryonic mesoderm on the yolk sac surface begins to form "blood islands".
 +
 +
<gallery mode="packed-hover" caption="Mesoderm and Ectoderm Cartoons">
 +
File:Mesoderm-cartoon1.jpg|Trilaminar Embryo
 +
File:Mesoderm-cartoon2.jpg|Paraxial and Lateral Plate
 +
File:Mesoderm-cartoon3.jpg|Somites
 +
File:Mesoderm-cartoon4.jpg|Somatic and Splanchnic
 +
</gallery>
  
 
===Identify===
 
===Identify===
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[[Carnegie stage 9]]
 
[[Carnegie stage 9]]
  
{{Template:Carnegie_stages}}
 
  
== Human Development Timeline  ==
+
== Carnegie Stage 10==
The table below shows human development features and approximate timing during the menstrual cycle to fertilization and the first 3 weeks of development.  
+
[[Carnegie stage 10|Human embryonic stage 10]] occurs at the beginning of week 4 development ({{GA}} week 6). This week will be covered in detail in the next practical class. The virtual slide image below shows a dorsal view of the embryo at the beginning of week 4.
  
The timing assumes fertilization the day after ovulation and the "weeks" refer to embryonic development and differ from clinical weeks (shown in brackets, from last menstrual period) and "stages" refer to Carnegie stages of development.
 
  
 +
{{SlideStage10bf10}}
  
== Week -2 ==
 
(Clinical Week 1)
 
  
 +
{{Carnegie_stages}}
  
{| class="prettytable" width=100%
 
|-bgcolor="lightsteelblue"
 
| <center>'''Day'''</center>
 
| <center>'''Menstrual cycle'''</center>
 
| '''Event'''
 
  
|-
+
== Additional Information==
| <center>1</center>
+
{{Med Prac additional Information}}
| Menstrual Phase
+
===Human Development Timeline===
| [[File:Menstrual cycle.png|90px|left|link=Menstrual Cycle]]
+
The table below shows human development features and approximate timing during the menstrual cycle to fertilization and the first 3 weeks of development.  
 
 
[[Menstrual Cycle]] changes: Uterine endometrium (loss), Ovary (Follicle Development)
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>2</center>
 
| &nbsp;
 
| [[File:Human-_menstrual_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]]
 
 
 
|-
 
| <center>3</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>4</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-
 
| <center>5</center>
 
| Proliferative Phase
 
| [[File:Smear- early proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]][[File:Ova41he.jpg|90px|link=Menstrual Cycle]] [[Menstrual Cycle]] changes: Uterine endometrium (proliferation), Ovary (Follicle Development)
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>6</center>
 
|
 
|
 
 
 
|-
 
| <center>7</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|}
 
 
 
== Week -1 ==
 
(Clinical Week 2)
 
 
 
 
 
{| class="prettytable" width=100%
 
|-bgcolor="#AFEEEE"
 
| <center>'''Day'''</center>
 
| '''Menstrual cycle'''
 
| '''Event'''
 
 
 
|-
 
| <center>8</center>
 
| Proliferative Phase
 
|
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>9</center>
 
| &nbsp;
 
| [[File:Smear-_mid-proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_mid-proliferative_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Ovary10x.jpg|90px]] [[File:Ova20he.jpg|90px]] [[Menstrual Cycle]] - Mid proliferative
 
 
 
|-
 
| <center>10</center>
 
| &nbsp;
 
| &nbsp;
 
  
|-bgcolor="#AFEEEE"
+
The timing assumes fertilization the day after ovulation and the "weeks" refer to embryonic development and differ from  Gestational Age ({{GA}}, clinical weeks shown in brackets, from last menstrual period) and "stages" refer to Carnegie stages of development.
| <center>11</center>
 
| &nbsp;
 
| &nbsp;
 
  
|-
+
<br>
| <center>12</center>
+
{{First Trimester Timeline}}
| &nbsp;
+
<br>
| &nbsp;
+
{{Carnegie_stage_table_1}}
 
 
|-bgcolor="#AFEEEE"
 
| <center>13</center>
 
| &nbsp;
 
| [[File:Smear-_late-proliferative.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_late_proliferative_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Menstrual cycle.png|90px|link=Menstrual Cycle]] [[Menstrual Cycle]] - Late Proliferative
 
 
 
|-
 
| <center>14</center>
 
| Ovulation
 
 
 
Capacitation
 
| [[Image:Human oocyte.jpg|90px]] [[File:Follicle 001 icon.jpg|90px|link=Development_Animation_-_Ovulation]]
 
 
 
|}
 
 
 
== Week 1 ==
 
[[Week 1]] (Clinical Week 3)
 
 
 
 
 
{| class="prettytable" width=100%
 
|-bgcolor="#AFEEEE"
 
| <center>'''Day'''</center>
 
| <center>'''Stage'''</center>
 
| '''Event'''
 
 
 
|-
 
| <center>1</center>
 
| Secretory PhaseStage 1
 
| [[Image:Early_zygote.jpg|90px]] [[File:Smear-_secretory.jpg|90px|link=Menstrual_Cycle_-_Histology]] [[File:Human-_secretory_uterine_endometrium.jpg|90px|link=Menstrual_Cycle_-_Histology]] Fertilization, Secretory Phase
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>2</center>
 
| Stage 2
 
| [[Image:Stage2.jpg|90px]] [[File:Week1 001 icon.jpg|90px|link=Development_Animation_-_Week_1]] Morula, Blastula
 
 
 
|-
 
| <center>3</center>
 
| &nbsp;
 
|
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>4</center>
 
| Stage 3
 
| [[Image:CSt3.jpg|90px]] Blastocyst Hatching (zona pellucida lost)
 
 
 
|-
 
| <center>5</center>
 
| &nbsp;
 
| [[File:Smear-_late_secretory.jpg|90px]] [[File:Human-_late_secretory_uterine_endometrium.jpg|90px]] Late Secretory, Blastocyst (free floating)
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>6</center>
 
| Stage 4
 
| Adplantation
 
 
 
|-
 
| <center>7</center>
 
| Stage 5
 
|  [[File:Week2_001 icon.jpg|90px|link=Development_Animation_-_Implantation]]
 
 
 
|}
 
 
 
== Week 2 ==
 
[[Week 2]] (Clinical Week 4)
 
 
 
 
 
{| class="prettytable" width=100%
 
|-bgcolor="#AFEEEE"
 
| <center>'''Day'''</center>
 
| <center>'''Stage'''</center>
 
| '''Event'''
 
 
 
|-
 
| <center>8</center>
 
|
 
|  [[File:Week2_001 icon.jpg|90px|link=Development_Animation_-_Implantation]] Implantation
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>9</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-
 
| <center>10</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>11</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-
 
| <center>12</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>13</center>
 
| Stage 6
 
| [[File:Chorion 001 icon.jpg|90px|link=Development Animation - Chorionic Cavity]] Chorionic Cavity
 
 
 
|-
 
| <center>14</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|}
 
 
 
== Week 3 ==
 
[[Week 3]] (Clinical Week 5)
 
 
 
 
 
{| class="prettytable" width=100%
 
|-bgcolor="#AFEEEE"
 
| <center>'''Day'''</center>
 
| <center>'''Stage'''</center>
 
| '''Event'''
 
 
 
|-
 
| <center>15</center>
 
|
 
|
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>16</center>
 
| Stage 7
 
| [[File:Stage7-bf1.jpg|90px|link=Carnegie_stage_7]] [[File:Stage7-sem2.jpg|90px|link=Carnegie_stage_7]] [[Image:Stage7.jpg|90px|link=Carnegie_stage_7]]
 
 
 
|-
 
| <center>17</center>
 
| &nbsp;
 
| &nbsp;
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>18</center>
 
| Stage 8
 
| [[Image:Stage8_human.jpg|90px|link=Carnegie_stage_8]] [[File:Neuralplate_001 icon.jpg|90px|link=Development Animation - Neural Plate]] [http://embryology.med.unsw.edu.au/Notes/neuron.htm Neural]  neurogenesis, neural groove and folds are first seen
 
 
 
|-
 
| <center>19</center>
 
| &nbsp;
 
| [[Image:Stage8_SEM1.jpg|90px|left]]
 
 
 
|-bgcolor="#AFEEEE"
 
| <center>20</center>
 
| Stage 9
 
| [[File:Stage9_bf2c.jpg|90px|link=Carnegie_stage_9]] [[File:Stage9_sem1b.jpg|90px|link=Carnegie_stage_9]] [http://embryology.med.unsw.edu.au/Notes/skmus6.htm Musculoskeletal]  somitogenesis, first somites form and continue to be added in sequence caudally
 
 
 
[http://embryology.med.unsw.edu.au/Notes/neuron.htm Neural]  the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open
 
 
 
[http://embryology.med.unsw.edu.au/Notes/ncrest.htm Neural Crest]  mesencephalic neural crest is visible [http://www.ncbi.nlm.nih.gov/pubmed/17848161 PMID: 17848161]
 
 
 
|-
 
| <center>21</center>
 
| &nbsp;
 
| [http://embryology.med.unsw.edu.au/Notes/heart.htm Heart]  cardiogenesis, week 3 begins as paired heart tubes.
 
 
 
|}
 
  
 
== Next ==
 
== Next ==
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If you have finished and need some more help understanding this period of development, I have included some links to Online References.  
 
If you have finished and need some more help understanding this period of development, I have included some links to Online References.  
 +
  
 
If you have finished and are interested in looking at tissues involved in this period of development, I have included some links to Histology Images.
 
If you have finished and are interested in looking at tissues involved in this period of development, I have included some links to Histology Images.
 +
* [[Ovary_Development#Histology|Ovary Histology]]
 +
* [[Menstrual Cycle - Histology]]
  
  
Note that this Practical has discussed mainly development of the embryo as placental development will be covered in detail in another practical ('''Practical 8 - Placenta and Fetal Membranes''').
+
Note that this Practical has discussed mainly development of the embryo as placental development will be covered in detail in another practical ([[BGDA Practical - Fetal Development|Placenta and Fetal Membranes]]).
 
 
The next Practical will continue on through embryonic development ('''Practical 6 - Implantation to 8 Weeks''').
 
 
 
==Terms==
 
The selected list of terms below are extracted from the original UNSW Embryology Glossary, many of the links go to those original website pages. The full list of glossary terms should be used for any new terms not listed below.
 
 
 
====acroplaxome====
 
 
 
The sperm structure which forms the acrosome plate with intermediate filament bundles of the marginal ring at the leading edge of the acrosome.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_5.htm Fertilization])
 
 
 
====acrosin====
 
 
 
A spermatazoa acrosomal protein has a role in fertilization including that of lysis of the zona pellucida (a serine protease) and in secondary zona pellucida (ZP) binding. Stored in mature spermatazoa as proacrosin.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_5.htm Fertilization] | [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=102480 OMIM Entry])
 
 
 
====acrosome====
 
 
 
The spermatazoa cellular structure containing a packet of enzymes located that allows it to dissolve a hole in the specialized extracellular matrix (zona pellucida, egg coat) surrounding the oocyte (egg). This enzymic digestion then allows the spermatazoa to penetrate and fertilize the egg. This structure is formed from the normal cellular organelle the [Golgi apparatus.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_5.htm Fertilization])
 
 
 
====acrosome reaction====
 
 
 
The chemical change that enables release of acrosomal contents and allow a sperm to penetrate an egg.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1_5.htm Fertilization])
 
 
 
====adnexa====
 
 
 
(Latin, ''adnexae'' = appendages) Term used to describe any anatomical appendage (accessory structure, extension or outgrowth from the body). In reproductive anatomy used to describe appendages of the [U.htm#uterus uterus] "body"; ovaries, uterine tubes and uterus supporting ligaments.
 
 
 
====Artificial Insemination====
 
 
 
(AI) Fertility treatment, using placement of a sperm sample inside the female reproductive tract that can be carried out by a number of different techniques: intracervical insemination, intrauterine insemination, intratubal insemination.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====amenorrhea====
 
 
 
The absence of a menstrual period, it can be either primary (not yet had a period by age 16) or secondary (regular period that has now stopped for 3 months).
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/../wwwhuman/MCycle/Mcycle.htm#Abnormalities Human Menstrual Cycle])
 
 
 
====androgens====
 
 
 
The male sex hormones, eg testosterone.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/genitalXY.htm Genital System - Male])
 
 
 
====aneuploidy====
 
 
 
Term used to describe an abnormal number of chromosomes mainly (90%) due to chromosome malsegregation mechanisms in maternal meiosis I.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Defect/page21.htm Trisomy 21] | [http://embryology.med.unsw.edu.au/Notes/week1_4b.htm Meiosis])
 
 
 
====antral follicle====
 
 
 
(secondary follicle) Term used to describe the developmental stage of ovarian follicle development following preantral (primary) in describing the sequence (primordial, preantral, antral) of follicle development within the ovary. In humans, a number of primordial follicles will begin to develop into primary follicles, some of which will then form antral follicles (secondary), with only a single antral follicle developing into the ovulating follicle (Graafian) each menstrual cycle.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====antrum====
 
 
 
(Latin from Greek, ''antron'' = a cave, cavity; a nearly-closed cavity or bulge). Identified anatomically in many structures (ovarian follicle, bone, cardiac, gastric). In the ovary this refers to the follicular fluid-filled space within the follicle.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====ART====
 
 
 
acronym for '''A'''ssisted '''R'''eproductive '''T'''echnology. All treatments or procedures that involve the handling of human eggs and sperm for the purpose of helping a woman become pregnant. Types of ART include in vitro fertilization, gamete intrafallopian transfer, zygote intrafallopian transfer, embryo cryopreservation, egg or embryo donation, and surrogate birth.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization])
 
 
 
====ART cycle====
 
 
 
A process in which 1) an ART procedure is carried out, 2) a woman has undergone ovarian stimulation or monitoring with the intent of having an ART procedure, or 3) in the case of frozen embryos, embryos have been thawed with the intent of transferring them to a woman. A cycle begins when a woman begins taking fertility drugs or having her ovaries monitored.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====atresia====
 
 
 
(Greek, ''a'' = without + ''tresis'' = perforation) Term used for anatomical closing or absence of a cavity or opening that should exist. Used as an antomical, pathological and clinical term: esophageal atresia, biliary atresia, duodenal atresia, jejunal atresia, choanal atresia, vaginal atresia, urethral atresia, pulmonary atresia, bronchial atresia, tricuspid atresia.
 
 
 
====atretic follicle====
 
 
 
An ovarian follicle that fails to mature and degenerates. Also called "atresia" referring to the process of degeneration of the ovarian follicle. At any one time the majority of follicles are destined not to complete maturation and degeneration can occur at any stage (from type 4-7).
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Ovary Notes])
 
 
 
====Balbiani body====
 
 
 
(mitochondrial cloud) A collection of cell organelles (mitochondria, ER, and granulofibrillar material) asymmetrically located beside the nucleus in very young oocytes in some species. Appears similar to germinal granule precursors seen some species that contain a definitive germ plasm (flies, worms, and frogs).
 
 
 
(More? [http://www.pnas.org/cgi/content/abstract/104/1/187 PNAS - Mouse oocytes within germ cell cysts and primordial follicles contain a Balbiani body])
 
 
 
====Bulbourethral Gland====
 
 
 
(= Cowper's Gland) A male genital tract gland which secretes a small amount of a thick clear mucous fluid prior to ejaculation, the alkaline content apparently buffers acidity of the urethra. The equivalent female gland are Bartholin's glands.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/urogen.htm Urogenital Notes])
 
 
 
====Call-Exner bodies====
 
 
 
A feature seen in the developing ovarian follicle granulosa layer of some species, including human. Appears as a spherical space staining as an eosinophilic region and contains basal lamina components (type IV collagen and laminin) similar to thiose of the follicular basal lamina.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====centriole====
 
 
 
A pair of small cylindrical structures each about 0.2 micron in diameter and 0.4 micron long, that lie at right angles to one another; present at each pole of the mitotic spindle in animal cells and in some other eukaryotes.
 
 
 
====ciliated epithelium====
 
 
 
(Latin, ''cilium'' = eyelid) An epithelium named on the basis of the cells having surface hair-like appearance of a cilium; singular, cilium. In many tissues, cilia are found as epithelial cell apical surface motile specializations. In the uterine tube epithelium, after ovulation used to move the unfertilized egg, then the fertilized zygote, then blastocyst during the first week of development.
 
 
 
====clomiphene citrate====
 
 
 
(CC) A fertility drug taken orally to promote the process of follicle/egg maturation in superovulation therapy. (CC) an anti-estrogen (MRL-41) therapy for WHO group II (eu-oestrogenic) infertility associated with polycystic ovary syndrome. Used for more than 40 years it is a simple, cheap treatment, with low side effects and yields a 25% live birth rate. Alternative therapeutics being considered are metformin, aromatase inhibitors and low-dose FSH.
 
 
 
(More? [http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=13901503&dopt=Abstract Greenblatt RB, Barfield WE, Jungck EC, Ray AW.] Induction of ovulation with MRL/41. Preliminary report. JAMA. 1961 Oct 14;178:101-4. | [http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15878925&dopt=Abstract Homburg R.] Clomiphene citrate--end of an era? A mini-review. Hum Reprod. 2005 Aug;20(8):2043-51.) | [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Notes - Ovary] | [http://embryology.med.unsw.edu.au/Notes/week1_5a.htm Week 1 - In Vivo Fertilization] | [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization] | [http://embryology.med.unsw.edu.au/Notes/week1_2.htm Week 1 - Abnormalities])
 
 
 
====cumulus oophorus====
 
 
 
(Latin ''cumulus'' = a little mound G. ''oon'' = egg + ''phorus'' = bearing) The granulosa cells that form a column of cells that attaches the oocyte to the antral follicle wall within follicles of the ovary. This column of cells is broken or separates during ovulation to release the oocyte from its follicle attachment. Other granulosa cells within the follicle include: membrana granulosa and [#corona_radiata corona radiata].
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====DAX1====
 
 
 
Acronym for "D"osage sensitive sex reversal (DSS), "A"drenal hypoplasia congenita (AHC) critical region on the "X" chromosome, gene "1" , (gene NR0B1) is a nuclear hormone receptor involved in female ovary development.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/urogen.htm Urogenital Notes] | [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=300473 OMIM Entry DAX1])
 
 
 
====DAZL====
 
 
 
Acronym for '''DAZ'''-'''l'''ike due to homology to DAZ ('''D'''eleted in '''AZ'''oospermia), a gene on the long arm of the Y chromosome that is frequently deleted in infertile men with nonobstructive azoospermia.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=601486 OMIM Entry DAZL])
 
 
 
====DET====
 
 
 
Acronym for '''D'''ouble-'''E'''mbryo '''T'''ransfers, two embryos transferred when women undergo Assisted Reproduction Technology compared to single-embryo transfer (SET).
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization])
 
 
 
====ductuli efferentes====
 
 
 
testis (male gonad) series of tubular structures which arise from the rete testis and conduct spermatazoa into the ductus epididymidis. Their columnar epithelium lining consisting of both absorptive and ciliated cells (giving rise to "cogwheel appearance) which removes much of the fluid associated with the spermatazoa leaving the testes (also by the upper epididymis) thereby increasing the spermatazoa concentration. (Spermatozoa Duct Pathway: seminiferous tubule‚ straight tubule‚ rete testis‚ ductuli efferentes‚ ductus epididymidis‚ ductus deferens)
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Spermatogenesis] | [http://embryology.med.unsw.edu.au/Notes/genitalXY.htm Genital - Male] | [http://embryology.med.unsw.edu.au/Notes/genital.htm Genital Notes])
 
 
 
====ductus epididymidis====
 
 
 
(epididymidis) The male testes tubular structure which arise from the ductuli efferentes and conduct spermatazoa into the ductus deferens (vas deferens). The long duct is lined by a tall pseudostratified columnar epithelium.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/genitalXY.htm Genital - Male] | [http://embryology.med.unsw.edu.au/Notes/genital.htm Genital Notes])
 
 
 
====dysmenorrhoea====
 
 
 
A period pain which can be primary (increased sensitivity to the prostaglandins) or secondary (pathological), can be common with no associated abnormality or in association with ovarian cysts or endometriosis.
 
 
 
(More? [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/MCycle.htm Human Menstrual Cycle])
 
 
 
====ectopic pregnancy====
 
 
 
(Greek, ''ektopos'' = out of place) A pregnancy in which the fertilized egg implants outside of the [U.htm#uterus uterus] usually in the fallopian tube, but also on the ovary, or the abdominal cavity. Ectopic pregnancy is a dangerous condition that must receive prompt treatment.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week2_2.htm Week 2 - Abnormalities])
 
 
 
====egg====
 
 
 
([O.htm#oocyte oocyte] or ovum) An alternative term used to describe the haploid female reproductive cell Germ Cell). The term is also used to describe the avian and reptilian shell enclosed structure.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://embryology.med.unsw.edu.au/OtherEmb/Chicken.htm Chicken Development] | [http://embryology.med.unsw.edu.au/OtherEmb/Frog.htm Frog Development])
 
 
 
====egg retrieval====
 
 
 
(also called oocyte retrieval) A clinical in vitro fertilization (IVF) procedure to collect the eggs contained in the ovarian follicles.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization])
 
 
 
====egg transfer====
 
 
 
(also called oocyte transfer) A clinical in vitro fertilization (IVF) technique to transfer of retrieved eggs into a woman's fallopian tubes through [L.htm#laparoscopy laparoscopy]. This procedure is used only in gamete intrafallopian transfer (GIFT) (see definition).
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization])
 
 
 
====embryo====
 
 
 
(Greek, ''en'' = in + ''bryein'' = to be full of) An egg that has been fertilized by a sperm and undergone one or more divisions. Also the set of early developmental stages in which a plant or animal differs from its mature form.
 
 
 
(More? [h.htm#human_embryo human embryo])
 
 
 
====embryo transfer====
 
 
 
Placement of an embryo or embryos into a woman's [U.htm#uterus uterus] through the cervix after in vitro fertilization (IVF) or in the case of zygote intrafallopian transfer (ZIFT) (see definition), into her fallopian tube.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====endocrine gland====
 
 
 
(Greek, ''endon'' = within) A gland (organ, tissue) that is specialized for secretion of a hormone into the bloodstream for general circulation.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/endocrine.htm Endocrine Notes])
 
 
 
====endometrial gland====
 
 
 
The mucous secreting gland associated with the epithelium lining the [U.htm#uterus uterus]. These glands develop and secrete each menstral cycle and are thought to provide initial blastocyst nutrition prior to implantation.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====endometriosis====
 
 
 
Endometrium found incorrectly located possibly in the muscular layer of the  uterus. Can also be seen as the presence of tissue similar to the uterine lining in locations outside of the uterus, such as the ovaries, fallopian tubes, and abdominal cavity.
 
 
 
([http://embryology.med.unsw.edu.au/Notes/week1.htm More? Week 1 Notes])
 
 
 
====endometrium====
 
 
 
The epithelium lining of the non-pregnant [U.htm#uterus uterus]. During pregnancy this epithelium undergoes changes described as the decidual reaction and is renamed the "decidua".
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/MCycle.htm Human Menstrual Cycle])
 
 
 
====epigenetics====
 
 
 
(Greek, ''epi'' = above, upon) gene silencing that occur without changes in the genes (DNA) sequence, this changes can also be inherited.
 
 
 
(More? [http://embryology.med.unsw.edu.au/MolDev/epigenetics.htm Molecular Mechanisms - Epigenetics] | [http://embryology.med.unsw.edu.au/DNA/DNA.htm DNA Introduction] | [http://www.sciencemag.org/feature/plus/sfg/resources/res_epigenetics.dtl Science - Epigenetics: A web tour] | [http://www.wellcome.ac.uk/en/genome/thegenome/hg02b002.html The Welcome Trust - Epigenetics])
 
 
 
====estrogens====
 
 
 
Sex hormone found in both male and female. In the female, this hormone is produced by the ovaries and is responsible for development of secondary feminine sex characteristics. Together with progesterone these hormones also regulate changes that occur each menstral cycle. In the male, Leydig cells produce estrogen into the rete testis fluid at variable levels in different species. During male embryonic development exposure to high levels of estrogen can lead to genital abnormalities.
 
 
 
====estrous cycle====
 
 
 
The cyclic alterations in animal female tract and in sexual receptivity related to hormone changes. When searching both American (estrous) and British (oestrous) spellings are used in the literature.
 
 
 
(More? [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/Ocycle.htm Menstrual Cycle - Estrous Cycle] | [http://embryology.med.unsw.edu.au/OtherEmb/mouse2.htm Mouse estrous cycle])
 
 
 
====gametes====
 
 
 
(Greek, ''gamos'' = marriage) A specialized reproductive cell through which sexually reproducing parents pass chromosomes to their offspring; a sperm or an egg.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====gamete intrafallopian transfer====
 
 
 
see GIFT
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm In Vitro Fertilization Notes])
 
 
 
====gameteogenesis====
 
 
 
The production of either the haploid germ cells of spermatazoa (male) or eggs (female).
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====genitalia====
 
 
 
(Latin, ''genitalia'' = ) The term used to describe either the external or internal male and female sexual and reproductive organs.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/urogen.htm Urogenital Notes])
 
 
 
====haploid====
 
 
 
(Greek, ''haploos'' = single) Having a single set of chromosomes as in mature germ/sex cells (egg, spermatazoa). Normally cells are diploid, containing 2 sets of chromosomes.
 
 
 
(More? [http://embryology.med.unsw.edu.au/DNA/DNA.htm DNA Notes])
 
 
 
====human chorionic gonadotrophin====
 
 
 
(hCG) Placental hormone initially secreted by cells (syncitiotrophoblasts) from the implanting conceptus during week two, supporting the ovarian corpus luteum, which in turn supports the endometrial lining and therefore maintains pregnancy. Hormone can be detected in maternal blood and urine and is teh basis of many pregnancy tests. Hormone also stimulates the onset of fetal gonadal steroidogenesis, high levels are teratogenic to fetal gonadal tissues.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/placenta.htm Placenta Notes] | [http://embryology.med.unsw.edu.au/Notes/week2.htm Week 2 Notes])
 
 
 
====last menstrual period====
 
 
 
(LMP) Clinical term used to describe the menstrual period that occurs before a pregnancy and is used as the date to calculate clinical pregnancy development (gestational age). Note that in humans this is approximately two weeks different from embryonic development, which begins at [F.htm#fertilization fertilization] around the mid-point of the menstrual cycle.
 
 
 
====Leydig cells====
 
 
 
(interstitial cells) Testis (male gonad) cell which secrete testosterone, beginning in the fetus. These cells are named after Franz von Leydig (1821 - 1908) a German scientist who histologically described these cells.
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====male factor====
 
 
 
Any cause of infertility due to deficiencies in sperm quantity, function, or motility (ability to move) that make it difficult for a sperm to fertilize an egg under normal conditions.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====manchette====
 
 
 
A transient microtubule structure formed in spermatids involved in the process of assembly of the mammalian sperm tail and mechanical shaping and condensation of the sperm nucleus.
 
 
 
(More? [[Spermatozoa Development]])
 
 
 
====mediastinum testis====
 
 
 
(Latin, ''medialis'' = middle) A single conical mass of connective tissue within the testis (male gonad) which extends from the tunica albuginea (cortical thick capsule surrounding the testis) into the seminiferous tubule region (medullary). Embedded within this connective tissue are the rete testis component of the duct conduction system for spermatazoa (Spermatozoa Duct Pathway: seminiferous tubule ‚ straight tubule ‚ rete testis ‚ ductuli efferentes ‚ ductus epididymidis ‚ ductus deferens)
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====medullary====
 
 
 
(Latin, ''medialis'' = in the middle) Term relating to the medulla; pith, marrow, inner portion of an organ. Usually combined with cortex (cortical) meaning the outer layer.
 
 
 
====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. Note all other non-germ cells divide by mitosis.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====meiotic sex chromosome inactivation====
 
 
 
(MSCI) The process of transcriptional silencing of the X and Y chromosomes that occurs only during male meiotic spermatogenesis. This is a specialised form of [#MSUC meiotic silencing of unsynapsed chromatin]. This specific silencing has also be called the second form of X chromosome inactivation, the first form occurs in all female embryo cells.
 
 
 
(More? [http://www.ncbi.nlm.nih.gov/pubmed/17329371 Meiotic sex chromosome inactivation.] Turner JM. Development. 2007 May;134(10):1823-3
 
 
 
====membrana granulosa====
 
 
 
The granulosa cells that line the developing follicles of the ovary. These cells proliferate to form the stratum granulosa and other granulosa cells are given specific names based upon their position within the follicle. In the antral follicle, membrana granulosa sits on the follicular basal lamina and lines the antrum as a stratified epithelium. The [C.htm#cumulus_oophorus cumulus oophorus] is a column of granulosa cells that attaches the oocyte to the follicle wall. The [C.htm#corona_radiata corona radiata] are the granulosa cells that directly surround the oocyte, and are released along with it at ovulation. Following ovulation the corona radiata provide physical protection to the oocyte and granulosa cells within the ovulating follicle contribute to [C.htm#corpus_luteum corpus luteum].
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====menopause====
 
 
 
(Greek, ''mene'' = moon, ''men'' = month, ''pause'' = end or cessation) The decrease in ovarian production of estrogen and progesterone leading to cessation of menstrual cycles, decrease in fertility, and end of female reproductive life. Usually occurs in the mid-40's, the term was first used by the French physician, de Gardanne in 1812.
 
 
 
(More? [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/Mcycle.htm#Menopause Human Menstrual Cycle] | [http://www.nlm.nih.gov/medlineplus/menopause.html Medline Plus - Menopause])
 
 
 
====menorrhagia====
 
 
 
Term used to describe heavy menstrual bleeding, is common in women of reproductive age (WHO data, affects 1011 out of 5322 women).
 
 
 
(More? [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/Mcycle.htm#Abnormalities Human Menstrual Cycle])
 
 
 
====menstrual age====
 
 
 
The gestation time calculated from the first day of the last menstrual period (LMP) prior to [F.htm#fertilization fertilization]. In humans, this differs from embryonic age by approximately two weeks.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====menstrual cycle====
 
 
 
The human reproductive cycle, an endocrine regulated change in female anatomy and physiology that occur over 28 days (4 weeks, a lunar month) during reproductive life (between puberty and menopause). This cycle ceases during pregnancy and differs from other non-primate vertebrates (eg rats, mice, horses, pig) females that have a reproductive cycle called the estrous cycle (oestrous, British spelling).
 
 
 
(More? [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/MCycle.htm Human Menstrual Cycle] | [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/Ocycle.htm Estrous Cycle])
 
 
 
====mitosis====
 
 
 
The normal division of all cells, except germ cells, where chromosome number is maintained. Note germ cell division (egg, sperm) is reductive meiotic division.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====Mullerian Inhibiting Substance====
 
 
 
(MIS, Anti-Mullerian Hormone, AMH, Mullerian inhibiting hormone, MIH). A sertoli cell secreted glycoprotein (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. The main role is to inhibit paramesonephric (Mullerian) duct development in males. Postnatally, after puberty it is also expressed in females by ovarian granulosa cells and has a role in follicle development.
 
 
 
(More?  [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=600957 OMIM - AMH])
 
 
 
====oocyte====
 
 
 
(Greek, ''oo'' = egg, ovum) The term used to describe the haploid egg or ovum formed within the ovary (female gonad) and released to enter the uterine tube and be transported to the [U.htm#uterus uterus]. The mature oocyte is the cell released from the ovary during ovulation.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====oogenesis====
 
 
 
(Greek, ''oo'' = egg + ''genesis'' = origin, creation, generation) process of diploid oogonia division and differentiation into an haploid oocyte (egg) within the ovary (female gonad). Mammalian meiosis will only be completed within the oocyte if [F.htm#fertilization fertilization] occurs.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====oogonia====
 
 
 
(Greek, ''oo'' = egg) diploid germ cells within the ovary (female gonad) which provide the primary oocytes for oocyte (egg) formation. In humans, all oogonia form primary oocytes within the ovary before birth.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====oophorus====
 
 
 
(Greek, ''oo'' = egg + ''phorus'' = carrying, egg-bearing) cumulus oophorus, used to describe the granulosa cells within the follicle that tether or link the oocyte to the wall of the follicle.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====ovarian factor====
 
 
 
A cause of infertility due to problems with egg production by the ovaries.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====ovarian hyperstimulation syndrome====
 
 
 
(OHSS) Condition associated with fertility drugs for in vitro fertilization and other reproductive abnormalities.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_5b.htm Week 1 - In Vitro Fertilization] | [http://www.nlm.nih.gov/medlineplus/ency/article/007294.htm Medlineplus - OHSS])
 
 
 
====ovarian monitoring====
 
 
 
The use of ultrasound and/or blood or urine tests to monitor ovarian follicle development and hormone production.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis])
 
 
 
====ovarian stimulation====
 
 
 
The use of drugs to stimulate the ovaries to develop follicles/eggs. (More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis] | [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/MCycle.htm Human Menstrual Cycle])
 
 
 
====ovary====
 
 
 
The two female gonads where female germ cells (oocytes, eggs) are generated and also the source of  estrogen and progesterone the female hormones regulating secondary sex characteristics and menstrual cycle uterine changes. The ovary is embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are lost in females.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis] | [http://embryology.med.unsw.edu.au/wwwhuman/MCycle/MCycle.htm Human Menstrual Cycle])
 
 
 
====oviduct====
 
 
 
(uterine horn, fallopian tube, oviduct, salpinx) see [#uterine_tube uterine tube]. A pair of tubular structures designed to transport the oocyte (egg) from the ovary to the [U.htm#uterus uterus] body.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://www.lab.anhb.uwa.edu.au/mb140/CorePages/FemaleRepro/femalerepro.htm#Fallopian Blue Histology - Female Reproductive System])
 
 
 
====ovulation====
 
 
 
The term used to describe the process of the mature follicle releasing the oocyte or ovum (and support cells) from the ovary surface into the peritoneal cavity. In humans, generally a single oocyte is released from a cohort of several maturing follicles. More than one follicle may be released (superovulation) following reproductive therapeutic treatment.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3a.htm Week 1 - Oogenesis] | [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====rectouterine pouch====
 
 
 
(Pouch of Douglas or rectovaginal) Anatomical description of the female peritoneal cavity lying between the back wall of the [U.htm#uterus uterus] and rectum.
 
 
 
====reductive division====
 
 
 
Term describing meiosis where diploid DNA content becomes haploid (halved).
 
 
 
====rete ovarii====
 
 
 
A group of epithelial tubules located at the hilum of the ovary possibly mesonephric origin.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/urogen.htm Urogenital Notes])
 
 
 
====rete testis====
 
 
 
The duct (epithelial tubules) conduction system for spermatazoa embedded within the mediastinum (connective tissue) located in the center of the testis (male gonad) derived from the mesonephric duct, and allow spermatazoa to travel from the seminiferous tubules to the vasa efferentia. (Spermatozoa Duct Pathway: seminiferous tubule ‚Üí straight tubule ‚Üí rete testis ‚Üí ductuli efferentes ‚Üí ductus epididymidis ‚Üí ductus deferens)
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
===RU 486===
 
 
 
RU 486 (or Mifepristone) is a steroid hormone similar in structure to the natural hormone progesterone, which is used as a birth control drug.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/wwwhuman/MCycle/RU486.htm RU486])
 
 
 
====Sertoli cells====
 
 
 
The supporting cells in the testes (male gonad) that induce primordial germ cells to commit to sperm development. Support is nutritional and mechanical, as well as forming a blood-testis barrier. In development these cells secrete anti-Müllerian hormone, which causes the Müllerian (paramesonephric) duct to regress, and help to induce other somatic cells to differentiate into Leydig cells. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist.
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====sperm====
 
 
 
The male haploid reproductive cell, often used generically (and incorrectly) to describe these cells and the fluid of the ejaculate. Term is a shortened form of scientifically correct term [[#spermatazoa spermatazoa]].
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====spermatazoa====
 
 
 
The male haploid reproductive cell, produced by meiosis in the testis (male gonad).
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====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 spermiogenesis].
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1_3b.htm Week 1 - Spermatogenesis])
 
 
 
====spermiogenesis====
 
 
 
(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).
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====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.
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====spermatogonial stem cells====
 
 
 
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.
 
 
 
(More? [[Testis Development]] | [[Spermatozoa Development]])
 
 
 
====sry====
 
 
 
(Sry, human; Testis-Determining Factor, TDF; Testis-Determining Factor on Y, TDY ) Gene name ====s====ex-determining ====r====egion of ====Y====, the gene locus on the Y chromosome encoding the male "testis determining factor", a protein transcription factor and a member of the high mobility group (HMG)-box family of DNA binding proteins. See also the transcription factor SRY-related protein, SOX9 (SRY-related high-mobility group (HMG) box 9)
 
 
 
(More? [http://embryology.med.unsw.edu.au/MolDev/MolDev.htm Molecular Notes] | [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes] | [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=480000 OMIM])
 
 
 
====stimulated cycle====
 
 
 
An ART cycle in which a woman receives drugs to stimulate her ovaries to produce more follicles.
 
 
 
(More? [http://embryology.med.unsw.edu.au/Notes/week1.htm Week 1 Notes])
 
 
 
====stroma====
 
 
 
(Greek, ''stroma'' = "a cover, table-cloth, bedding") Histological term used to describe supportive cells within an organ, tissue or structure. The term is often paired with [P.htm#parenchyma parenchyma], which describes the functional cells of an organ, tissue or structure. All organs can therefore be functionally divided into these 2 components, stromal/parenchymal.
 
 
 
====stromal cells====
 
 
 
(Greek, ''stroma'' = "a cover, table-cloth, bedding") Descriptive term in the ovary, for cells surrounding the developing follicle that form a connective tissue sheath (theca folliculi). This layer then differentiates into 2 layers (theca interna, theca externa). This region is vascularized and involved in hormone secretion.
 
 
 
====testes====
 
 
 
(Latin ''testis'' = "witness") The two male gonads (singular testis) where male germ cells (spermatozoa) are generated and also the source of testosterone (male hormone). Embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are preserved in male gonad development and lost in females.
 
 
 
(More? [[Testis Development]])
 
 
 
====testis====
 
 
 
(Latin ''testis'' = "witness", plural testes) The male gonad where male germ cells (spermatozoa) are generated and also the source of testosterone (male hormone). Embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are preserved in male gonad development and lost in females.
 
 
 
(More? [[Testis Development]])
 
  
====testis-determining factor====
+
The next Practical will continue on through embryonic development ([[BGDA Practical - Implantation to 8 Weeks|Implantation to 8 Weeks]]).
  
(TDF, Sry, Testis-Determining Factor on Y, TDY ) Protein name for the protein transcription factor product of the Sry gene on the Y chromosome responsible for maleness. This protein is a member of the high mobility group (HMG)-box family of DNA binding proteins. See also the transcription factor SRY-related protein, SOX9 (SRY-related high-mobility group (HMG) box 9)
+
===References===
  
(More? [http://embryology.med.unsw.edu.au/Notes/MolDev/MolDev.htm Molecular Notes] | [http://embryology.med.unsw.edu.au/Notes/Notes/week1.htm Week 1 Notes] | [http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=480000 OMIM])
+
<references/>
  
  
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[[Category:Carnegie Stage 8]] [[Category:Carnegie Stage 9]]
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[[Category:Carnegie Stage 8]] [[Category:Carnegie Stage 9]] [[Category:Week 3]]

Latest revision as of 15:50, 5 May 2019

BGDsmall.jpg
Practical 3: Oogenesis and Ovulation | Gametogenesis | Fertilization | Early Cell Division | Week 1 | Implantation | Week 2 | Extraembryonic Spaces | Gastrulation | Notochord | Week 3

Introduction

This page is a overview of events that occur in human development up to week 3 post-fertilization. From this Practical understand concepts of: fertilization, blastocyst development, implantation, bilaminar and trilaminar embryo formation, development of embryonic cavities and brief understanding of early placenta development.

By the end of week 3, segmentation of the trilaminar embryo 3 germ layers has begun:

Human development timeline graph 01.jpg

  1. Ectoderm - central neural plate and lateral parts form epidermis
  2. Mesoderm - midline notochord, adjacent somites, formation of the internal embryonic space (intraembryonic ceolom)
  3. Endoderm - epidermal lining of gastrointestinal tract and yolk sac lining

Note

Use the links to Carnegie stage 7, Carnegie stage 8 and Carnegie stage 9 to see a number of different views of the human embryo in the third week of development.

The timeline at the bottom of this page should give you a better perspective of the sequence of early developmental events. You would not be expected to know exact days (as they are only approximate anyway) it is more important to get the weeks and sequence right.


Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Stage 7

Stage7-sem2.jpg

Facts

Human embryonic stage 7 occurs during week 3 between 15 to 17 days.

The embryo is now 0.4 mm diameter in size.

The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images.

Events

Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.

Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.

From the primitive node a tube extends under the ectoderm in the opposite direction to the primitive streak. This tube forms first the axial process then notochordal process, then finally the notochord.

The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract.

Stage 7 - Implanted Conceptus

Stage7 bf5.jpg

 ‎‎Mobile | Desktop | Original

Stage 7 | Embryo Slides

Carnegie Stage 8

Stage8 SEM1.jpg

Facts

Human embryonic stage 8 occurs during week 3 between 17 to 19 days.

The embryo is now 1.0 - 1.5 mm in size.

Events

Gastrulation is continuing as cells migrate from the epiblast, continuing to form mesoderm.

Mesoderm lies between the ectoderm and endoderm as a continuous sheet except at the buccopharyngeal and cloacal membranes. These membranes have ectoderm and endoderm only and will lie at the rostral (head) and caudal (tail) of the gastrointestinal tract.

From the primitive node a tube extends under the ectoderm in the opposite direction to the primitive streak. This tube forms first the axial process then notochordal process, then finally the notochord.

The notochord is a key to embryonic folding and regulation of ectoderm and mesoderm differentiation. It lies in the rostrocordal axis and the embryonic disc will fold either side ventrally, pinching off a portion of the yolk sac to form the lining of the gastrointestinal tract.

Identify

  • embryonic disc
  • primitive node, primative streak, primative groove
  • connecting stalk
  • cut amniotic membrane

Carnegie stage 8


Carnegie Stage 9

Stage9 sem4c.jpg

Facts

Human embryonic stage 9 occurs during week 3 between 19 to 21 days.

The embryo is now 1.5 to 2.5 mm in size and somites have begun to form and number between 1 to 3 somite pairs during this stage.

The initial images are displayed unlabeled to allow you to explore the embryo for yourself, linked labeled versions are also available for some images.

Stage9 sem1.jpg

Events

Ectoderm - Neural plate brain region continues to expand, neural plate begins folding over the notochord. Gastrulation continues through the primitive streak region.

Mesoderm - Paraxial mesoderm segmentation into somites begins (1 - 3 somite pairs). Lateral plate mesoderm begins to vacuolate, dividing it into somatic and splanchnic mesoderm and to later form the intra-embryonic coelom. Prechordal splanchnic mesoderm begins to form the cardiogenic region, from which the primordial heart will develop.

Endoderm - Notochordal plate still visible which will form the notochord. Endoderm is still widely open to the yolk sac and germ cells form part of this layer. Extra-embryonic mesoderm on the yolk sac surface begins to form "blood islands".

Identify

  • Neural groove and neural folds, the mesoderm showing first somite bulges, that segments beside the neural groove to form somites but extends laterally to margin of embryonic disc lateral plate mesoderm, where it merges with the covering extraembryonic mesoderm.
  • The intra-embryonic coelom develops in the middle of the lateral plate mesoderm.


Carnegie stage 9


Carnegie Stage 10

Human embryonic stage 10 occurs at the beginning of week 4 development (GA week 6). This week will be covered in detail in the next practical class. The virtual slide image below shows a dorsal view of the embryo at the beginning of week 4.


Stage 10 - Dorsal View

Stage10 bf10.jpg

 ‎‎Mobile | Desktop | Original

Stage 10 | Embryo Slides


Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline


Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

Human Development Timeline

The table below shows human development features and approximate timing during the menstrual cycle to fertilization and the first 3 weeks of development.

The timing assumes fertilization the day after ovulation and the "weeks" refer to embryonic development and differ from Gestational Age (GA, clinical weeks shown in brackets, from last menstrual period) and "stages" refer to Carnegie stages of development.


First Trimester Timeline 
Links: human timeline | first trimester timeline | second trimester timeline | third trimester timeline
Gestational Day GA
Stage
Event
1
Menstrual Phase
Menstrual cycle.png

menstrual cycle changes: uterus endometrium (loss), ovary (follicle development)

2
  Human- menstrual uterine endometrium.jpg
3
 
4
   
5
Proliferative Phase Smear- early proliferative.jpgOva41he.jpg menstrual cycle changes: uterus endometrium (proliferation), ovary (Follicle Development)
6
7
   
8
Proliferative Phase
9
  Smear- mid-proliferative.jpg Human- mid-proliferative uterine endometrium.jpg Ovary10x.jpg Ova20he.jpg menstrual cycle - Mid proliferative
10
   
11
   
12
   
13
  Smear- late-proliferative.jpg Human- late proliferative uterine endometrium.jpg Menstrual cycle.png menstrual cycle - Late Proliferative
14
ovulation

Capacitation

Human ovulation 06.jpg Human oocyte.jpg Follicle 001 icon.jpg
Fertilization Day
Stage
Event
1
Secretory Phase

Stage 1

Early zygote.jpg Stage1 size with ruler.jpgSmear- secretory.jpg Human- secretory uterine endometrium.jpg fertilization, zygote, Secretory Phase
2
Stage 2 Stage2.jpg Week1 001 icon.jpg morula, Blastula
3
  Human-blastocyst-day-3-6-icon.jpg blastocyst
4
Stage 3 CSt3.jpg blastocyst Hatching (zona pellucida lost)
5
  Smear- late secretory.jpg Human- late secretory uterine endometrium.jpg Late Secretory, blastocyst (free floating)
6
Stage 4 Adplantation
7
Stage 5 Week2 001 icon.jpgStage5 bf11L.jpg
8
Week2 001 icon.jpg implantation
9
   
10
   
11
   
12
   
13
Stage 6 Stage6 bf03.jpgChorion 001 icon.jpg Chorionic Cavity
14
   
Day
Stage
Event
15
16
Stage 7 Stage7-bf1.jpg Stage7-sem2.jpg Stage7.jpg gastrulation, ectoderm, mesoderm, endoderm
17
   
18
Stage 8 Stage8 human.jpg Neuralplate 001 icon.jpg neural neurogenesis, neural groove and folds are first seen
19
 
Stage8 SEM1.jpg
20
Stage 9 Stage9 bf2c.jpg Stage9 sem1b.jpg Musculoskeletal somitogenesis, first somites form and continue to be added in sequence caudally (1 - 3 somite pairs).

neural the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open

Neural Crest mesencephalic neural crest is visible[1]

21
  heart cardiogenesis, week 3 begins as paired heart tubes.
Day
Stage
Event
22
Stage 10 Stage10 bf2c.jpg Stage10 sem10c.jpg Neuraltube 001 icon.jpg

Neural Crest differentiation at spinal cord level from day 22 until day 26

neural folds begin to fuse near the junction between brain and spinal cord, when Neural Crest cells are arising mainly from the neural ectoderm

Neural Crest trigeminal, facial, and postotic ganglia components visible[1]

Neural Crest migration of vagal level neural crest cells begins (7-10 somite stage)

neural rostral neural tube forms 3 primary brain vesicles (week 4)

respiratory Week 4 - laryngotracheal groove forms on floor foregut.

23
  heart begins to beat in Humans by day 22-23, first functioning embryonic organ formed.
24
Stage 11 Stage11 bf2c.jpg

thyroid - thyroid median endodermal thickening in the floor of pharynx

neural rostral (or cephalic) neuropore closes within a few hours; closure is bidirectional, it takes place from the dorsal and terminal lips and may occur in two areas simultaneously. The two lips, however, behave differently.

ventricular Optic ventricle appears and the neural groove/tube space is initially filled with amniotic fluid.[2]

25
Stage 12 Stage12 bf2b.jpg Stage12 sem1.jpg

pituitary Week 4 hypophysial pouch, Rathke's pouch, diverticulum from roof

liver septum transversum forming liver stroma and hepatic diverticulum forming hepatic trabeculae[3]

neural caudal neuropore takes a day to close (closure is approximately at future somitic pair 31/sacral vertebra 2)

neural secondary neurulation begins

ventricular onset of the ventricular system and separates the ependymal from the amniotic fluid.[2]

neural crest cardiac crest, neural crest from rhombomeres 6 and 7 that migrates to pharyngeal arch 3 and from there the truncus arteriosus[1]

neural crest vagal neural crest enter the foregut (20-25 somite stage)

26
   
27
   
28
Stage 13 Stage13 bf1c.jpg Stage13 sem1c.jpg neural the neural tube is normally completely closed, ventricular system now separated from amniotic fluid. Neural crest at spinal level is segregating, and spinal ganglia are in series with the somites. Spinal cord ventral roots beginning to develop.[4]

telencephalon cavity appears

Neural - Vascular Development - hindbrain is supplied by two parallel neural arteries (or channels) that obtain their blood supply from carotid-vertebrobasilar anastomoses given by the pharyngeal arch arteries; trigeminal artery, the otic artery, hypoglossal artery, and the proatlantal artery.[5]

liver epithelial cord proliferation enmeshing stromal capillaries[3]

smell Crest comes from the nasal plates[6]

integumentary 4 weeks - simple ectoderm epithelium over mesenchyme

integumentary 1-3 months ectoderm- germinative (basal) cell repeated division of generates stratified epithelium; mesoderm- differentiates into connective tissue and blood vessels

vision Optic vesicle lies close to the surface ectoderm. The surface ectoderm overlying the optic vesicle, in response to this contact, has thickened to form the lens placode.[7]

Diaphragm - pleuroperitoneal fold (PPF) first discernible in human embryos (CRL 6mm).[8]

29
pituitary Week 5 elongation, contacts infundibulum, diverticulum of diencephalon

heart Week 5 septation starts, atrial and ventricular

respiratory Week 5 left and right lung buds push into the pericardioperitoneal canals (primordia of pleural cavity)

Respiratory Week 5 to 17 lung histology - pseudoglandular

hearing Week 5 cochlear part of otic vesicle elongates (humans 2.5 turns)

30
   
31
   
32
Stage 14 Stage14 bf2l.jpg Stage14 sem1c.jpg Placodes sensory placodes, lens pit, otocyst, nasal placode, primary/secondary vesicles, fourth ventricle of brain

somite continued segmentation of paraxial mesoderm (somite pairs), heart prominence

head 1st, 2nd and 3rd pharyngeal arch, forebrain, site of lens placode, site of otic placode, stomodeum

Body - heart, liver, umbilical cord, mesonephric ridge visible externally as bulges.

limb upper and lower limb buds growing.

Abdominal Wall mesoderm of the primary body wall coalesced in the ventral midline to create the abdominal cavity.[9]

neural first appearance of the future cerebral hemispheres. Cerebellar plate differentiated to an intermediate layer, and future rhombic lip identifiable[10]

Neural - Vascular Development - basilar artery forms from the consolidation of the neural arteries.[5]

ventricular Subarachnoid space initially as irregular spaces on the ventral surface of the spinal cord.[11]

liver hepatic gland and its vascular channels enlarge, hematopoietic function appears[3]

vision lens placode is indented by the lens pit.[7]

33
Stage 15 Stage15 bf1c.jpg

neural cranial nerves (except olfactory and optic) are identifiable in more advanced embryos[12]

Neural - Vascular Development - vertebral arteries form from transverse anastomoses between cervical intersegmental arteries, beginning with the proatlantal artery and proceeding downward to the 6th intersegmental artery,[5]

vision lens pit is closed. The lens vesicle and optic cup lie close to the surface ectoderm and appear to press against the surface.[7]

34
 
35
  vision 35 to 37 days retinal pigment present
36
pituitary Week 6 - connecting stalk between pouch and oral cavity degenerates

parathyroid Week 6 - diverticulum elongate, hollow then solid, dorsal cell proliferation

thymus Week 6 - diverticulum elongate, hollow then solid, ventral cell proliferation

adrenal Week 6 - fetal cortex forms from mesothelium adjacent to dorsal mesentery, medulla neural crest cells from adjacent sympathetic ganglia

respiratory Week 6 - descent of heart and lungs into thorax. Pleuroperitoneal foramen closes

tongue Week 6 - gustatory papilla, caudal midline near the foramen caecum (week 6 to 7 - nerve fibers approach the lingual epithelium)

37
Stage 16 Stage16 bf1c.jpg Neural first parasympathetic ganglia, submandibular and ciliary, are identifiable[13]

Neural - Vascular Development - development of the middle cerebral artery is first identified as small buds originating proximal to the anterior cerebral artery on the anterior division of the primitive internal carotid artery.[5]

limb upper limb bud nerves median nerve, radial nerve and ulnar nerve entered into hand plate, myoblasts spindle shaped and oriented parallel to limb bud axis.

Abdominal Wall muscle cell migration about 25% of the hemicircumference of the abdominal cavity, the lateral plate mesoderm has become more condensed and thicker in the area around the myoblasts.[9]

heart outflow tract elliptical configuration with four cushions, the two larger fusing at this stage. Semilunar valve leaflets form at the downstream end of the cushions

head lip and palate components of the upper lip, medial nasal prominence and maxillary process present, median palatine process appears.

Eyelid prior to the development of the eyelids, one small sulcus or groove forms above the eye (eyelid groove) and another below it.[7]

38
   
39
   
40
   
41
Stage 17 Stage17 bf1c.jpg
  • neural
    • telencephalon areas of the future archicortex, paleocortex, and neocortex, visible. Beginning of future choroid plexus[14]
    • ventricular primordium of the epidural space appears first on the ventral part of the vertebral canal and develops rostro-caudally[15]
  • smell olfactory nerve fibres enter the brain[6]
  • Eyelid sulcus (groove) above and below eye deepen and eyelid folds develop (below first and then above)[7]
  • Diaphragm - pleuroperitoneal fold (PPF) no longer separated from the diaphragm (CRL 14mm)[8]
  • Abdominal Wall muscle cells now migrated approximately 50% of the distance to the ventral midline, inner and outer layers were not discernible yet.[9]
42
  heart separation of common cardiac outflow (aortic arch and pulmonary aorta)
Day
Stage
Event
43
pancreas Week 7 to 20 pancreatic hormones secretion increases, small amount maternal insulin

respiratory Week 7 - enlargement of liver stops descent of heart and lungs

44
Stage 18 Stage18 bf1c.jpg

limb bone forms by endochondrial ossification and throughout embryo replacement of cartilage with bone (week 5-12).

neural smell vomeronasal fibres and nervus terminalis[6]

liverobturation due to epithelial proliferation, bile ducts became reorganized, continuity between liver cells and gut[3]

ventricular duramater appears and spaces surround the circumference of the spinal cord, which coalesce and contain many blood vessels.[15]

Female uterus opening of the paramesonephric (Müllerian) duct to the coelomic cavity formed as an invagination of the coelomic epithelium[16]

Abdominal Wall separation of the myoblasts into distinct inner and outer layers, with unidirectional orientation. Abdominal wall thicker in the region where secondary structures were forming compared with the primary body wall region, dorsally outermost layer of connective tissue approximately half of this thickness.[9]

45
   

liver (stage 18 to 23) biliary ductules developed in periportal connective tissue

produces ductal plates that receive biliary capillaries[3]

46
   
47
   
48
Stage 19 Stage19 bf1c.jpg
  • vision - (stage 19 -22) eyelid folds develop into the eyelids and cover more of the eye as the palpebral fissure takes shape. The upper and the lower eyelids meet at the outer canthus in Stage 19.[7]
  • cardiovascular
  • Respiratory - first generation of subsegmental bronchi now complete, see bronchial tree reconstruction[20] (plates 3 and 4).
  • gastrointestinal tract - anal membrane defined.
  • renal - Cloacal membrane ruptures from urinary pressure at stage 18 or stage 19,
  • genital
    • testis - Rete testis develops from the seminiferous cords at stages 19–23, and tunica albuginea forms.[21].
    • ovary - Rete ovarii cords are developing.[22]
    • uterus Müllerian duct grows independently from the invagination of the coelomic epithelium during stages 19-23[16]
  • musculoskeletal
    • Sternum right and left sternal bars are present.[23] (figs. 7-17 and 7-22)
    • Abdominal Wall segregation of the myoblasts into four distinct muscle groups with unidirectional orientation of myoblasts. Myoblast migrated over half of the distance to the ventral midline, abdominal wall thickest where the muscles migrated and the outermost layer of connective tissue comprises approximately half of the total thickness of the abdominal wall. Rectus muscle completely separated after migrating over half the distance to the midline.[9]
  • neural
    • rhombencephalon migration for olivary and arcuate nuclei begins.
    • choroid plexus of the fourth ventricle present.
    • stria medullaris thalami reaches the habenular nuclei.
    • habenular commissure begins to develop.
    • accessory olivary nucleus appears[24]
    • Neural - Vascular Development - middle cerebral artery becomes more prominent, the plexi fuse into a single artery and further branches pierce the cerebral hemisphere.[5]
49
   
50
Stage 20 Stage20 bf1c.jpg

Head scalp vascular plexus visible

limb upper limbs begin to rotate ventrally

neural amygdaloid body has at least four individual nuclei[24]

oculomotor nerve shows a dorsolateral and a ventromedial portion

rhombic lip (rhombencephalon) formation of the cerebellum (intermediate layer) and of the cochlear nuclei

cerebellum cell layer (future Purkinje cells) develops

choroid plexuses of the fourth and lateral ventricles

Eyelid the inner canthus is established.[7]

51
  gastrointestinal tract anal membrane perforates
52
Stage 21 Stage21 bf1c.jpg

neural cortical plate appears in the area of future insula[25]

Neural - Vascular Development - formation of the anterior communicating artery.[5]

limb upper and lower limbs rotate

Intraembryonic Coelom pericardioperitoneal canals close

Abdominal Wall Myoblasts have reached the ventral midline and myotubes were present and oriented uniformly within all muscle groups. The rectus abdominis formed distinct bundles of muscle. Connective tissue layers comprised the majority of the thickness of the abdominal wall, outermost layer of connective tissue accounted for the majority of this thickness.[9]

53
   
54
Stage 22 Stage22 bf1c.jpg neural neocortical fibres project to epithalamus, to dorsal thalamus, and to mesencephalon[25]

limb fingers and toes lengthen

smell Stage 22 to early fetal period - migratory streams of neurons from the subventricular zone of the olfactory bulb towards the future claustrum[6]

Uterus Vagina fused duct (uterovaginal canal) bifurcated at the caudal portion at Carnegie stages 22 and 23[16]

55
Genital 8 Weeks Testis - mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione

Genital 8 to 12 Weeks - hCG stimulates testosterone production

Tongue Week 8 - nerves penetrate epitheilai basal lamina and synapse with undifferentiated, elongated, epithelial cells (taste bud progenitor cell)[26]

56
Stage 23 Stage23 bf1c.jpg Stage 23 defines the end of the embryonic (organogenesis) period

Mesoderm heart prominence, ossification continues

Head nose, eye, external acoustic meatus, eyelids, external ears, rounded head

Body - straightening of trunk, umbilical cord, intestines herniated at umbilicus

limb upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits

Extraembryonic Coelom chorionic cavity is now lost by fusion with the expanding amniotic cavity

neural rhombencephalon, pyramidal decussation present, nuclei and tracts similar to those present in the newborn cerebellum present as only a plate connected to midbrain and hindbrain through fibre bundles[27]

Axial Skeleton vertebral column 33 or 34 cartilaginous vertebrae (20-33 mm in total length), vertebral pedicles, articular and transverse processes identifiable (no spinous processes)[28]

Abdominal Wall Rectus muscle forms 2 or 3 distinct layers with myotube orientation uniform in all muscles. The external oblique and internal oblique started to expand in thickness, transversus a thin layer of muscle.[9]

 
Week 8 Stomach Week 8 - Gastrin containing cells in stomach antrum. Somatostatin cells in both the antrum and the fundus.

Genital - Female Development paired paramesonephric (Müllerian) ducts contact each other and are fused into a single tube that separates again and returns to the mesonephric (Wolffian) ducts. The paramesonephric ducts have not yet reached the urogenital sinus.[16]

57-63
Week 9 Beginning of Fetal Development


Historic Embryology
Embryology History George Streeter In 1949 the embryologist George Streeter[29] used the replacement of cartilage within the humerus by bone marrow as an arbitrary definition of the embryo to fetus transition.
"If the onset can be recognized in a given specimen, that specimen is straightway classed as a fetus."


CRL 43 mm, femur length 6 mm

9 weeks CRL 50 mm - genital genitalia in both sexes look identical[30]

uterus - paramesonephric ducts come into apposition with the urorectal septum and begin to fuse

Day
Stage
Event
64
Size comparison embryo-fetus actual.jpg

Gastrointestinal Tract Week 10 intestines in abdomen

Pituitary growth hormone and ACTH detectable

Pancreas Week 10 glucagon (alpha) differentiate first, somatostatin (delta), insulin (beta) cells differentiate, insulin secretion begins

Tongue Week 10 shallow grooves above the taste bud primordium

Stomach Week 10 - Glucagon containing cells in stomach fundus.

Nail Development fingernails appear

outer ear Week 10 - Meatal plug extends in a disc-like fashion, the meatus is boot-shaped with a narrow neck and the sole of the meatal plug spreading widely to form the future tympanic membrane medially. Proximal portion of the neck starts to be resorbed.

inner ear Week 10 - neural-crest-derived melanocytes migrate into the cochlea. They penetrate the basement membrane of the lateral wall epithelium and develop into the intermediate cells of the stria vascularis.[31]

65
   
66
 
67
   
68
 
69
   
70
Week 10 - CRL 55 mm, femur length 9 mm, biparietal diameter 17 mm
Day
Stage
Event

neural - Cerebrum appearance of the first sulcus (week 11-15, GA 13-17 weeks)[32]

71
Size comparison embryo-fetus actual.jpg

Thyroid colloid appearance in thyroid follicles, iodine and thyroid hormone (TH) synthesis

Stomach Week 11 - Serotonin containing cells in both the antrum and the fundus.

72
   
73
 
74
   
75
 
76
   
77
Week 11 - CRL 68 mm, femur length 12 mm, biparietal diameter 20 mm
Systems  
Systems: bone timeline | eye neural crest timeline | heart abnormality timeline | hearing EAM timeline | muscle timeline | ovary timeline | placental villi timeline | shoulder timeline | smell timeline | spleen timeline | ventricular timeline


Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Next

Finished Lab 3 !

If you have finished and would like to apply your knowledge, I have also included some Clinical Questions based around this period of development.

If you have finished and need some more help understanding this period of development, I have included some links to Online References.


If you have finished and are interested in looking at tissues involved in this period of development, I have included some links to Histology Images.


Note that this Practical has discussed mainly development of the embryo as placental development will be covered in detail in another practical (Placenta and Fetal Membranes).

The next Practical will continue on through embryonic development (Implantation to 8 Weeks).

References

  1. 1.0 1.1 1.2 O'Rahilly R & Müller F. (2007). The development of the neural crest in the human. J. Anat. , 211, 335-51. PMID: 17848161 DOI.
  2. 2.0 2.1 O'Rahilly R & Müller F. (1990). Ventricular system and choroid plexuses of the human brain during the embryonic period proper. Am. J. Anat. , 189, 285-302. PMID: 2285038 DOI.
  3. 3.0 3.1 3.2 3.3 3.4 Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
  4. Müller F & O'Rahilly R. (1988). The development of the human brain from a closed neural tube at stage 13. Anat. Embryol. , 177, 203-24. PMID: 3354839
  5. 5.0 5.1 5.2 5.3 5.4 5.5 Menshawi K, Mohr JP & Gutierrez J. (2015). A Functional Perspective on the Embryology and Anatomy of the Cerebral Blood Supply. J Stroke , 17, 144-58. PMID: 26060802 DOI.
  6. 6.0 6.1 6.2 6.3 Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 Pearson AA. (1980). The development of the eyelids. Part I. External features. J. Anat. , 130, 33-42. PMID: 7364662
  8. 8.0 8.1 Clugston RD, Zhang W & Greer JJ. (2010). Early development of the primordial mammalian diaphragm and cellular mechanisms of nitrofen-induced congenital diaphragmatic hernia. Birth Defects Res. Part A Clin. Mol. Teratol. , 88, 15-24. PMID: 19711422 DOI.
  9. 9.0 9.1 9.2 9.3 9.4 9.5 9.6 Nichol PF, Corliss RF, Yamada S, Shiota K & Saijoh Y. (2012). Muscle patterning in mouse and human abdominal wall development and omphalocele specimens of humans. Anat Rec (Hoboken) , 295, 2129-40. PMID: 22976993 DOI.
  10. Müller F & O'Rahilly R. (1988). The first appearance of the future cerebral hemispheres in the human embryo at stage 14. Anat. Embryol. , 177, 495-511. PMID: 3377191
  11. Patelska-Banaszewska M & Woźniak W. (2005). The subarachnoid space develops early in the human embryonic period. Folia Morphol. (Warsz) , 64, 212-6. PMID: 16228957
  12. Müller F & O'Rahilly R. (1988). The development of the human brain, including the longitudinal zoning in the diencephalon at stage 15. Anat. Embryol. , 179, 55-71. PMID: 3213956
  13. Müller F & O'Rahilly R. (1989). The human brain at stage 16, including the initial evagination of the neurohypophysis. Anat. Embryol. , 179, 551-69. PMID: 2751117
  14. Müller F & O'Rahilly R. (1989). The human brain at stage 17, including the appearance of the future olfactory bulb and the first amygdaloid nuclei. Anat. Embryol. , 180, 353-69. PMID: 2802187
  15. 15.0 15.1 Patelska-Banaszewska M & Woźniak W. (2004). The development of the epidural space in human embryos. Folia Morphol. (Warsz) , 63, 273-9. PMID: 15478101
  16. 16.0 16.1 16.2 16.3 Hashimoto R. (2003). Development of the human Müllerian duct in the sexually undifferentiated stage. Anat Rec A Discov Mol Cell Evol Biol , 272, 514-9. PMID: 12740945 DOI.
  17. Keibel F. and Mall FP. Manual of Human Embryology II. (1912) J. B. Lippincott Company, Philadelphia.
  18. Congdon ED. Transformation of the aortic-arch system during the development of the human embryo. (1922) Contrib. Embryol., Carnegie Inst. Wash. Publ 277, 14:47-110.
  19. Teal SI., Moore GW. and Hutchins GM. Development of aortic and mitral valve continuity in the human embryonic heart. (1986) Amer. J. Anat., 176:447-460.
  20. Wells LJ. Development of the human diaphragm and pleural sacs. (1954) Contrib. Embryol., Carnegie Inst. Wash. Publ. 603, 35: 107-134.
  21. Jirásek JE. Development of the Genital System and Male Pseudohermaphroditism. (1971) Johns Hopkins Press, Baltimore.
  22. Wilson KM. Origin and development of the rete ovarii and the rete testis in the human embryo. (1926) Carnegie Instn. Wash. Publ. 362, Contrib. Embryol., Carnegie Inst. Wash., 17:69-88.
  23. Gasser RL. Atlas of Human Embryos. (1975) Harper & Row, Hagerstown, Maryland.
  24. 24.0 24.1 Müller F & O'Rahilly R. (1990). The human brain at stages 18-20, including the choroid plexuses and the amygdaloid and septal nuclei. Anat. Embryol. , 182, 285-306. PMID: 2268071
  25. 25.0 25.1 Müller F & O'Rahilly R. (1990). The human brain at stages 21-23, with particular reference to the cerebral cortical plate and to the development of the cerebellum. Anat. Embryol. , 182, 375-400. PMID: 2252222
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Cite this page: Hill, M.A. (2021, July 26) Embryology BGDA Practical 3 - Week 3 Summary. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_3_-_Week_3_Summary

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