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Sperms have what stages of development in order
- Spermatogonia 2n
- Spermatocye (Primary 4n and Secondary 2n)
- Spermatogenesis 1n
- - Spermatid
- - Spermatazoa (motile)
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When do primary oocytes start meiosis
By the seventh month of development
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Primary oocytes are arrested in what phase of meiosis 1
Diplotene
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Usual site of fertilization of the oocyte is in the
Ampullary region of Fallopian tube (1/3 outer part)
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Viability of gametes last for how long after their release
Oocytes (24 hrs), Sperm ( 48 hrs)
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What oocyte is released at ovulation
Secondary Oocyte in 2nd meiotic division
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How many sperms reach secondary oocyte in ampullary region of fallopian tube
About 300 to 500
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Spermatozoa can’t fertilize oocyte unless they undergo
Capacitation and acrosome reaction
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What layers do the sperm have to penetrate before reaching the ovum
- Corona radiata
- Zona Pellucida
"After a corona your in the zone"
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What happens once the sperm penetrates the oocyte plasma membrane
There is a fast block, and a slow block preventing other sperm from entering
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When does meiosis II start in the secondary oocyte
After the sperm enters
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Nucleus of ovum and sperm after penetration is called
- Female Pronucleus
- Male Pronucleus
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When is fertilization finished and in turn the zygote made
When the male pronucleus and female pronucleus fuse
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After the 3rd cleavage, the compacted ball of cells are held together by
Tight junctions
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During cleavage the compact cells don't grow because
They are held together by Zona pellucida 
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At about 3 days, the zygote is a ball of cells called the
Morula (about 12-16 cells)
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As cleavage continues, the morula does what
Passes down the uterine tube towards the uterus.
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About day 4, the embryo does what
Enters the uterine cavity, the zygote is divided into 2 parts, an outer cell mass called the trophoblast and inner cavity called a blastocyst cavity
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The trophoblast gives rise to
Part of the placenta and the embryoblast (inner cell mass)
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The entire zygote is called the
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When does the zona pallucida dissappear
While the blastocyst sits in the uterine cavity for about two days
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On about day 6, the trophoblast (outer shell)
Becomes sticky by L-selectins, and attaches to the uterine epithelium and works its way in
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Following the L-selectins attaching to the uterine, integrins of trophoblast bind to
Laminins of epithelium causing attachment to fibronectin for migration to occur
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By end of 1st week of development
The blastocyst is superficially implanted
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Embryoblast is
The cell mass in the blastocyst
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During the second week of development the embryoblast and the trophoblast
Grow at different rates
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What happens to the embryoblast at days 7 and 8
It seperates into two layers the epiblast (columnar) and hypoblast (cuboidal)
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The hypoblast and epiblast layers form the
Bilaminar germ disc, this will form the tissues of the embryo
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Days seven and eight the trophoblast divide into what two layers
- SYNCYTIOTROPHOBLAST
- CYTOTROPHOBLAST
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The amnion is, and develops where and when
A protective membrane that develops in the epiblast and is eventually surrounds the entire embryo, starts development on the 8th day
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When is the embryo completely embedded in the endometrium and have the fibrin plug
Days 9-10
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What portion of the newly formed embryo is attached to the maternal endometrial stroma
Syncytiotrophoblast
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Where and when does the maternal blood flow in
- Lacunar spaces in the syncytiotrophoblast (Day 28)
- Can be mistaken for a period and can interfere with an pregnancy dating
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The extraembryonic mesoderm is found where
- Covering over the secondary yolk sac and amnion
- Lines the inside of the cytotrophoblast
- Inner layer of the chorionic cavity
- Space between the cytotrophoblast and the primative yolk sac
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The only place where the extraembryonic mesoderm traverses the chorionic cavity is in the
Connecting stalk
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The connecting stalk becomes the
Umbilical cord
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The prechordal plate is a
"uniquely thickened portion" of the endoderm that is in contact with ectoderm (cranial development occurs here)
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Placenta praevia
is an complication in which the placenta is attached to the uterine wall close to or covering the cervix
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An ectopic pregnancy, is a complication of pregnancy in which
The pregnancy implants outside the uterine cavity
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What is the main enzyme used to break down the corona radiata for the sperm to enter
Acrosin
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Why doesn't the mothers body detect the foreign sperm and chromosome and destroy it
Major Histocompatibility complex class 1B molecule (HLA-G). This blocks recognition of conceptus as foreign tissue
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Heusers membrane
Forms the lining of the primitive yolk sac (days 9-10)
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By day 12 the hypoblast
Begin to grow over the inside of the Heusers membrane
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