Lect 1 Flashcards
What stages make up prenatal?
Day one - end of week 2 : pre embryonic
Week 3- end of week 8: embryonic
Week 9- birth ( week 38) : fetal
What is embryology?
The study of prenatal development
Normal human structure/variation and prenatal care
What is the main even in pre embryonic stage?
Implantation of the zygote into the uterine wall
What are the main events in embryonic stages
The creation of germ layers and organogenesis
What occurs during the fetal stage?
Growth and maturation of organ systems
What’s the difference between gestational age and fertilisation age?
Gestational is obstetric, starts from 1st day of last normal menstral period, where as fertilisation would have occurred sometime prior to this event ( about 2 weeks -14 days)
How long is the first trimester?
13 weeks
When does almost 50% of spontaneous abortions happen?
The pre embryonic period ( day 1 - end of week 2)
Most birth defects appear in what stage?
Embryonic period , when organogenesis is occurring
Define conceptus
All structures that are derived from the fertilised egg( placenta, anything that is not normally in the mom before fertilisation
What is induction?
Initiation of embryonic cell migration
What is gametogenesis?
Gamete production and preparation for fertilisation - occurs through mitosis, meiosis, and maturation
What state is the cell in before DNA replication occurs?
You have 1 diploid ( mom and dad) cell, 2n: 46 single chromatid chromosomes (23 mom: 23 dad) … This is normal
What cell type do you have after DNA replication occurs during gametogenesis?
1 diploid cell -(mom and dad ) but doubled ..4n : 46 DOUBLE chromatid chromosomes
After DNA replication Is the 1st mitosis decision. What does the cells look like ?
2 HAPLOID cells, (1 for maternal material and 1 with paternal material) but each has 2n: 23 double chromatid chromosomes
What stage do you have 4 separate haploid cells (n:23 single chromatid chromosomes) ?
After the second mitosis decision
When does OOgenesis begin ?
Prenatal ,is DNA replication portion of meiosis
When does spermatogenesis begin?
Puberty is continuous. 86 day cycle
When does meiosis one occur in famale OOgenesis?
Meiosis I occurs prenatal ( like DNA replication) and completes during ovulation
When does meiosis II begin/ complete for females?
Meiosis II begins at ovulation and completes at fertilisation
What are the products of meiosis for males and females?
Females make 1 oocyte ( and 3 polar bodies) males make 4 spermatids that mature into sperm around 86 days
What are the three important factors of meiosis ?
1- forms diploid cell/ fertilisation 23 mom 23 dad single chromatid chromosomes
2- random assortment
3- variation and recombination
If there is a chromosomal abnormality during meiosis what can happen ?
~ 25% spontaneous abortions and ~10% major birth defects
What is it when chromosome pairs do not separate properly?
Nondisjunction - can cause monosomy or trisomy
What is trisomy 21?
Down syndrome - extra chromosome at chromosome 21
When you have one chromosome missing?
Turner syndrome . 45, X monosomy .. At 23 you have x but no Y
What causes Klinefelter syndrome?
You have an extra chromosome: 47 xxy trisomy.
When is the oocyte in MEIOTIC arrest?
After birth, before ovulation of the oocyte, correlation between increased wait in MEIOTIC arrest and increase risk to environmental influences.
What is the male reproductive pathway?
TED EU: testis, epididymis, ductus deferens, ejaculatory duct, urethra
What happened in the epididymis ?
Storage of sperm, sperm become motile, and released at ejaculation
Where does OOgenesis ocur?
I the ovary
What is capacitation?
7 hour conditions of sperm, removes glycoproteins coat on spermatids head
Where does fertilisation typically occur?
Ampulla of uterine tube
If more than one spam fertilises the egg it is called…
Polyspermy
Before fertilisation what stage is the oocyte in?
The oocyte is arrested in meiosis II until fertilisation ( meiosis I was complete at ovulation)
What is the “enzymatic drill”?
The acrosome reaction where the sperm drills through the zone polucida of the oocyte .
What does the acrosome reaction trigger?
The zone reaction, where the ZP hardens to prevent polyspermy
If polyspermy occurs, what can be the cause of this?
The zone reaction did not occur quick enough
What is the result of the some membrane fusing with the oocyte?
Completing on meiosis II
What are the fertilisation sequence of events?
1.) capacitation 2.) corona radiate penetration 3.) Acrosome and Zona reactions 4.) fusion and meiosis II completion 5.) zygote and sex is formed
What is a pro nuclei ?
A haploid
What percentage of couples are infertile?
15-30% reasons - insufficient sperm #, poor motility, PID, Ovulation disorders, endometriosis, cysts
When is the greatest risk of spontaneous abortions ?
Pre embryonic period
When is the greatest risk of birth defects?
Embryonic period ( week 3- end of 12)
