Development Flashcards
Gestation Period
The time span from fertilization to birth ( 38 weeks )
Prenatal period ( before birth )
Embryological development: developing human for the first 2 months after fertilization ( the embryo )
Fetal development: from 9 weeks until birth ( is not the fetus and not the embryo )
By the end of the 3rd month, the placenta is now functioning
Events before fertilization
This all occurs in the uterine tubes within 24 hours after ovulation
Fertilization likely 2 days before to 1 day after ovulation
Oocyte travels towards the uterus through the uterine tubes and the movement of cilia
The sperm swim towards the oocyte by flagella
-uterine contractions help the sperm move towards the oocyte
Final maturation of the sperm occurs inside the female
-acrosomal membrane becomes fragile
Sperm spends 7 hours in the female reproductive tract before capable of fertilization
*sperm only survives 48 hours in female
*Oocyte viable 24 hours after ovulation
Embryonic period
Extends from fertilization through the eighth week of development
Fertilization
The merging of genetic information between a
Haploid sperm cell and a haploid secondary oocyte merging into a single diploid nucleus
Fertilization of an egg
Sperm penetrates the corona radiata and the zona pellucida around the oocyte
Acrosome enzymes
allows the sperm to penetrate the corona radiata
Fertilization cycle
Day1-12
- Zygote
Day 1: Begins mitotic division, known as cleavage. First division takes about 6 hours
Day 2: two days after fertilization, a second cleavage is completed, now 4 cells (blastomeres)
Day 3: there are 16 cells. all small cells are blastomeres
Day 4: the clusters are now a morula, still surrounded by the zona pellucida
On day 4 or 5: Morula enters uterine cavity, nourished by the uterine milk.
At the 32 cell stage , the fluid inside morula rearrange the blastomeres into blastocyst.
Day 6 or 7: blastocyst implants to endometrium wall of uterus
Day 8: trophoblast develops into syncytiotrophoblast and cytotrohoblast, becoming part of the chorion.
The embryo blast develops two layers, cells of those structures form bilaminar embryonic disc.
The amniotic cavity forms from the epiblast & fills with amniotic fluid
Yolk sac is formed
Day 9: lacunae form
Day 12: yolk sac and lacunae form lacunar networks
Blastocyst
Two cells populations:
Embryoblast and trophoblast
Placenta
provides nutrients to embryo
The chorion
Blocks antibody production by the mother
Promotes the production of T lymphocyte
Produces human chorionic gonadotropin
Secretes estrogens after the first 3-4 weeks of pregnancy and progesterone by the 6th week
Gastrulation
first major event of the 3rd week
- Bilaminar disc transforms into a two dimensional trilaminar disc, made up of ectoderm, mesoderm and endoderm
- Involves rearrangement and migration of epiblast cells
Placentation
Process of forming the placenta
Produced hormones used to sustain the pregnancy
Site of exchange for nutrients and wastes between the mother and fetus
Placenta
Two parts
Fetal portion
maternal portion
True labor
Stage of dilation
Stage of expulsion
Placental stage