Fertilization & Development Flashcards
3 Periods
Germinal stage, Embryonic period, and Fetal period
First 2 weeks of fertilization
Germinal stage
A complex multi-step process that is complete within 24 hours
Fertilization
The fertilization takes place in…
Fallopian tube
This links an ovary to the uterus
Fallopian tube
It takes about ___-___ for the sperm to reach the egg
30 - 45 minutes
Phase in the menstrual cycle when the ovary releases an egg (ovum)
Ovulation
Ovulation happens on day ____ of a 28-day menstrual cycle
Day 14
Estrogen levels rise as a result of increased estrogen production by hormonally active granulosa cells within the follicle
Notes lang ito
After ovulation, the egg is capable of fertilization for only 12 to 24 hours
Notes
Sperm can remain within the female reproductive tract for
5 days
To fertilize an egg, sperm must penetrate the __________ and the ___________
- corona radiata (granulosa cells)
- zona pellucida
What is the glycoprotein layer outside of the oocyte’s plasma membrane
Zona pellucida
1mL of sperm normally contains 100 million sperm
True
Receptor for the sperm in the zona pellucida
Glycoprotein ZP3
After fertilization (at about 24 hours), the zygote begins mitotic division called _______. The first division takes about _______. Successive divisions take less time
- Cleavage
- 6 hours
By the second day after fertilization, a second cleavage is completed yielding _____
4 cells
By the end of the______ there are 16 cells. Each division yields smaller and smaller cells (blastomeres).
- Third day
By the fourth day the cluster of cells resembles a mulberry and is called a ______. It is still surrounded by the zona pellucida and is still the size of the zygote.
- Morula
On day 4 or 5, the morula enters the uterine cavity and is nourished by uterine milk, a glycogen-rich secretion from endometrial glands in addition to stored nutrients from the cytoplasm.
Notes
Occurs when a fertilized egg grows outside the uterus
Ectopic pregnancy
At the 32-cell stage (Day 5), the fluid now inside the morula, rearranges the blastomeres into a large, fluid filled blastocyst cavity (blastocoel). The mass is now called a _______
Blastocyst
2 different populations arose when blastocyst is formed.
The __________ (inner cell mass) will develop
into the embryo.
The __________ (outer cell mass) will develop
into the outer chorionic sac surrounding the
fetus, and the fetal portion of the placenta.
- Embryoblast
- Trophoblast
The blastocyst remains free in the uterine cavity for about 2 days and then implants by attaching to the endometrium at around 6 days after fertilization.
Notes: When the blastocyst is attached to the endometrium, implantation occurs.
True or false:
Implantation usually occurs in either the anterior portion of the fundus or the body of the uterus.
False. It occurs in the “posterior” portion of the fundus
True or false:
The outer cell mass orients toward the endometrium
False. The “inner” cell mass orients toward the endometrium
After implantation, the endometrium is called the ________.
Decidua
About 8 days after implantation, the trophoblast develops into the ____________ and _________.
A. Embryoblast and blastocytes
B. Embryblast and trophoblast
C. Hypoblast and epiblast
D. Syncytiotrophoblast and cytotrophoblast
D. Syncytiotrophoblast and cytotrophoblast
At around 8 days, the embryoblast also develops into two layers: _____________ and __________
A. Embryoblast and blastocytes
B. Embryblast and trophoblast
C. Hypoblast and epiblast
D. Syncytiotrophoblast and cytotrophoblast
C. Hypoblast and epiblast
Hypoblast means
Primitive endoderm
Epiblast means
Primitive ectoderm
It surrounds the entire embryo
Amniotic fluid
Also on the 8th day, the exocoelomic membrane forms that, together with the hypoblast forms the _________
On the 9th day, small spaces called ________
By the ______ day, they fuse to form _________
- Yolk sac
- Lacunae form
- 12th day
- Lacunar networks
About the 12th day after fertilization, the
extraembryonic mesoderm develops.
The extraembryonic mesoderm together with the trophoblast forms the chorion which surrounds the embryo and, later, the fetus.
Notes
Hormone typically found in identifying pregnancy
Human chorionic gonadotropin (hCG)
The chorion:
○ Blocks antibody production by the mother
○ Promotes production of T lymphocytes to
suppress the immune response in the uterus
○ Produces human chorionic gonadotropin (hCG)
Notes :)) basahin :)) mo :))
The first major event of the 3rd week of development is ?!
Gastrulation!
The two-layered embryonic disc transforms into a trilaminar (three-layered) embryonic disc which are:
Ectoderm, mesoderm, endoderm
True or false:
Gastrulation is associated with the rearrangement and migration of cells from the hypoblast
False: It is from the epiblast
The first step in gastrulation is formation of the _________
A. Primitive streak
B. Primitive node
C. Embryonic disc
D. Notochord
A. Primitive streak
It establishes the head and tail ends of
the embryo.
Primitive streak
After the cells of the epiblast move inward below the primitive streak and undergo what?
Invagination (process of being turned inside out or folded back)