REB 16. Pregnancy Flashcards
What is the common site of fertilization?
Ampulla
- the upper 1/3rd of the oviduct
What are the ends of the fallopian tubes called?
Fimbria - because they are fimbriated ends
When must fertilization occur by (in regards to the ovum)? How is this different to how long the sperm may survive in female reproductive tract?
- must occur within 24 hours after the ovulation
- sperm can survive about 48 hours, but may live up to 5 days in female reproductive tract
When released from the ovary, the oocyte is surrounded by 2 layers:
[1] Corona Radiata (outer)
- layer of follicular cells
[2] Zona Pellucida (inner)
- matrix of glycoproteins
When does human fertilization begin?
when sperm breaks through corona radiata to bind to SUGAR GROUP on zona pellucida
What are the 3 parts of the sperm?
[1] Head
[2] Midpiece
[3] Tail
What is special about the head of the sperm?
it contains enzymes to break through the Corona Radiata and Zona Pellucida
Explain how the sperm breaks through the outer layers of the ovum/oocyte to fertilize it.
[1] sperm breaks through Corona Radiata via the enzymes of its head
[2] sperm binds to ZP3 receptors on Zona Pellucida
[3] binding of sperm leads to triggering the acrosome reaction in which hydrolytic enzymes in the acrosome are released onto Zona Pellucida
[4] acrosomal enzymes digest Zona Pellucida creating a path for the sperm
[5] sperm and oocyte fuse
[6] sperm nucleus enters the ovum cytoplasm
[7] the sperm stimulates release of Ca2+ stored in cortical granules of ovum
[8] Ca2+ inactivates ZP3 receptors leading to the blockage of polyspermy
What happens 1 hour after fertilization?
the sperm and egg nuclei fuse
What happens 3 to 4 days after fertilization?
zygote remains within ampulla (of oviduct) and undergoes mitotic cell divisions
- morula is created!
After fertilization, there is a rising level of progesterone from the corpus luteum which stimulates…?
release of glycogen from the endometrium
- used as energy by the early embryo
- after 3 to 4 days, the morula is allowed to enter the uterus because enough nutrients were allowed to accumulate
What happens 6 to 7 days after ovulation/fertilization under the influence of progesterone?
- uterine lining being prepared for implantation
- uterus is in its secretory, progestational phase
- stores up glycogen + becomes righly vascularized (builds up wall)
The endometrium is suitable for implantation after how long?
1 week after ovulation
- at this stage, morula has descended into uterus and differentiated into blastocyst
What are the layers of the blastocyst? What are the functions of each layer?
[1] Inner Cell Mass
- becomes the embryo
[2] Trophoblast
- becomes the placenta
- makes fuel + raw materials available for embryo
During implantation, what happens to trophoblastic cells?
[1] release enzymes permitting trophoblastic cells to penetrate endometrium
[2] cells degenerate - becoming fetal portion of placenta
At the area of implantation, what changes does the endometrial tissue undergo?
- it enhances its ability to support the embryo
- now called the decidua
What is the relationship between the decidua and the blastocyst?
- the blastocyst burrows into the decidua
- a layer of endometrial cells covers over the surface of the hole
- the trophoblastic layer continues to digest surrounding decidual (endometrial) cells providing energy for the embryo
On what day is the embryo embedded in the decidua?
day 12