Fertilization & Implantation

Question 1

Where does fertilization occur?

Answer 1

In the ampulla of the fallopian tube.

Question 2

In a 28 day menstruation cycle, ovulation occurs on day […].

Answer 2

14

Question 3

[…] induces the primary oocyte to complete […] and to arrest in […]

Answer 3

LH surge

Meiosis 1

Metaphase 2 of meiosis 2

Question 4

Describe the rupture of the ovary to release the follicle.

Answer 4

Question 5

Once the secondary oocyte is released from the ovary into the peritoneum, how does it get into the fallopian tube?

Answer 5

Fimbriae of fallopian tube sweep it into the infundibulum of tube

Question 6

Once a secondary oocyte is in the infundibulum of fallopian tube, how does it move within tube?

Answer 6

Tubal peristalsis moves the oocyte into the ampulla of the tube

Question 7

Describe the transport of male gametes once ejaculated into the female vagina.

Answer 7

Ejaculate is deposited in upper vagina (fornix). Semen is alkaline so it protects sperm from acidic vaginal environment. Thin vaginal mucus also facilitates sperm function / survivial. Sperm are rapidly delivered to the fundus of the uterus within minutes due to rapid contraction of uterus. These sperm are not the ones that ultimately end up fertilizing the egg however. Instead, it is the slowly transported sperm that reach the fallopian tubes after 2-4 days that are most likely to fertilize the egg. The reason for this is b/c they must undergo capacitation and in order to fertilize.

Question 8

What is capacitation of male gametes?

Answer 8

Question 9

Once the slow transported sperm rech the fallopian tube, what do they do?

Answer 9

They bind to the isthumus epithelium for ~ 24 hours and undergo capacitation, then after capacitation they shed their cholesterol rich outer layer and are highly motile and have a burst of energy to carry them to the ampulla

Question 10

What is the acrosome reaction and the Zona reaction?

Answer 10

Question 11

Following penetration of the zona pellucida, the oocyte completes […] becoming the female […]

Answer 11

second meiotic division

Pronucleus

Question 12

Describe the process of zygote formation once the egg has been penetrated by the sperm

Answer 12

Question 13

What does ferilization accomplish?

Answer 13

Question 14

What is cleavage?

Answer 14

Question 15

The Morula consits of […] and enters the uterus on day […] after fertilization

Answer 15

20 blastomeres

4

Question 16

Describe the formation of a blastocyst.

Answer 16

Trophoblast cells –> become placenta

Embryoblast cells –> give rise to all cells of embryo

Question 17

Embryo enters the uterus on day […] after fertilization as a […]

Answer 17

5

Blastocyst

Question 18

On day […] the blastocyst adheres to the endometrium

Answer 18

6

Question 19

Describe the process of initial blastocyst implantation.

• When does it happen?
• What 2 cell populations are involved and how?
• What forms on the deep surface of the embryoblast?

Answer 19

Question 20

When does the blastocyst become embedded into the endometrium?

Answer 20

Syncytiotrophoblasts invade deeper and embed blastocyst on day 8

Question 21

When is blood supply for blastocyst established?

Answer 21

Invasion of maternal capillaries (spiral arterie) create lacunae, establishing primordial uteroplacental circulation on day 10

Question 22

Answer 22

Question 23

Answer 23

Question 24

What is the luteal placental shift?

Answer 24

Initially, the corpus luteum secretes progesterone for 14 days. Around day 10, the blastocyst secretes hCG which keeps the corpus luteum from dying off as it normally would at the end of the 14 day cycle. The corpus luteum secretes progesterone to maintain the uterine environment until the embryo is able to establish its own circulation and matures to be able to secrete its own progesterone. This happens around week 8 (week 8 embryologically speaking, week 10 obstetrically speaking). At this point, progesterone starts to increase and hCG starts to decrease as the embryo is able to produce its own progesterone and no longer needs the corpus luteum.

Question 25

What are the possibilities for development of dizygotic twins?

Answer 25

2 separate ova fertilized by different sperm (possible to have 2 different fathers born from same mother simultaneously)

Question 26

What are the possibilities for development of monozygotic twins?

Answer 26

1 fertilized ovum divides into 2 zygotes, timing of division determines chorionicity and amnionicity

Question 27

The maternal component of the placenta is derived from the […]

The fetal component of the placenta is derived from the […]

Answer 27

Decidua basalis

Villous chorion

Question 28

What are the functions of the placenta?

Answer 28

Gas Ex

Eliminate waste

Transport nutrients

Synthesis and secretion of peptide and steroid hormones (endo)

Question 29

Answer 29

Question 30

Describe how the placenta develops its blood supply.

Answer 30

Cytotrophoblast cells from villous chorion invade teh decidua and remodel the lining of the maternal spiral arteries such that the arteries spill blood into large cavities that surround the villous chorion so that the fetus can get plenty of oxygen and nutrients. Blood returns to mother through maternal veins.

Question 32

True/False: the mother’s circulation and fetus’s circulation are connected via the umbilical arteries and veins.

Answer 32

False - there is no direct connection between the blood supplies

Question 33

What is chorionic villus sampling?

Answer 33

Question 34

Describe the structure of the placenta wrt blood supply.

Answer 34

From the umbillical arteries and vein, a network of blood supply develops that consist of chorionic villi that grow into the decidua of the mother’s endometrium.

Question 35

What are the transport functions of the placenta?

• Simple diffusion?
• Facilitated diffusion?
• Active transport?
• Endo/exocytosis?

Answer 35

Question 36

What are the endocrine functions of the placenta? (i.e. what hormones does it produce/secrete?)

Answer 36

Question 37

What factors facilitate gas Ex mom –> placenta?

Answer 37