Lecture33- Fertilization & Pregnancy

Question 1

During the act of intercourse, the male ejaculates x sperms into the vagina and only y enter fallopian tunes. The sperm remain viable for p days

Answer 1

300 m sperms are ejacrulated
Only 100-200 enter Fallopian tube
Sperm are viable for 3 days

Question 2

Secondary oocyte lasts for x days following ovulation

Answer 2

1 day (24 hours)
Fertilization may occur if intercourses takes place 3 days b4 ovulation

Question 3

T/F- only one sperm is able to penetrate the Corona radiata

Answer 3

False. Several are able to.

However, only one is able to penetrate the Zona Pellucida and allow nucleus to enter cytoplasm

Question 4

Describe the process of fertilization

Answer 4

-Sperm makes its way through the Corona radiata
-Acrosomal enzymes digest portion of zona pellucida
-Sperm bind to receptors on pellucida and fuse with plasma membrane
-Sperm nucleus enters the cytoplasm of oocyte
-Depolarization of egg decreases attraction of sperms to egg
-Cortical granules are released; binding and detaching receptors from pellucida (sperm can No longer fuse with membrane) - [ Zona pellucida now termed FERTILIZATION MEMBRANE]
Egg finishes Meiosis II
-Sperm and egg pro nuclei come together and enclose themselves in nuclear envelope

Question 5

What are the 4 processes of development?

Answer 5

Cleavage- mitotic division of zygote (increase in # of cells) size is relatively the same
Growth- Increase in size of divided cells
Morphogenesis- shaping of embryo through cell migration
Differentiation- cells take specific structure and function

Question 6

When is the human termed embryo?

Answer 6

When the embryonic disc and germ layers form (2 weeks- 8)

Question 7

Describe the early embryonic structure? (Blastocyte)

Answer 7

Consists of an inner cell mass (that develops into embryo)
And Trophoblast, or chondrion ( that will become part of the placenta)
^fertilization membrane sheds later on.], before implantation

Question 8

When does the trophoblast attach to the uterine wall?

Answer 8

5-6 days

Question 9

When does complete implantation occur? (And how would you know)?

Answer 9

7-10 days (when the blastocyst is completely in the endometrium)

Question 10

What is the function of HcG and when is it secreted?

Answer 10

It continues to allow the corpus luteum to be viable (instead of wearing off after2 weeks) (to secrete mostly progesterone and some estrogen)
It is secreted when complete implantation occurs (7-10 days)

Question 11

Which harmone(s) are responsible for supporting the endometrium and inhibiting the contraction of the uterine muscle?

Answer 11

Estrogen and progesterone

Question 12

What is the failure rate of 
Condom
Coitus interruptus 
And
Vasectomy
As a form of male contraception?

Answer 12

Condom (2-12% failure)
Withdrawal before ejaculation (20-30% failure)
Vasectomy (0%)

Question 13

Describe the contraceptive pill and state its failure rate

Answer 13

Combination of synthetic estrogen and progestins to cause negative feedback on GnRH and prevent ovulation (<1% failure)

Question 14

What is the female diaphragm and its failure rate?

Answer 14

It is a contraceptive that is analogous to the male condom (20% failure rate)

Question 15

What is the the failure rate of the IUD, or the loop?

Answer 15

<2%

Question 16

What is the temp method of contraception?

Answer 16

Tracking temperature Of body- if it increases by around 0.5•C do not partake in intercourse because ovulation has occurred (4% failure rate)

Question 17

What is the rhythm method, and its failure rate?

Answer 17

Avoiding intercourse at time of ovulation by using Calender (cycle must be regular)
20-30% failure

Question 18

What is tubal ligation?

Answer 18

Sterilization- Fallopian tubes are banded, cauterized, tied, cut, and clipped.
0% failure

Question 19

For how long does the corpus luteum play a vital role in keeping the endometrium lining?

Answer 19

Until around 2 months, when the placenta takes over the role of secretion of progesterone and placenta

Question 20

State some differences between M & F reproductive systems

Answer 20

• Gonads reside outside the abdominal cavity M; ovaries reside inside abdominal cavity F
• release of gametes are continuous (some 1 ° spermatids undergo mitosis)M; release of grafiaan follicle 1/month F (all primary oocytes start meiosis I)
• gamete reserve is replenished throughtout life M; gamete reserve limited # F
• Test only exhibits -ve feedback on FSH directly and LH indirectly M; can exhibits +ve feedback as well F
• male tract activity is non rhythmic ; female tract is rhythmic monthly or on the length of pregnancy
• Male tract only serves sperm transport, store, and maturation; F serves sperm and egg transport, store, maturation, fertilization

Question 21

Define fertility and estimate its prevelance

Answer 21

Inability of a couple to achieve pregnancy after a couple of years
Previous is around 15%

Question 22

How common is infertility in M as compared with F, and what are the causes?

Answer 22

It is equally common with Males compared with females
For males- low sperm count AND OR large production of abnormal spermatozoa caused by environmental factors (such as radiation)
For females- overweight

Question 23

How do you treat infertility?

Answer 23

First treat underlying causes
Female sterility drug that stimulate ovulation
Assisted reproductive technologies as last resort

Question 24

Give examples and explain some Assistive reproductive technologies

Answer 24

-Artificial insemination by donor
For low sperm count males, ejaculate multiple times and collect the sperm. Then the Spermatozoa is placed in vagina by physician
-IVF
Fertility drugs are administered to immature eggs in the lab for them to mature
Then it is intubated with concentrated sperm
Embryo is transferred to the uterus (15-20% SUCCESS)
-Gamete Intrafallopian Transfer
Higher success rate than IVF
Collect eggs and spermatozoa and reintroduce them in the Fallopian tube with speed at the same time (fertilization is in Fallopian tubes)
Viable only if Fallopian tubes are intact and sperm are normal