OBSTETRICS AND GYNECOLOGY EXAMINATION
SUMMARY
PART 1 OBSTETRICS
1. Fertilization, implantation and development of the fertilized egg.
Fertilization - fusion of haploid spermatozoa with a haploid oocyte à a zygote (diploid cell)
• Zygote then divides by mitosis
• Remember – the spermatocyte and oocyte were generated by meiosis
Fertilization:
• Takes place in uterine tube –
o after oocyte is released from ovary (ovulation) it travels along the uterine
tube facilitated by vili on the uterine tube wall
o sperm travels: vagina à cervix à uterus à uterine tube
• cervical mucus catches the weak spermatozoa + nourishes the small one à helps
strong spermatozoa to survive up to 7 days
• uterus contracts from the bottom upwards to the top to facilitate movement of
sperm
• 500-800 spermatozoa reach the uterine tubes (from total 3-5 million), during
journey they undergo further maturation called
capazitation Oocyte + spermatozoa:
The process of fertilization: • Oocyte has 2 surrounding
• After the travel from vagina to uterine tube, as the layers:
several sperm become close to the oocyte, the fertilisin o Zona pellucida –
degrades the acrosomes – reveals the head of sperm inner layer
o Corona radiate –
• Then the head of the spermatozoa releases enzymes:
outer layer
o Hyaluronidase
• Oocyte constantly releases
o Neuroamidase fertilisin
o Acrosine • Head of spermatozoa is
§ These enzymes help the sperm to surrounded by acrosome
penetrate the corona radiate of the
oocyte
§ Acrosine then helps the fastest sperm to penetrate the zona pellucida
• The fastest spermatozoa enter the cytosol and the
zona pellucida immediately undergoes structural
changes so that acrosine can no longer destroy it,
therefore no other sperm can enter
FERTILIZATION TAKES PLACE APPROX. 12 HOURS AFTER
OVULATION
END RESULT = DIPLOID ZYGOTE
,Implantation -
• Preimplantation:
o Zygote undergoes mitotic divisions as it keeps travelling towars the uterine
cavity
o After around 3 days the zygote reaches the lumen of the uterus
o And is now 32 cells and a MORULA
o The cells of the morula continue to divide and the end result is
o BLASTOCYST
§ Blastocyst travels along uterine endometrium (decidua) and develops
specific cell layers (on day 5-6)
Layers of the blastocyst:
• Outermost: trophoblasts
• Fluid filled blastocyst cavity
• Innermost – embryoblast which consists of endoderm, and ectoderm
• Nidation/Implantation:
o Occurs after 7 days, takes around 5 days
o For the previous 6 days, the fertilized egg released mediators that stimulate
endometrium to undergo decidual changes:
§ Increased vascularization
§ Round cell shape
o This helps to prepare the egg for implantation + growth
o Before the placenta develops, blastocyst nourished by nutrients in ECM of
decidua = histotrophic phase
o Blastocyst usually implants in upper and posterior part of uterus
§ Zona pellucida dissolves, blastocyst sticks to the decidua of the
endometrium à this process is called apposition
• Pole of the embryo ALWAYS POINTS TOWARDS THE
ENDOMETRIUM
Trophoblasts - outermost layer of the blastocyst develops into 2 layers:
1. Syncytiotrophoblasts (outer)
2. Cytotrophoblasts (inner)
Trophoblast + 2 cell layers grows and digs into the endometrium until the complete
blastocyst is inside the endometrium and surrounded by it:
• Decidua capsularis – part of endometrium that surrounds most of the blastocyst
• Decidua basilaris – surrounds only the lower part of the blastocyst
Implantation can cause bleeding which can be mistaken for mensturation
Further development:
• Inside the trophoblast, cavities called lacunae form
• Enzymes released from trophoblasts injure and damage maternal vessels in the
endometrium à maternal vessels rupture à mothers blood runs into lacunae à
placenta starts to form
• Blastocyst now has contact with mothers blood:
o hCG from syncytiotrophoblasts can be found in the mothers blood and urine
à + pregnancy test
§ APPROX 10-12 DAYS AFTER FERTILIZATION
,3 cavities develop inside blastocyst:
• Blastocyst cavity becomes yolk sac below embryblast
• Embryoblast develops à amniotic cavity
• Chorionic cavity
The trophoblast is now called CHORION
Embryoblast (2 layers) now becomes 3 layers:
1. Ectoderm – gives rise to skin + nervous system
2. Mesoderm – gives rise to bones muscles + vessels
3. Ectoderm – gives rise to internal organs
Why does the mother’s immune system not attack the growing embryo?
• high immunotolerance of uterus!
• Trophoblasts (outermost cells of embryo) have low antigenicity
• increased synthesis of glucocorticoids decreases strength of maternal immune
system
Important numbers and terms:
a) Post- conceptionem (p.c.) -> after fertilization
b) post – menstruationem (p.m.) -> every day after the last day of previous menstruation -
> usually a pregnancy is calculated from this point, even though fertilization took place
actually 14 days later (ovulation occurs on day 14 of menstruation, and fertilization occurs
shortly after).
So a women has her last day of menstruation of previous cycle, then 14 days later ovulation
and fertilization take place). And then, another 14 days later the women realises that her
menstruation is not starting because of pregnancy!)
Birth takes place approximately 268 days after fertilization. But since we calculate the
duration of pregnancy from the last day of the last menstruation (which was
approximately 14 days before menstruation), we say that a pregnancy takes 280 days (282
is more exact but seems like 280 is better to remember)
280 days are 40 weeks which are 10 month -> Yes, boys and girls, pregnancy takes frickin 10
month!!!!!!
If you want to calculate, when a women is supposed to deliver her baby, you take the last
day of her last menstrual bleeding and add 280 days to it!!!!!!
, Ovulation
The ovulation process is important if subsequent fertilization is to take place. This is an
exquisitely timed phenomenon dependent on a host of hormonal interactions involving a
variety of endocrine glands. Tubal function must also be adequate or the ovum will not be
picked up by the fallopian tube to be fertilized within the ampulla.
Fertilization
Following ovulation, the ovum with its cumulus oophorus cells are picked up by the fimbria
of the fallopian tube. The ovum has now formed the first polar body. It remains in the
ampulla portion of the tube and is viable for about 18 to 24 hours. If fertilization does not
occur, the ovum disintegrates and is destroyed by the tube. Sperm will remain viable in the
female reproductive tract for about 48 hours, although this can be quite variable. Sperm
present in the ampulla meet the cumulus oophorus mass and penetrate by chemical and
mechanical means to reach the zona pellucida. One sperm penetrates the zona pellucida,
the second polar body is formed, and the nuclear material of the sperm enters the vitelline
membrane. The diploid chromosome number is re-established, and mitotic cell division can
now occur.
Implantation
After fertilization occurs, the ovum remains in the fallopian tube for about 72 hours. During
this time there are several cellular division, but the size of the fertilized ovum does not
increase. Around 72 hours the zona pellucida fragments and falls away. The ovum enters the
uterine cavity for 60 to 72 more hours, and the central cavity begins to form. A definite cell
mass is formed on one side of the blastocyst by the time implantation occurs. The
trophoblast cells burrow into the endometrial stroma to form syncytiotrophoblast. Primitive
amniotic and chorionic cavities begin to form, and a germ disk is recognizable soon after
implantation.
2. Diagnosis and differential diagnosis of pregnancy.
Prior to diagnosing pregnancy in a woman of reproductive age, the following questions must
be answered:
• Is the patient pregnant?
• If yes, where is the fetus? Inside or outside the uterus
• What is the position of the fetus inside the uterus?
• What is the gestational age?
• Does the development of the fetus match the gestational age?
• Is the structure of the fetus normal or with deviations?
• Is it a single birth or multiple birth pregnancy?
Diagnosis of pregnancy – there is diagnosis of early pregnancy and late pregnancy
SUMMARY
PART 1 OBSTETRICS
1. Fertilization, implantation and development of the fertilized egg.
Fertilization - fusion of haploid spermatozoa with a haploid oocyte à a zygote (diploid cell)
• Zygote then divides by mitosis
• Remember – the spermatocyte and oocyte were generated by meiosis
Fertilization:
• Takes place in uterine tube –
o after oocyte is released from ovary (ovulation) it travels along the uterine
tube facilitated by vili on the uterine tube wall
o sperm travels: vagina à cervix à uterus à uterine tube
• cervical mucus catches the weak spermatozoa + nourishes the small one à helps
strong spermatozoa to survive up to 7 days
• uterus contracts from the bottom upwards to the top to facilitate movement of
sperm
• 500-800 spermatozoa reach the uterine tubes (from total 3-5 million), during
journey they undergo further maturation called
capazitation Oocyte + spermatozoa:
The process of fertilization: • Oocyte has 2 surrounding
• After the travel from vagina to uterine tube, as the layers:
several sperm become close to the oocyte, the fertilisin o Zona pellucida –
degrades the acrosomes – reveals the head of sperm inner layer
o Corona radiate –
• Then the head of the spermatozoa releases enzymes:
outer layer
o Hyaluronidase
• Oocyte constantly releases
o Neuroamidase fertilisin
o Acrosine • Head of spermatozoa is
§ These enzymes help the sperm to surrounded by acrosome
penetrate the corona radiate of the
oocyte
§ Acrosine then helps the fastest sperm to penetrate the zona pellucida
• The fastest spermatozoa enter the cytosol and the
zona pellucida immediately undergoes structural
changes so that acrosine can no longer destroy it,
therefore no other sperm can enter
FERTILIZATION TAKES PLACE APPROX. 12 HOURS AFTER
OVULATION
END RESULT = DIPLOID ZYGOTE
,Implantation -
• Preimplantation:
o Zygote undergoes mitotic divisions as it keeps travelling towars the uterine
cavity
o After around 3 days the zygote reaches the lumen of the uterus
o And is now 32 cells and a MORULA
o The cells of the morula continue to divide and the end result is
o BLASTOCYST
§ Blastocyst travels along uterine endometrium (decidua) and develops
specific cell layers (on day 5-6)
Layers of the blastocyst:
• Outermost: trophoblasts
• Fluid filled blastocyst cavity
• Innermost – embryoblast which consists of endoderm, and ectoderm
• Nidation/Implantation:
o Occurs after 7 days, takes around 5 days
o For the previous 6 days, the fertilized egg released mediators that stimulate
endometrium to undergo decidual changes:
§ Increased vascularization
§ Round cell shape
o This helps to prepare the egg for implantation + growth
o Before the placenta develops, blastocyst nourished by nutrients in ECM of
decidua = histotrophic phase
o Blastocyst usually implants in upper and posterior part of uterus
§ Zona pellucida dissolves, blastocyst sticks to the decidua of the
endometrium à this process is called apposition
• Pole of the embryo ALWAYS POINTS TOWARDS THE
ENDOMETRIUM
Trophoblasts - outermost layer of the blastocyst develops into 2 layers:
1. Syncytiotrophoblasts (outer)
2. Cytotrophoblasts (inner)
Trophoblast + 2 cell layers grows and digs into the endometrium until the complete
blastocyst is inside the endometrium and surrounded by it:
• Decidua capsularis – part of endometrium that surrounds most of the blastocyst
• Decidua basilaris – surrounds only the lower part of the blastocyst
Implantation can cause bleeding which can be mistaken for mensturation
Further development:
• Inside the trophoblast, cavities called lacunae form
• Enzymes released from trophoblasts injure and damage maternal vessels in the
endometrium à maternal vessels rupture à mothers blood runs into lacunae à
placenta starts to form
• Blastocyst now has contact with mothers blood:
o hCG from syncytiotrophoblasts can be found in the mothers blood and urine
à + pregnancy test
§ APPROX 10-12 DAYS AFTER FERTILIZATION
,3 cavities develop inside blastocyst:
• Blastocyst cavity becomes yolk sac below embryblast
• Embryoblast develops à amniotic cavity
• Chorionic cavity
The trophoblast is now called CHORION
Embryoblast (2 layers) now becomes 3 layers:
1. Ectoderm – gives rise to skin + nervous system
2. Mesoderm – gives rise to bones muscles + vessels
3. Ectoderm – gives rise to internal organs
Why does the mother’s immune system not attack the growing embryo?
• high immunotolerance of uterus!
• Trophoblasts (outermost cells of embryo) have low antigenicity
• increased synthesis of glucocorticoids decreases strength of maternal immune
system
Important numbers and terms:
a) Post- conceptionem (p.c.) -> after fertilization
b) post – menstruationem (p.m.) -> every day after the last day of previous menstruation -
> usually a pregnancy is calculated from this point, even though fertilization took place
actually 14 days later (ovulation occurs on day 14 of menstruation, and fertilization occurs
shortly after).
So a women has her last day of menstruation of previous cycle, then 14 days later ovulation
and fertilization take place). And then, another 14 days later the women realises that her
menstruation is not starting because of pregnancy!)
Birth takes place approximately 268 days after fertilization. But since we calculate the
duration of pregnancy from the last day of the last menstruation (which was
approximately 14 days before menstruation), we say that a pregnancy takes 280 days (282
is more exact but seems like 280 is better to remember)
280 days are 40 weeks which are 10 month -> Yes, boys and girls, pregnancy takes frickin 10
month!!!!!!
If you want to calculate, when a women is supposed to deliver her baby, you take the last
day of her last menstrual bleeding and add 280 days to it!!!!!!
, Ovulation
The ovulation process is important if subsequent fertilization is to take place. This is an
exquisitely timed phenomenon dependent on a host of hormonal interactions involving a
variety of endocrine glands. Tubal function must also be adequate or the ovum will not be
picked up by the fallopian tube to be fertilized within the ampulla.
Fertilization
Following ovulation, the ovum with its cumulus oophorus cells are picked up by the fimbria
of the fallopian tube. The ovum has now formed the first polar body. It remains in the
ampulla portion of the tube and is viable for about 18 to 24 hours. If fertilization does not
occur, the ovum disintegrates and is destroyed by the tube. Sperm will remain viable in the
female reproductive tract for about 48 hours, although this can be quite variable. Sperm
present in the ampulla meet the cumulus oophorus mass and penetrate by chemical and
mechanical means to reach the zona pellucida. One sperm penetrates the zona pellucida,
the second polar body is formed, and the nuclear material of the sperm enters the vitelline
membrane. The diploid chromosome number is re-established, and mitotic cell division can
now occur.
Implantation
After fertilization occurs, the ovum remains in the fallopian tube for about 72 hours. During
this time there are several cellular division, but the size of the fertilized ovum does not
increase. Around 72 hours the zona pellucida fragments and falls away. The ovum enters the
uterine cavity for 60 to 72 more hours, and the central cavity begins to form. A definite cell
mass is formed on one side of the blastocyst by the time implantation occurs. The
trophoblast cells burrow into the endometrial stroma to form syncytiotrophoblast. Primitive
amniotic and chorionic cavities begin to form, and a germ disk is recognizable soon after
implantation.
2. Diagnosis and differential diagnosis of pregnancy.
Prior to diagnosing pregnancy in a woman of reproductive age, the following questions must
be answered:
• Is the patient pregnant?
• If yes, where is the fetus? Inside or outside the uterus
• What is the position of the fetus inside the uterus?
• What is the gestational age?
• Does the development of the fetus match the gestational age?
• Is the structure of the fetus normal or with deviations?
• Is it a single birth or multiple birth pregnancy?
Diagnosis of pregnancy – there is diagnosis of early pregnancy and late pregnancy
