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Embryo(Topic2)1stWeekofDev't

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von dawn S.

step 1 (con’t)

● The primordial follicle will start to grow day by day, forming the ___. The growing follicle is surrounded by ____cells and _____ cells.

● Together, the FSH and granulosa cells produce _____ and _____. The …….. stimulates the ovary causing a vascular spasm, causing the follicle to come out, thereby leading to ovulation.

● At the time of ovulation, the _____ takes charge and prepares the ___. The ___ cells and ____ become the corpus luteum. It is vascularized in preparation if after ovulation and fertilization takes place, this will be the place where implantation takes place.

● If fertilization does not take place, this …….. will degenerate.

● If no pregnancy takes place, _____ decreases and the corpus luteum is maintained by __ which also produces ________.

● The primordial follicle will start to grow day by day, forming the vesicular follicle. The growing follicle is surrounded by granulosa cells and theca cells.

● Together, the FSH and granulosa cells produce prostaglandin and estrogen. The prostaglandin stimulates the ovary causing a vascular spasm, causing the follicle to come out, thereby leading to ovulation.

● At the time of ovulation, the LH takes charge and prepares the corpus luteum. The theca cells and blood vessels become the corpus luteum. It is vascularized in preparation if after ovulation and fertilization takes place, this will be the place where implantation takes place.

● If fertilization does not take place, this corpus luteum will degenerate.

● If no pregnancy takes place, progesterone decreases and the corpus luteum is maintained by LH which also produces progesterone.

(step 2 con’t)

● When the egg is fertilized, it travels down to the fallopian tube and goes down the _____ where it will be embedded and implantation takes place.

● Before a sperm can travel into the cervix, the normal volume for sperm is __. The male normally produces _______sperm cells per ejaculation, but only ……… of these are active, normal, and considered fertile.

● Normal seminal volume during ejaculation is _____

● Semen liquifies in ______ minutes.

● When a patient comes in for a fertility test, ask the patient to get a sample within the vicinity of the hospital if he is an hour or longer away from the hospital. To have a good amount of sample, ask the patient to abstain from any sexual activity before the testing.

● To know if the problem of infertility is from the male or female, the first testing is done with the __, but can be done at the same time as the _____.


● When the egg is fertilized, it travels down to the fallopian tube and goes down the uterus where it will be embedded and implantation takes place.

● Before a sperm can travel into the cervix, the normal volume for sperm is 500. The male normally produces 200-300 million sperm cells per ejaculation, but only 500 of these are active, normal, and considered fertile.

● Normal seminal volume during ejaculation is 2-6ml

● Semen liquifies in 30 minutes.

● When a patient comes in for a fertility test, ask the patient to get a sample within the vicinity of the hospital if he is an hour or longer away from the hospital. To have a good amount of sample, ask the patient to abstain from any sexual activity before the testing.

● To know if the problem of infertility is from the male or female, the first testing is done with the male, but can be done at the same time as the female.


Phases of Oocyte Penetration

● After reaching the ______, sperm cells become less motile and cease their migration. At ovulation, they only become active again due to:

○ _______ produced by the cumulus cells

surrounding the egg.

● The sperm must first undergo capacitation and acrosome reaction before it can penetrate an oocyte.

○ ______: conditioning period of the sperm in the

female reproductive tract. This usually lasts for _____ hours in humans. During the capacitation period, epithelial

interactions between the sperm and mucosal surface of

the uterine tube occur. The glycoprotein coat and seminal

plasma proteins of the sperm are removed from the

plasma membrane, which will then expose its acrosomal

region.

○ ______: occurs after the sperm binds to the

______. This will cause the release of enzymes

needed to penetrate the …...

■ These enzymes include __- and ____-like substances.

● After reaching the isthmus, sperm cells become less motile and cease their migration. At ovulation, they only become active again due to:

○ Chemoattractants produced by the cumulus cells

surrounding the egg.

● The sperm must first undergo capacitation and acrosome reaction before it can penetrate an oocyte.

○ Capacitation: conditioning period of the sperm in the

female reproductive tract. This usually lasts for 7 hours in

humans. During the capacitation period, epithelial

interactions between the sperm and mucosal surface of

the uterine tube occur. The glycoprotein coat and seminal

plasma proteins of the sperm are removed from the

plasma membrane, which will then expose its acrosomal

region.

○ Acrosome reaction: occurs after the sperm binds to the

zona pellucida. This will cause the release of enzymes

needed to penetrate the zona pellucida.

■ These enzymes include acrosin- and trypsin-like substances.

Three Phases of Fertilization

● Phase 2: _________

○ After successfully penetrating the zona radiata, the

sperms will now penetrate the zona …..

○ __________: a glycoprotein shell that surrounds the

egg.

■ Facilitates sperm_______, induces acrosome

reaction.

○ Release of acrosomal enzyme (_____) makes it possible for the sperms to penetrate zona pellucida → contact of the sperm with the oocyte’s plasma membrane.

○ _____: structures lining the plasma membrane of the oocyte. They release lysosomal enzymes which will change the properties of zona pellucida (zona reaction); this prevents sperm _______ and inactivate species-specific receptor sites for spermatozoa on the zona surface.

○ Other spermatozoa have been found embedded in the

zona pellucida, but only one seems to be able to

penetrate the oocyte.

● Phase 2: Penetration of zona pellucida

○ After successfully penetrating the zona radiata, the

sperms will now penetrate the zona pellucida.

○ Zona pellucida: a glycoprotein shell that surrounds the

egg.

■ Facilitates sperm binding, induces acrosome

reaction.

○ Release of acrosomal enzyme (acrosin) makes it possible for the sperms to penetrate zona pellucida → contact of the sperm with the oocyte’s plasma membrane.

○ Cortical granules: structures lining the plasma membrane of the oocyte. They release lysosomal enzymes which will change the properties of zona pellucida (zona reaction); this prevents sperm penetration and inactivate

species-specific receptor sites for spermatozoa on the

zona surface.

○ Other spermatozoa have been found embedded in the

zona pellucida, but only one seems to be able to

penetrate the oocyte.

DEVELOPMENT OF ZYGOTE FROM THE TWO-CELL STAGE TO THE LATE MORULA STAGE

● Once the zygote reaches the ____-cell stage, it will continue to divide through a series of mitotic divisions, thereby increasing the number of cells.

● As these cells undergo cleavage division, they will decrease in size, and are now called _______. Until the eight-cell stage, they form a loosely arranged clump.

● After the ______ cleavage, blastomeres maximize their contact with each other and form a compact ball of cells, held tightly big tight junctions.

○ _________: segregation of the inner cells from the outer cells

● 3 days after fertilization, the cells of the compacted embryo divide into a _______ (16 cells), also termed as _______.

○ Inner cells (inner cell mass) → _______

○ Outer cells (outer cell mass) → _______ → _______

○ Fluid cavity _______ cavity



● Once the zygote reaches the two-cell stage, it will continue to divide through a series of mitotic divisions, thereby increasing the number of cells.

● As these cells undergo cleavage division, they will decrease in size, and are now called blastomeres. Until the eight-cell stage, they form a loosely arranged clump.

● After the third cleavage, blastomeres maximize their contact with each other and form a compact ball of cells, held tightly big tight junctions.

○ Compaction: segregation of the inner cells from the outer cells

● 3 days after fertilization, the cells of the compacted embryo divide into a morula (16 cells), also termed as mulberry.

○ Inner cells (inner cell mass) → embryo proper

○ Outer cells (outer cell mass) → trophoblast → placenta

○ Fluid cavity amniotic cavity



STEP 3 -_______

● In fertilization, one sperm is eventually able to make it through and combine with the egg to form a _______

● The fertilized egg begins to divide into clamps of cells as it travels through the fallopian tube towards the uterus.

● After 4-6 days of cell division, it matures into a STEP 3 -Fertilization to implantation

● In fertilization, one sperm is eventually able to make it through and combine with the egg to form a ZYGOTE.

● The fertilized egg begins to divide into clamps of cells as it travels through the fallopian tube towards the uterus.

● After 4-6 days of cell division, it matures into a _______, and it is ready to be implanted into the uterus.

● The wall of the uterus has three layers:

○ _______ - peritoneal covering lining the outside wall

○ _______ - a thick layer of smooth muscle

○ _______ - mucosa lining the inside wall and also has

three layers:

■ The endometrium has 3 layers:

1. _______ layer (stratum _______ ) - highly vascular

2. _______ layer (stratum _______ )

- vascular and with associated glands

3. _______ layer / _______

(stratum _______ ) - usual part that degenerates if no fertilization takes place

STEP 3 -Fertilization to implantation

● In fertilization, one sperm is eventually able to make it through and combine with the egg to form a ZYGOTE.

● The fertilized egg begins to divide into clamps of cells as it travels through the fallopian tube towards the uterus.

● After 4-6 days of cell division, it matures into a BLASTOCYST, and it is ready to be implanted into the uterus.

● The wall of the uterus has three layers:

○ Perimetrium - peritoneal covering lining the outside wall

○ Myometrium - a thick layer of smooth muscle

○ Endometrium - mucosa lining the inside wall and also has

three layers:

■ The endometrium has 3 layers:

1. Basal layer (stratum basalis) - highly vascular

2. Spongy layer (stratum spongiosum)

- vascular and with associated glands

3. Upper layer / Compact layer

(stratum compactum) - usual part that degenerates if no fertilization takes place

IMPLANTATION

● Fertilized egg (___) attached to the lining of the _____ to grow and develop.

o ______ – lining of the uterus

● Happens a week after ovulation, in an early stage of pregnancy, and an entirely a natural process.

o Implantation happens after the ___ that is on the _____ day.

● Most cases, it takes place around 9 days after ovulation, but sometimes it can occur as early as 7 days or as late as 12 days.

o It depends if it is a ____-day cycle, ____-day cycle or even less.

o At the time of implantation, the mucosa of the uterus is in

the _______ phase, during which time uterine glands and

arteries become coiled, and the tissue becomes succulent.

As a result, three distinct layers can be recognized in the

endometrium: a _______ layer, an _______ layer, and a thin _______ layer. Normally, the human blastocyst implants in the endometrium along the anterior or posterior wall of the body of the uterus, where it becomes embedded between the openings of the glands.

●Blastocyst begins to wedge itself into the endometrial lining of the uterus – this takes about ____ days to complete.

● After implantation, cell division begins to specialize, forming what will become the embryo’s body and the placenta.

● Fertilized egg (BLASTOCYST) attached to the lining of the uterus to grow and develop.

o Endometrium – lining of the uterus

● Happens a week after ovulation, in an early stage of pregnancy, and an entirely a natural process.

o Implantation happens after the ovulation that is on the 14th day.

● Most cases, it takes place around 9 days after ovulation, but sometimes it can occur as early as 7 days or as late as 12 days.

o It depends if it is a 28-day cycle, 24-day cycle or even less.

o At the time of implantation, the mucosa of the uterus is in

the secretory phase, during which time uterine glands and

arteries become coiled, and the tissue becomes succulent.

As a result, three distinct layers can be recognized in the

endometrium: a superficial compact layer, an intermediate

spongy layer, and a thin basal layer. Normally, the human

blastocyst implants in the endometrium along the anterior

or posterior wall of the body of the uterus, where it becomes embedded between the openings of the glands.

●Blastocyst begins to wedge itself into the endometrial lining of the uterus – this takes about 5 days to complete.

● After implantation, cell division begins to specialize, forming what will become the embryo’s body and the placenta.

Author

dawn S.

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