Embryo(Topic2)1stWeekofDev't

First week of development: ______ → ______ → ______.

● _____: one of the ovaries releases a mature egg

● _____: sperm cell from male combine with mature egg to form a fertilized egg

● ______: fertilize egg lodges itself into the endometrial lining of the uterus.

STEP 1 — ____________

● Making the egg (______) and sperm (_____).

● Male testes produce new _____ cells a day.

● _____ is only released one at a time, once per _____.

● Sperm cells stick around for _____ days.

● Eggs are more short-lived, surviving only around_____ hours after ovulation.

● The female, for the whole menstrual cycle of _____ days, usually ovulates on the _____th day.

● Overall _____ is only the day of ovulation and the several days leading up to it.

● It is usually an allowance or the fertile window a few days before the peak of the ovulation and also a few days after ovulation.

step 1 (con’t)

● It includes the fertile period of the female and male. For females, it starts during ____ period (about the time when a woman starts to menstruate, at least about the age of __). It does not start from the reproductive organ, but from the _____.

● The hypothalamus secretes the _______ that stimulates the ______ gland to release ______. The …… are the ______ & ______.

● The ___ stimulates the ovary to release follicles. The ovary will release several follicles, but only one of these will mature to becomethe mature follicle or ____. The …….. together with the ______ will help the growing follicle to mature until a woman reaches her ovulation period.

step 1 (con’t)

● In ovulation, the _____ is released from the ovary, moving down to the fallopian tube and staying there for _____ hours, where it can be fertilized.

● In the ovarian cycle, it is a release of an oocyte from a mature follicle.

● It is triggered by a surge of _____ production.

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 ________.

step 1 (con’t)

● The oocyte, in ___ of meiosis ___ , is discharged from the ovary together with a large number of ______ cells.

● Follicular cells remaining inside the collapsed follicle differentiate into ____cells.

Note: The large size of the corpus luteum, caused by hypertrophy and accumulation of lipid in granulosa and theca interna cells. The remaining cavity of the follicle is filled with fibrin.

step 1 (con’t)

● Ovarian Follicles undergo sudden growth spurt by FSH & LH. They create a cystic swelling bulge in the surface of the ovaries and soon after, ______ appears.

● Because of LH surge caused by high ______ levels in the blood, stigma starts to balloon out forming a vesicle, rupturing and expelling the ______ with the ______ .

● The expelled secondary oocyte is surrounded by the ______ and one or more layers of follicular cells, which are radically arranged as the ______ forming the ______ complex.

step 1 (con’t)

● The finger-like fimbriae moves back and forth the ovaries “sweeping” the oocyte into the _______.

● When the stigma (swelling) ruptures, the secondary oocyte is expelled from the ovarian follicle with the follicular fluid.

● After ovulation, the wall of the follicle collapses and is thrown into folds thus the follicle is transformed into a glandular structure, the corpus luteum.

● Only 1% of sperm deposited in the vagina enter the cervix, where they may survive for many hours. Movement of sperm from the cervix to the uterine tube occurs by muscular contractions of the uterus and uterine tube and very little by their own propulsion. The trip from cervix to oviduct can occur as rapidly as ___ minutes or as slow as _____ days.

________: when the sperm cell from male combines with a mature egg to form a fertilized egg.

● Occurs in the ___region of the ____ tube (……).

● …… - the widest part of the tube and is close to the ovary.

● Sperm may remain viable in the female reproductive tract for several days.

● The movement of sperm from the cervix to the uterine tube can be as fast as __ minutes, or as slow as __ days.

○ The movement of the sperm is assisted by the muscular

contractions of the uterus and the uterine tube; the

sperm alone moves through ______.

● Once the egg is fertilized, it will travel down the __ of the __ where it will be implanted. The uterus is lined with ___________.

STEP 2 - ________

● Sperm released in ejaculation travel through the ___ and into the _____ where they make way to the fallopian tube where the egg lies in wait.

● When the sperm enters through the cervix, it goes to the uterus, travels to the ___, then meets the egg cell to the which is the widest part and where the follicles grow forming the _____ and where _____ and _____ take place.

● Spermatozoa are not able to fertilize the oocyte immediately upon arrival in the female genital tract but must undergo (1) _____ and (2) the ________ to acquire this capability. Thus, speeding to the ampulla is not an advantage because capacitation has not yet occurred, and such sperm are not capable of fertilizing the egg.

(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 _____.

During the last few days of maturation of vesicular follicles,

____, produced by follicular and thecal cells, stimulate increased production of ____ by the pituitary gland, and this hormone causes the follicle to enter the mature vesicular [___] stage, to complete meiosis ___ and to enter meiosis __, where it is arrested in ____ approximately ___ hours before ovulation.

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.

Three Phases of Fertilization

● Phase 1: ____________

○ Of all the sperm deposited in the female reproductive

tract, only _____ to _____ reach the site of fertilization. These sperms will now aid in the penetration of the barrier of the oocyte, the _______ . Only one of these sperms will fertilize the egg.

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.

Three Phases of Fertilization

Phase 3: ____________

○ After penetrating the zona pellucida, the sperm will now

adhere to the oocyte. The adhesion is mediated by the

interaction of the oocyte’s _____ and the sperm’s

_______.

○ The adhesion of the successful sperm to the oocyte

results in the fusion of their _______.

■ In humans, both the _____ and the_____ of the

sperm enters the oocyte’s _____ , but the

_____ is left behind on the oocyte

surface.

The Results of Fertilization

● _______ (from 23 → 46)

○ Haploid numbers are from the father’s and mother’s

gametes.

● ________

○ Chromosomal sex of the embryo is determined at

fertilization

○ X-carrying sperm → _______ (……)

○ Y-carrying sperm → _______ (……)

● ________

○ If the oocyte is not fertilized, it will degenerate ____ hours

after ovulation.

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

FORMATION OF BLASTOCYST

● When the morula enters the uterine cavity, fluid begins to penetrate through the zona pellucida into the intercellular spaces of the inner cell mass.

● The intercellular spaces become confluent, and form a single cavity called ___________. The embryo is now a __________.

● Now,

○ Inner cells → __________

○ Trophoblast → __________

○ Blastocyst 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

THE _____ CYCLE

● A regular _____-day cycle

● Depends on hormonal activity

○ ______: secretes gonadotropin releasing hormone

○ Pituitary glands: secretes follicle stimulating hormone

THE OVARIAN CYCLE (con’t)

● Has three phases:

○ ___________

■ Begins at the ______

■ Under the influence of _________; parallels the growth of follicles

○ _________

■ Begins _______ in response to _________ produced by corpus luteum

■ If fertilization does not occur:

● The compact and spongy layers of the ___________ shed the menstrual phase.

■ If fertilization occurs:

● The ….. assists in implantation and contributes to the formation of the _______

■ Later in gestation, the ………. will assume the

role of hormone production, and the _________ degenerates.

THE OVARIAN CYCLE (con’t)

○ ____ or _______

■ If the oocyte is not fertilized, venules and sinusoidal spaces gradually become packed with blood cells, and an extensive diapedesis of blood into the tissue is seen.

● Blood, and small pieces of stroma and glands break away and are expelled from the uterus.

● The ______ layer is the only part that is retained.

■ If fertilization takes place, the _____ implants into the uterus, and in between uterine glands at the level of the compact and spongy layer.

STEP 4 - _____

● During OVULATION, ovaries release the eggs. When the sperm enters the fallopian tube, it fertilizes the egg within ____ hours of ovulation.

o During the peak period (____ day)

● Fertilized egg, known as ___, travels down the_____

● Zygote multiplies several times to form a ___ which enters the uterine cavity in ___ days after fertilization – implants in a day or

2.

○ In the peak of fertilization/ fertility.

● Whole process from fertilization to implantation takes ____days.

● Implantation occurs between the ___ and __day of the regular menstrual cycle.

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.

Stages of Implantation

● 1st Stage - ___________ (endometrium), embryo is about 5-6 days old, adplantation.

● 2nd Stage - ___________ so it is secured in the uterus, adhesion of blastocyst to the endometrium.

● 3rd Stage - ___________ , ovum located in the endometrial cavity, the endometrium grows and the cavity is wrapped better.

o As the stages progress, the egg adheres more

(Just read) Summary:

● Blastocyst is caught in the crevice of zona pellucida (ovulation) It then rolls to the surface of the epithelium deepens into the endometrium attached deeply into the endometrium gets deeper into the uterus

Importance of Ovulation:

● Sometimes women complain on Hypogastric pain (slight pain on the hypogastric area) – might be appendicitis / uterine infection (must be ruled out) – because during early pregnancy, women complain about slight pain (usually at the hypogastric area) – try to ask their history of menstruation because there is this called _______ or

“middle pain” which usually occurs during the middle of menstrual cycle or ovulation.

● _______(German for “middle pain”)

o Normally occurs near the middle of the menstrual cycle.

Remember:

● Ovulation period occurs on the ___th day – pain usually occurs – different from dysmenorrhea – a little bit painful.

○ 1st day of menstruation is day ___

○ Under ultrasound, ___ are observed in the reproductive organ – indicating ____ – _____period.

○ Suitable time to conceive a child.

(just read)

WHY IS THERE MITTELSCHMERZ (fertility pain or ovulation pain)?

● During ovulation, LH is released as well as a little of progesterone and Gonadotropins – that causes spasms thereby causing pain (ovulation pain).

● The hypothalamus stimulates the ovarian cycle (starts at the age of puberty) – it specifically stimulates the anterior pituitary gland to release gonadotropins, FSH, and LH.

(read) Important Events in the Cycle (refer to Figure 12):

● Follicular Phase (before the 14th day):

○ FSH is being released (green), responsible for growing and maturing the follicles – peak of FSH and Estradiol –

FOLLICULAR PHASE.

● Ovulation (starts at the 14th day):

○ LH peaks (blue) which stimulate the release of egg.

○ Progesterone also starts to peak which prepares

(thickens) the endometrium (becomes succulent,

produces more arteries, more blood that can be used

during pregnancy).

● Luteal Phase (Progestational Phase):·

○ Progesterone peaks; corpus luteum changes color due to more blood vessels (more lectin).

○ Body temp also peaks - from the normal temp 37°C

becomes 38°C (basal temp rises) – females become hotter

during ovulation – in “heat”.

■ Ovulation is generally accompanied by a rise in

basal temperature – can be monitored to aid

couples in becoming pregnant or preventing

pregnancy.

● If fertilization takes place within the 28-day cycle:

○ The corpus luteum of pregnancy will take over so that the blastocyst will be implanted there – no abortion takes

place.

● If no fertilization takes place:

○ The endometrium will degenerate as well as the corpus

luteum – the corpus albicans will then take place.

Clinical Significance:

● During consultation with a patient or couple that have a problem with child conception, the doctor should examine this cycle.

○ Check the ovulation (is the patient ovulating?)

■ If not ovulating: Give the patient a medication that can increase the anterior pituitary hormone – which could induce ovulation.

■ Clomiphene citrate [Clomid] is a drug given early in the menstrual cycle used to increase FSH concentrations to stimulate ovulation in women who do not ovulate or to those who ovulate irregularly. Also, it is given to stimulate

egg development for use in in vitro fertilization procedures.

○ Check the hormone concentration

■ Some women fail to ovulate because of low

concentration of gonadotropins.

■ An agent to stimulate gonadotropin release is therefore administered in order for ovulation to be employed.

■ Although such drugs are effective, they often produce multiple ovulations, so that the likelihood of multiple pregnancies is 10 times higher in these women than in the general population.

○ Check the body temperature (is the body temperature

rising?)

○ Is the endometrium developed? – give supplemental

progesterone

○ Check the male partner

■ If a patient does not want to get pregnant, advise them of contraceptive pills. There are pills that contain FSH or only LH. Others contain estradiol or estrogen and others have progesterone hormone alone.