embryo-1st wk devt

_________TO ____________

• ____________ – one of the ovaries release a mature egg

• ____________–when the sperm cells from male combine with a mature egg to form a fertilized egg

• ____________ – when the fertilized egg lodges itself into the endometrial lining of the uterus

Stages of 1st week of Development :

Step 1:

Step 2:

Step 3:

Step 4:

Under the influence of GnRH from the hypothalamus, the

pituitary releases the gonadotropins, _____ and _____.

Follicles are stimulated to:

grow by _____ and to

mature by _____and _____

hormone?

Ovulation occurs when concentrations of ____ surge to high

levels.

____ also promotes development of the corpus luteum.

hormone?

During the last few days of maturation of vesicular follicles,

_______, produced by follicular and thecal cells, stimulate

increased production of LH by the pituitary gland , and

this hormone causes the follicle to enter the mature vesicular [Graafian] stage, to complete meiosis I, and to enter meiosis II, where it is arrested in metaphase approximately 3 hours before ovulation.

hormone?

The high concentration of LH causes increase in ________

which causes muscular contractions in the

ovarian wall.

zona?

Some of the cumulus oophorus cells rearrange themselves around the zona pellucida to form the ________

After ovulation, granulosa cells remaining in the wall of

the ruptured follicle are vascularized. Under the influence

of LH, these cells develop a yellowish pigment and

change into lutein cells which forms the ___________

If fertilization does not occur, the corpus luteum will

shrink because of the degeneration of lutein cells or

________ and it forms a fibrotic scar tissue called the

________

If the oocyte is fertilized, degeneration of the corpus

luteum is prevented by _________which is secreted by the syncitiotrophoblast of the developing embryo.

Corpus luteum continues to grow, forming the corpus luteum of pregnancy (________).

Fertilization: Sperm released in ejaculation travel through

the cervix and into the uterus where they make way to the

fallopian tube where the egg lies in wait

The process of fertilization occurs in the ______ region of the fallopian tube.

Phases of Fertilization

o Phase 1:

o Phase 2:

o Phase 3:

As the spermatozoon moves closer to the female

pronucleus, its nucleus becomes swollen, forming the

______ (tail detaches and degenerates).

Results of Fertilization

o

o

o

The two-celled zygote (reached approximately 30 hours after fertilization) undergoes a series of cleavage division, forming _________

After the 3rd cleavage, they compact (through compaction held by _________), segregating inner cells from outer cells.

Three days after fertilization, 16-cell ______ is formed, with

inner cell mass (inner cells) and outer cell mass (surrounding cells).

Inner cell mass → ______ of embryo proper

Outer cell mass → trophoblast → _______

As morula enters the uterine cavity, fluid penetrates to the

intercellular spaces of the inner cell mass, forming the

__________ (morula → blastocyst).

STEP 3

Fertilization to implantation

After 4-6 days of cell division, it matures into a

________, and its ready to implant into the uterus

hormone?

Implantation of the blastocyst has caused development of a large corpus luteum of pregnancy. Secretory activity of the endometrium increases gradually due to large amounts of __________ produced by the corpus luteum of pregnancy.

STEP 4 - Implantation

Fertilized egg (BLASTOCYST) attached to the lining of the

uterus to grow and develop.

STAGES OF IMPLANTATION

1 st Stage – ______attaches to the uterine wall

(___), embryo is about 5-6 days old – _____

2nd Stage – ______ egg penetrates the uterine wall,

3rd Stage – ______ embeds deeply inside the uterine wall,

Uterus at Time of Implantation

o Uterus mucosa is in ______ (coiled uterine

glands and arteries, and succulent tissues).

o Three distinct layers of the endometrium becomes

recognizable:

(1)

(2)

(3)