CHAPTER 3. First Week of Development: Ovulation to Implantation

Gondatropin-releasing hormone (GnRH)

Controlled and produced by the hypothalamus

Hypothalamus

produces GnRH

Gonadotropins

anterior pituitary tropic hormones, follicles stimulating hormone (FSH) and luteinizing hormone (LH) which stimulate the gonads (ovaries and testes) to produce gametes and to secrete sex steroids

FSH and LH

gonadotropins

Hormones that stimulate and control cyclic changes in the ovary

FSH

Stimulate the growth of 15-20 primary-stage/ preantral follicles

1

Normally, how many follicles reach full maturity

Atresia/ atretic

the follicles that did not reach maturity becomes

Corpus Atreticum

When a follicle becomes atretic, the oocyte and surrounding follicular cells degenerate and are replaced by connective tissue, forming

Follicular (Granulosa) cells

supportive cells that surround the oocyte and respond to FSH

Growth Differentiation Factor 9

Growth Factor that promotes granulosa-cell proliferation

Transforming growth factor-beta family

Growth differentiation factor 9 is part of family

Estrogen

Produced by the Theca interna and granulosa cells

Androstenedione and Testosterone

Produced by the Theca Interna

Theca Interna

Produces Androstenedione and Testosterone

Theca Interna and Granulosa cells

Produces Estrogen

GDF-9

Growth factor that promotes granulosa-cell proliferation

Granulose cells

converts androstenedione and testosterone into estrone and 17 beta-estradiol

Follicular or Proliferative phase

uterine endometrium enters this phase as a result of estrogen production

cervical mucus

the thinning of ________ occurs to allow passage of pserm

anterior lobe

This part of the pituitary gland is stimulated to secrete LH

LH

The anterior part of the pituitary gland is stimulated to secrete _____

maturation-promoting factor

Due to LH surge, there are elevated concentrations of _________, causing oocytes to complete meiosis I and initiate Meiosis II

Luteinization

stimulates production of progesteron by follicular stromal cells

graafian follicle

mature vesicular follicle

follicular rupture and ovulation

LH surge causes the follicle to

25 mm

vesicular follicle grow rapidly to a diamter of ______ to become a mature vesicular (graafian) follicle

Metaphase, 3 hours

Upon initiation of Meiosis II, the oocyte is arrested in ______ approximately _______ before ovulation

Stigma

the surface of the ovary begins to bulge locally, and at the apex of an avascular spot appears

collagenase activity

high concentration of LH increases _________

digestion, collagen fibers

High collagenase activity results in the _______ of _______ surrounding the follicle

Prostaglandin levels (increase)

________ respond to the LH surge and causes local muscular contractions in the ovarian wall

Ovulation

This is process in which as contraction continues, it extrudes the oocyte, which together with its surrounding granulosa cells from the region of the cumulus oophorus br4eaks free

corona radiata

some of the cumulus oophorus cells then rearrange themselves around the zona pellucida to form the

Corpus luteum

formed by lutein cells, and secrete estrogen and progesterone

Lutein Cells

forms the corpus luteum, yellowish pigment

Progestational or secretory phase

The phase in preparation for the implantation of the embryo

estrogen and progesterone

Secreted by the corpus letuem

peristaltic muscular contraction

movement that propels the oocyte in the uterine tube

3-4 days

the fertilized oocyte reaches the uterine lumen in approximately ________

Corpus Albicans

The corpus luteum shrinks due to degeneration of lutein cells and forms a mass of fibrotic scar tissue

luteolysis

Degeneration of lutein cells

human chorionic gonadotropin (hCG)

if oocyte is fertilized, degeneration of the corpus luteum is prevented by this hormone

syncytiotrophoblast

This secretes the human chorionic gonadotropin of the developing embryo

corpus luteum graviditatis

The corpus luteum continues to grow and forms the corpus luteum of pregnancy or ________

abortion

removal of the corpus luteum of pregnancy before the 4th month leads to _______

ampullary region of the uterine tube

Fertilization occurs in ________. The widest part of the tube

fertilization

the process by which male and female gametes fuse

1%

only ____ of sperm deposited in the vagina enter the cervix where they may survive for many hours

30 minutes, 6 days

The trip from cervix to oviduct can occur as rapidly as ________ or as slow as________

1. Capacitation

2. Acrosome reaction

The spermatozoa must undergo __________ and _________ to fertilize

Capacitation

a period of conditioning in the female reproductive tract that in the human last approximately 7 hours

1. Penetration of the corona radiata

2. Penetration of the zona pellucida

3. Fusion of the oocyte and sperm cell membranes

3 phases of fertilization

Acrosome reaction

Occurs after binding to the zona pellucida

zona proteins

induces acrosome reaction

200-300 million spermatozoa

normal amount of spermatozoa deposited in the female genital tract

300-500 spermatozoa

amount of spermatozoa reaching the site of fertilization

zona

glycoprotein shell that surrounds the egg that faciliates and maintains sperm binding and induces the acrosome reaction

ZP3

Binding and acrosome reaction are mediated by the zona pellucida protein

cortical granules

releases lysosomal enzymes which alter the properties of the zona pellucida

1. Cortical and Zona Reactions

2. Resumption of the Second Meiotic Division

3. Metabolic Activation of the Egg

As soon as the spermatozoon has entered the oocyte, the egg responds in 3 ways:

Cortical and Zona Reactions

This is a result of the release of cortical oocyte granules, which contain lysosomal enzymes

- reaction prevent polyspermy

- Oocyte membrane becomes impenetrable to other spermatozoa

- Zona pellucida alters its structure and composition to prevent sperm binding and penetration

specific reactions that prevennts polyspermy

polyspermy

penetration of more than one spermatozoon into the oocyte

resumption of the second meiotic division

The oocyte finishes its second meiotic division immediately after entry of the spermatozoon

second polar body

One of the daughter cells which receives hardly any cytoplasm

definitive oocyte

the other daughter cell

female pronucleus

the other daughter cell's chromosome arrange themselves in a vesicular nucleus known as the _______

metabolic activation of the egg

the spermatozoon moves forward until it lies clos to the female pronucleus. Formation of the male nucleus

male pronucleus

the nucleus of the spermatozoon becomes swollen and forms _______.

1. Restoration of the diploid number of chromosomes

2. determination of the sec of the new individual

3. initiation of cleavage

main result of fertilization are as follows

cleavage

series of mitotic division of the zygote

30 hours after fertilization

two-cell stage occurs

40 hours after fertilization

four-cell stage occurs

3 days after fertilization

12-16 cell stage occur

compaction

an increase contact between blastomeres, forming a tightly organized cell mass

inner and outer cell population

compactions establishes

blastomeres

Cells produced by cleavage

inner cell mass

Inner cells of the morula are

outer cell mass

surrounding cell mass

inner cell mass

gives rise to tissues of the embryo proper

trophoblast

the outer cell mass forms the

placenta

the trophoblast later contributes to the

blastocoele

the intracellular becomes confluent, and a single cavity ______ is formedr

blastocyst

at this time, where the morula enters the uterine caivity, the embryo is called

embryoblast

cells of the inner cells mass are called

trophoblast

outercell mass

forms the epithelial wall of the blastocyst

L-selectin

these are present on the trophoblast cells and the carbohydrate receptor on the uterine epithelium mediate initial attachment of the blastocyct to the uterus

carbohydrate receptors

interact with L-selectin to mediate initial attachment of blastocyst to the uterus

selectins

carbohydrate-binding proteins involved in interactions between leukocytes and endothelial cells that allow leukocyte capture

fibronectin and laminin

extracellular matrix molecules

integrins

following capture by selectins, futher attachment and invasion of the trophoblast involves _______, these are expressed by the trophoblast

integrin receptors for laminin

promote attachment

fibronectin

stimulate migration

epiblast and hypoblast cells

early blastocyst stage, cells in the embryoblast differentiate

dorsal-ventral polarity

near the time of implantation, epiblast and hypoblast cells segregate according to their specifications. This establishes the ________ in the embryo

epiblast

these are cells that forms a layer dorsally to the blastocyst cavity

hypoblast

cells that forms a layer ventral and adjacent to the blastocyst cavity

Anterior visceral endoderm *AVE

some hypoblast cells are specified to the form the ________, these cells migrate to what will become cranial end of the embryo

AVE

classified as endoderm

nodal antagonist

AVE secretes _________