EMBRYOLOGY: First Week of Development Ovulation to Implantation (copy)

What are the female Gonadotropins?

Lutenizing Hormone (LH) and Follicle Stimulating Hormone (FSH)

What effect does the production of estrogen have?

stimulates the endometrium to enter the Proliferative Phase

How soon before ovulation does the Secondary oocyte arrest its meiotic division?

3 hours

How is the oocyte removed from the ovary in ovulation

Follicular sweeping and contractions in the ovarian wall

After ovulation, what is the fate of the Granulosa Cells of the Oocyte?

they become vascularized and are transformed into yellow Lutein Cells.

What structure do Lutein Cells become?

Corpus Luteum

What constitutes the large size of the Corpus Luteum?

hypertrophy and accumulation of lipids

What is the function of the Corpus Luteum?

Secretion of estrogen and progesterone

What is responsible for the production of progesterone by the oocyte?

Corpus Luteum

When do females begin to undergo monthly cycles?

At puberty

What controls female reproductive cycles?

The Hypothalamus

What role does the hypothalamus play in female reproductive cycles?

It releases GnRH, which stimulates the pituitary gland to release Gonadotropins

What do gonadotropins do?

they stimulate and control changes in the ovary

What is the role of FSH in the ovary?

it stimulates 15 - 20 follicles to grow and mature

How many follicles reach full maturity and are released from the ovary?

1

What hormone is produced from a growing follicle?

Estrogen

What effect does the surge of LH have?

Causes primary oocyte to complete meiosis I and begin meiosis II

Causes progesterone to be produced

Causes ovulation

What triggers Progesterone to be produced?

surge in LH

What triggers ovulation?

surge in LH

What phase of Meiosis II is the secondary oocyte arrested in before ovulation?

Metaphase II

What causes the endometrium to enter the Secretory Phase?

Progesterone production

At what Phase is the uterus at the time of ovulation?

Secretory Stage

When does a fertilized oocyte reach the uterine lumen?

3-4 days

What is the fate of the Corpus Luteum if no fertilization occurs?

it shrinks after 9 days and becomes scar tissue

What is the scar tissue that is formed on an unfertilized oocyte?

Corpus Albicans

What is the fate of the endometrium if no fertilization occurs?

it enters the Menstrual Phase due to the decrease in progesterone.

What causes the decrease in progesterone of an unfertilized oocyte?

Shrinking of the Corpus Luteum, which secretes progesterone

What is the fate of the Corpus Luteum if fertilization occurs?

it is prevented from shrinking by Human Chorionic Gonadotropin

What secretes Human Chorionic Gonadotropin?

syncytiotrophoblast

What does the maintained Corpus Luteum develop into?

Corpus Luteum of Pregnancy

What is the function of the Corpus Luteum of Pregnancy?

to produce progesterone until the fourth month

What produces progesterone after the fourth month of pregnancy?

The trophoblastic component of the placenta

What occurs of the Corpus Luteum of Pregnancy is removed before the fourth month?

Abortion

Where does fertilization occur?

Ampulla

Why is the ampullay tube the most suitable region for fertilization?

it is the widest part of the tube and closest to the ovary

How do sperm move from the cervix to the uterine tube?

the are moved by uterine muscle contractions

How long does the trip from the cervix to the uterine tube usually take?

30 minutes to 6 days

When do sperm become less motile?

At the isthmus

How do sperms become motile again after leaving the Isthmus

Chemoattractants make them motile and swim to the ampulla

What are the key processes for sperm to undergo before being able to fertilize an oocyte?

Capacitation

Acrosomal Reactions

How long does the process of Capacitation last?

7 hours

What occurs during capacitation?

Glycoprotein coat and Seminal plasma proteins are removed from the plasma membrane

Where does capacitation occur?

uterine tube

When does the Acrosome Reaction Occur?

After binding to Zona Pellucida

What induces the Acrosome reaction?

Zona Proteins

What occurs during the Acrosome Reaction?

Enzymes, Acroson and Trypsin like substances are released

What is the Zona Pellucida?

the glycoprotein shell surrounding plasma membrane of an oocyte

What is the function of the Zona Pellucida?

facilitates the binding of sperm and the acrosome reaction

What mediates the binding of sperm and triggers the acrosome reaction?

ZP3 ligand

What allows the sperm to penetrate the Zona Pellucida and make contact with the oocyte plasma membrane?

Acrosomal Enzymes

What occurs when the head of the sperm contacts the oocyte surface?

the permeability and composition of the zone pellucida changes

lysosomal enzymes are released from cortical granules and prevents sperm penetration and receptor inactivation

What are the three phases of fertilization?

Penetration of the Corona Radiata

Penetration of the Zona Pellucida

Fusion of the Membranes

What mediates the adhesion of the sperm to the oocyte?

Integrins on the oocyte and disintegrins on the sperm

What occurs after the sperm adheres to the oocyte?

plasma membranes fuse

How does the oocyte respond to the entering of sperm?

Cortical and Zonal Reactions

Resumption of Meiosis II

Activation

What important event of fertilization prevents Polyspermy?

the Coronal and Zonal reactions

What is the result of the oocyte's second meiotic division?

a second Polar Body and a definitive oocyte

the female pronucleus is also produced

What are the three main results of fertilization?

restoration of the diploid chromosome number

determination of sex

initiation of cleavage

What is cleavage?

a series of mitotic divisions where the zygote increases its number of cells

What kind of cells increase in number via mitosis and become smaller with each division?

Blastomeres

What is Compaction?

the process of blastomeres forming a compact ball and maximize contact with one another

What holds compact cells together?

tight junctions

What is a morula?

a 16-cell embryo

when is a morula formed?

3 days after fertilization

When does a morula become a blastocyst?

as it enters the uterine cavity

What is the blastocoel?

the fluid-filled cavity in the blastocyst.

What are the inner cells of the Blastocyst called?

the Embryoblast

What are the outer cells of the Blastocyst called?

the Trophoblast

When does the zona pellucida disappear?

day 6

When can implantation begin?

When the Zona Pellucida disappears and allows the trophoblastic cells to penetrate the uterine epithelial cells

What mediates the attachment of the trophoblast to the epithelium?

L-Selectin on the trophoblast and the carbohydrate receptors on the oocyte

What further allows the attachment and invasion of the Blastocyst?

Integrins

What Phase is the endometrial wall in during implantation?

Secretory Phase

What are the three Uterine Layers?

Endometrium

Myometrium

Perimetrium

What are the three phases the Endometrium goes through during the Menstrual Cycle?

Proliferative Phase

Secretory Phase

Menstrual Phase

When does the Proliferative Phase occur?

after the Menstrual Phase

What occurs during the Proliferative Phase?

Follicle growth due to Estrogen

regeneration of glands and arteries

What Initiates the Secretory Phase?

Progesterone

Under what conditions does the Menstrual Phase occur?

only if there is no fertilization

When does the Secretory Phase occur?

2-3 days after ovulation

What are the 3 endometrial layers?

Compact Layer

Spongy Layer

Basal Layer

When does the Menstrual Phase occur?

3-4 days after ovulation

What occurs during the menstrual phase?

the compact and spongy layers of the endometrium are shed

there is diapedesis of blood from venues and superficial arteries which are expelled

glands and storm are expelled

What regenerates after menstruation?

the basal layer of the endometrium during the proliferative phase

What is the role of the endometrium when fertilization occurs?

Assists with implantation and the formation of the placenta.