Oogenesis Flashcards
What is the purpose of follicular fluid?
Regulate the function Maturation of the oocyte Prepare follicule Stimulatory/inhibitory factors environment for sperm capacitation
What are the two purposes of the ovary?
Cyclic production of ova
Production of steroid hormones
Which follicule is responsible for the largest amount of estrogen?
Largest follicle
How many follicles does each species usually ovulate?
Cows-One
Sheep-One or two
Sows- 20-30
Mares-One, two is more common than we think
What is the final follicle growth length?
12-34 days but could take 6 months
The antrum formation and final growth depend on what?
Gonadotropins
What does the hormonally induced proliferation and differentiation of theca and granulosa cells lead to?
Follicles become able to produce Estradiol and respond to FSH and LH
What will follicles that produce Estrodiol gain that is necessary for ovulation and lueinizatin?
LH receptors
What are the three Dynamics of antral follicles?
Recruitment
Selection
Dominance
What are the three purposes of the steroid hormones made by the ovary?
1) Maintain development of the genital tract
2) Facilitate migration of the early embryo
3) Secure embryo implantation
Describe the Recruitment dynamic
A cohort of small antral follicles begin to grow and produce E2. Some of these follicles will undergo atresia.
Describe the Selection dynamic.
The emerging of dominant follicles from the previously recruited antral follicles. They may become atretic or dominant.
Describe the dominance dynamic.
Selected follicles proceed towards becoming dominant as they make more E2 and inhibin.
How is dominance characterized?
One or more preovulatory follicles exert a major inhibtory effect on the other antral follicles from the recruited and selected cohort.
How long does the follicular wave take in comparison to the estrus cycle.
It takes 20% of the estrus cycle
T/F
Follicular growth and atresia occur throughout the estrus cycle.
True
What happens to follicles during metestrus?
A group of follicles is recruited but they become atretic
When can Ovulation not occur?
When P4 is high
What happens to the follicle during diestrus?
second follicular wave starts to develop but also undergo atresia. Makes a small amount of E2.
What is GnRH?
Gonandotropin Releasing Hormone
Where is GnRH produced?
The brain’s hypothalamus
How is GnRH released when P4 is high?
It is released slowly, causing FSH and LH to be released slowly
When do the third wave of follicles develop?
After luteolysis, and one or more follicles will develop into the preovulatory follicle
When do follicular waves of antral follicles occur?
Prepubertally, during pregnancy, anestrus and postpartum recovery
When is the second rise in FSH?
20-30 hours after the preovulatory surge of LH and FSH
Cystic ovaries have high levels of what?
Androstenedione
T/F Ovarian Follicle secrete numerous proteins?
True
What is Follicular fluid?
Serum transudate that contains steroids and glycoproteins
Where are the steroids and glycoproteins found in the follicular fluid synthesized from?
Follicular wall
What happens to the hormones of large antral follicles as ovulation approaches?
E2 and P4 levels are high
What are the functions of follicular fluid?
Regulate granulosa cells Prepare follicle for the corpus luteum formation Mature the oocyte Ovulation Sperm capacitation Egg transport to the oviduct
What makes up follicular fluid?
Oocyte maturation inhibitor
Relaxin
Luteinization inhibitor
Inhibin
What are the four phases of oocyte maturation?
Mitotic Division, Nuclear Arrest, Cytoplasmic Growth, Resumption of Meiosis
T/F Germ cells are mitotically divided before and after birth.
False only before birth. The female is born with all the eggs she will ever have
Why is the last mitotic division important?
Because the new primary oocyte enters meiotic prophase
What happens in the phase of prophase arrest?
Meiotic prophase is stopped and the oocyte nucleus becomes dormant until puberty
Describe the cytoplasmic growth phase
The primary oocytes accumulate larger volumes of ctyoplasma and devolp the zona pellucida
Where are Gap junctions formed?
Between plasma membrane oocytes and granulosa cells
After ovulation several granulosa cells are still on the oocyte. What are these called?
The corona radiata
What frees the oocyte from the granulosa layer during ovulation?
Cumulus cell dissociattion
How long after the LH surge does meiosis occur?
3 hours
What occurs about 2 hours before ovulation?
Granulosa cells penetrate through the lamina basalis and prepare for the invasion of the theca cells
What is the stigma?
The area of the follicle apex that becomes thin and ruptures releasing follicular fluid and oocye
What is needed to stimulate collagenase activity?
P4
PGF2a is needed for what?
To rupture the follicle
Preovulatory follicle undergo what three changes during ovulation?
Cytoplasmic and nuclear maturation
Disruption of cumulus cells
Thinning and rupture of the wall
