Lecture 3: Female tract, oogenesis and endocrine control (I) Flashcards
Describe the Ovarian Cycle
- Following puberty, waves of ovarian follicles become activated
- activated follicles can be recognised by the changes in the morphology and number of granulosa cells that surround the oocyte.
- It takes about 85 days from the time of activation of a follicle to when it starts to form an antrum (containing follicular fluid) and be capable of ovulation.
- With each menstrual cycle (or continuously) groups of developing follicles are stimulated to grow very rapidly
- The follicular wave(s).
- During the follicular phase of the cycle one follicle will dominate over the others in terms of growth.
- Usually in women there is only one dominant follicle which goes on to be ovulated
- In some other species there are multiple dominant follicles each of which is ovulated and fertilised.
The population of oogonia expands via mitosis to produce…..
oocytes that undergo meiosis and arrest at the prophase of meiosis I.
Describe the 2 cell theory of follicular steriodogenesis
It is believed that Thecal cells are produce Androgens and Progesterones from Cholesterol in response to LH.
Then the androgens cross the basement membrane. The Androgens are then aromatised to Estrogens (then estradiol) by the _granulosa cell_s in response to FSH
The androgens cross the basement membrane. The Androgens are then aromatised to _________by the _______in response to _____
Then the androgens cross the basement membrane. The Androgens are then aromatised to Estrogens (then estradiol) by the granulosa cells in response to FSH
What is a culmulus oophrous?
Cumulus oophorus refers to an appearance in the ovary in which multiple granulosa cells enlarge around a developing oocyte.
These support cells (“cumulus cells”) serve multiple functions in the maturation of the oocyte.
Describe the features of the Primordial follicle
- Thin zona pellucida
- Flattened single layer granulosa cells
- GC are surrounded by stromal cells
Where are the different proteins found in the zona pellucida
Three proteins make up the zona pellucida
ZP-1 present in primordial follicles
ZP2 and ZP3 added to activated follicles
Corpus Luteum is producing…..
Predominantly Progestrones
The vast majority of oocytes will never be ovulated instead they die via a process termed _______.
The vast majority of oocytes will never be ovulated instead they die via a process termed atresia.
What is zona pellucida made up of?
What is the role of zona pellucida?
Three proteins make up the zona pellucida
ZP-1 present in primordial follicles
ZP2 and ZP3 added to activated follicles
Important for filtering normal sperm and in blocking polyspermy (sperm from other species)
Label
Oocytes remain arrested at______ until puberty when _______.
Oocytes are contained in ______in the _______or _______ of the ovary.
Oocytes remain arrested at prophase I until puberty when some follicles are activated. Oocytes are contained in follicles in the xortex or outer layer of the ovary.
Describe the features of Tertiary follicles
- Oocyte with cytoplasm (about to ovulate)
- Zona Pellucida
- Granulosa cells attached to the egg (sending proccesses through to the oocyte)
- Cumulus oophorous
- Granulosa cells attached to the wall
- Theca interna
- Theca externa
What is this?
Tertiary follicle
Describe the features of Secondary Follicles
1) Granulosa cells are multilayered and cuboidal
2) The granulosa cells express FSH receptors. The granulosa cells in response to FSH produce e_strogen and inhibin and AMH_
4) Theca cells express LH receptors. They produce Androgen
Briefly describe oogonia/oocyte number throughout someone’s life
Max number of germ cells is at around 6 months of gestational age.
~7million oocytes
Then they die rapidly quickly until the baby girl is born. Then the decline gradually decreases.
Describe the features of Small tertiary follicles
- Antrum containing follicular fluid
- Granulosa cells are multilayered and cuboidal
- Theca interna
- Theca externa
Describe the body temperature changes with ovulation
A small increase in temperature overlies a progesterone peak.
Basal body temperature increases following ovulation.
What is the AMH?
Antimullerian hormone
Suppresses follicular recruitment and development.
Comes from the granulosa cells of the bigger follicles
Describe the Steriod pathway
- Steroid
- Progestone
- Androgens
- A are aromatised to Oestrogen
Label
Zona pellucida
Draw he Hormone concentration changes across the menstrual cycle with references to the ovarian cycle
What are the different follicles and what is their life span?
1) Primordial follicles
* 12-50 years arressted state
2) Primary follicles
* 2-3 months active growth
3) Secondary follicles
* 2 weeks rapid growth
4) Tertiary or Graafian follicles
Describe the Endocrine control of the ovarian cycle
Day 1: Day of menstrual bleed
- Follicle has died
- Decreased progesterone and estrogen results in increased FSH (FSH is binding to the slowly developing follicles, and starting to allow granulosa cells to proliferate)
- Granulosa cells are also starting to produce estrogen.
- So estrogen is going back to the pituitary and exerting _negative feedbac_k. This results in reduction in production of FSH
- But estrogen reaches a certain concentration, where its function goes from inhibitory to excitatory (positive feedback).
- This stimulates the release of LH (and some FSH)
- LH acts on the theca cells to produce more estrogen.
- After ~12 to 24 hours after LH peak you get ovulation
Ovulation
- Once the follicle has ovulated, the granulosa cells start to leutinize
- The theca interna cells produce estrogen but more importantly, progesterone.
- The progesterone is transported away into the uterus and acts on the endometirum and the myometrium.
How does a oognoia become a oocyte?
1) Following the mitotic divisions (that produce a large number of germ cells- oogonia in the developing ovary), meiosis begins, but is not completed.
2) Meiosis halts just prior to metaphase 1 at end of prophase
3) Oogonia is now called oocytes
4) They remain arrested until ovulation at 12-50 years.
Label
Describe the features of the Primary follicle
Cuboidal granulosa cells
Describe the Endocrine control of follicular development
Gonadotrophin-independent growth until Secondary, then change to Gonadotrophin-dependent growth
The bigger follicles are repressing activation of the primordial follicles via AMH (antimullerian hormones)
As it develops, there is i_ncreasing FSH receptors_ associated with the follicles, because there are more granulosa cells. The granulosa cells are also producing estrogen. They pump estrogen out into the woman. Now (secondary-tertiary) there are lots of granulosa cells that are responsive to FSH. Now you get massive rate of proliferation because they have hormonal input driving proliferation and production of granulosa cells.
What happens to the follicle after the egg is released?
- The oocyte goes down the fallopian tube, but the follicle remains behind.
- Corpus luteum (yellow body)
- Thick wall structure
- They are responsible for producing large quantity of steroids.
- They thicken they die away
- Happens in 14 days
What are the 4 regions of the fallopian tube?
1) Infundibulum (have fimbriae)
2) Ampulla (widening)
3) Isthmus (tube)
4) Intramural/interstitial portion
