oogenesis, the female tract and endocrine control (1) Flashcards Preview

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Flashcards in oogenesis, the female tract and endocrine control (1) Deck (27):

define oogenesis

formation and development of an ovum (mature oocyte)


what constitutes a follicle

oocytes and surrounding support cells

- they're located near the surface of the ovaries in the cortex


at what age does a female have the greatest number of oocytes

4 months in utero a fetal female will have around 7 million oocytes formed

- start to die to about 1 million at birth and then continue to gradually decline till the age of ~50


describe mitosis

proliferation of stem cells - produce large numbers of germ cells (oogonia) in the developing ovary

2n (23 chromosomes - 2 pairs)
oogonium cell divides and creates two identical copies of these chromosomes


describe meiosis

reductive division

primary oocytes rest at meiosis 1 in the ovary until they are recruited (if that happens) into the follicular wave


describe meiosis on the oocyte

oocyte undergoes meiosis and produces one daughter cell to become the main ooctye and one daughter cell to become the first polar body (nucleus)


when and how are follicles activated

following puberty waves of ovarian follicles become activated

they can be recognised by changes in the morphology and number of granulosa cells that surround the oocyte


timeframe for a follicle and ovulation

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


describe the dominance of the follicular phase

one follicle will dominate over the others in terms of growth, as only one dominant follicle goes on to be ovulated


describe the timeframe of follicular growth

1. primordial follicles

(12-50 years arrested state)

2. primary follicles

(2-3 months active growth e.g. 85 days)

3. secondary follicles

(2 weeks rapid growth)

4. tertiary follicles


what defines a primordial follicle

oocyte has a very thin zona pellucida and a single layer of granulosa cells (flat)
- stromal cells on the outside of granulosa cells


primary follicles

once follicular cells are activated they become a primary follicle and form cuboidal granulosa cells


cells of secondary follicles

granulosa cells
- proliferate forming a multilayered cuboidal structure
- express FSH receptors and produce oestrogen, AMH and inhibin

Theca cells
- express LH receptors
- produce androgens


steriod pathway


(can go backwards)


describe the two cell theory of follicular steriodogenesis (how oestrogen is made)

theca cells that sit outside the basement membrane in response to LH make progesterone and androgens

the androgens then move across into the basement membrane into granulosa cells to be aromatised into oestrogens


defining factors of a small tertiary follicle

anturm forms containing follicular fluid

has both a theca interna and a theca externa


zona pellucida

contains 3 proteins

ZP-1 = present in primordial follicles
ZP2 and ZP3 added to activated follicles

important for filtering normal sperm and in blocking polyspermy (selective barrier)
also blocks other species


define atretica

primordial follicles rest until puberty essentially however a lot of them die off via atretica

(most oocytes once activated are not ovulated but become atretic = die)



antimullerian hormone

suppresses follicular recruitment and development
from primordial to primary

comes from granulosa cells of the bigger follicles (represses development of other follicles)


how is an egg released


pressure build up from fluid inside the ovary and it bursts - oocyte released
controlled process


formation of corpus luteum

granulosa cells become lutenised cells and undergo proliferation referred to as the corpus luteum. They produce prodominately progesteron


hormone control of the ovarian cycle

1. corpus luteum regresses, oestrogen and progesterone levels are low, see increased levels of FSH
2. FSH stimulation leads to increased follicular growth
3. about day 6-7 theres selection of the dominant follicle with increased oestrogen
4. oestradiol supress FSH (& LH) in the pituitary
5. oestrogen levels rise, by day 12, threshold conc of estradiol is exceeded. Causing a switch from negative to positive feedback
6. oestrogen-mediated positive feedback triggers a rise in GnRH leading to increased LH surge
7. LH surge induces ovulation
8. corpus luteum develops, increased progesterone
9. elevated progesterone levels inhibit GnRH, decreased FSH & LH
10. Demise of the corpus luteum


describe inhibin

feeds back at the level of the pituitary to inhibit production of FSH


regions of fallopian tubes

infundibulum - region where oocyte is picked up

ampulla - widening

isthmus - main

interstitial portion - passing into uterine body


structure of Fallopian tube

-epithelial lining
- muscular coat
- serosal coat

-respond to steroids


effect of estrogen in the fallopian tubes

E2 promotes:

- increase in cilia
- increase in secretory activity
- increase in muscular activity


effect of progesterone in fallopian tubes

-decreases muscular activity
-decrease in cilia, but increase in the beat Hz after estrogen priming
- decrease in the volume of secretions