Reproductive System Flashcards
What’s the difference between the types of sex steroids testes and ovaries produce
Testes secrete mostly androgens and some oestrogens
Ovaries secrete more oestrogen and also secrete progesterone
Which two steroid hormones control spermatogenesis and also oogenesis (formation of egg and sperm)
LH and FSH
What’s the difference majorly in spermatogenesis and oogenesis
Oogenesis happens cyclically every 4 weeks new egg released
Sperm continuous reproduction
What is connected to the ovaries
Fimbriae (end of Fallopian tube)
And the Fallopian tube
Which layer on the uterus is shed during menstruatikn if no fertilised egg present
The endometrium
What is the muscle layer of the uterus called (which oxytocin allows contraction of)
Myometrium
Which part of meiosis does the oocyte stop at before it develops into secondary and then ovum within the ovaries
Prophase I
Explain the structure of the oocytes which later become the ovum in oogenesis
They exist as primordial follicles
The oocyte is surrounded by Stroma cells and follicular cells
Why are you born with many more oocytes than acctually later develop into a matured egg released
Most oocytes die before puberty or after the first menstruation due to programmed cell death
What is the ovarian cycle and what is it in sync with
The maturation of oocytes into the ovum and release of the ovum into Fallopian tube
It is in sync with the uterine cycle/menstrual cycle
What is the phase called which is the development of the primordial follicles
The follicular phase
What happens in the pre Antral follicular phase
Primordial follicle develops into a primary follicle due to paracrine factors released causing growth into a primary follicle
Which hormone stops all primordial follicles developing into primary follicles
Antimullerian hormone produced by primary follicles themselves
Explain the structure of the primary follicle in the pre Antral follicular phase
Oocyte becomes surrounded by granulosa cells
And a zona pellucida glycoprotein layer
Why is the zona pellucida of the primary follicle important
Because it acts as a sperm binding site for fertilisation
How do cells communicate in the primary follicle
Gap junctions
How does a matured pre Antral follicle differ from a primary follicle
Thicker layers of granulosa cells
Thecal cells appear
Zona pellucida stays the same
How do granulosa cells form thecal cells
Release paracrine factors into the stroma cells and these form thecal cells
What happens in the antral phase of the follicular phase
Thecal cells become apparent
Thicker pellucida
Thicker granulosa cells
Fluid filled sac within the granulosa cells appears
How does stimulation of growth differ in antral to pre antral folliclular phase
No longer dependant on paracrine factors and due to
FSH hormone
What does FSH do in the antral late phase of follicular phase
Triggers production of LH receptors on granulosa cells
Increases expression of aromatase enzyme which converts androgens into oestrogens in granulosa cells
Which hormone produced in the ovaries by thecal cells in high production causes hypothalamus stop releasing more FSH
Oestrogen
Which cells actually produce the androgens converted to oestrogens in granulosa cells
Thecal cells
What does decrease in FSH when too much oestrogen is produced from androgen in granulosa cells cause
Cell death in most antral follicles causing dominant one to be chosen for release
What surrounds the oocyte in the dominant follicle
Pellucida glycoprotein layer and corona radiata
What does LH response by dominant follicle cause
Undergoes meiotic division up to metaphase 2 (forming secondary oocyte and polar body when it develops into ovum)
Also lowers oestrogen in late follicular phase by inhibiting aromatase
What does FSH cause pre ovulation cause important for ovum release
Causes cytokine production And hydrolytic enzymes released by thecal and granulosa cells
= degrade the ovary wall
When does oestrogen decrease
When LH and increases
Or when FSH decreases
What happens when the ovary wall and follicle ruptures
Corona radiata, ovum and the pellucida layer are released and took in via the fimbriae
Why is the corona radiata important
Capture of egg by the fimbriae
What does the ovary form when the ovum is released
Corpus luteum
When are LH levels increased
When oestrogen has increased- it tries to eradicate this by causing thecal cells to produce more androgens
Lowers oestrogen by inhibiting aromatase enzyme
What happens in the luteal phase
Granulosa cells fill with lipid
They produce progesterone
Oestrogen decreases due to increased LH (stops aromatase)
Then goes back to normal levels
What happens to the corpus Leuteum if not pregnant
Forms corpus albicans and slowly degrades
Why do LH and FSH increase when corpus albicans is produced
Because low oestrogen and progesterone due to less sterofenic tissues like granulosa cells can’t produce progesterone or oestrogen from androgens
What happens in the luteal phase of pregnant
Placenta release human chorionic gonadotropin
Allows corpus luteum to stay intact
What is released in high frequencies of gonadotropin RH and low frequencies
FSH= high frequency (egg maturation)
LH- low frequency = triggers ovulation
Why is there high progesterone and oestrogen originally in the luteal phase
Because low LH before surge and also no feedback of oestrogen causes constant production
Important functions of FSH
Stimulates growth of immature follicles
Upregulates aromatase expression increasing oestrogen levels
Induce expression of LH receptors in granulosa cells in the late follicular cells to allow ovulation
Why do antral follicles die at fast rates
When oestrogen is produced in high amounts when FSH released this causes FSHbto stop being released and thus stops promoting follicle maturation
What is the importance of LH in the late follicular phase
The surge is to stop oestrogen production further as it inhibits aromatase
LH also needed to allow oocyte to go under division until metaphase II to form the matured ovum from secondary oocyte and polar body
Low levels of LH allow progesterone secretion from granulosa cells in the luteal phase
LH causes granulosa to secrete hydrolytic enzymes to degrade ovary wall
Why is oestrogen important
Prepared the reproductive tract for potential fertilisation and pregnancy
Why is progesterone important in luteal phase (due to low LH)
Promotes uterine secretions to maintain support for fertilised egg if pregnant
When is LH high
When FSH is present and progesterone is not present
Which hormones in granulosa cells in ovaries repress FSH production
Inhibin a and B
What causes an LH surge pre ovulation
High levels of oestrogen increase LH due to low FSH frequency
High levels of oestrogen then inhibited by LH
