Exam #4: Female Reproductive Physiology I Flashcards
What are the general functions of the ovaries?
- Principal female reproductive organ
- Estrogen and progesterone production (steroidegenesis)
- Storage and release of the ovum (oogenesis)
What are the hypothalamic peptide hormones?
GnRH
Oxytocin
GnRH= gonadotropin releasing hormone
What are the pituitary peptide hormones?
FSH
LH
Prolactin
What is the ovarian peptide hormone?
Inhibin
What are the ovarian steroid hormones?
Estradiol
Progesterone
Androstenedione
Testosterone
Review the synthesis of peptide hormones.
- 3-200 aa
- Synthesized as an inactive pre-prohormone
- Post-translational processing
- Stored in vesicles
List the important characteristics of peptide hormones.
- Circulate free
- Bind cell surface receptors i.e. NOT going to cross the membrane
- Hydrophilic i.e. water soluble
- Release is Ca++ dependent
What are the typical receptors for peptide hormones? Review the mechanisms that occur following binding of a peptide hormone with these receptors.
1) RTK
- Transmembrane receptor
- Intrinsic enzymatic activity
- Bind hydrophilic hormones
2) GPRC
- Transmembrane receptor
- Couple to G proteins
- Bind hydrophilic hormones
Review the synthesis of steroid hormones. What is the general sequence in synthesis of the steroid hormones?
- Steroid hormones are derived from cholesterol
- Sequence:
1) Progesterone
2) Androgen
3) Estrogen
List the important characteristics of steroid hormones.
- Lipophilic
- Circulate bound to plasma proteins
- Cross membranes
- Intracellular receptors that regulate gene transcription
*NOT stored in vesicles
Why is protein binding in circulation important in regards to the metabolism of hormones?
- Binding to a plasma protein protects against degradation and INCREASES the half-life
- Half-life free«_space;Half-life bound
What are the two principal sites of degradation of hormones?
1) Site of action
2) Liver
*Note that steroid hormones will be conjugated in the liver to make them more water soluble for excretion
What are the effects of estrogen on the uterus?
1) Proliferation of the endometrial stroma*****
2) Development of endometrial glands
3) Increased size of the uterus
What are the effects of estrogen on the ovaries & vagina?
Increase in size
What is the effect of estrogen on bone?
Inhibition of osteoclast activity that inhibits bone resorption and stimulates bone growth
What is the effect of estrogen on cervical mucous?
Estrogen makes cervical mucus thin & stringy, which provides channels that guide sperm
Note that this is OPPOSITE the effects of PROGESTERONE
What are the effects of progesterone on the uterus?
1) Promotes secretory changes of the endometrium & of the uterus i.e. getting the endometrium ready for implantation
2) Decreases frequency & intensity of uterine contractions
3) Decreases prostaglandin production
What is the effect of progesterone on cervical mucous? What hormone is this effect opposite to?
Production of a thick & tacky mucous that has an increased viscosity
*Progesterone containing contraceptives increase viscosity of cervical mucous to prevent sperm from reaching egg
Outline the process of oogenesis.
N/A
When does the female have the highest number of potential oocytes?
Birth
What is the difference between mitosis and meiosis?
Mitosis= 1x DNA replication & 1x splitting into two daughter cells
Meiosis= 1x DNA replication with 2x rounds of division
What is the difference between a primary oocyte and a secondary oocyte?
Primary=immature egg arrested until the reproductive years
- Diploid
- Arrested in meiosis I
Secondary= immature egg that is selected to continue meiosis in reproductive years
- Haploid
- End of meiosis II
How does meiosis differ between males and females?
Males= 4 sperm i.e. 4 gametes
Females= 1 gamete i.e. loss of 3 “polar bodies”
- Get a secondary oocyte and a polar body after meiosis I in the female
- Meiosis II yields 3x polar bodies and one gamete
*This is referred to as “chromosomal wastage”
What is the primoridal follicle?
This is the primary oocyte PLUS a layer of granulosa cells that surround it
What important hormone is secreted by the primordial follicle?
Oocyte-maturation inhibiting factor
*Regulates meiotic events
What is the primary follicle?
Proliferation of the granulosa cells surrounding the primary oocyte has occured, and now there is a mass of granulosa cells surrounding the primary oocyte
- Happens in the reproductive years
Outline & diagram the hypothalamic-pituitary-gonadal (HPG) axis.
1) Hypothalamus
- GnRH
2) Anterior Pituitary
- FSH
- LH
3) Gonads i.e. ovaries
- Estrogen
- Progesterone
- Inhibins
*Note that these steroid hormones function in a “long-loop” negative & positive feedback, primarily at the level of the anterior pituitary
What is the average duration of the female reproductive cycle?
28 days
What major events occur during the female monthly sexual cycle.
- Fluctuations in hormones
- Follicle maturation
- Endometrial lining of the uterus develops in preparation for fertilization & then is shed if NOT fertilized
What is the difference between the Follicular & Luteal Phases of the sexual cycle?
Follicular= Day 1
- Follicle development
- Endometrial proliferation
- Ovulation
Luteal= After ovulation
- Corpus Luteum forms
- Endometrial differentiation
- Menses if fertilization does NOT occur
Describe the release of GnRH from the hypothalamus.
Released in a pulsatile fashion
- Pulse duration= 5-25 min
- Frequency= Q1-2 hours
*****This stimulates the ant. pit. to release FSH & LH ; thus, throughout the different phases of the cycle there are pusatile changes in FSH & LH
What is the net effect of estrogen feedback in the follicular phase?
Negative feedback on hypothalamus and anterior pituitary
**Note that this is NOT a complete shut-down; it is more just holding things in check
When does the effect of estrogen feedback change? What are the relative levels of estrogen at this point?
Mid-cycle
*****Estrogen levels have peaked at this point
What is the net effect of estrogen feedback mid-cycle?
Positive i.e. increases FSH & LH, resulting in a surge of these gonadotropins mid-cycle
What is the net effect of estrogen & progesterone feedback in the luteal phase? Which predominates?
Negative feedback that is now PRIMARILY mediated by PROGESTERONE
*****Note that now this is more of a “shutting off”
What is the role of the inhibins in the female montly cycle?
Inhibition of the HPG axis
When do inhibins exert their effects? Which inhibins predominate throughout the different phases of the female monthly sexual cycle?
1) Follicular phase= Inhibin B that mostly regulates FSH secretion
2) Just after ovulation= Inhibin B turns off FSH secretion after ovulation
3) Luteal phase= Inhibin A is secreted by the CL and inhibits LH & FSH, decreasing ovarian steroid production
