Sexual Differentiation, Puberty, and Menstruation Flashcards
Wolffian Ducts
Mesonephric ducts that develop in males to become the epididymis, vas defrens, and seminal vesicles
Mullerian Ducts
Paramesonephric ducts that develop in females to become uterus and fallopian tubes.
Sequential Process of Sexual Differentiation
Establishment of genetic sex, development of gonads, then development of secondary sex characteristics.
When do testes develop?
Week 6-7
When do ovaries develop?
Week 9
Until what point are gonads bipotential?
Week 5
What determines genetic sex of embryo?
SRY (sex determining region) on Y chromosome, located in unpairing region.
Pairing region of y chromosome
Small region where crossing over can occur with X chromosome. SRY sits outside of this region.
Swyer’s Syndrome (Deletion/mutation of SRY gene)
XY individual with a uterus, fallopian tubes, and a cervix. Present at time of puberty with delayed sexual maturation and amenorrhea, but normal pubic hair. All gonads are normal, but gonadectomy needed because tumors likely.
What happens if SRY is translocated to X chromosome.
XX individual with male characteristics and genitalia.
Sertoli Cells
Located next to developing sperm. Secrete AMH (antimullerian hormone) that causes paramesonephric ducts to wither.
Interstitial Cells of Leydig
Secrete testosterone, stimulates Wolffian duct growth and differentiation into epididymis, vas deferens, seminal vesicles, and ejaculatory ducts.
Granulosa Cells
Secrete estradiol
Theca cells
Secrete progesterone.
Why won’t a fetus with testes become female?
Because AMH and testosterone secreted!
How and when do penis/scrotum differentiate.
At weeks 9-10, due to presence of DHT.
Why does Wolffian duct regression occur in females?
No testosterone.
5alpha-reductase
Converts Testosterone into DHT, which stimulates growth of penis/scrotum.
What happens when there’s no DHT?
Labia and clitoris develop
Testicular Feminization (Androgen Insensitivity syndrome)
XY. Androgen receptor defect, Testosterone and DHT cannot be sensed. Causes a phenotypic female that doesn’t menstruate and has a blind ending vagina. Also has sparse pubic and axillary hair. It’s a spectrum though.
Congenital Adrenal Hyperplasia
Enzyme deficiency in adrenals, most commonly in 21-hydroxylase causes a backup of 17-OH progesterone and progesterone, and a lack of cortisol, shifts adrenals to make more androgens. So, there’s a masculinization of female external genitalia at birth, with normal uterus fallopian tubes, etc. Also, aldosterone deficient (hyperkalemic, hypovolemic, salt wasting).
Puberty endpoint
The creation of viable gametes
Maturation of the hypothalamus
At birth, the HPTestes axis is very active, but turns off at 24 mos. During puberty it somehow turns on again.
What substance’s pulses determine puberty?
GnRH, type of pulse will affect LH or FSH differently.
Prepubertal period hormone levels
GnRH low, LH, FSH low, low T and E
Pubertal hormone levels
Increase in pulse frequency amplitude of GnRH release. Increases in FSH and LH pulses, increase in E and T, beginning of folliculogenesis and spermatogenesis.
When in a female’s life is FSH/LH highest?
Menopause.
Gonadarche and Adrenarche
Signs of puberty in girls.
Primordial germ cells
Precursor cells to gametes, move from their origin in the hindgut of the embryo to the gonads. Eventually become spermatogonia/oogonia.
Male vs female gonadogenesis
In males it’s continuous, in females there’s a fixed limited pool of oocytes.
Meiosis
46 Ds, becomes 23 ds, becomes 23 ss.
When are oocytes arrested in meiosis?
Primary oocyte is arrested in prophase I of meiosis I until ovulation, where it is completed. Secondary oocytes completes meiosis II at fertilization.
What hormone dominates the follicular phase of the menstrual cycle?
Estrogen.
What happens just before day 14
Progesterone spike. LH spike on day 14.
What hormone dominates the luteal phase?
Both estrogen and progesterone.
Are variations in cycle length normal?
Yes
What does follicle growth include
Growth of granulosa cells, development of antrum, growth of oocyte
Granulosa Cells respond to what and secrete what?
Respond to FSH and secrete estrogen. Will not work without theca cells
Theca cells respond to what and secrete what?
Respond to LH and secrete androgens which are aromatized by granulosa cells into estrogen.
How is estradiol production controlled?
GnRH causes LH secretion which causes theca cell to produce androgens. These androgens are converted to estradiol in granulosa cells after FSH stimulates aromatase activity.
How many follicles start at the beginning of a menstrual cycle?
20-50 that had started growing 2-3 months ago.
How is only 1 follicle selected for dominance?
One that has the most FSH receptors.
How does the LH surge occur at day 14?
Because the hypothalamus and pituitary become more sensitive to estradiol.
What does the LH surge do to cause ovulation?
Meiotic division 1 is complete. Starts and arrests meiosis 2. Cumulus cells loosened.
How is the egg extruded from the follicle?
Progesterone causes prostaglandin and enzyme release to cause the walls to break down.
How does the ruptured follicle become the corpus luteum?
Thecal cells and blood vessels invade. Granulosa cells hypertrophy and terminally differentiate.
What does the corpus luteum do?
Secretes progesterone and estradiol.
What causes endometrial thickening?
Estradiol
What causes stromal cell differentiation (decidualization)
Progesterone causes glandular proliferation.
When does menstruation occur?
When the corpus luteum degenerates.
What does hCG do?
Maintain the corpus luteum, act a lot like LH and FSH.
