________ produce steroid hormones from __________.
The LH surge causes _________ production.
progesterone (progesterone during pregnancy inhibits new follicles from developing and ovulating--> to sustain current pregnancy)
Describe the pathway of LH in a male.
hypothalamus--> GnRH--> anterior pituitary--> LH pulse--> leydig cells--> testosterone production--> sertoli cells--> spermatogenesis OR testosterone--> DHT--> circulation OR testosterone--> estradiol
Describe the pathway of FSH in a male.
hypothalamus--> GnRH--> anterior pituitary--> FSH--> sertoli cell--> ABP (androgen-binding protein)--> ABP binds testosterone in lumen of seminiferous tubules--> accumulutes in lumen--> critical for normal spermatogenesis
Why does ABP accumulate in the lumen of the seminiferous tubules and bind testosterone?
ABP is too large to pass through the luminal walls
Describe negative feedback of GnRH in males.
FSH--> sertoli cells--> inhibin and ABP--> inhibin goes to pituitary--> inhibits FSH secretion
Describe the pathway of gonadotropins in a female.
LH and FSH stimulate follicular growth--> increase in estradiol--> hypothalamus--> GnRH surge--> anterior pituitary--> LH surge--> ovulation
Describe the general pathway for steroid hormones.
steroid secreted by gonad--> enters blood and goes to target tissue--> causes change in target tissue--> steroid in blood passes through liver--> liver renders steroid water soluble--> steroid re-enters blood--> goes to kidney and bile--> excreted in urine and/or feces
Steroid hormones are metabolized in the _________.
After steroid hormones have been metabolized, they are excreted as __(2)__.
glucuronide or sulfate
Primordial germ cells develop in the ________; they then migrate to the _______ and then the ________.
yolk sac; hindgut; undifferentiated gonad
Primary oocytes increase in number right after __________; subsequently, they decrease in number by _______.
fertilization; atresia and ovulation (after puberty, until menopause)
Describe the series of events that occur during maturation of a primordial germ cell to a zygote.
[primordial germ cell] mitosis--> [oogonia] mitosis--> [primary oocytes] mitosis then meiosis--> [4n primary oocytes] nuclear arrest at meiotic prophase--> [after puberty] LH surge (meiotic inhibitors removed)--> meiosis resumes--> [secondary oocyte] meiosis is arrested at metaphase--> [secondary oocyte] ovulation]--> fertilization---> sperm trigger completion of meiosis--> zygote
Primordial germ cells and oogonia are ________ (number of chromosomes).
Primary oocytes goes from _______ to ________ (number of chromosomes).
2n (diploid); 4n
The secondary oocyte is __________ (number of chromosomes).
The second meiotic division occurs after __________, but meiosis is arrested at __________ until _________.
ovulation; metaphase; fertilization
Meiosis is arrested at the ________ and _________ stages.
4n primary oocyte; 2n secondary oocyte
Describe the maturation of a primary oocyte to a follicle.