Endocrinology - Lecture 5 Flashcards
What are the primary reproductive organs?
testes in the male and ovaries in the female
What are the 2 functions of gonads?
- gametogenesis
- secretion of sex hormones
What are the 3 kinds of sex hormones?
- testosterone (men)
- estrogen and progesterone (fem)
Are the differences in reproductive endocrinology in males and female quantitative or qualitative?
quantitative
What does estrogen maintain in males?
bone density
Where is estrogen produced in males?
in tissues
What does aromatase convert testosterone to?
estrogen
What does estrogen deficiency in males lead to?
- increased to body fat
- contributes to sexual desire and erectile function
What secretes GnRH?
hypothalamus
Where does GnHR travel to?
anterior pituitary
What 2 pituitary gonadotropins does the GnRH stimulate the release of?
FSH and LH
What do FSH and LH stimulate the development of?
spermatozoa/ova and sex steroids
What do sex steroids exert effects in?
gonads
What is the principal function of the testes? (2)
spermatogenesis and steroidogenesis
What are precursor germ cells called?
spermatogonia
Where does the process of spermatogenesis take place?
in the coiled seminiferous tubules
How long does the process of maturation from immature spermatozoon take?
60 days
What are the 2 cell types critical for maturation of spermatozoa?
Leydig cells and Sertoli cells
Where are Leydig cells located?
outside seminiferous tubules
Where are Sertoli cells located?
within the seminiferous tubules
In response to LH, what do Leydig cells synthesize?
androgens
What do Sertoli cells envelop during their development?
germ cells
What do Sertoli cells synthesize in response to FSH? (2)
ABP and inhibin
What kind of concentrations does spermatogenesis depend on?
androgen
How much higher do androgen concentration in seminiferous tubules need to be compared to androgen concentration in circulation otherwise spermatogenesis ceases?
10x higher
Sertoli cells ensure high ___ concentration within seminiferous tubules.
androgen
What 2 feedback loops regulate testicular androgen?
- hypothlamic-pituitary-Leydig cell axis
- hypothalamic-pituitary-seminiferous-tubules axis
What do Leydig cells produce?
androgen
What does androgen inhibit the release of (3)?
GnRH, LH and RSH
What does non steroidal inhibin secreted by sertoli cells inhibit?
FSH
What 2 things do ovaries produce?
mature eggs and steroid hormones
What does ovary contain at birth?
oocytes
How many oocytes are there at birth?
2 millions
How many ova are left after puberty?
400,000
What are oocytes surrounded by?
granulosa cells
What is the basement membrane of the oocytes made up of?
primordial follicles
What is the fundamental reproductive units of the ovary?
primordial follicles
When does the growth of primordial follicles into primary follicles begin by?
an unknown initiating events
What is growth of primary follicles controlled by? (2)
gonadotropins and steroid hormones
What is degeneration of follicles called?
atresia
What occurs during the initial stages of oocyte development in follicular growth?
initially, enlargement and differentiation of the oocyte take place, leading to the elaboration of the zona pellucida, an acellular layer rich in glycoproteins surrounding the oocyte.
What happens to granulosa cells during the formation of primary follicles, and what influences this process?
granulosa cells divide and increase to 2 or more layers, forming primary follicles. This process is influenced by FSH and estrogens, with estrogens being important for the expression of LH receptors on granulosa cells.
Describe the development of a secondary follicle.
under the influence of FSH and LH, the primary follicle develops into a secondary follicle. The secondary follicle expresses receptors for FSH, estrogens, and LH. Additionally, the follicular antrum appears, containing secretions from granulosa cells.
What happens to granulosa cells under the combined influence of FSH and LH in the formation of the preovulatory follicle?
under the combined influence of FSH and LH, granulosa cells elaborate follicular fluid. This fluid takes up the larger portion of the preovulatory follicle, also known as the late secondary follicle, Graafian follicle, or mature follicle.
What does follicular development lead to? (2)
- follicular atresia
- ovulation
What does a ruptured follicle transform into?
corpus luteum
What does the corpus luteum secrete?
progesterone and estrogens
What 2 cells contribute to the formation of the corpus luteum?
theca and granulosa cells
When does the corpus luteum produce large amounts of progesterone and estrogens? When does it stop?
a few days following ovulation and stops unless implanation of fertilized ovum happens
What does the corpus luteum transform into upon implantation?
corpus luteum of pregnancy
What limits the lifespan of corpus luteum?
absence of implantation
What induces luteal regression?
prostaglandins
What does luteal regression decrease?
steroidogenesis
What can trigger the initiation of the next reproductive cycle?
decrease of plasma progesterone and estrogen
Why does the endometrium thicken prior to day one of the menstrual cycle?
due to estradiol
What induces the appearance of specialized glycogen-secreting glands?
progesterone
What are the levels of estradiol and progesterone when bleeding begins?
very low
What reduces the blood supply in the endometrium?
the blood vessels constricting
What do low estradiol and progesterone increase?
FSH secretion
What do low estradiol and progesterone decrease?
non-steroidal ovarian inhibin
Under the influence of what hormones do cohots of ovarian follicles develop?
FSH
What does FSH stimulate to proliferate?
granulosa cells
What does FSH do to the production of estrogen and granulosa cell proliferation?
increase
What happens during day 8 of the menstrual cycle?
one follicle becomes dominant and committed to further development
What does the dominant follicle produce increasingly more of?
estradiol
What does increasing estradiol do to uterine endometrium proliferation?
stimulate it
What is the endometrium by day 13?
very thick
What does estradiol produce during day 13?
endometrial progesterone receptors
Although moderate estradiol concentrations stimulate ___ synthesis, they inhibit ___ release.
LH
Under the influence of developing follicle, ___ concentrations continue to build.
estrogen
What happens during day 14 of the mestrual cycle?
elevated estrogen concentrations stimulate LH release
What kind of feedback does estrogen exert?
negative feedback
What does estrogen do to GnRH and LH release?
decrease it
What happens to the ovary follicle at day 14?
it’s huge and ovum is ejected
What do pills contain?
estrogen and progesterone
What does the pill suppress the release of?
LH and FSH
What happens during the luteal phase?
egg and corpus luteum degenerates
How long does the luteal phase last for?
14 days
What is unfertilized egg taken by at ovulation?
fimbria
What stage does the egg start dividing?
blastocyst
What does the blastocyst differentiate into?
trophoblast and inner cell mass
What does the trophoblast become?
placenta
What will form the embryo?
inner cell mass
What does trophoblast start to synthesize around the time or implantation?
HCG
What is the function of HCG?
stimulates the corpus luteum to contrinue secreting gonadal steroids
When is the fetoplacental unit formed?
about 12th week of pregnancy
What forms the biological pregnancy test?
HCG
What hormone stimulates the growth of alveoli?
progesterone
Why does most breast enlargement happen?
due to deposition under the glandular tissue
Under which hormones does ductal and alveolar structures develop?
estrogen, progesterone, prolactin, human placental lactogen
What is milk production during pregnancy controlled by?
prolactin
What inhibits the secretion of milk production?
high estrogen levels
After parturition, levels of estrogen ___, while levels of prolactin remain ___.
decrease, high
What causes ducts to contract and cause milk ejection?
oxytocin
What can be transmitted from the mother to infant through breastmilk?
infectious agents
What does maintained nursing stimulate?
prolactin production
What does prolactin production inhibit the secretion of?
FSH and LH
If suckling is not frequent enough then ovulation and pregnancy may ___.
occur
What is menopause?
loss of ovarian steroid production
What does the lack of estrogen during menopause induce?
hot flases, dry vagina, restlessness, bone loss
What is the most reliable indicator for onset of menopause?
constantly high levels of plasma FSH
What does menopause cause cessation of?
ovarian steroid hormone production - eleminated - feedback loop and rise in FSH and LH
