CH 8 Male Reproductive Sys Flashcards
Where are Sertoli Cells located?
Seminiferous tubules
Tract sperm from Sertoli Cells to Vas Deferens.
Sertoli Cells in seminiferous tubules –> rete testis –> efferent ductules –> epididymis –> vas deferens
What cells are responsible for secreting Testosterone?
Leydig cells
What are the functions of Sertoli Cells?
form blood-testes barrier, signal spermatogenesis, produce inhibin B
What does the Epididymis do?
H+ secretion & acidification of luminal fluid
What do the Seminal Vesicles do?
secretion and storage of fructose-rich product
What does the Prostate do?
secretes acid proteins
What do the Bulbourethral glands do? (Cowper’s)
secrete mucus upon arousal
What cell does LH bind to?
Leydig Cells
What cell does FSH bind to?
Sertoli Cells
What stimulates inhibin B release?
FSH on Sertoli Cells
What receptor does Testosterone bind to?
Androgen Receptor AR
What substances and Testosterone be converted to? What are their effects?
dihydroxytestosterone DHT (most potent androgen) or 17B-estradiol (inhibitory effects on LH)
What does Inhibin B do?
negative feedback response to FSH stimulation from Sertoli Cells
What does Activin do?
produced locally by pituitary to stimulate FSH release (counteracts inhibin B)
What enzyme converts androsetenedione to testosterone?
17-beta-hydroxysteroid dehydrogenase
What enzyme converts Testosterone to 17-B-extradiol
Aromatase (mainly in adipose tissue)
What step of Testosterone synthesis is exclusive to the Gonads?
Androstenedione –> Testosterone (17-B-hydroxysteroid dehydrogenase)
Why would Inhibin B levels be clinically evaluated?
it correlates to total sperm count - evaluated as an index of spermatogenesis
What are the binding proteins for testosterone? where are they found?
sex hormone-binding globulin SHBG (circulation); androgen-binding protein ABP (testis)
How is testosterone degraded?
testosterone –> androstenedione –> 17-ketosteroid
How is 17B-estradiol degraded?
17B-estradiol –> esterone –> catecholesterogens (degraded by COMT) or 16-alpha-hydroxyesterone (converted to estriol)
What enzyme converts testosterone to DHT?
5alpha-reductase (type 1 & type 2, which generates more DHT than type 1)
How is DHT degraded?
3-alpha-androstenediol (via 3alpha-hydroxysteroid dehydrogenase)
What is Finasteride used for?
treatment of benign prostatic hyperplasia and prostate cancer (5alpha-reductase inhibitor – can’t form DHT)
How does testosterone differ from DHT?
testosterone controls sexual differentiation, libido, pubertal growth, and stimulation of spermatogenesis. DHT plays a major role in embryonic and pubertal external virilization (development of external genitalia, pubic hair, etc)
How does differentiation into a male occur?
SRY gene signals differentiation of primordial cells to Sertoli Cells, which secrete Mullerian Inhibitory Factor, causing Wolffian Duct to proliferate. DHT causes growth of prostate and penis and fusion of labioscrotal folds. Leydig Cells secrete Insulin-like peptide 3 INSL3, which participates in testicular descent.
What are the 3 steps of development of male phenotype?
determination of genetic sex, gonadal sex, and lastly, phenotypical sex
Why is cryptorchidism important?
cryptorchidism (descent of scrotum) is important because spermatogenesis requires lower temperatures
How does Leptin affect growth?
Increase in amplitude of GnRH pulses and amplitude of GH secretory bursts.
What hormone stimulates spermatogenesis?
Testosterone
How does testosterone effect adipocytes?
stimulates lipylosis
How does Hypergonadism work? (testosterone)
premature virilization (can be gonadotropin dependent or independent) - enlargements of penis and testicles, body hair, spontaneous erections, acne
How does Hypogonadism work? (testosterone)
decrease in bone and muscle mass (weakness), and libido in adults, appear more female-like
Klinefelter syndrome
additional X chromosome - results in male infertility, hypogonadism, androgen deficiency, and impaired spermatogenesis
How does hyperprolactinemia effect males?
prolactin inhibits GnRH – hopygonadotropic hypogonadism
