11 Male Reproductive Hormones Flashcards
What are the two main functions of the testis?
Spermatogenesis and testosterone synthesis
how much does the temperature of the testis differ from core body temperature?
2 degrees celsius below core temperature
what acts as a countercurrent heat exchanger to cool blood entering the testes?
pampiniform plexus
what raises and lowers testes in response to temperature changes?
cremasteric muscle
what is cryptorchidism?
failure of fetal testis to descend
what hormone regulates the descent of the testis?
testosterone
what are the coiled loops called in which germinal epithelial cells differentiate into mature sperm?
seminiferous tubules
which cells are joined together by tight junctions to form the blood-testis barrier?
Sertoli cells
which cells provide the signals that initiate spermatogenesis and sustain spermatid development?
sertoli cells
what cells are responsible for phagocytizing damaged sperm cells?
Sertoli cells
what do sertoli cells secrete prior to puberty that is essential for spermatogenesis, and what enzyme do they use to make it?
estradiol, via aromatase
what cells synthesize estradiol after puberty into adulthood?
Leydig cells, as well as immature germ cells and spermatozoa
T/F: testicular estrogens inhibit androgen production.
T
What stimulates secretion of androgen binding protein from sertoli cells?
FSH
what is the function of androgen-binding protein?
binds testosterone and estradiol and carries these steroids to maturing sperm in the lumen of seminiferous tubules
how do sertoli cells maintain immune privilege in the seminiferous tubules?
they produce the FAS ligand that binds to the FAS receptor on T lymphocytes and triggers apoptosis
what major proteins do sertoli cells secrete?
androgen binding proteins, transferrin, plasminogen activator
what is a proteolytic enzyme important in spermiation?
plasminogen activator, which converts plasminogen to plasmin
what two hormones secreted by the fetal testes regulate phenotypic gender expression?
testosterone and mullerian-inhibiting substance
Outline the pathway of the mature sperm.
testis -> epididymus -> vas deferens -> prostate gland -> penile urethra
where does maturation of sperm reach completion?
epididymus
how long does it take sperm to travel through the epididymus?
12-26 days
What is the enlarged area of the vas deferens just before it enters the prostate, and what does it store?
ampulla, sperm storage
where along the male reproductive tract do the seminal vesicles empty their contents?
ampulla of vas deferens
what fluid do the seminal vesicles secrete, and what is its function?
seminal fluid; it adds bulk to semen and also contains fructose, ascorbic acid, and prostaglandins, which facilitate movement of sperm through female reproductive tract
what male reproductive organ secretes a thin, milky, alkaline fluid containing citrate, ca2+, clotting enzyme, and profibrinolysin?
prostate
what is the purpose of prostatic fluid?
it adds bulk to semen and neutralizes acidic fluid of vas deferens and vaginal secretions
what do bulbourethral glands secrete?
A clear, viscous fluid that acts as a lubricant
T/F: the average number of sperm ejaculated is 60 - 70 million/ml, and less than 20 million results in infertility
t
what is the difference between emission and ejaculation?
emission is an involuntary discharge, as during sleep;
ejaculation is the discharge of semen from an erect penis at the moment of sexual climax
what is the function of the clotting enzyme of prostatic fluid?
it causes the fibrinogen of the seminal vesicle to form a weak coagulum that holds semen in deeper region of vagina
what is the activation of sperm for final process of fertilization known as?
capacitation
what is the function of fertilization promoting peptide produced in the prostate gland?
it is essential for capacitation of the sperm; it increases adenylyl cyclase activity in the sperm
what hormone stimulates leydig cells to secrete testosterone?
LH
physiological levels of what hormone increase leydig cell LH receptors
prolactin
which hormone stimulates sertoli cells to secrete ABP and produce nutrients for spermatogenesis?
FSH
what effect does growth hormone have on spermatogenesis and the testes?
It promotes early division of spermatogonia and is important for background metabolic function of testes
T/F: both sexes use a common enzymatic pathway for steroid biosynthesis
T
which enzyme catalyzes the conversion of testosterone to estradiol?
aromatase
T/F: the majority of testosterone circulates in the blood as free unbound hormone.
F; only 2% is free, and the rest is bound to sex steroid-binding globulin or albumin
GnRH from the hypothalamus stimulates secretion of what two homones from the anterior pituitary?
LH and FSH
what hormone do sertoli cells secrete that selectively inhibits FSH secretion?
inhibin Beta
what is the role of the hormone activin?
its roles is to antagonize inhibin beta secretion and stimulate FSH release
which fetal hormone is responsible for development of male body characteristics?
fetal testosterone
which hormone is secreted within the first three months of birth to induce masculinization of the brain?
there is a peak of testosterone secretion shortly after birth, which is aromatized to estrogen. estrogen is what induces masculinization of the brain.
how do female fetuses avoid masculinization of the brain from estrogen?
they use alpha fetoprotein to bind up the estrogen
what is the decrease in male sexual function due to decline in testosterone called?
male climacteric
what is the effect of testosterone in males after puberty?
testosterone causes enlargement of the penis, scrotum, and testes, and results in the development of secondary sexual characteristics
T/F: testosterone increases hepatic synthesis of VLDL and decreases synthesis of HDL, leading to an increased risk of coronary artery disease?
T
what is the intracellular mode of action of testosterone?
testosterone diffuses into cells and is metabolized to dihydrotestosterone (DHT) by 5 alpha reductase. DHT binds to an intracellular receptor, and the DHT-receptor complex binds to DNA sequences to initiate transcription
what direct effects does testosterone have on tissues that lack the 5 alpha aromatase enzyme?
development of epididymis, vas deferens, and seminal vesicles; effects on musculature and skeleton; effects on spermatogenesis, libido and deepening of voice
what effects does DHT have on its target tissues?
growth of prostate, male pattern baldness, activity of sebaceous glands, growth of pubic and underarm hair, and growth of penis
T/F: growth of malignant prostatic cancer cells is stimulated by LSH.
F; it is stimulated by testosterone
what are some of the symptoms of teratoma?
may secrete estrogens and cause gynecomastia or hCG which leads to higher testosterone levels (increased gonad size and function)
