Male Reproduction (Schmidt)

Question 1

network of veins that acts as a heat exchanger, cooling blood as it enters the testes

Answer 1

pampiniform plexus

Question 2

raises and lowers testes in response to temperature changes

Answer 2

cremasteric muscle

Question 3

failure of the testes to descend

Answer 3

cryptorchidism

Question 4

coiled mass of loops (800 ft!) in which germinal epithelial cells differentiate into mature sperm

Answer 4

seminiferous tubules

Question 5

what fetal hormone is responsible for the descent of the testes into the scrotum?

Answer 5

testosterone

Question 6

failure of the testes to descend is called what?

Answer 6

cryptorchidism

Question 7

Spermatogenesis occurs within what structure?

Answer 7

testicular seminiferous tubules

Question 8

testosterone synthesis and secretion is mediated by what cells?

Answer 8

leydig cells

Question 9

Which one of these is NOT an important function of Sertoli cells?
A. they form the blood-testis barrier and a conduit through which germ cells migrate during development
B. they mediate testosterone synthesis
C. they nurture and control the process of spermatogenesis
D. they convert testosterone into estradiol (prior to puberty)
E. they secrete an androgen-binding protein

Answer 9

B. Testosterone synthesis is mediated by Leydig cells.

Question 10

as sertoli cells differentiate, aromatase expression declines and estrogen synthesis shifts to what cells?

Answer 10

leydig cells

Question 11

what is the functional significance of the androgen-binding proteins that are secreted by sertoli cells?

Answer 11

they bind testosterone (made by leydig cells) and carry it into the fluid of the seminiferous tubules, keeping it in a continuously available form to maturing sperm

Question 12

what are the two hormones needed to regulate phenotypic gender expression and what cells secrete them?

Answer 12

testosterone secreted by leydig cells; Mullerian inhibiting substance (MIS, or anti Mullerian hormone) secreted by sertoli cells

Question 13

outline the pathway of mature sperm:

seminiferous tubules –> _______ –> vas deferens –> ampulla –> _______ –> urethra

Answer 13

epididymus; prostate gland

Question 14

From testis sperm empty into this structure, which is a coiled in which maturation is completed (that is, sperm become capable of movement and fertilization)

Answer 14

epididymus

Question 15

site of sperm storage

Answer 15

ampulla (the widened portion of the vas deferens)

Question 16

structure that secretes thin, milky alkaline fluid (citrate, Ca+2, clotting enzyme, profibrinolysin) into the ejaculatory duct, which adds bulk to semen and neutralizes acidic fluid of the vas deferens and vaginal secretions

Answer 16

prostate gland

Question 17

secrete a clear, viscous, mucus-like fluid that functions as lubricant

Answer 17

bulbourethral (cowper’s) glands

Question 18

activation of sperm for final process of fertilization

Answer 18

capacitation

Question 19

Which of the following regarding capacitation is FALSE?
A. Capacitation is the process whereby sperm are activated for the final process of fertilization
B. Destabilization of the sperm head provides for greater binding between sperm and oocyte
C. Capacitation decreases the permeability of the sperm’s cell membrane to Ca++
D. Capacitation is facilitated by the removal of steroids and non-covalently bound epididymal/seminal glycoproteins
E. Tripeptide FPP (fertilization promoting peptide) produced in the prostate gland is essential for this process because it increases adenylyl cyclase activity in the sperm.

Answer 19

C. Capacitation makes a sperm’s membrane more permeable to Ca++.

Question 20

True or False: FSH release is vital for stimulation of the Leydig cells to produce testosterone during spermatogenesis.

Answer 20

False. FSH stimulates Sertoli cells to make estradiol from testosterone for spermatogenesis. It is LH that stimulates the Leydig cells to secrete testosterone.

Question 21

Testosterone converted to estradiol via what enzyme?

Answer 21

aromatase

Question 22

Testosterone is metabolized to the much more potent ________ in some, but not all target tissues

Answer 22

dihydrotestosterone

Question 23

True or false: most testosterone is circulating freely in the blood.

Answer 23

False. Only about 2% is freely circulating, while the rest is bound to sex steroid-binding globulin or albumin.

Question 24

FSH stimulated Sertoli cells secrete what hormone, which

selectively inhibits FSH secretion in an important negative feedback mechanism for control of spermatogenesis?

Answer 24

inibin B

Question 25

This hormone is expressed in several tissues including the pituitary, and its role is to antagonize inhibin B action and stimulate FSH release

Answer 25

activin

Question 26

Absence of these hormones, due to nonfunctional testes or genetic absence of androgen receptors will result in a male (XY) who develops female sexual characteristics

Answer 26

androgens

Question 27

why is it that female brains are not "masculinzed" by the aromatization of testosterone to estrogen, as male brains are?

Answer 27

female fetuses have alpha-fetoprotein that binds the maternal estrogen so that female brains are not affected

Question 28

term that describes a turning point decrease in male sexual function due to declining testosterone

Answer 28

(male) climacteric

Question 29

True or false: although levels of testosterone decline with age, LH levels are often not elevated

Answer 29

True.

Question 30

``` The release of testosterone during puberty causes all of the following to increase except: A. muscle mass B. red blood cell production C. retention of Ca++ D. VLDL synthesis E. HDL synthesis ```

Answer 30

E. An increase in VLDL and a decrease in HDL synthesis following puberty leads to increased risk of coronary artery disease.

Question 31

testosterone diffuses into target cells and is metabolized to 5α-dihydrotestosterone (DHT) via what enzyme?

Answer 31

5α reductase

Question 32

True or false: testosterone can function directly on some tisues that lack metabolizing enzyme/DHT.

Answer 32

True. Examples of testosterone mediating a direct effect on target tissues include: a. development and differentiation of the epididymis, vas deferens and seminal vesicles (internal genitalia) b. effects on musculature and skeleton c. effects on spermatogenesis d. libido e. promotes erythropoiesis f. deepening of voice during puberty

Question 33

Which of the following statements concerning the regulation of testosterone secretion is TRUE? A. Testosterone enhances its own rate of secretion by exerting long-loop positive feedback on the hypothalamus. B. Descent of the testis into the scrotum is regulated by testosterone secreted by the fetal testis. C. Testosterone secretion is stimulated via paracrine effects mediated by estradiol, which is secreted by pre-pubertal Sertoli cells. D. Testosterone secretion reaches its maximal rate during the male climacteric. E. Testosterone secretion immediately after the birth of a baby boy is responsible for development of the prostate gland.

Answer 33

B. A is incorrect because testosterone negatively feedsback to the hypothalamus. C is incorrect because estradiol does not mediate the secretion of testosterone - rather, LH stimulates leydig cells to synthesize and secrete testosterone, which is converted to estradiol in the sertoli cells D is incorrect because testosterone secretion declines during the male climacteric. E is incorrect because it is fetal testosterone that is responsible for the development of the prostate gland.

Question 34

A healthy, 16-year-old boy (5'6" tall and weighing 136 lbs.) exhibits the following symptoms: small penis, poor muscular development, high-pitched voice, and no growth of facial hair. Clinical analyses indicate that his serum testosterone and sperm count are both very low. Injections of GnRH fail to elevate his serum LH and FSH levels. However, injections of HCG and FSH for several weeks result in normal sperm count, elevated testosterone levels and eventual development of secondary sex characteristics. Based on these data, the best explanation for this young man's original problem would be which of the following? A. Sertoli cells in his testes express non-functional FSH receptors B. Inadequate secretion of GnRH by his hypothalamus C. Cryptorchidism D. Pituitary gonadotropes express non-functional GnRH receptors E. Sertoli cells in the testes hypersecrete inhibin B.

Answer 34

D