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Flashcards in Reproduction 2 Deck (71):
1

What is the major hypothalamic hormone in the HPG axis?

GnRH/LHRH- absolutely required and must be released in a pulsatile fashion

2

What is the major pituitary hormone in the HPG axis?

LH and FSH

3

What does LH do?

stimulates steroidogenesis in the ovaries and testes

4

What does FSH do?

stimulates gametogenesis in the ovaries and testes

5

What are some regulators of GnRH?

Kisspeptin, gonadal steroid hormones

GnIH, prolactin, neurotransmitters (GABA), cortisol (stress), growth factors (TGFα/β), neuropeptides (opiods, melatonin)

Almost all inhibit GnRH

6

What does Kisspeptin do?

Required to increase release of GnRH at time of puberty.

Presumed signal for pubertal onset

Mutations in KISS1 receptor cause hypogonadotropic hypogonadism

7

What do inhibins and activins do in the pituitary?

Inhibins inhibit FSH specifically

Activins are expressed in the pituitary and the gonads, stimulate FSH-beta, LH-beta, and GnRH receptor synthesis in the pituitary

8

Where is inhibin B especially expressed?

gonads

9

How is LH activated?

via fast GnRH pulses

10

How is FSH activated?

via slow GnRH pulses

11

What cells have a high number of FSH receptors?

Sertoli cells: form the blood-testes barrier

12

What are the six things that FSH stimulates in the testes?

Stimulates spermatogenesis - Increases sperm motility

Stimulates growth of seminiferous tubules – primary determinant of testes size

Stimulates androgen binding protein (ABP) – maintains high local T

Stimulates aromatase

Stimulates inhibin

Stimulates growth factors

13

What does aromatase do?

Converts estosterone to estradiol

14

What cells have a high number of LH receptors?

Leydig cells

15

What effects does LH have on Leydig cells?

Stimulates steroidogenesis from cholesterol
Androgens = 19 carbon steroids
Stimulates StAR protein – rate limiting
Stimulates Leydig cell growth

16

Where are testosterone precursors made?

extragonadal tissues: brain, adrenal, skin, adipose tissue

17

What is the primary source of circulating T?

Testes

18

in what form is testosterone found in the blood?

bound to SHBG

19

What is testosterone converted to intracellulary

DHT or estrogens

20

What common receptor does T and DHT bind?

Androgen receptor (AR) - a nuclear steroid receptor

DHT has higher affinity

21

How much of the daily production of testosterone is excreted as free testosterone?

22

What is the remaining, non-excreted testosterone converted to?

17-ketosteroids & DHT --> conjugated to water soluble forms and excreted.

23

What does masculinization of the brain require?

T to E conversion

24

What is DHT responsible for?

male pattern baldness

25

during fetal development, what does testosterone stimulate?

epididymis, vas deferens, seminal vesicles

26

during pubertal development, what does testosterone stimulate?

penis, seminal vesicles, musculature, voice, skeleton, spermatogenesis

27

during fetal development, what does DHT stimulate?

penis, penile urethra, scrotum, prostate

28

during pubertal development, what does DHT stimulate?

scrotum, prostate, male pattern hair distribution, beard, sebaceous glands

29

What is the functional anatomy of the penis?

Glandular and muscular tissue

Penile urethra

30

What are the male accessory glands?

Seminal vesicles

Prostate gland

Bulbourethral gland (Cowper’s gland)

31

What is the functional anatomy of the testes?

Seminferous tubules

scrotum

32

What is cryptorchidism?

"hidden testes"

Most common congenital abnormality of urogenital tract, often result of undescended testes that remain in abdominal cavity

33

when and where do the testes descend from?

The testes descend from the peritoneal space during embryonic development

34

Where does counter-current heat exchange happen in the testes?

venous blood in the pampiniform plexus to the blood in the testicular artery

35

What is the distribution of cell types in the testes?

80% germinal tissue and 20% supportive connective tissue with Leydig cells

36

What is the peritubular space?

Leydig cells, myoid cells, blood supply

37

What is the intratubular space?

Sertoli cells, developing germ cells, lumen

38

Where does spermatogenesis occur?

The adluminal compartment

39

What creates the blood-testes barrier?

tight junctions between sertoli cells

40

What is found in the basal compartment?

stem cell niche

41

What supports sperm development in the lumen?

High T concentrations

42

What does inhibin do in the testes?

augments LH-induced testosterone production in Leydig cells

43

What does activin do in the testes?

inhibits LH-induced testosterone production in Leydig cells

44

What is spermatogenesis?

the process by which spermatogonia become 4 haploid spermatids

45

What is spermiogenesis?

maturation of spermatids into spermatozoa

46

What is spermiation?

release of spermatozoa from Sertoli cells into lumen

47

Where does spermatogenesis, spermiogenesis, and spermiation occur?

all processes occur in the seminiferous tubules

48

describe the maturation of spermatozoa after release into the lumen

Spermatozoa initially immobile – passive movement from seminiferous tubule to rete testis.

development of the acrosome

Acquisition of receptors necessary for binding to ovum.

Deceased cytoplasm and cell volume.

increased motility

49

What is the acrosome?

sperm “cap” containing hydrolyzing enzymes used to penetrate ovum

50

when is sperm maturation fully complete?

when the sperm enters the vagina (capacitation)

51

What is the composition of semen?

10% sperm (150-600 million)

70% fluid from seminal vesicles

10% fluid from epididymis, prostate, bulbourethral glands

52

describe the anatomy and function of the seminal vesicles

paired, with inferior bladders, forms the ejaculatory duct

releases fructose, citric acid, other nutrients

pH – seminal vesicle fluid makes semen more alkaline (~7.3-7.7) promotes optimum motility and survival

53

describe the anatomy and function of the prostate

surrounds prostatic urethra

first fluid to be expelled in ejaculate

secretes factors that prevents clumping of sperm

proteolytic enzymes important for liquefaction of sperm

54

discuss benign prostatic hyperplasia

PSA used to diagnose prostate growth

55

describe the anatomy and function of the bulbourethral (Cowper's) gland

Immediately below prostate

Secretes mucous into urethra upon arousal – pre-ejaculate

56

What occurs in the flaccid state?

Helicine arteries constrict, restricting blood flow - controlled by tonic sympathetic activity

57

What occurs in an erection?

relaxation of vascular smooth muscle (corpora cavernosa and corpora spongiosum) leads to increased blood flow in cavernous tissue

Engorgement compresses outflow pathway and creates tumescence (swelling)

58

What neural control is an erection under?

parasympathetic!

59

What is the parasympathetic chain of events that leads to an erection?

parasymp neurons release ACh and NO

Ach can bind muscarinic receptors and activate PLC (via Gαq)

This increases calcium and activates NO synthase

NO activates guanylyl cyclase

60

What do somatic nerves do and what are they important for?

stimulate striated penile muscles causing greater pressure (ischiocavernosus muscle, bulbospongiosus muscle)

important for ejaculatory force, not for maintaining and erection

61

Discuss the effects of Viagra

Inhibits phosphodiesterases that would normally decrease cGMP

Maintains chronic state of vasodilation

Not specific to penile circulation – can cause heart problems

Still requires CNS arousal

62

Define emission

movement of the ejaculate into the prostatic/proximal part of the urethra

sets the stage for ejaculation

63

discuss the sympathetic control of emission

Direct innervation of smooth muscle cells via alpha adrenergic receptors results in peristaltic rhythmic contractions via smooth muscle of portions of vas deferens, seminal vesicles, prostate

64

What stimulates the ejaculation reflex?

entry of semen to bulbous urethra from prostatic urethra

65

What is the neural control of ejaculation?

Spinal cord reflex as well as neural control -- lack of direct voluntary control

Afferents reach sacral spinal cord (S2-S4) triggering efferent somatic motor neurons via the pudendal nerve

66

What propels semen through the urethra?

Rhythmic contractions of ischiocavernosus and bulbospongiosus muscles

67

What are the three categories of male fertility disorders?

Pre-testicular, testicular, post-testicular

68

What is primary pre-testicular fertility disorder?

hypergonadotropic hypogonadism

High FSH/LH, low T/DHT

ex: Klinefelter syndrome, enzyme deficiencies

69

What is tertiary/secondary pre-testicular fertility disorder?

hypogonadotropic hypogonadism

Low GnRH, low FSH/LH, low T/DHT

ex: Kallman syndrome, panhypopituitarism, hyperprolactinemia (most common)

70

What are causes of testicular fertility disorders?

Klinefelters, cryptorchidism

varicocele (dilated scrotal veins - most common cause of subfertility in men) - no counter-current heat exchange

71

What are causes of post-testicular fertility disorders?

Ductal obstructions, premature ejaculation, impotence