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FHB Block 4 > Reproduction 2 > Flashcards

Reproduction 2 Flashcards

1
Q

What is the major hypothalamic hormone in the HPG axis?

A

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

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2
Q

What is the major pituitary hormone in the HPG axis?

A

LH and FSH

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3
Q

What does LH do?

A

stimulates steroidogenesis in the ovaries and testes

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4
Q

What does FSH do?

A

stimulates gametogenesis in the ovaries and testes

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5
Q

What are some regulators of GnRH?

A

Kisspeptin, gonadal steroid hormones

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

Almost all inhibit GnRH

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6
Q

What does Kisspeptin do?

A

Required to increase release of GnRH at time of puberty.

Presumed signal for pubertal onset

Mutations in KISS1 receptor cause hypogonadotropic hypogonadism

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7
Q

What do inhibins and activins do in the pituitary?

A

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

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8
Q

Where is inhibin B especially expressed?

A

gonads

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9
Q

How is LH activated?

A

via fast GnRH pulses

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10
Q

How is FSH activated?

A

via slow GnRH pulses

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11
Q

What cells have a high number of FSH receptors?

A

Sertoli cells: form the blood-testes barrier

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12
Q

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

A

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

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13
Q

What does aromatase do?

A

Converts estosterone to estradiol

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14
Q

What cells have a high number of LH receptors?

A

Leydig cells

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15
Q

What effects does LH have on Leydig cells?

A

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

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16
Q

Where are testosterone precursors made?

A

extragonadal tissues: brain, adrenal, skin, adipose tissue

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17
Q

What is the primary source of circulating T?

A

Testes

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18
Q

in what form is testosterone found in the blood?

A

bound to SHBG

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19
Q

What is testosterone converted to intracellulary

A

DHT or estrogens

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20
Q

What common receptor does T and DHT bind?

A

Androgen receptor (AR) - a nuclear steroid receptor

DHT has higher affinity

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21
Q

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

A
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22
Q

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

A

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

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23
Q

What does masculinization of the brain require?

A

T to E conversion

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24
Q

What is DHT responsible for?

A

male pattern baldness

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25
Q

during fetal development, what does testosterone stimulate?

A

epididymis, vas deferens, seminal vesicles

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26
Q

during pubertal development, what does testosterone stimulate?

A

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

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27
Q

during fetal development, what does DHT stimulate?

A

penis, penile urethra, scrotum, prostate

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28
Q

during pubertal development, what does DHT stimulate?

A

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

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29
Q

What is the functional anatomy of the penis?

A

Glandular and muscular tissue

Penile urethra

30
Q

What are the male accessory glands?

A

Seminal vesicles

Prostate gland

Bulbourethral gland (Cowper’s gland)

31
Q

What is the functional anatomy of the testes?

A

Seminferous tubules

scrotum

32
Q

What is cryptorchidism?

A

“hidden testes”

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

33
Q

when and where do the testes descend from?

A

The testes descend from the peritoneal space during embryonic development

34
Q

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

A

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

35
Q

What is the distribution of cell types in the testes?

A

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

36
Q

What is the peritubular space?

A

Leydig cells, myoid cells, blood supply

37
Q

What is the intratubular space?

A

Sertoli cells, developing germ cells, lumen

38
Q

Where does spermatogenesis occur?

A

The adluminal compartment

39
Q

What creates the blood-testes barrier?

A

tight junctions between sertoli cells

40
Q

What is found in the basal compartment?

A

stem cell niche

41
Q

What supports sperm development in the lumen?

A

High T concentrations

42
Q

What does inhibin do in the testes?

A

augments LH-induced testosterone production in Leydig cells

43
Q

What does activin do in the testes?

A

inhibits LH-induced testosterone production in Leydig cells

44
Q

What is spermatogenesis?

A

the process by which spermatogonia become 4 haploid spermatids

45
Q

What is spermiogenesis?

A

maturation of spermatids into spermatozoa

46
Q

What is spermiation?

A

release of spermatozoa from Sertoli cells into lumen

47
Q

Where does spermatogenesis, spermiogenesis, and spermiation occur?

A

all processes occur in the seminiferous tubules

48
Q

describe the maturation of spermatozoa after release into the lumen

A

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
Q

What is the acrosome?

A

sperm “cap” containing hydrolyzing enzymes used to penetrate ovum

50
Q

when is sperm maturation fully complete?

A

when the sperm enters the vagina (capacitation)

51
Q

What is the composition of semen?

A

10% sperm (150-600 million)

70% fluid from seminal vesicles

10% fluid from epididymis, prostate, bulbourethral glands

52
Q

describe the anatomy and function of the seminal vesicles

A

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
Q

describe the anatomy and function of the prostate

A

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
Q

discuss benign prostatic hyperplasia

A

PSA used to diagnose prostate growth

55
Q

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

A

Immediately below prostate

Secretes mucous into urethra upon arousal – pre-ejaculate

56
Q

What occurs in the flaccid state?

A

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

57
Q

What occurs in an erection?

A

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
Q

What neural control is an erection under?

A

parasympathetic!

59
Q

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

A

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
Q

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

A

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

important for ejaculatory force, not for maintaining and erection

61
Q

Discuss the effects of Viagra

A

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
Q

Define emission

A

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

sets the stage for ejaculation

63
Q

discuss the sympathetic control of emission

A

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
Q

What stimulates the ejaculation reflex?

A

entry of semen to bulbous urethra from prostatic urethra

65
Q

What is the neural control of ejaculation?

A

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
Q

What propels semen through the urethra?

A

Rhythmic contractions of ischiocavernosus and bulbospongiosus muscles

67
Q

What are the three categories of male fertility disorders?

A

Pre-testicular, testicular, post-testicular

68
Q

What is primary pre-testicular fertility disorder?

A

hypergonadotropic hypogonadism

High FSH/LH, low T/DHT

ex: Klinefelter syndrome, enzyme deficiencies

69
Q

What is tertiary/secondary pre-testicular fertility disorder?

A

hypogonadotropic hypogonadism

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

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

70
Q

What are causes of testicular fertility disorders?

A

Klinefelters, cryptorchidism

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

71
Q

What are causes of post-testicular fertility disorders?

A

Ductal obstructions, premature ejaculation, impotence

FHB Block 4 (13 decks)

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