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Reproduction 2 Flashcards

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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
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

FHB Block 4 (13 decks)

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