Male Reproductive System (McCumbee and Richardson)

Question 1

Kartagener Syndrome

Answer 1

Pts. have immotile cilia and are infertile

Question 2

Spermatogonial proliferation

Answer 2

Spermatogonia divide mitotically to renew stem cells and expand the differentiating spermatogonia

*Differentiating spermatogonia undergo incomplete cytokinesis leaving intracellular bridges for the transport of molecules b/w cells

Question 3

Spermatogonial meiosis

Answer 3

During prophase, homologous chromosomes pair and are held together by the synaptonemal complex which facilitates recombination; remnant of this is the chiasmata

First division => Homologous pairs separate (2C); is now a secondary spermatocyte

Second division => Sister chromatids separate (1C); are now four haploid spermatids

Question 4

Spermiogenesis (Spermy-spermy-grow-grow)

Answer 4

1. Chromatin is inactivated via condensation by protamines; replaces the Histones in chromatin
2. Excess cytoplasm is collected into the residual body and digested by Sertoli cells
3. Acrosome cap is formed and contains hyaluronidase, acrosin, neuraminidase, and acid phosphates

Question 5

Phases of acrosomal cap formation

Answer 5

1. Golgi- Pro-acrosomal granules bud from the Golgi complex and fuse to the anterior membrane
2. Cap & Acrosomal- Vesicle spreads over surface
3. Maturation- Assumes characteristic shape

Question 6

Flagellum Formation

Answer 6

Part of spermy-spermy-grow-grow that involves the migration of centrioles near the membrane and are arranged in a 9+2 arrangement

*Occurs @ same time as acrosomal cap formation

Question 7

Factors that impair spermy-spermy-grow-grow

Answer 7

Irradiation

Excess steroid hormones

Elevated temperature

Vitamin A deficiency

Question 8

Ducts

Answer 8

Intratesticular: Tubuli recti and rete testis

Extratesticular: Efferent ducts, epididymis, vas deferens, urethra

*Sperm gain motility during storage in the epididymis

Question 9

Sperm cycle stages

Answer 9

One cycle= Amount off time to make it thru all 6 stages
*16 days

Maturation of Sperm= 4 cycles X 16 days = 64 days

*Are developed asynchronously along the tubule to release sperm continuously

Question 10

Structure of Sperm

Answer 10

Head- Contains haploid nucleus and acrosomal cap

Mid-piece- Contains axoneme, mitochondrial sheath, and outer dense fibers

Principal piece- Contains axoneme, outer dense fibers, and fibrous sheath

End piece- Contains ONLY axoneme

Question 11

Bioavailable testosterone

Answer 11

Free testosterone+ Testosterone-albumin

-Is only weakly bound to albumin

Question 12

LH Receptor

Answer 12

Stimulation causes increased cAMP

=> Increased StAR, Increased P450cc, and Increased 17a-hyrdoxylase

Question 13

5a-reductase inhibitors

Answer 13

Used to treat prostatic cancer

*Enzyme normally forms the metabolically hyperactive dihydrotestosterone

Question 14

Aromatase in males

Answer 14

Primarily found in adipose, CNS nuclei, and some Leydig/Sertoli cells

*Converts testosterone to estradiol

Question 15

Primary stimulus for Leydig cell development

Answer 15

hCG

Question 16

Testosterone/Sperm production in male lifespan

Answer 16

Neonate- High

Childhood- Random surge but normally low

Adolescence- Increasing

Adult- Highest

Elder- Steady decrease
*Also a steady increase in SHBG

Question 17

Androgen actions in the adult

Answer 17

• Promote vocal cord thickening (deeper voice)
• Promote EPO secretion (increased Hcrt)
• Promote bone growth and resorption (also closure of epiphyseal plate)
• Promote hair growth
• Promote protein anabolism

Question 18

Blood-testis barrier

Answer 18

Formed by tight jnxns b/w Sertoli cells; prevents the development of autoantibodies against sperm

*Are connected to developing germ cells via gap jnxns

Question 19

ABP

Answer 19

Secreted by Sertoli cells when stimulated by FSH or testosterone; helps to keep testosterone levels elevated in the seminiferous tubules

Question 20

AMH receptor mechanism

Answer 20

Two threonine kinase receptors will dimerize after AMH binding and phosphorylate Smad 3

=> NLS is activated and Smad3 combines w/ Smad4 when it enters the nucleus and activates transcription of genes promoting apoptosis

Question 21

Inhibin B

Answer 21

Blocks GnRH stimulated release of FSH @ the gonadotrope (adenohypophysis)

• Production is stimulated by FSH and testosterone to provide negative feedback
• Has NO EFFECT on LH release

Question 22

Endocrine regulation of spermatogenesis

Answer 22

Pituitary: FSH => Increased Sertoli fnxn (growth factors for sperm, ABP, Inhibins)
LH => Produce testosterone to assist Sertoli fnxn

• Testosterone will activate genes, produce some estradiol, and promote ABP production
• Intact hypothalamic-pituitary-gonadal system required for all of this

Question 23

Events in epididymis

Answer 23

Sperm become motile and are decapacitated

*Spend a month here

Question 24

GnRH secretion

Answer 24

Must be in a pulsatile fashion to promote spermy-spermy-grow-grow

*Continuous release results in a fnxnal castration

Question 25

HPG axis control

Answer 25

Pre-pubescent: Under CNS inhibition Puberty: Increased LH surges @ night Decreased negative feedback inhibition of testosterone Increased GnRH pulses and increased sensitivity =>Increased FSH and LH

Question 26

Helicine Arteries

Answer 26

Supply the cavernous spaces of the penis; are constricted in the flaccid state

Question 27

Erectile Response

Answer 27

Lower tactile stimulus or psychic stimulation leads to the release of NO and VIP; occurs via the pudendal or corticospinal tract respectively => Dilation of helicine arteries increases blood flow and compressed the venous outflow

Question 28

Viagra action

Answer 28

Acts on PDE5 which breaks down cGMP *cGMP is formed by guanylyl cyclase and promotes vasodilation and boners

Question 29

Emission

Answer 29

Sympathetic neurons reach the accessory glands via the hypogastric nerve and release NER on a2-drenergic receptors => rhythmic contractions of smooth muscle to move semen *Also prevents retrograde movement into the bladder by closing the internal urethral sphincter

Question 30

Ejaculation

Answer 30

Filling of the urethra sends afferent signals via the pudendal nerve which responds w/ wavelike contractions of the bulbospongiosus to eject the load

Question 31

Gynecomastia

Answer 31

Estrogens stimulate the growth of the female breasts (prior to growth there is no difference); could also occur w/ exposure to excess PRL

Question 32

Kallman's Syndrome

Answer 32

A type of tertiary hypogonadism caused by deficient production of GnRH - testes will have arrested spermy-spermy-grow-grow and androgen deficiencies (decreased muscles, pubic hair, high-pitched voice, infantile genitali) * Caused by a failure of the GnRH secreting cells to migrate from the olfactory placode => Anosmia

Question 33

TGF-B Family

Answer 33

"Transforming Growth Factor" Includes Inhibins, activins, and AMH; all secreted by Sertoli cells

Question 34

Treatment of Klinefelter's

Answer 34

Androgen replacement therapy can restore some secondary sexual characteristics and reverse gynecomastia but cannot induce spermatogenesis -Due to hyalinization of the seminiferous tubules