5. Sexual function and fertilisation Flashcards Preview

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Flashcards in 5. Sexual function and fertilisation Deck (15)
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1
Q

what changes do sperm undergo in the epididymis

A

Sperm maturation, dependent on epididymis maturation by androgens:

  1. concentration
  2. completion of sperm modelling, eg acrosomal shaping
  3. become motile (although are still transported via muscular epididymal contractions)
  4. surface membrane coated with glycoproteins - for protection and oocyte interaction
2
Q

describe the production of semen

A

i. spermatozoa are secreted from epididymis via vas deferens…
ii. vas deferens unites with seminal vesicle duct to form ejaculatory duct, where spermatozoa are added to seminal fluid
iii. fluid continues down duct into prostate gland where alkaline prostatic fluid is added
iv. semen now in urethra then receives secretions of bulbourethral glands
v. expelled during ejaculation

3
Q

what % of semen is derived from seminal vesicles and what is the function of this

A

60-70%

1- alkaline fluid: neutralises acid in male urethra and female repro. tract
2- fructose: main energy source for anaerobic glycolysis
3- clotting factors (semenogelin)
4- prostaglandins: female immune response suppression? stimulate muscular activity in female tract?

4
Q

what % of semen is derived from prostate and what is the function of this

A

25%

1- zinc: stabilise sperm cell chromatin
2- citric acid: calcium ion chelator which initially offsets clotting
3- proteolytic enzymes: for breakdown of clotting proteins, re-liquefying semen in 10-20mins
4- acid phosphatase

5
Q

what % of semen is derived from bulbourethral and what is the function of this

A

<1%

1- alkaline fluid
2- mucous: lubrication of urethral lining and end of penis, prevents sperm diffusion out of semen

6
Q

name the 4 phases of the male sexual response

A
  1. excitement phase
  2. plateau phase
  3. orgasmic phase (emission + ejaculation)
  4. resolution phase
7
Q

describe the spinal reflex involved in the excitement phase

A

i. psychogenic and tactile stimulation…
ii. sensory afferents of penis and perineum…
iii. efferent impulses:
- somatic - pudendal n.
- autonomic (PNS) - pelvic n.

8
Q

describe the effects of stimulation in the excitement phase

A

i. post-ganglionic fibres release ACh… binds to M3 Rs on endothelial cells… increased [Ca2+]i… NOS activation and NO formation… relaxation of vascular SM

ii. haemodynamic changes:
- arterial vasodilation in copora cavernosa… increased penile blood flow
- engorgement of corpora cavernosa occludes emissary venous drainage…

ii. erection

9
Q

what is the main difference between erection and ejaculation

A

erection = parasympathetic control

ejaculation = sympathetic control

10
Q

what are the 2 parts of the male orgasmic phase

A

i. emission: sympathetic stimulation… smooth muscle contraction in vas deferens, prostate and seminal vesicles… mov. of semen into prostatic urethra
ii. ejaculation: filling of internal urethra stimulates pudendal n. (S2-4)… contraction of SM of glands, ducts and internal urethral sphincter (prevents retrograde ejaculation)… voluntary rhythmic striated muscle contraction (pelvic floor and perineal muscles - ischiocavernosus and bulbospongiosus)… expulsion of semen

11
Q

how does the character of cervical mucus change over course of menstrual cycle - why

A
  • prior to ovulation (oestrogen alone): thin, stretchy Spinnbarkeit mucus - facilitates sperm entry
  • post-ovulation (oestrogen + progesterone): thick, sticky mucus plug - protects conceptus from outside invasion
12
Q

what change occurs in sperm in the female reproductive tract

A

capacitation:
1- reorganisation of sperm cell membrane - allows fusion with oocyte cell surface

2- tail mov. changes from beat to whip-like action - propels sperm forward

3- removal of protein coat of sperm, exposing acrosome enzyme - capable of undergoing acrosome reaction

13
Q

why can hyperprolactinaemia cause infertility

A

increased serum prolactin… increased dopamine (prolactin inhibiting hormone) as -ve FB… also inhibits gonadotropins… decreased FSH and LH… decreased oestrogen so no LH surge and no ovulation

14
Q

suggest a treatment option for hyperprolactinaemia amenorrhea

A

bromocriptine dopamine agonist - inhibits AP production of prolactin

15
Q

which drug might be used to increase fertility in an annovulatory women

A

clomiphene citrate

weak oestrogenic effect… binds oestrogen Rs and decreases their conc. by inhibiting process of R replenishment… H-P axis blinded to circulating levels of endogenous oestrogen… increases GnRH (no negative feedback) and FSH… follicle maturation and oestrogen release…. drug is stopped causing LH surge and ovulation due to very high Oe level