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SHP - Pharmacology & Therapeutics > Male Reproductive System > Flashcards

Male Reproductive System Flashcards

1
Q

Where is spermatozoa produced, stored and delivered?

A
  • Produced in the testis
  • Stored in the epididymis
  • Travels down the vas deferens to be delivered by the penis
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2
Q

What are the general structural features of the testes and why are they externalised?

A
  • Scrotal sac is thin-walled with lots of sweat glands; cooling unit (2-3 degrees cooler than body temp - externalisation as sperm unable to develop at 37 degrees)
  • Dartos and cremaster muscle contract in the cold
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3
Q

Where does the sperm mature and what key cell also resides here?

A
  • Seminiferous tubules (where meiosis occurs and subsequent spermatozoa formation)
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4
Q

What does the vas deferens do?

A

Joins the urethra with the prostate gland and further to the testes, supplying spermatozoa.

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5
Q

What are seminal vesicles and where are they located?

A
  • Vesicles located just before the prostate/alongside the ejaculatory duct/under the bladder
  • Produces 60% of semen volume secretions
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6
Q

What substances make up serum secretions from seminal vesicles and what role do they play?

A
  • Prostaglandins (may reduce uterine motility; receptors in the uterus respond to semen?)
  • Fructose (oxidative substrate for spermatozoa; flagella tail, high energy demand)
  • Prolactin, endorphins, inhibin (functions not known)
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7
Q

What role do the prostate/bulbourethral glands play?

A

Alkaline addition to semen (counteract acidic vagina)

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8
Q

Roughly how much semen is produced per ejaculation in fertile men and what can cause sterility?

A
  • 3-5 mL per ejaculation
  • 100 million sperm/mL (in fertile men)
  • Sterility can arise from abnormal sperm or a low count (
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9
Q

What occurs with repeated ejaculation in a short period?

A
  • Reduction in sperm count
  • Reduction in semen volume
    “Whilst it may be fun”
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10
Q

What are the 3 components of spermatozoa?

A
  • Head; contains 23 chromosomes (meiotic cell division) and enzymes in acrosomal cap (at anterior) aid penetration of ovum
  • Mid piece; contains mitochondrial sheath to power cell movement
  • Tail; flagellations provide motive force
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11
Q

How fast does the spermatozoa travel in the vagina and what is its survival time?

A
  • 44mm/min in vagina

- 2 day survival time

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12
Q

What is the process of capacitation?

A

When fully grown, spermatozoa move from the seminiferous tubules to rete testis (sperm concentrated and other fluids reabsorbed) and epididymis for final maturation

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13
Q

What is spermatogenesis?

A
  • Process where undifferentiated primordial germ cells (spermatogonia; mitosis yield spermatocytes, which undergo meiosis to…) are converted into specialised motile sperm (spermatozoa) with 23 chromosomes with either X or Y chromosome
  • 100-200 million sperm/day produced by cell division in seminiferous tubules (contrary to oocytes with fixed number decreasing through life)
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14
Q

What is spermatogenesis dependent on?

A
  • Associated with movement of ‘germ cell’ from epithelial side of sertoli cell (nursing role) to the lumen; process takes 70 days
  • Dependent on testosterone; secreted from leydig cells (4-10mg/day) exerting paracrine effects with high local concentration of testosterone
  • Dependent upon oestrogens; conversion of testosterone to oestrogens by aromatase (CYP19) within Sertoli cells. Oestrogen appear important for spermatogenesis by precise role unknown.
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15
Q

How are sertoli cells related to the seminiferous tubule?

A
  • Seminiferous tubules within testes are site of meiosis and subsequent production of spermatozoa
  • Epithelium costs of sertoli cells (tall/columnar cells), which play a role in nourishing sperm and concentrating testosterone
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16
Q

What do sertoli cells do?

A
  • Nourishes/nurses spermatozoa
  • Secretes androgen binding protein (ABP) which helps to maintain a high level of testosterone within the seminiferous tubule lumen by preventing testosterone (lipid soluble) from diffusing across the plasma membrane
17
Q

How is anterior pituitary regulation involved in spermatogenesis?

A
  • FSH, LH, testosterone and oestradiol all co-ordinate in the regulation of spermatogenesis
  • Hypothalamus releases GnRH which stimulates the anterior pituitary to secrete LH & FSH which in turn are picked up by receptors in the testes (LH on leydig cells, FSH on sertoli, both on germ cells)
18
Q

How do the levels of FSH & LH remain steady during spermatogenesis?

A
  • Negative feedback loop with inhibin (from FSH > sertoli) and testosterone (LH > leydig)
  • Inhibin -ve feedback to anterior pituitary (decreased FSH secretion)
  • Testosterone -ve feedback to both hypothalamus and anterior pituitary (reduction of GnRH and LH secretion)
19
Q

What role does inhibin play?

A

A peptide released by Sertoli cells to regulate FSH secretion.

20
Q

How else does testosterone affect the body apart from in spermatogenesis?

A

Receptive neurones lie in limbic structures in the brain (not just the hypothalamus) influencing sexual and aggressive behaviour.

21
Q

Does dihydrotestosterone have any effect on gonadotropin hormones?

A

There are not inhibitory effects seen; unlike with testosterone (OG).

22
Q

How does an elevated plasma testosterone as a result of exogenous input affect gonadotropin levels?

A
  • Suppression of anterior pituitary hormone secretion (plus hypothalamic GnRH?); decrease in FSH and LH (negative feedback)
  • Thus decrease in sperm density = infertility
23
Q

What is the effect of increasing FSH levels exogenously?

A

Results in a small increase in sperm density.

24
Q

What is the effect of increasing LH levels exogenously?

A
  • Results in a small (and slow) increase in sperm density
25
Q

What can be shown from the results of increasing FSH and LH respectively independently exogenously?

A
  • Results consistent with thought that FSH & LH work synergistically at the testis to promote spermatogenesis
  • Shown in failure of either exogenous FSH or LH to restore sperm count to normal
26
Q

Why do body builders who self-administer exogenous androgens have smaller gonadal/plasma ratio for testosterone activity and smaller testicles?

A
  • Excessive negative feedback brought by exogenous androgen administration
  • Less LH produced thus lower intracellular testosterone from leydig cells
  • Thus insufficient spermatogenesis (ABP not produced as much by sertoli cells; insufficient testosterone)
  • Suppression of anterior pituitary hormones = smaller testicles (trophic effect)

SHP - Pharmacology & Therapeutics (2 decks)

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