Components of male reproductive axis:

1
Components of male reproductive axis

• Brain (hypothalamus GnRH)
• Pituitary gland (LH, FSH)
• Gonads
• germ cells (sperm)
• sex hormones (androgens)

2
Testes

• reside in scrotal sac (95oF)
• made of lobules of seminiferous tubules
• sem. tubules contain sperm, Sertoli cells
• Sertoli cells nurse cells
• Sertoli cells under influence of FSH

3
Testes, contd.

• interstitial (Leydig) cells surround sem. tubules
• Leydig cells make testosterone in response to LH
• in tubules sperm organized according to
  developmental stage

4
Spermatogenesis

• Spermatogonia - undifferentiated divide
  mitotically
• Primary spermatocytes - larger in appearance
  undergo 1st meiotic division
• Secondary spermatocytes - undergo 2nd meiotic
  division

5
Spermatogenesis, contd.

• Spermatids - haploid undergo spermiogenesis
• Spermatozoa
• head (acrosome and nucleus)
• middle piece (mitochondria)
• tail (contractile elements)

6
Spermatozoa

• sperm exit testes thru a series of ducts
• in epididymis sperm mature (2-4 days)
• then, enter vas deferens until ejaculation (or
  reabsorption)
• must undergo capacitation in female reprod. tract
• takes 16 days to complete process
• about 700 million sperm are produced / day

7
Male Accessory Organs

• Epididymis maturation of spermatozoa
• Vas deferens houses sperm until ejaculation
• Ejaculatory duct receives secretions from vas
  deferens and seminal vesicles upon ejaculation
• Seminal vesicles secrete basic, yellow substance
  that provides bulk, fluidity, nutrients,
  prostaglandins to semen

8
Male Accessory Organs, contd.

• Prostate secretes thin, milky substance that
  neutralizes acidic vagina contributes coagulant
  and decoagulant
• Cowpers gland secretes mucoid substance to
  lubricate and neutralize urine residue in urethra

9
Anatomy of penis

• three portions
• root
• tubular shaft
• glans penis
• has 3 masses of erectile tissue
• 2 corpora cavernosa (above urethra, extending
  from glans to root)
• corpus spongiosum (surrounds urethra, enters
  glans)

10
Erection

• erectile tissues fill with blood due to sexual
  arousal
• vasocongestion - more blood enters than leaves
• controlled by central nervous system
• Nitric oxide (NO) gt cGMP gtgt vasocongestion

11
Ejaculation

• when sexual arousal reaches peak
• first phase emission
• sperm move from epididymis and vas deferens to
  ejac. duct
• seminal vesicles, prostate, Cowpers gland
  release secretions
• second phase expulsion
• muscles contract at base of penis
• semen is expelled

12
Impotence

• erectile dysfunction
• 60 of cases have physiological basis
• common cause low blood pressure to penis
• oral therapy (Viagra)

13
Viagra

• oral therapy for erectile dysfunction
• facilitates action of nitric oxide in erectile
  tissue
• NO causes muscle relaxation thru stimulation of
  cyclic GMP
• cyclic GMP normally degraded by phosphodiesterase
  (PDE)
• Viagra inhibits PDE