1. Male Reproduction Felix E. Grissom, Ph.D. 2219 Numa P.G. Adams
Howard University
Tel

2. Male Reproductive Anatomy and Physiology
Testis
Epididymis
Vas deferens
Seminal vesicle
Prostate
Bulbourethral
Ejaculatory duct
Urethra
Penis

3. Major Testicular Steroids
() = Relative activity where T activity=100
Androgens are C19 steroids
Majority of 5 a-DHT is formed in peripheral tissues

4. Male Sex Steroid Synthesis
Cholesterol may be from plasma or de novo synthesis
T may be converted in peripheral tissues to estradiol & androstenedione
Androstenedione is the major source of estradiol in men
Delta-5 pathway is the major route in men

5. Transport of Sex Steroids in Males
Major Sex Steroid Binding Proteins
Testosterone-Estrogen Binding Protein
One high affinity binding site (T1/2=22 seconds)
Binding affinity order for sex steroids =
DHT (100) >T (33) >E (25)
Albumin
One low affinity binding site (T 1/2-=1 second)
Cortisol Binding Globulin
No binding to DHT, T or E2. Binds Progesterone
Normal Distribution in Blood
TEBG (30%), Albumin (68%), Free (2%)
Active fraction includes free + albumin-bound fraction

6. Androgen Activity Increased Spermatogenesis Increased Bone Growth
Increased bone matrix, calcium deposition and promotes epiphyseal closure
Increased Nitrogen Balance
Increased muscle mass, larynx size
Increased atheletic performance
Increased basal metabolic rate, red blood cell density oxygen utilization
Altered Skin Function
Increased thickness, melanin deposition sebaceous gland secretion

7. Androgen Activity Androgen-Receptor Interactions
Both testosterone (T) and dihydrotestosterone (DHT) interact with same androgen receptor
DHT has a higher affinity for the androgen receptor than T
T-Androgen Receptor Interaction
Feedback regulation of gonadotropin secretion
Differentiation of Wolffian duct in utero
DHT-Androgen Receptor Interaction
External genitalia differentiation in utero
Virilization during puberty

8. Male Reproductive Anatomy and Physiology
Figure 26-9a: ANATOMY SUMMARY: Male Reproduction

9. Spermatogenesis: Sperm Production in the Testis
Seminiferous tubules
Spermatids
Spermatocytes
Spermatozoa
Sertoli cells
Interstitial tissue
Leydig cells
Capillaries

10. Testicular Compartmentalization

11. Sertoli Cell Function Sertoli Cells
Nourish healthy cells & phagocytize damaged germ cells
Synthesize luminal proteins
Maintain tubular fluid
Convert androgens to estrogens
Are site for hormonal modulation of tubular function

12. Spermatogenesis: Sperm Production in the Testis
Figure 26-9b-e: ANATOMY SUMMARY: Male Reproduction

13. Spermatozoa Structure and Functions in Review
Head
Acrosome:
Nucleus:
Midpiece
Centrioles:
Mitochondria:
Tail: flagellum
Microtubules:
Figure 26-10: Sperm structure

14. Regulation of Spermatogenesis
GnRH  LH  Leydig cells  testosterone  20 sex charact.
GnRH  FSH  Sertoli cells  spermatoctye maturation
Inhibin feedback – FSH, testosterone – short & long loops

15. Regulation of Spermatogenesis
Figure 26-11: Hormonal control of spermatogenesis

16. Testicular Cell Interactions
Sertoli cell products estradiol, inhibin, activin and other proteins modulate leydig cell activity
Sertoli cell products modulate germ cell function
Leydig cell testosterone modulate peritubular & Sertoli cell function
Peritubular cell products influence Sertoli cell activity

17. Hypothalamic-Pituitary regulation of Testicular Function