Sexual Maturation in Males Flashcards
Puberty/Sexual Maturation
Gradual acquisition of reproductive competence
Why does maturation occur?
Due to increased GnRH secretion and increased sensitivity of hypothalamic-pituitary gonadal cell to hormonal stimulation
What is puberty influenced on?
Genetics and environment (nutrition, health, photoperiod, and psychosocial aspects)
Definition of sexually mature male
Ejaculate contains threshold spermatozoa for fertilization - differs in species but accepted definition
When does male anatomy develop?
Majority in utero, but reproductive organs continue to develop after birth
Postnatal development of testes
Consistent, scrotal circumference increases linearly
Seminiferous tubules growth pattern
Growth of outer diameter of tubule occurs at a slightly different rate than inner diameter
-both increase at 25 weeks of age and spike ~45 weeks
- growth is termed “lumination of tubules”
When does development of seminiferous tubules occur?
When greater release of testosterone occurs.
-episodic release of testosterone makes it difficult to detect changes (requires serum sampling to visualize hormone fluctuations)
Bovine Infants (0-5 weeks)
Low frequency of GnRH pulses, no LH pulses, low testosterone, increased responsivity of FSH secretion
Bovines 6-15 weeks
Increased frequency of GnRH pulses, LH pulses begin,, FSH secretion continues, testosterone remains low, gonadotropins prime Leydig and sertoli cells to receive hormones later
Bovines 16-25 weeks
GnRH pulses decrease in frequency, LH and FSH secretion drops, some growth of seminiferous tubular epithelium, testosterone is low
Bovines 36-45 Weeks
GnRH pulses increase, LH and FSH secretion increase, proliferation and increased activity of Leydig and Sertoli cells, testosterone increases, lumination of tubules, spermatogenesis begins
> 45 Weeks
Puberty is reached, GnRH, LH, FSH and testosterone secretion is established
-sensitivity to HPG cells to hormone stimulation and feedback established
-reproductive competence is achieved
4 weeks following puberty (reaching threshold)
Concentration of sperm, cells per ejaculate, % motility, % normal sperm, and % live sperm all increase
Average puberty in horses?
83 weeks, hormone release follows similar pattern to bovines
-2 years after reproductive competence is achieved, seminal characteristics and sexual behaviour are both improved
