The following will be discussed in this chapter: Hormonal regulation of male reproductive function, hpg axis, mechanism and effects of testosterone activity, male secondary sex characteristics, female reproductive anatomy,. | 27 The Reproductive System: Part B Hormonal Regulation of Male Reproductive Function A sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes The hypothalamic-pituitary-gonadal (HPG) axis HPG Axis Hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to secrete FSH and LH FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone LH stimulates interstitial cells to release testosterone HPG Axis Testosterone is the final trigger for spermatogenesis Feedback inhibition on the hypothalamus and pituitary results from Rising levels of testosterone Inhibin (released when sperm count is high) Figure Anterior pituitary Inhibin GnRH Testosterone Via portal blood Interstitial cells Sustentacular cell Spermatogenic cells Seminiferous tubule Somatic and psychological effects at other body sites LH FSH 1 2 2 3 4 5 6 7 8 Stimulates Inhibits Mechanism and Effects of Testosterone Activity Testosterone Synthesized from cholesterol Transformed to exert its effects on some target cells Dihydrotestosterone (DHT) in the prostate Estrogen in some neurons in the brain Mechanism and Effects of Testosterone Activity Prompts spermatogenesis Targets all accessory organs; deficiency leads to atrophy Has multiple anabolic effects throughout the body Is the basis of the sex drive (libido) in males Male Secondary Sex Characteristics Features induced in the nonreproductive organs by male sex hormones (mainly testosterone) Appearance of pubic, axillary, and facial hair Enhanced growth of the chest and deepening of the voice Skin thickens and becomes oily Bones grow and increase in density Skeletal muscles increase in size and mass Female Reproductive Anatomy Ovaries: female gonads Produce female gametes (ova) Secrete female sex hormones (estrogen and progesterone) Accessory ducts include Uterine tubes Uterus Vagina Female . | 27 The Reproductive System: Part B Hormonal Regulation of Male Reproductive Function A sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes The hypothalamic-pituitary-gonadal (HPG) axis HPG Axis Hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH stimulates the anterior pituitary to secrete FSH and LH FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone LH stimulates interstitial cells to release testosterone HPG Axis Testosterone is the final trigger for spermatogenesis Feedback inhibition on the hypothalamus and pituitary results from Rising levels of testosterone Inhibin (released when sperm count is high) Figure Anterior pituitary Inhibin GnRH Testosterone Via portal blood Interstitial cells Sustentacular cell Spermatogenic cells Seminiferous tubule Somatic and psychological effects at other body sites LH FSH 1 2 2 3 4 5 6 7 8 .
