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CHAPTER 40: REPRODUCTIVE PHYSIOLOGY OF MALE (Puberty (Factor (breed …
CHAPTER 40: REPRODUCTIVE PHYSIOLOGY OF MALE
Spermatogenesis
Diploid stem cells (spermatogonia) divide mitotically → Progeny undergoes meiosis & differentiation → Haploid spermatids → Spermatozoa
Spermatocytogenesis
Spermatogonium → Type A spermatogonia [mito] → Intermediate Spermatogonia & other spermatogonia (maintain stem cell population) → Type B spermatogonia [mito] → Primary spermatocytes [meio] → Spermatozoa
Meiosis
One chromosomal duplication → Haploid condition of chromosomes (Secondary spermatocytes with duplicated chromatids) [meio I]
Secondary spermatocytes divide to form spermatids [meio II]
Spermiogenesis
Spermatids differentiate w/o dividing (in epididymis)
formation of acrosome
condensation & elongation of nucleus
formation of flagellum
extensive shedding of cytoplasm
Hypothalamic-Pituitary-Testicular Axis
Hypothalamus
GnRH
Testis
negative-feedback
of inhibin
negative-feedback of testosterone & estrogen
positive-feedback of testosterone to sex gland
Anterior pituitary Gland
FSH to Sertoli cells in seminiferous tubule
LH to Leydig cells
Puberty
Puberty =/= Sexual maturity
Puberty: male able to produce sufficient number of sperm to impregnate a female
Continuous process of endocrine changes
Factor
breed
energy intake
season of birth
Pulsatile stimulation of
-pituitary by GnRH
-gonad by LH & FSH
required for intiation & progression of puberty
Anabolic Steroids
Androgen derivatives that has been altered to maximize anabolic action and minimize androgenic side effect
Used to improve:
performance
stamina
physical strength
attitude
Side effect of sustained usage:
incomplete development of H-P-G axis
decreased testicular size
adverse affect on testes (reduction in no. of spermatogonia, decreased mean diameter of Leydig cells etc.)
Functional Structure
Scrotum
thermoregulation of testes
Testis
Leydig cells: production of androgens
Seminiferous tubule: spermatogenesis
Passage: seminiferous tubule → rete testis → epididymis → vas deferens → ampullae → urethra
Accessory sex gland
Seminal vesicle
Prostate gland
Bulbourethral gland
Ampullae (additional storage depot for spermatozoa)
Penis