Fertilization & Implantation
Topics for today:
• Structure of testes • Action of testosterone • Spermatogenesis • Steps of oogenesis • Fertilization • Implantation
Functional anatomy of testes
Site of sperm storage Site of androgen synthesis
Sperm passageway Interstitial tissue (between tubules)
Site of spermatogenesis
1 Micro anatomy of testes
Interstitial tissue, site of synthesis of testosterone OH
O testosterone
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Hormonal effects of androgens (general effects)
• produce a general ‘anabolic’ effect • stimulates protein synthesis (muscle tissue) and male body configuration • stimulates bone elongation and relatively quick closure of the epiphyseal plates • promotes male pattern of hair growth
Hormonal effects of androgens (reproductive system effects)
• promotes descent of testes into scrotum
2 Hormonal effects of androgens (reproductive system effects)
Stimulates growth of secondary sex glands
Stimulates function of these glands
secretes fructose, nutrient for spermatozoa
- secretes HCO3 rich fluid; neutralizes acid of vaginal epithelium
Hormonal effects of androgens (reproductive system effects)
• stimulates growth of ductus deferens and external genitalia
Seminiferous tubule gametogenisis
seminiferous tubule
3 spermatogonium
Meiotic stages of hypertrophy
spermatogenesis primary spermatocyte meiosis I
secondary spermatocytes meiosis II
spermatids
transformation spermatozoa
Structure and Biochemistry of Spermatozoa
Secretes hyaluronidase that can degrade zona pellucida
Meiotic stages of oogonium Oogenesis (2n) hypertrophy primary oocyte (2n)
Meiosis I
secondary 1st polar oocyte body (1n)
Meiosis II
2nd polar Ovum body (1n)
4 Gametogenesis comparison oogonium spermatogonium (2n) hypertrophy (2n)
primary oocyte primary (2n) spermatocyte (2n) meiosis I secondary secondary spermatocytes (1n) 1st polar oocyte body (1n) meiosis II spermatids (1n)
2nd polar ovum transformation body (1n) spermatozoa (1n)
Fertilization
zygote (diploid)
Implantation mitosis morula
fertilization
blastula
ovulation endometrium day 7
Chorion formation & release of chorionic gonadotropin
5 Early Embryo Stages
ovum fertilization Zygote cleavage morula blastulation blastula 0 d 3 d 5 d spermatozoan stage at implantation
Topic for Tuesday:
Embryo Development
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