3. Genetic Differentiation
1. H-Y Antigen- Histocompatability Y antigen
1. Male specific antigen present on the surfaces of cells
XY = H-Y antigen XX = Not present
2. NOT the sex determining gene in males.
2. Sry Gene - Sex determining region of Y chromosome
a. Gene for sexual development on the Y chromosome
b. Responsible for TDF- Testis determining factor production
c. Transcription factor which activates other “male” genes
d. Stimulates male development

5. XY chromosomal pair  TDF production
Testes Formation
A) Anti Mullerian Hormone (Sertoli cells)
Blocks development of the Mullerain duct
B) Androgens from testis promote Wolffian Duct
development
Hormones: testosterone and 5a dihydrotestosterone
Testosterone - stimulates development of Wolffian duct
5a Dihydrotestosterone - stimulates external development
of genitalia (scrotum, glands, penis)

6. Figure 4-5

7. Descent of the Testis Cont.
Phases of testicular descent
1) growth of body away from testes.
2) growth of distal gubernaculum.
Descendin, produced by fetal testes may regulated growth of the gubernaculum.
3) regression of gubernaculum.

9. Brain Sexual Differentiation
Masculinization of the Brain in the male:
testosterone from the fetal testis reaches the brain
testosterone is converted to estradiol by aromatase enzyme in the hypothalamus
Regression of Hypothalamic GnRH surge center by estradiol
Defeminization of the hypothalamus

10. Testosterone (T)
Brain
Hypotalamus T
Estradiol
aromatase enz.
Regression of
GnRH Surge center
Fetal testis
Surge center is responsible for the follicular ovulation

11. The Key to Initiation of Puberty
GnRH secretion in high frequency and high amplitude
The Key to Initiation of Puberty
Enough LH secretion to initiate follicular growth and/or spermatogenesis

12. High LH pulses and amplitudes and thus LH surge do not occur
Unless
Hypothalamic sensitivity to gonadal estradiol increases
Hypothalamus Sensitivity to E2 changes with age

13. Factors Impacting the Development of Hypothalamic GnRH neurons
1) Genetic and Breeds
2) Body Size and Composition
Degree of fatness and body weight
Metabolic signals
3) Environmental factors
Season
Photoperiod
Presence of the opposite sex

14. Hormone Receptor Classification
1) Plasma membrane receptor
2) Nuclear Receptors

15. Nuclear Receptors
                                        

16. Hormone Receptor Classification Cont.
Plasma membrane receptor
Nuclear Receptors
Protein hormones
Steroid hormones
Protein hormones Receptors
Intracellular receptors

17. Stages of the Estrous Cycle
Subdivision of the Follicular and Luteal Phases
Proestrus
Estrus
Metestrus
Diestrus
Follicular Phase
Luteal Phase

18. Follicular phase
Luteal Phase

19. CL
Follicle

20. Four Major Events
Gonadotropin (LH & FSH) release from the anterior pituitary
Follicular growth and maturation for ovulation
Sexual receptivity
Ovulation

22. What does LH Surge Do??
1) Weakening of the follicular wall and ovulation
2) Reconstruction and remodeling of the theca cells and granulosa cells
Preparation for progesterone synthesis
3) Oocyte (egg) maturation and completion of Oogenesis (egg division)

24. Mitotic
Step 1-3
Meiotic
LH Surge