PSYC 2850 - Human Sexuality - Class 6

Course Code
Psychology 2800
Thisis P S Y C2850- Human Sexuality N O T P S Y C2800

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March 9, 2011
Sex Differentiation & Inter-sexuality
Sexual Differentiation
Sexual determination: formation of a zygote and whether or not it will be chromosomal
male or female
The genital ridge (embryonic gonads) is bipotential (testes and ovaries develop from
the same precursor, homologues)
The SRY gene determines how the genital ridge differentiates
SRY gene codes for testes transcription faction
A pair of Dax-1 genes govern development of ovaries (all male embryo’s also has this
gene, but is inactive as it is not in a pair)
Developing embryos possess both a male and a female set of embryonic internal
reproductive organs
Male - Wolffian duct (epididimus, vas deferens, seminal vesicles, ejaculatory duct)
Felmale - Mullerian duct (fallopian tubes, uterus, cervix, upper vaginal canal)
Embryonic internal reproductive organs must masculinize (wolffian) and de-
feminize (mullerian) in a male ..or...feminize (mullerian) and de-masculinize
(wolffian) in a female
Testes secrete:
Anti-mullerian hormone (AMH)
During embryonic development, a single bipotential proto-genital exists
Genital swelling develops into the labia majora and the scrotum
Cloaca at develops into the gastrointestinal and urogenital systems at 6 weeks they
Fold of skin that forms upon separation is a raphe
Proto-genital produces an enzyme called 5-alpha reductase
5-alpha reductase converts testosterone into 5 alpha dihydrotestosterone
Why does the vas deferens follow such a seemingly unnecessarily circuitous route?
The structure of the vas deference is a by-prodcut of an adaptation
Gubernaculum pulls testes down into scrotal swelling over the ureter which creates the
circutious route of the vas deferens
Puberty is triggered by signals from the body and the production of kisspeptin by the
hypothalamus (typically at 120lbs in males and 103lbs in females)
Memarche - first menstruation
Humans exhibit reproductive bimaturism (girls 12-14 yrs, boys 14-16 yrs)
Puberty lasts longer in males and is a slower process
Tanner stages describe pubertal changes in males and female
Puberty is marked by genital and breast changes in women
Puberty is marked by genital changes in men
There has been a historical decrease in age menarche
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