Chapter 10
I. sexual development (Text p. 298)
A. Background (Video, text p. 299)
1. Sexually dimorphic behaviors differ in males and females
2. Sex refers to genetic or physiological characteristics
3. Gender refers to socially-influenced identity, role and/or behavior
4. Intersex refers to combinations of biologically male and female characteristics
B. Production of Gametes and Fertilization
1. Gametes
a. Ova and sperm
b. Contain single set of chromosomes (which usually come in a pair)
2. Sex chromosomes: X and Y
a. Father’s sperm carries either X or Y
b. Control the development of glands that will produce sex hormones
3. Genetic sex
(p. 299)
a. XX = female
b. XY = male
C. Development of the Sex Organs
1. Categories
a. Gonads: testes or ovaries
i.
Develop first
ii.
Produce gametes and hormones
iii.
Gonad is undifferentiated at 6th week
iv.
SRY
a.
Sex-determining region Y
b.
On Y-chromosome
c.
Causes gonad to become a testis
v.
Without SRY, gonad develops into ovary
vi.
Hormonal effects
a.
Organizational: alter development
b.
Activational: occurs in developed organism
b. Internal sex organs
(p. 300)
i.
All embryos have precursors to male and female internal organs
a.
Müllerian system
1.
Precursor to female structures
2.
Develop in absence of hormones
b.
Wolffian system
1.
Precursor to male structures
2.
Needs hormone to develop
ii.
Testicular hormones
a.
Anti-Müllerian hormone
1.
Defeminizing effect
b.
Androgens
1.
Masculinizing effect
2.
Testosterone: from testis
3.
Dihydrotestosterone
a.
Made from testosterone by 5
-reductase
α
iii.
Disorders
a.
Androgen insensitivity syndrome
1.
Androgen receptors don’t work
2.
Androgens can’t masculinize; no Wolffian development
3.
Anti-Müllerian hormone still works; no Müllerian development
4.
External genitalia are female but reproduction is not possible
b.
Persistent Müllerian duct syndrome
1.
Two causes
a.
No anti-Müllerian hormone
b.
No receptor for anti-Müllerian hormone
2.
In males, androgens masculinize, but defeminization fails
3.
Born with male and female internal sex organs
c.
Turner syndrome
1.
XO
2.
No Y, therefore no testis
3.
Need two X chromosomes for ovary, therefore no ovary
4.
Not accurate—women with Turner’s syndrome can have ovaries and, in fact, can be fertile
c.
External genitalia
(p. 302)
i.
No hormone = female
ii.
Dihydrotestosterone = male
D. Sexual Maturation
1. Sex characteristics
a. Primary: gonads, internal sex organs, external genitalia
b. Secondary: enlarged breasts, widened hips, beard, deep voice
2. Puberty
a. Hypothalamus secretes gonadotropin-releasing hormone (GnRH)
(p. 302)
(p. 303)
i.
Stimulates production of release of gonadotropic hormones
a.
Luteinizng hormone (LH)
b.
Follicle stimulating hormone (FSH)
ii.
GnRH also under control of kisspeptin (a peptide)
a.
Kisspeptin produced in arcuate nucleus of hypothalamus
b.
Leptin
c.
Released by fat cells
ii.
Accelerates puberty
a.
Acts on receptors found on kisspeptin-secreting neurons in arcuate nucleus
iii.
Suppresses appetite
c.
Steroid sex hormones (Table 10.1, text p. 303)
d.
Gonadotropins stimulate release
ii.
Ovaries produce estrogens such as estradiol
iii.
