4+5+6+7+8

• Fetus

  Male or female depends on Y chromosome and the gonads (testes in male and ovaries in female)

  
• Differentiation of primitive (embryonic) gonads

  Genetically determined (XY or XX)

  
• Formation of male genitalia

  Depends on testosterone hormone and other androgens (the functional hormones of testes)

  
• Absence of testicular tissue

  Fetus is female
• Taking antiandrogens


  Develops a feminine boy
• Male sexual behavior


  Due to action of testosterone on the brain in early development
• Testes and ovaries


  Remain quiescent until adolescence

  
• At adolescence testes and ovaries

  Activated by pituitary hormones (FSH and LH) to secrete sex hormones: Testosterone in male and Estrogen and Progesterone in female

  
• Sex hormones


  Cause appearance of adult male features or onset of menstrual cycle in female

  
• In Female: Ovarian function regress with age and menstrual cycle cease (stop) - Menopause
• In Male: Testicular function slowly declines with age BUT the production of sperms persists
• Testes


  Dual function: spermatogenesis and secretion of androgens

  
• Ovaries


  Dual function: oogenesis and secretion of estrogens and progesterone

  
• Testes


  Secrete small amount of estrogens and large amount of androgens

  
• Androgens

  Steroid hormones have sex and muscling functions
• Ovaries

  Secrete large amount of estrogens, progesterone and small amount of androgens

  
• Estrogens

  Have sex and feminizing functions
• Progesterone


  Prepare the uterus for pregnancy and breast for lactation

  
• Androgens


  Secreted from adrenal cortex in both sexes

  
• Androgens


  Converted into estrogen in fat and other extragonadal and extra-adrenal tissues

  
• In pregnancy: the ovaries


  Secret Relaxin polypeptide that loosens the ligaments of the pubic symphysis and soften cervix to facilitate delivery of the fetus

  
• Secretory and gametogenic functions

  Depends on pituitary gonadotropins (FSH and LH)
• Pituitary gland


  Secretes FSH and LH in cyclic pattern in postpubertal female and noncyclic pattern in postpubertal male

  
• Testes and ovaries


  Secret Inhibin that produce negative feedback inhibition on the pituitary gland and reduce FSH secretion

  
• Cyclic change in FSH and LH secretion

  Necessary for occurrence of menstruation, pregnancy and lactation in female
• Sex chromosomes


  The X and Y chromosomes

  
• Y chromosome


  Necessary and sufficient for production of testes
• Y chromosome


  Contains, in the tip of its short arm, the sex determining region that coded for a protein called SRY protein

  
• SRY


  Bind DNA and act as transcription factor for many genes necessary for testicular differentiation "including MIS"
• Spermatogonium cells


  Diploid cells of XY pattern

  
• Male sperm


  Either X or Y pattern
• Oogonia cells


  Diploid cells of XX pattern
• Female ovum


  X pattern
• In the two-stage meiotic division in the female

  Only one cell survives as the mature ovum
• In the male, the meiotic division

  Results in the formation of four sperms, two containing the X and two the Y chromosome
• When a sperm fertilizes an ovum

  It produces two possible zygotes: 1. Zygote with XY pattern and develops into a genetic male 2. Zygote with XX pattern and develops into a genetic female
• Fertilization thus produces a male zygote with 22 pairs of autosomes plus an X and a Y or a female zygote with 22 pairs of autosomes and two X chromosomes
• In embryonic life there is a condensed tissue near the adrenal gland


  Called genital ridge
• Primitive gonad

  Arises from this ridge
• The gonads


  Develops a cortex and medulla