XX - Female
XY - Male
Embryos identical until 7 weeks, sex is determined after that point when hormones are are present or absent.
Y chromosome carries 'testis-determining factor', (TDF), which triggers male sex hormones called androgens.
Androgens stimulates production of male sex organs in fetus.
Testes develop first in abdominal cavity, then descend toward scrotum and finish at birth.
Female Hormone Regulation
Menstrual cycle regulates hormones and releases an ovum at optimal time.
Cycle lasts about 28 days and includes two events, ovarian cycle and uterine cycle.
1. Follicle (small bag) develops
2. Ovum released
3. Corpus Luteum (yellow body) left behind
4. Corpus Luteum produces progesterone
5. Corpus Luteum disintegrates and produces a corpus albicans.
On a diagram, yellow round bodies appear, and as the cycle progresses they get smaller. Corpus albicans is the smallest.
Human Chorionic Gonadotropin (hCG)
Maintains the corpus luteum.
Remains at high levels for two months then decreases by four months.
Corpus luteum is maintained for the duration of the pregnancy.
Placenta secretes estrogen and progesterone for the remainder of pregnancy.
Female Hormone Pathway
Anterior Pituitary -> Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH)
Effect: Causes ovulation
After ovulation, corpus luteum develops and secrets progesterone (endometrium thickening and maintaining) and Estrogen (endometrium thickening + secondary sex characteristics)
Effect: Stimulate follicle cells to develop
Follicle cells secrete estrogen (endometrium thickening, secondary sex characteristics).
Male hormone pathway
Follicle Stimulating Hormone
Target: Leydig cell, interstitial cell
Target: Sertoli Cells
Effect: Testosterone (secondary sex characteristics, suppert spermatgenesis)
*Effect: Inhibin (inhibits FSH production)