1. Connections Between the Endocrine and Reproductive Systems

2. Regulation of Male Sex Characteristics
Spermatogenesis – Sperm production in the seminiferous tubules Testosterone – Aids in development and maintenance of male secondary sex characteristics

3. Regulation of Male Sex Characteristics
If a surplus of sperm are produced, inhibin, a hormone, is released by the testes, which acts as a negative feedback loop on the pituitary gland
If a surplus of testosterone is released into the blood, it acts as a negative feedback loop on the hypothalamus

4. Regulation of the Menstrual Cycle

5. Follicular Phase: Day 1 to 13
Follicle growth and egg maturation
GnRH from Hypothalamus  FSH from Pituitary  Egg Growth
Egg growth inhibits ovaries from producing estrogen  endometrium lining to be shed within the first five days

6. Ovulation: Day 14
GnRH  LH  mature egg is released from the ovary and it is swept into the uterine tube by the fimbriae
Growing follicles produce estrogen so endometrium begins to thicken

7. Luteal Phase: Day 15 to 28
Egg moves down the uterine tube and waits to be fertilized
If no fertilization occurs it will disintegrate
Estrogen causes endometrium to continue development, but levels will run low around day 28 and signal menstruation

8. Regulation of Childbirth
Positive Feedback Loop
As the head of the baby pushes on the cervix, the pituitary secretes oxytocin
Oxytocin stimulates increased uterine contractions and pushes baby into the cervix

9. Regulation of Lactation
Prior to delivery of the baby estrogen and progesterone promote duct and alveoli development in the breasts
Alveoli produce the milk
Ducts bring the milk to the nipples for infants to access