Connections Between the Endocrine and Reproductive Systems

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

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

Regulation of the Menstrual Cycle

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

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

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

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

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