Female Reproductive System

Basic Anatomy Ovary (gonads) Follicles containing oocytes (immature egg cells) Corpus luteum Fallopian Tubes Pathway from ovary to uterus – site of ideal fertilization Uterus Destination for fertilized egg to implant and be sustained Vagina Entry for sperm Exit for baby

Basic Anatomy – The Brain Pituitary Gland: Releases Hormones Hypothalamus: Tests blood levels for various hormones and decides what should come next – sends signals to pituitary

Basic Hormones FSH - Follicle Stimulating Hormone Secreted by the pituitary gland (both male and female) Stimulates the follicle to form and grow (effect in female) LH - Lutenizing Hormone Causes ovulation (release of a mature egg) and causes the corpus luteum to form (effect in female) GnRH - Gonadotropin Releasing Hormone Secreted by the hypothalamus (at the base of the brain next to the pituitary gland) (both male and female) Causes the pituitary gland to increase production of FSH (both male and female)

Cow’s Head

Follicle Stage Days 5-13 Increased FSH levels cause: Follicle to enlarge Follicle to produce more estrogen

Follicle Stage (cont) Increased estrogen levels cause endometrium to thicken hypothalamus (brain) to tell pituitary (also brain) to release more FSH and LH

Ovulation Around day 12-15 Peak levels of FSH and LH cause Follicle to rupture Egg is released into fallopian tube (about the diameter of a human hair) Egg has 24 hours to be fertilized or it will die

Luteal Stage Days 16-29 Peak of lutenizing hormone stimulates corpus luteum (Latin for yellow body) to form from empty follicle

Luteal Stage (cont) Corpus luteum secretes some estrogen and, as it grows, increasing amounts of progesterone cause: Endometrium wall to thicken FSH and LH drop to see if pregnancy occurs (takes 6-7 days for zygote to travel and implant)

Basic Hormones (cont.) Estrogen Progesterone Secreted by the follicle and the corpus luteum Causes the outer lining of the uterus (endometrium) to thicken Progesterone Secreted by the corpus luteum HCG - Human Chorionic Gonaditropin Secreted by the implanted embryo Causes progesterone levels to stay high and maintain a thickened uterine wall Levels are detected by pregnancy tests – if it is there, then there is a pregnancy (no false positive but can get a false negative)

Pregnancy? If pregnancy occurs: Embryo implants and placenta starts releasing HCG so mom’s body knows it’s pregnant Initially, mom maintains progesterone and estrogen after month 3, baby does it on its own This keeps endometrium wall thick and Prevents hypothalamus from secreting GnRH which prevents the pituitary from producing FSH and starting all over. Isabella at 1 week old James at 1 week old

Menstrual Phase If no implantation has occurred Corpus luteum breaks down Progesterone drops Days 1-5 Endometrium breaks down and is expelled Hypothalamus detects low progesterone and estrogen and release GnRH Pituitary releases FSH…..

Summary of Events

What do birth control pills do? There are several different brands but the main categories work in one of two ways: Keep estrogen at artificially high levels – simulating levels during pregnancy. This stops the hypothalamus and therefore the pituitary from starting the cycle over and releasing an egg No egg = no chance for pregnancy (1/100 chance = 99% accuracy!) Use progestin alone or with estrogen Progestin makes it difficult for implantation to occur and for sperm to travel to the fallopian tubes. Note: progestin is a synthetic version of progesterone and is similar in how it works After 21 or so days, the hormones stop (placebo or no pill) and the body prepares for the next cycle by menstruating