Male and Female Reproductive Systems

The Menstrual Cycle The menstrual cycle typically lasts 28 days; approximately 1 month. One cycle is the amount of time from the beginning of one period to the beginning of the next period. The beginning of a period is marked by the release of the blood and lining from the inside of the uterus. This flow of blood typically lasts 3-7 days and is called menstruation. Menstrual cycle story

The Menstrual Cycle After menstruation, the ovaries release hormones that tell the uterus to grow a new lining and prepare to receive a new egg. As the uterus prepares a new lining, one of the ovaries releases an egg. This is called ovulation. Ovulation occurs about halfway through a woman’s cycle. The egg travels through the Fallopian tube. If it is not fertilized it breaks down and is released with the lining and blood of the uterus.

Menstrual Cycle Timeline

Menstrual Cycle Timeline

The Menstrual Cycle and Fertilization If the egg is fertilized by a sperm cell, the egg will implant in the lining of the uterus and begin to develop. Zygote: The first cells of a new organism; the time from fertilization to implantation. Embryo: The zygote is called an embryo from implantation to 8 weeks. Fetus: After 8 weeks of development, the embryo is known as a fetus.

Sperm Formation MEIOSIS forms sperm in gametes Sperm forms in testes Scrotum keeps cooler than rest Semen is sperm plus protecting fluid Semen leaves testes through the vas deferens (sperm ducts) to the urethra before it exits. Mrs. Degl

Ovum Formation MEIOSIS forms the eggs (ova) Eggs are formed before birth 1 egg per month is matured and released from ovaries, most of the time Eggs travel through the fallopian tube where they may become fertilized Mrs. Degl

Fertilization Occurs in upper 1/3 of Fallopian tube Only 1 sperm can fertilize an egg Fertilized egg = zygote An average woman is pregnant (gestational period) for 9 whole months. That is 40 weeks. Babies can survive if they are born earlier, but they may have complications due to being premature. Mrs. Degl

Implantation Fertilized eggs are implanted into thick walls of uterus Membranes dig into uterus to form placenta Zygote grows into an embryo Embryo gets air and nutrients through the umbilical cord Mom’s uterus grows with the baby Mrs. Degl

1st Trimester = 1st 12 weeks Heart develops first Neural tube develops All body systems appear by Week 8 – Now a Fetus Mrs. Degl

2nd Trimester = up to 24 weeks Most growth Looks more like a baby Some preemies survive at this stage Mrs. Degl

3rd Trimester = Up to 40 weeks More growth Kicking, rolling, stretching Eyes open – Week 32 Lungs mature Rotates to head-down position, unless baby is breech Mrs. Degl

Birth Labor Uterine contractions begin Cervix dilates to 10 cm. Birth Uterus pushes baby through vaginal canal Placenta delivered after baby Cesarean Section (c-section) is a surgery that cuts through the uterus to deliver the baby if it cannot be born vaginally Mrs. Degl