Reproduction of Living Organisms Success Criteria Students will

Reproduction of Living Organisms

Success Criteria • Students will become familiar with the human reproductive processes from the menstrual cycle to birth. • Students will describe the development of a pre-born human from the zygote stage up to fetus stage. • Students will be able to choose methods of contraception and protection from Sexually Transmitted Infections (STIs).

The Menstrual Cycle (p. 265) • About 28 days from beginning to end. The lining of the uterus changes thickness over the cycle. A thicker lining helps a fertilized ovum (zygote) stick to the uterus and begin development. • Day 1: Menstruation (period) • The unfertilized ovum is shed • Day 8: Follicles begin developing the ovum and the lining of the uterus starts to thicken. The ovum may be fertilized in the ovaries.

The Menstrual Cycle (p. 265) • Day 13: Ovulation • Ovum is in the fallopian tubes. Best time for fertilization. Body temperature increased by about 0. 5 OC. • Day 24: Lining of the uterus is at its thickest point. Ovum is reaching the end of the fallopian tubes. • Day 26: Unfertilized ovum dies in the uterus.

Pregnancy (p. 266) • Several million male gametes (sperm) are deposited into the vagina. • The sperm swim towards the uterus, then the fallopian tubes. • Only several thousand will reach the ovum, and only a single sperm will fertilize the ovum. • Fertilization may occur in the ovaries or the fallopian tubes; rarely in the uterus.

Pregnancy (p. 266) • Fertilization: The moment a sperm enters the ovum, it is a zygote. A single-celled living thing with a full set of genes. • Cell division: occurs in the fallopian tubes, doubling the number of cells up to 16 cells. • Implantation in the uterus: The zygote is now an embryoblast and attaches to the thick lining of the uterus.

Embryo and Placenta • After 10 -14 days, the embryoblast has developed into an embryo. • The embryo needs protection and food, much like a plant seed. • Protection: Amniotic sac contains the embryo and amniotic fluid • Food: Placenta carries nutrients and oxygen from the mother through the umbilical cord.

Embryo to Fetus • Pregnancy is divided into three stages called trimesters • First Trimester (Week 1 -13) • • Placenta develops Week 4, 1 cm, brain, heart, limbs and eyes begin to form. Heart beats. Week 8, 3 cm, embryo is now a fetus. Bone cells develop. Week 12, 8 -10 cm, sex can be determined, fetus can move.

Embryo to Fetus • Pregnancy is divided into three stages called trimesters • Second Trimester (Week 14 -26) • Week 16, 16 cm, skeleton forms, most organs present. • Week 20, 25 -30 cm, hair forms, sounds heard. • Week 24, 27 -35 cm, lungs have formed but cannot be used on their own.

Embryo to Fetus • Pregnancy is divided into three stages called trimesters • Third Trimester (Week 27 -40) • • The fetus grows rapidly and requires many nutrients from the mother. Week 28, 38 cm, fetus can open eyes. Week 32, 42 cm, settles into a head down position, optimal for birth. Week 36, 50 cm, recognizes its mother’s voice.

Dangers to the fetus • All nutrients come from the mother’s blood. Harmful substances in the blood stream will reach the fetus and may cause malformations. • Cigarette smoke limits oxygen, prevents growth and organ development. • Alcohol affects the brain, nervous system, and physical development. Leads to Fetal Alcohol Syndrome (FAS). • Drugs, both legal and illegal, can cause malformations or mental illness. Always consult a doctor before taking drugs while pregnant.

Birth • The pituitary gland, arguably, causes pregnancy. Now it will end the pregnancy. • The pituitary gland produces a hormone called oxytocin which stimulates contractions of the uterus, causing labour (the birthing process).

Contraception (p. 276 -p. 277) • If pregnancy doesn’t appeal to you, there are ways to prevent it without ceasing sexual intercourse with the opposite sex. • We can either stop the sperm from reaching the ovum, or stop the zygote from implanting in the uterus.

Contraception (p. 276 -p. 277) • Prevent fertilization • Billings method and Basal body temperature method are quite risky and prone to error. • Female condoms, Diaphragms, Spermicides, Oral contraceptives, Birth control patches • None of these methods are 100% effective, but condoms and oral contraceptives are 99. 99% effective.

Contraception (p. 276 -p. 277) • Prevent fertilization • There are surgical options to prevent fertilization • Expensive, but 100% effective • Tubal ligation, Visectomy

Contraception (p. 276 -p. 277) • Prevent implantation • Intrauterine Device (IUD) • Highly effective, but must be installed by a healthcare provider • May cause infections in women who have not had children before

Sexually Transmitted Infections • Condoms are the most popular form of contraception because they also are effective at preventing STIs • No other contraception method can prevent STIs • Medical gloves and denture dams are also effective against STIs (for hands and mouths, not genitals)

Sexually Transmitted Infections • STIs are extremely contagious and can be passed through blood, semen, or vaginal fluid. • AIDS, Condyloma, and Genital Herpes are not curable and will stay with the infected for the reminder of their lives. • AIDS patients risk shortening their lifespan by 10 -20 years if they do not receive regular treatment. • For these reasons, condoms should always be used during sexual intercourse. Couples must be tested for infection before having unprotected sex.