2. Click the mouse button or press the space bar to display information. Conception and Heredity Fertilization, or conception, is the union of an ovum and a sperm. Conception usually occurs in the upper-third portion of a Fallopian tube.

3. Click the mouse button or press the space bar to display information. Fertilization is the joining of an egg cell and a sperm cell.

4. Click the mouse button or press the space bar to display information. Heredity is the passing of characteristics from biological parents to their children and is determined at conception. What to Know About Conception and Heredity All body cells, except sperm and ova, contain 23 pairs of chromosomes. A chromosome is a threadlike structure that carries genes. A gene is a unit of hereditary material.

5. Click the mouse button or press the space bar to display information. Chromosomes in men and women What to Know About Conception and Heredity –In both males and females, one pair of chromosomes is called the sex chromosomes. In females, the pair of sex chromosomes is identical and is called XX. Every ovum produced by a female contains an X chromosome. In males, the pair of sex chromosomes is not identical and is called XY. Sperm produced by a male contain either an X chromosome or a Y chromosome.

6. Click the mouse button or press the space bar to display information. Chromosomes in men and women What to Know About Conception and Heredity –The sex of a baby is determined by the sex chromosome from the father. A fertilized ovum with an XX set of chromosomes develops into a female. A fertilized ovum with an XY set of chromosomes develops into a male.

7. Click the mouse button or press the space bar to display information. Amniocentesis is a diagnostic procedure in which a needle is inserted through the uterus to extract fluid from the amniotic sac. What to Know About Conception and Heredity –The amniotic sac is a pouch of fluid that surrounds a fetus. –Cells extracted from the amniotic fluid are analyzed to determine if any genetic defects are present.

8. Click the mouse button or press the space bar to display information. An ultrasound is a diagnostic procedure in which high high-frequency sound waves are used to provide an image of the developing baby. What to Know About Conception and Heredity –Ultrasound can be used to confirm pregnancy and the sex of the fetus, and to help a doctor diagnose any problems the mother might be having.

9. Click the mouse button or press the space bar to display information. Pregnancy An embryo is a developing baby through the second month of growth after conception. A fetus is a developing baby from the ninth week after conception until birth.

10. Click the mouse button or press the space bar to display information. What to Know About Pregnancy The outer cells of the embryo and the cells of the endometrium form the placenta. The placenta is an organ that anchors the embryo to the uterus. Other cells form the umbilical cord, which is a rope-like structure that connects the embryo to the placenta.

11. Click the mouse button or press the space bar to display information. What to Know About Pregnancy How pregnancy is determined –Absence of a menstrual period may indicate pregnancy. –If conception has occurred, a female usually has other symptoms of pregnancy, such as fatigue and morning sickness. –A female who misses a period and also has other symptoms of pregnancy should have a pregnancy test. –Pregnancy usually lasts nine months and is divided into trimesters or three-month periods.

12. Click the mouse button or press the space bar to display information. What to Know About Pregnancy The first trimester –At the end of the first month, the embryo has a heartbeat, a two-lobed brain, and a spinal cord. –By the end of the second month, the embryo is recognizable as a human and is called a fetus. –By the end of the first trimester, the heart has four chambers.

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14. 8 Weeks

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16. What to Know About Pregnancy The second trimester –By the end of the fourth month, fingernails, toenails, eyebrows, and eyelashes have developed. –Movement of the fetus can be felt by the mother, and the fetus can bend its arms and make a fist. –During the fifth month, the heartbeat can be detected by a stethoscope.

17. Click the mouse button or press the space bar to display information. 14 Weeks

18. Click the mouse button or press the space bar to display information. 18 Weeks

19. Click the mouse button or press the space bar to display information. 20 Weeks (5 Months)

20. Click the mouse button or press the space bar to display information. Six Months

21. Click the mouse button or press the space bar to display information. What to Know About Pregnancy The third trimester –Optimum development occurs at about 40 weeks after conception. –A premature baby is a baby that is born before 38 weeks of pregnancy. –A baby born between 38 and 40 weeks of pregnancy is considered to be full-term.

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23. 32 Weeks

24. Click the mouse button or press the space bar to display information. 40 Weeks

25. Click the mouse button or press the space bar to display information. What to Know About Childbirth A physician gives the baby an Apgar score, which is a rating of physical characteristics of an infant at one and five minutes after birth. Characteristics, such as heart rate, color, respiratory effort, and reaction to sucking, are scored and used to predict the health of the baby.

26. Click the mouse button or press the space bar to display information. What is an Apgar Score? Five factors are used to evaluate the baby's condition and each factor is scored on a scale of 0 to 2, with 2 being the best score: activity and muscle tone pulse (heart rate) grimace response (medically known as "reflex irritability") appearance (skin coloration) respiration (breathing rate and effort) A baby who scores a 7 or above on the test at 1 minute after birth is generally considered in good health.

27. Click the mouse button or press the space bar to display information. What to Know About Childbirth The postpartum period is the span of time that begins after the baby is born. The breasts secrete a watery substance believed to provide the baby with immunity to certain diseases. The breasts also secrete a hormone that stimulates the breasts to secrete milk.

28. Click the mouse button or press the space bar to display information. What to Know About Childbirth Multiple births –Two babies born at the same time are called twins. Identical twins develop from the same ovum and sperm and have identical chromosomes. Fraternal twins develop when two ova are released from an ovary and are fertilized at the same time by different sperm. –Three babies born at the same time are called triplets. Multiple births of more than three babies are rare.

29. Click the mouse button or press the space bar to display information. Complications During Pregnancy and Childbirth Ectopic pregnancy, which can be caused by tissue scarring from STDs, is a pregnancy that occurs outside of the uterus. Ectopic pregnancy can be fatal to females.

30. Click the mouse button or press the space bar to display information. Complications During Pregnancy and Childbirth Miscarriage is the natural ending of a pregnancy before a baby has developed enough to survive on its own outside the mother’s body. Cesarean section is a procedure in which a baby is removed from the mother by making an incision through the mother’s abdomen and uterus and removing the baby. Stillbirth is a fully developed baby that is born dead.

31. End of the Lesson