1 Pregnancy Chapter 4

2 Pregnancy New human enters the world 9 months as baby grows Lots of changes Genes come from mom and dad Control how babies grow and develop even before they are born

3 Conception Cell = is the smallest unit of life that is able to reproduce itself Life begins with joining of two separate cells one from the male and one from the woman Sperm – male sex cell Ovum – female sex cell – egg Conception –union of the ovum and sperm cells

4 Zygote – single cell formed at conception; also called a fertilized egg Fallopian tubes – two hollow tubes that connect to the uterus and have fingerlike projections that reach toward each ovary Uterus – organ in which the baby develops and is protected until birth Genetic factors- traits that are passed though the genes

5 Process Hormones cause follicles to grow and fill with fluid Ovum is released once a month (ovulation) Travels toward fallopian tubes Ovum moves through the tubes ready to join the sperm Dozen sperm approach the ovum and only one enters

6 Genetic Factors & the Unborn Baby Genetic factors are passed onto the baby Genetic blueprint gives cells instructions for family-like traits Baby boy’s cells receive instructions on whether he will be bald later in life for example

7 Heredity & Steve Steve is 5 Asks many questions Shares traits with other 5 yr olds His DNA is his own Chromosomes – threadlike structures that carry genes in living cells Contain information nature needs to make Steve human

8 Chromosome & Genes Human baby has 46 chromosomes 23 from mom and 23 from dad One gene can decide a trait or many genes can decided

9 Dominant & Recessive Genes Dominant – traits that always show in a person even if only one gene of the pair is inherited for that trait Recessive – traits that typically do not show in a person unless both genes for the trait are inherited

10 People can pass on traits that don’t show up in the parents Color blindness and hemophilia are example of a single recessive gene People have both dominant and recessive genes for height

11 Sex Chromosomes Females have XX Males have XY Sex chromosome in the father’s sperm determines whether a child will be a boy or a girl

12 Multiple Pregnancy Two or more babies develop Far less common than single pregnancies Fertility drugs can cause multiple pregnancies Twins = 1 of 35 births 3 or more = 1 in 540

13 Fraternal Births Two ova and differ in genetic make up Twins, triplets, etc May or may not be same gender Look different at birth Chorion membrane surrounds each baby

14 Identical Births Single ovum Twins, triplets, etc Very similar in appearance May be mirror twins Same gender Share one chorion membrane

15 Mixed Types Triplets are often mixed pregnancies Two identical, one fraternal

16 Stages in Prenatal Development Development that takes place between conception and birth Germinal stage –first stage of prenatal development, which lasts about two weeks after conception Conception marks the beginning of the germinal stage

17 Zygote remains a single cell for about a day and a half 3 rd day it is a hollow ball of 32 cells Enters the uterus where it divides for 3 more days (free floating) 10 to 12 days the ball is embed in the wall of the uterus See page figure 4-12

18 Chorion and amnion (fluid filled sac) begin to form Placenta (organ filled with blood vessels) Develop against the wall of the uterus Umbilical cord contains 3 blood vessels that connect the child with the placenta See page 122 figure 4-13

19 Embryonic Stage Second stage of prenatal development Most critical stage of pregnancy Almost all body systems develop during this stage Lasts 6 weeks Baby is now called an embryo Changes happen quickly Tiny arms, legs, fingers, toes and a face Major organs are present Cartilage is soft, elastic, flexible tissue that provides structure Receives both good and harmful substance through placenta

20 Fetal Stage Third stage Last 9 weeks after conception until birth Baby now called a fetus All parts of the body mature Overall size increases Mother looks pregnant

21 Two Milestones in Fetal Stage 1. Hear baby’s heartbeat for first time Will begin to feel the baby move (quickening) Baby can turn, swallow, and suck its thumb 2. At 7 months (age of viability) Most babies could survive if they were born (28 th week of pregnancy)

22 Although baby is viable The closer to the nine months the better Baby’s lungs become stronger In the ninth month fetus receives immunities from mom Baby turns head down for delivery

23 Using Your Knowledge 1. Technology/Science. Go on line to research genetic counseling. What job duties do professionals in this field have, and what technologies do they use to investigate which genes a child might inherit from parents? Use a computer to compose a short report on your findings.

24 2. Science. Collect pictures of identical and fraternal siblings and note how alike or different they are. Try to find various pictures of the same people taken over several years.

25 Making Observations 1. Observe your physical features. Which features seem to come from your mother’s family and which from your father’s family? Which features do you share with other relatives?

26 2. Observe brothers and sisters. Which characteristics do they share? How are they different?