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Lesson 21

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Lesson 21 Powered By Docstoc
					What You’ll Learn
1. Explain how a baby is conceived and how the
   baby’s sex and inherited traits are determined.
2. Explain how pregnancy
   is determined.
3. Explain why prenatal
   care is important.
4. Describe the three
   stages of labor.



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Key Terms
 • fertilization                            • labor
 • chromosome                               • afterbirth
 • gene
 • amniocentesis
 • ultrasound
 • embryo
 • placenta
 • fetal alcohol
   syndrome (FAS)
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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.


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What to Know About Conception
and Heredity
• Heredity is the passing of characteristics from
  biological parents to their children and is
  determined at conception.
• 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.


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What to Know About Conception
and Heredity
• Chromosomes in men and women
  – 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.

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What to Know About Conception
and Heredity
• Chromosomes in men and women
  – 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.
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What to Know About Conception
and Heredity
• Genes
  – All chromosomes carry genes that contain
    hereditary material.
  – Sex-linked characteristics are hereditary
    characteristics, such as color vision or blood
    clotting, that are transmitted on the sex
    chromosomes.



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What to Know About Conception
and Heredity
• Inherited characteristics
  – Inherited characteristics are determined by
    genes carried on chromosomes.
  – If the maternal and paternal genes for a trait
    are different, one will override the other.
    • A dominant gene is a gene that overrides the
      expression of the other gene.
    • A recessive gene is a gene whose expression is
      overridden by the other gene.

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What to Know About Conception
and Heredity
• Genetic counseling
  – Genetic counseling is a process in which
    a trained professional interprets medical
    information concerning genetics to
    prospective parents.




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What to Know About Conception
and Heredity
• Amniocentesis is a diagnostic procedure in
  which a needle is inserted through the uterus to
  extract fluid from the amniotic sac.
   – 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.


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What to Know About Conception
and Heredity
• An ultrasound is a diagnostic procedure
  in which high high-frequency sound waves
  are used to provide an image of the
  developing baby.
                                             – 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.

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Pregnancy




 • After conception, a fertilized ovum continues to
   divide and move through the Fallopian tube.
 • The cell divisions form a cluster of cells by the
   time they reach the uterus.
 • These cells attach to the endometrium, which is
   the lining of the uterus.
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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.


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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.




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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.
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What to Know About Pregnancy




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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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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.


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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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Prenatal Care



                       • Prenatal care is the care that is
                         given to the mother and baby
                         before birth.
                       • Prenatal care includes medical
                         examinations, proper nutrition,
                         childbirth and child-care
                         education, and avoidance of
                         risk behaviors.
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What to Know About Prenatal Care
• Premature birth or low birth weight may result
  when a developing baby does not receive
  adequate nutrients.
   – Premature birth is the birth of a baby before
     it is fully developed—less than 38 weeks
     from the time of conception.
   – A low birth weight is a
     weight at birth that is less
     than 5.5 pounds.


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What to Know About Prenatal Care
• A pregnant female needs to check with her
  physician before she takes any prescriptions
  or over-the-counter drugs.
• A female should not drink alcohol during
  pregnancy.
• Fetal alcohol syndrome, or FAS, is the
  presence of severe birth defects in babies born
  to mothers who drink alcohol during pregnancy.
• Smoking and breathing smoke from tobacco
  products increase the risk of complications,
  miscarriage, and stillbirth during pregnancy.
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What to Know About Prenatal Care
• A miscarriage is the natural ending of a
  pregnancy before a baby is developed enough
  to survive on its own outside the mother’s body.
• A stillbirth is the birth of a dead fetus.
• Babies born to mothers who use drugs can be
  born prematurely, have low birth weight, and can
  be addicted to drugs.
• Caffeine may be linked to birth defects.
• Folic acid is one nutrient known to prevent
  birth defects.
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Childbirth




                          • Labor is the process of childbirth.
                          • During labor, muscular
                            contractions of the uterus start,
                            become more intense, last longer,
                            and become more frequent.


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Childbirth


                          • A discharge or gushing of water
                            from the vagina indicates the
                            amniotic sac has broken.
                          • Bloody show, which is the
                            discharge of the mucous plug
                            that sealed the cervix during
                            pregnancy, also may be
                            experienced.

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What to Know About Childbirth
• Labor is considered to have three distinct stages.
• Stage 1: Dilation of the cervix
   – The first stage of labor can last from two
     hours to many hours.
   – The cervical opening
     enlarges eight to ten
     centimeters—wide
     enough for the baby
     to move through.


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What to Know About Childbirth
• Stage 2: Delivery of the baby
  – The second stage begins when the cervix is
    completely dilated and ends with the delivery
    of the baby.
  – Crowning is the
    appearance of the
    baby’s head
    during delivery.
  – Once the baby has been eased out of the
    birth canal and begins to breathe on its own,
    the umbilical cord is cut.
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What to Know About Childbirth
• Stage 3: Delivery of the placenta
  – The third stage of labor is the expulsion of
    the afterbirth.
  – The afterbirth is the placenta that is
    expelled after delivery.




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What to Know About Childbirth
• When the baby is breathing on its own, the
  umbilical cord is clamped and cut off.
• 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.


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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.




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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.
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What to Know About Childbirth
• Childbirth classes
  – Childbirth classes are available from
    hospitals, health centers, and other
    organizations to prepare prospective parents
    for the birth of their baby.
  – Special exercise classes also are offered for
    pregnant females to help them stay fit during
    pregnancy and prepare for childbirth.



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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.



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Complications During Pregnancy
and Childbirth
• Rh incompatibility is a mismatch between the
  blood of a pregnant female and the blood of the
  developing baby.
• Toxemia of pregnancy is a condition
  characterized by a rise in the pregnant female’s
  blood pressure, swelling, and leakage of protein
  into the urine. Untreated toxemia can be fatal to
  females and their developing babies.



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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.
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                                                                          3A, 3D
Study Guide
1. Match the following terms and definitions.
___ chromosome
 B                                             A. an organ that anchors the embryo
___ placenta                                      to the uterus
 A
___ postpartum period                          B. a threadlike structure that carries
 C
                                                  genes
___ Apgar score
 E
                                               C. the span of time that begins after
___ crowning
 D                                                the baby is born
                                               D. the appearance of the baby’s head
                                                  during delivery
                                               E. a rating of physical characteristics
                                                  of an infant at one and five
                                                  minutes after birth


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                                             3A, 3D
Study Guide
2. Identify the following statements as
   true or false.
  _______ Fraternal twins have identical chromosomes.
   false
  _______ A baby born before 38 weeks is classified
    true
          as premature.
  _______ By the end of the third month of pregnancy,
   false
          the baby’s heartbeat can be detected by
          a stethoscope.
  _______ The sex of a baby is determined by the sex
   false
          chromosome of its mother.


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                                             3A, 3D
Study Guide
3. Describe how the sex of a baby is determined.
  Every ovum produced by a female contains an
  X chromosome. Sperm produced by a male
  contains either an X chromosome or a Y
  chromosome. When the sperm fertilize the ovum
  to create a complete set of 46 chromosomes,
  the combination of the sex chromosomes will
  either be XX or XY. An XX combination will result
  in a female baby. An XY combination will result in
  a male baby.


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Lesson Resources


tx.healthmh.com/conception_and_heredity
tx.healthmh.com/pregnancy
tx.healthmh.com/childbirth
tx.healthmh.com/study_guide
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