Unit Eight Reproduction in Humans

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Unit Eight Reproduction in Humans
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A. From Conception to Birth

• Learning Objectives
• What happens to a fertilized egg in the first two
  weeks after conception?
• When do body structures and internal organs
  emerge in prenatal development?
• When do body systems begin to function well
  enough to support life?

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From Conception to Birth

• Periods of Prenatal Development
• Period of the Zygote (Weeks 1-2)
• After fertilization, the zygote travels down the
  fallopian tube and is implanted in the uterine
  wall
• Period of the Embryo (Weeks 3-8)
• Body structures, internal organs, and the three
  layers of the embryo (ectoderm, mesoderm,
  endoderm) develop
• The amniotic sac fills with fluid and the
  umbilical cord connects the embryo to the placenta

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From Conception to Birth

• Period of the Fetus (Week 9-Birth)
• Week 9 - Differentiation of the ovaries and
  testes
• Week 12 - Circulatory system begins to function
• Week 16 - Movement felt by mother
• Week 32 - Age of viability (able to live on its
  own)

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B. Influences on Prenatal Development

• Learning Objectives
• How is prenatal development influenced by a
  pregnant womans age, her nutrition, and the
  stress she experiences while pregnant?
• How do diseases, drugs, and environmental hazards
  sometimes affect prenatal development?
• What are some general principles affecting the
  ways prenatal development can be harmed?
• How can prenatal development be monitored? Can
  abnormal prenatal development be corrected?

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Influences on Prenatal Development

• General Risk Factors
• Nutrition
• Inadequate maternal nutrition may result in
  premature birth and/or low birth weight
• Alcohol, drugs, and tobacco increase the risk of
  brain damage and/or low birth weight
• Stress
• Studies show extreme maternal stress is
  associated with low birth weight and premature
  births as well

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Influences on Prenatal Development

• Teratogens agents that cause birth defects
• Drugs
• Alcohol, aspirin, caffeine, narcotics, marijuana,
  nicotine
• May cause Fetal Alcohol Syndrome, brain damage,
  low birth weight, slowed growth, and dependence

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Influences on Prenatal Development

• 2. Infections or diseases
• AIDS, Herpes, Syphilis, and German measles
  (Rubella) are very dangerous infections for a
  mother to have
• If a pregnant woman is infected with German
  measles there is a risk of damage to the unborn
  child ? often the pregnancy must end
• AIDS can be passed on to an unborn baby and also
  HIV medications can be damaging to a baby
• Effects include neurological disorders, deafness,
  blindness, mental disability, damage to bones,
  eyes, ears, or heart

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Influences on Prenatal Development

• 3. Environmental Hazards
• - Lead, Mercury, X-Rays
• - Effects may include mental disability,
  retarded growth, cerebral palsy, impaired memory
  and verbal skills, and leukemia

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C. Prenatal Diagnosis and Treatment

• Genetic Counseling
• Helps to assess the chances of inherited
  disorders
• Prenatal Diagnosis
• Ultrasound is the use of sound waves to produce a
  picture of the fetus
• Karyotyping can show chromosome abnormalities
• Amniocentesis allows the taking of a sample of
  the amniotic fluid to test for fetal disorders
• Chorionic Villus Sampling is taken from the
  placenta and can be done earlier than
  amniocentesis

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D. Labor and Delivery

• Learning Objectives
• What are the different phases of labor and
  delivery?
• What role do feedback mechanisms play?
• What are some complications that can occur during
  birth?

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Labor and Delivery

• Stages of Labor
• Stage 1 lasts approximately 12-24 hours for the
  first birth and includes contractions and the
  enlargement of the cervix to 10 cm
• Stage 2 includes the actual birth of the baby and
  can last about an hour
• Stage 3 lasts a few minutes and involves
  expelling of the placenta

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Labor and Delivery

• Feedback Mechanisms
• Can be negative or positive and simple or complex
  ? childbirth
• Organisms detect and respond to a stimuli (a
  change in the environment)
• Corrective actions are taken to eventually
  restore homeostasis

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Labor and Delivery

• Positive Feedback
• A change in the environment triggers a response
  that leads to a greater change or response ? this
  does not maintain homeostasis
• Ex. In childbirth, contractions push the babys
  head against the mothers uterus.
• The uterus responds to this by having stronger
  contractions, which push against the babys head
  even more
• The uterus continues to push against the babys
  head until until the cervix is fully dilated and
  it moves into the vagina ? birth canal

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Labor and Delivery Birth Complications

• Hypoxia, or inadequate blood and oxygen to baby.
• Complications may result in cesarean section
  (C-section).
• Births before the 36th week are called premature
  or pre-term.

• Babies weighing less than 5.5 pounds have low
  birth weight.
• Babies weighing less than 3.3 pounds have very
  low birth weight.
• Below 2.2 pounds is called extremely low birth
  weight.

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Labor and Delivery

• Childbirth Classes
• Explain what happens during pregnancy and
  delivery
• Teaches techniques to manage the pain of
  childbirth ? Lamaze technique
• The emphasis is on natural methods, relaxation,
  and coaching so women feel confident about their
  abilities and giving birth

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Labor and Delivery

• Infant Mortality
• Infant Mortality is the number of infants out of
  1,000 births that die before the age of 1 year.
• U.S. mortality rate is about 1, or 9 of 1000.
• 15 industrialized nations have lower infant
  mortality than U.S.
• Possible factors include low birth weight
  resulting from a lack of prenatal care, poor
  nutritional habits, and stress.

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