Assisted Reproductive Technology

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Assisted Reproductive Technology

• Chapter 2

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Central Points

• Sperm and eggs are formed in specialized organs
• Males and females have different reproductive
  organs
• Infertility is a problem in some areas of the
  world
• Medical techniques can assist infertile
  individuals
• Legal cases will decide treatment of frozen
  embryos

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2.1 How Are Sperm and Eggs Made?

• Eggs and sperm are human gametes
• Females
• Ovaries produce eggs by meiosis and secrete
  estrogens
• Males
• Testes produce sperm by meiosis and secrete
  androgens

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Animation Meiosis and Sexual Reproduction (sperm
formation)
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2.2 Male Reproductive System

• Testes form in the abdominal cavity before birth
• Descend into the scrotum
• A duct system transports sperm out of the body
• Glands secrete fluids to maintain sperm viability
  and motility
• Organ of copulation is the penis

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Male Reproductive System
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Male reproductive system
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Sperm Production

• Sperm are produced by spermatogenesis in the
  seminiferous tubules
• Move to epididymis for storage
• Muscles move sperm to the vas deferens
• Then move sperm to the urethra and out

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Vasectomy

• Vas deferens is cut
• Sperm are absent

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Spermatogenesis

• Occurs in seminiferous tubules, begins at
  puberty, and continues throughout life
• Spermatogonia divide by mitosis
• Spermatocytes divide by meiosis to produce
  spermatids (23 chromosomes)
• Spermatids form mature sperm with tails

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Spermatogenesis
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Animation Spermatogenesis
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2.3 Female Reproductive System

• Ovaries produce eggs by oogenesis
• Fertilization occurs in fallopian tubes
• Fertilized egg or zygote moves into the uterus
• Outer uterine layer myometrium
• Inner uterine tissue endometrium
• Cervix opens into the vagina

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Female Reproductive System
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Female reproductive system
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Egg Production or Oogenesis (1)

• Occurs in the ovary
• Follicles consist of a developing egg surrounded
  by an outer layer cells
• Oogonia divide by meiosis during embryonic
  development and stop
• Oocytes remain arrested until ovulation

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Egg Production or Oogenesis (2)

• Meiosis is not completed until after
  fertilization
• Lifetime supply of developing eggs at birth
• Sperm and egg nuclei fuse to form a diploid zygote

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Oogenesis
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2.4 Infertility

• Requirements for a successful conception
• A healthy sperm and a healthy egg unite to form a
  zygote
• Place for fertilization to occur (a fallopian
  tube)
• Place for the fetus to grow (a uterus)

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Age and Infertility
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Causes of Infertility in Women
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Problems that Affect or Prevent Ovulation

• Hormone levels (most common cause of infertility)
• Absent or damaged ovaries
• Premature menopause

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Other Causes of Infertility in Females

• Secondary amenorrhea
• Fallopian tube blockage

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Causes of Infertility in Males

• Low sperm count
• Low sperm motility
• Impotence including erectile dysfunction
• Aspermia

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Other Factors Influence Fertility

• Personal habits
• Environmental factors
• Age associated with decreased fertility and
  increased risk of chromosomal abnormality
• Sexually transmitted diseases
• Social factors

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2.5 Assisted Reproductive Technologies (ART)

• Three of the most common
• Donation of gametes
• In vitro fertilization (IVF)
• Surrogacy

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Donation of Gametes

• Measure hormone levels and may treat with
  estrogen or testosterone
• If hormone treatments unsuccessful, gamete
  donation from a sperm and/or egg donor

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Sperm and Egg Donor Ads
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Sperm Donation

• Widely used for almost 50 years
• Known or unknown donors
• Frozen in liquid nitrogen
• Sperm banks offer sperm from qualified donors
• Web sites offer ability to choose the traits of
  the donors

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Artificial Insemination

• Sperm is placed into the womans uterus at
  ovulation
• Sperm donation or sperm from several ejaculations
  can be pooled and concentrated
• Sperm can be retrieved from the epididymis or the
  testis using microsurgery

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Egg Donation

• Egg donation is more difficult
• Retrieval is time-dependent and involves surgery
• Donor undergoes hormone treatment and laparoscopy
• Freezing is difficult, and eggs are used for IVF
  immediately after retrieval

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In Vitro Fertilization (IVF)
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Surrogacy

• Two types
• Egg donor surrogacy
• Gestational surrogacy
• Surrogate may be relative, friend, or paid
  stranger

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New Ways to Make Babies