The Biology of Reproduction and Development

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The Biology of Reproduction and Development
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Sexual Reproduction

• Sexual Reproduction is the production of
  specialized cells and the fusion (joining
  together) of their nuclei to produce a fertilized
  egg cell.
• Involves 2 parents
• Offspring is not identical to the parents
• Fusion of Nuclei in the egg cells

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Key Ideas of Reproduction

• The human reproductive process begins with the
  production of reproductive cells called gametes
  at the age of puberty.
• The female gametes are the eggs (ovum) and the
  male gametes are called sperm.
• Gametogenesis is the process in which gametes are
  produces.
• This process occurs in a specialized organs
  called the gonads.

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Human Female Reproduction

• The female gonads are the ovaries, and the gamete
  produced is the ovum (egg).
• The ovum is larger than the sperm and contains
  stored nutrients in the form of yolk.

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Female Reproductive System
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Vital Female Reproductive Organs

• Ovaries the gonad within which the ovum and the
  sex hormones are produced
• Oviduct (Fallopian tube) funnel shaped tube
  which transports ova from the ovary to the uterus
• Uterus muscular organ found in females within
  which the fetus develops
• Vagina muscular tube which connects the uterus
  to the outside of the female body through which
  the fetus is born

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Human Male Reproduction

• The male gonads are the testes, and the gamete
  produced is sperm.
• The testes are held in a sac called the scrotum.

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Male Reproductive System
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Vital Male Reproductive Organs

• Testes male gonad within which produces sperm
  and testosterone
• Scrotum sac of skin, below male genital organ,
  containing two testes
• Urethra tube carrying sperm from the testes to
  outside of the body
• Penis the male external genital organ
  containing the urethra through which both urine
  and sperm leave the body

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Sperm meets egg

• During sexual intercourse the penis transfers
  sperm into the vagina.
• After sexual intercourse, the sperm cells swim
  through the female reproductive tract and enter
  the oviducts.
• If they meet with an egg in the oviduct, the egg
  and sperm cell may fuse.

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Fertilization

• The fusion of sperm cell nucleus and an egg cell
  nucleus is known as fertilization. This process
  takes place in the oviduct.
• The fertilized egg is know referred to as a
  zygote.
• The appropriate number of chromosomes has also
  been restored.

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Implantation

• The zygote passes down the oviduct and enters
  into the uterus.
• Continuous cell divisions result in the formation
  of a hollow ball of cells called a blastocyst.
• The zygote obtains nutrients from fluids secreted
  by the mother.
• On the sixth day, the zygote/ball of cells
  implants in the uterine wall.

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Embryonic development

• The zygote undergoes a series of rapid mitotic
  cell divisions called cleavage.
• The process begins by the zygote dividing into
  two identical cells, followed by four, then
  eight, ect.
• Three cell layers are formed and are called
  primary germ layers.
• This begin the process of forming all the
  tissues, organs and systems in an animal and is
  known as differentiation.

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Internal Development

• The growth of the embryo continues in the body of
  the parent which provide nutrition and
  protection.
• This development occurs within the uterus.
• The placenta, is formed from embryonic and
  maternal tissues.
• Through this structure the exchange of nutrients,
  wastes, and respiratory gases between the mother
  and embryo occurs.

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Human Reproductive Process

• The developing embryonic membranes become part of
  the placenta and umbilical cord.
• After eight weeks of development the embryo is
  called the fetus.
• The period of time between fertilization and
  birth is called gestation.
• Gestation in humans usually lasts nine months or
  approximately 266 days.

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Prenatal Development

• The period before birth is referred to as
  prenatal development of pregnancy.
• During this time, it is essential that the
  expectant mother provide food prenatal care for
  herself and the fetus.
• The mother should eat nutritious foods, avoid
  alcohol, tobacco and drugs, and receive proper
  medical attention regularly.
• Good prenatal care is important in the production
  of a healthy baby.
• Using tobacco, alcohol and drugs is thought to
  cause Low Birth Weight Syndrome and Fetal Alcohol
  Syndrome as well as other birth defects.