Inheritance and Selection

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Inheritance and Selection

• Human Reproduction

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Lesson Aims

• To ensure all students know the structure and
  function of the human sex organs.
• To understand the process of human fertilisation
• To be aware of the sequence of events in the
  development of a human foetus
• To understand the structure and function of the
  placenta.

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Human sex organs

• Answer all questions on the sheet you are given.
• Stick the sheet in your exercise books.

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Fertilsation
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Fertilisation

• Ejaculation produces about 5 ml of semen which
  contains 450 million sperm.

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Fertilisation

• Although thousands of sperm may reach an egg,
  only one enters it.

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Fertilisation

• To be successful the sperm must meet the egg in
  the Fallopian tube.

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Fertilisation

• The tail of the sperm remains outside as the head
  travels through the egg cytoplasm to the nucleus.

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Fertilisation

• Fertilisation occurs when the sperm nucleus fuses
  with the egg nucleus to form a zygote. This is
  the moment of conception.

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Diary of human development

• Week 0
• Egg is fertilised in the fallopian tube.

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Diary of human development

• Week 1
• Embryo becomes attached to the lining of the
  uterus (womb).

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Diary of human development

• Week 2
• Foetus eyes begin to develop. Its legs and arms
  are tiny bumps.

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Diary of human development

• Week 6
• Foetus begins to look like a human. Ears, hands
  and feet begin to grow. Heart begins to beat.

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Diary of human development

• Week 10
• Foetus fingers and toes grow. It can move its
  arms and legs a little it can swallow and frown.

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Diary of human development

• Week 14
• It is possible to determine the foetuss sex.

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Diary of human development

• Week 18
• Foetus has hair, eyebrows. Doctors can hear the
  heartbeat. Mother begins to feel its kicks.

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Diary of human development

• Week 26
• Foetus opens its eyes.

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Diary of human development

• Week 30
• If born now, the baby could live with special
  care.

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Diary of human development

• Week 34
• Baby has grown a lot of fat in the last 4 weeks,
  to keep it warm when it is born.

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Diary of human development

• Week 38
• Baby is born.

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The Placenta

• Stick the diagram of the placenta in your books

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The placenta

• The zygote divides as it passes to the uterus and
  becomes and embryo.
• The embryo implants in the thick lining of the
  uterus.

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The placenta

• Finger like extensions called villi project from
  the embryo into the lining of the uterus
  eventually forming the placenta.

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The placenta

• The embryo develops into a foetus attached to the
  placenta by the umbilical cord.

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The placenta

• An artery and a vein run through the umbilical
  cord and connect the foetus blood system to the
  placenta.

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The placenta

• The foetus blood system IS NOT DIRECTLY CONNECTED
  to the blood system of the mother.

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The placenta

• The exchange of oxygen, food and wastes between
  the mother and foetus depends on diffusion across
  the thin wall of the placenta.

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The placenta

• Harmful substances such as nicotine, alcohol,
  drugs and virus can also pass across the placenta
  from the mother to the foetus.

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The placenta

• The _______ grows from the _______
• The foetus is connected to the placenta by the
  __________ _________ .
• In the cord there is an _______ and a _____
  coming from the foetus.
• The placenta brings the _______ of the foetus
  very ________ to the blood of the _______ but the
  different ___________ do not mix.

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The placenta

• ___ and ____ pass from the mothers ______ into
  the foetus. _____ , ______ and other _______
  substances pass from the _____ into the _______
  blood.
• Harmful substances such as _______, ______,
  ________ products and _____ can also pass into
  the foetus through the _________ from the mother.