Human growth and development-Conception to Birth

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Conception

This is the very first stage of the making of a human baby which is known as conception. This is when the sex cell or (gamete) from the males sperm and a

gamete from the woman’s ovum or egg cell join to form the embryo. Conception can only occur during , which happens about the middle of the month between menstrual periods.

The human baby’s life begins as a single cell which is formed when the sperm and egg cell join and the egg becomes fertilised, creating life. The fertilised egg (zygote) divides into two and continues to do so rapidly, at this stage some cells form the embryo and some of the placenta. These cells now resemble a mulberry, are called morulla and take about 4 days to travel along the fallopian tube and into the uterus. This point it is called a blastocyst.

The blastocyst now gets attached to the uterus wall by tiny projections called villi. Once it attached to the uterus it connects to the blood stream, so it is able to absorb oxygen and essential nutrients for fast growth. Around 10 to 14 days after conception the baby is called an embryo.

After conception and the embryo is formed development of it begins into a full term foetus. The 3 stages of development are known as trimesters.

First trimester

  • ‘Week 3(embryonic stage) - first period missed.
  • Foundation of the brain and nervous system is laid down
  • Amnion sac is formed around the embryo, which floats in a liquid (the amniotic fluid).
  • The placenta is formed, which lies against the uterus wall and acts as the liver, lungs and kidneys for the embryo and the foetus. The placenta is connected to the embryo’s circulatory system by the umbilical cord. Nutrients pass through to the embryo and digestive waste products and CO2 pass from the baby to the mother.’(Btec national early years, Penny tassoni)

  • Week 4 – the neural tube closes( if this does not close spina bifida occurs)The embryo is around 6.4mm in length

  • Week 5 – the baby’s heart be can be detected and the embryo is now the same size as a small seed.

  • Week 8 – the embryo is about 8mm long, and has developed the startle reflex. The formation of the eyes, ears, organs and limb buds is at a rudimentary stage.
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  • Foetal stage (week 12) – the baby is now called a foetus and all its body parts have grown they just need to be refined. The foetus can swallow, roll, somersault and has also developed the sucking reflex. The foetus organs are functioning it measures about 7.5cm and has downy hair and fingernails.

Second trimester

  • Week 15 – the foetus hears its first sounds
  • Week 16- the genitals of the foetus have formed. From this stage the sex of the baby can be determined all though difficult. A greasy wax substance covers ...

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