fertilisation

• Fertilisation


  The fusion of a sperm cell nucleus with an egg cell nucleus to form a diploid zygote
• Copulation


  1. Sexual intercourse

  2. Sperm travels through female reproductive tract
• Sperm can live and fertilise an egg for up to 5 days after being released into the female body
• The egg remains fertile for 12–24 hours
• Fertile period


  The time during the menstrual cycle when an egg is fertilised
• Infertility


  The inability to produce gametes or to conceive
• Causes of infertility


  • Inability to produce enough healthy sperm
  • Blocked fallopian tubes
  • Inability to produce eggs
• In vitro fertilisation (IVF)

  The fusion of an egg and a sperm outside the body
• IVF technique


  1. Monitoring follicles by ultrasound

  2. Removing eggs before ovulation

  3. Mixing eggs and sperm in a dish

  4. Transferring embryos to uterus
• Implantation


  When the embryo embeds into the endometrium
• In humans, pregnancy lasts for 38 weeks
• Placenta


  A disc-shaped structure formed from tissue of the mother and the embryo that has functions of exchange, barrier, and endocrine gland
• Morula


  A solid ball of cells
• Blastocyst


  A fluid-filled ball of cells
• Germ layer


  A group of cells in the embryo that give rise to the body organs
• Stages of labour


  1. First stage (6-18 hours)

  2. Second stage (20-60 minutes)

  3. Third stage (5-15 minutes)
• Just before labour begins

  Levels of progesterone and oestrogen drop, allowing the uterus to contract
• Lactation


  The production of milk
• Breast milk is the perfect food for a human baby
• Methods of contraception


  • Natural (e.g. rhythm method)
  • Mechanical (e.g. IUD, diaphragm, condom)
  • Chemical (e.g. the Pill)
  • Surgical sterilisation (female, male)