Fertilisation

• Ovum


  Egg cell
• Ovum


  • Contains zona pellucida (protective coating)
  • Contains haploid nucleus
  • Contains cortical granules
  • Surrounded by follicle cells
• Sperm

  • Contains many mitochondria
  • Contains acrosomes (digestive enzymes)
  • Has a flagellum
• Fertilisation

  1. Acrosome reaction occurs

  2. Sperm head fuses with egg cell membrane

  3. Cortical reaction occurs

  4. Nuclei fuse to form diploid zygote
• Sperm cell


  The male gamete which contains a long tail, an acrosome and lots of mitochondria and is specialised to fertilise an egg cell
• Acrosome


  An organelle found in the head of sperm cells which is specialised to digest the outer coating of an egg cell during fertilisation
• Zona pellucida


  The tough outer layer of the egg cell which is composed of glycoproteins and is used to prevent multiple sperm cells from fertilising the egg
• Number of chromosomes in a gamete


  23
• Acrosome Reaction

  Acrosome membrane fuses with the front of the sperm cell

  Digestive enzymes from the acrosome are released

  Digestive enzymes begin to digest the zona pellucida
• Cortical Reaction


  Vesicles in the egg cell release cortical granules between the zona pellucida and the cell membrane

  The zona pellucida thickens and becomes impenetrable to other sperm