Fertilisation

• Functions of the Placenta


  • It allows the diffusion of oxygen, dissolved food substances and antibodies from the maternal blood to the fetal blood to occur.

  • It allows the diffusion of metabolic waste products from the fetal blood to the maternal blood to occur.

  • It produces oestrogen and progesterone.

  
• Umbilical Cord


  • carries fetal blood to and from the placenta

  • Two umbilical arteries carry carbon dioxide and metabolic waste products away from the fetus.

  • One umbilical vein carries oxygen and food to the fetus

  • two umbilical arteries and one umbilical vein

  
• Functions of the Amniotic Fluid


  • It cushions and protects the fetus.

  • It allows the fetus to move about a little.

  • It lubricates the birth canal during childbirth.

  
• Why Is the Fetal Blood System Not Continuous with the Maternal Blood System? 


  • Mother’s blood pressure is much higher than the fetus’.

  • The blood group of the mother and fetus may be different, if continuous agglutination can occur

  • Pathogens and toxins do not enter directly into the fetus’ bloodstream.
• Toxins that can diffuse from maternal blood to fetal blood


  • alcohol
  • drugs
  • nicotine
  • caffeine
• Delayed Umbilical Cord Clamping


  • Attached placenta can cause infections
• Sexual Intercourse


  • When a male becomes sexually stimulated, blood is pumped into the penis faster than it can return to the bloodstream
  • the penis becomes stiff and and erect to allow it to enter the vagina of a female
  • semen containing sperm is ejaculated into the vagina, along a liquid made by the prostrate gland
  • the sperm swim up the oviducts
• Fertilisation

  • the process by which the nucleus of the male gamete fuses with the nucleus of the female gamete to produce a zygote

  1. only one sperm nucleus enters the egg. the sperm nucleus and egg nucleus fuse and a fertilized egg (zygote) is formed
  2. the remaining sperm which do not fertilise the egg eventually die
• Embryo Development - Implantation (1)

  1. The cilia lining the inner surface of the oviduct sweep the fertilized egg along the oviduct. Peristalsis movements in the wall of the oviduct also help move the zygote to the uterus
  2. the zygote divides by mitosis to form a ball of cells, forming the embryo. The embryo travels down the fallopian tube. The energy needed for cell division is provided by nutrients stored in the egg
  3. the embryo is embedded in the uterine lining, usually occurs seven days after fertilisation

  
• Embryo Development - Placenta (2)

  1. soon after implantation, villi which contain the blood capillaries of the embryo begin to grow from the embryo into the uterine lining
  2. the villi and the uterine lining make up the placenta
  3. the umbilical cord attaches the embryo to the placenta

  
• Embryo Development - Amniotic Sac (3)

  1. The amniotic sac begins to develop at the same time as the placenta
  2. the amniotic sac encloses the embryo in the amniotic cavity (amniotic fluid filled space)
  3. the embryo continues to develop, about 10 to 12 weeks after fertilisation, the major organs are formed. Embryo becomes fetus