Types of placenta

• Types of placenta based on gross shape and contact points

  • Diffuse - Almost the entire surface of the allanto-chorion is involved in formation of the placenta (Horses and pigs)
  • Cotyledonary - Multiple, discrete areas of attachment are formed by interaction of patches of allanto-chorion with endometrium (Ruminants)
  • Zonary - The placenta takes the form of a complete or incomplete band of tissue surrounding the foetus (Carnivores - dogs, cats, seals, bears)
  • Discoid - A single, disc-shaped placenta is formed (Primates and rodents)
• Types of placenta based on layers between foetal and maternal blood

  • Epitheliochorial: Swine, equine, cattle
  • Synepitheliochorial: Sheep and goats
  • Endotheliochorial: Carnivores
  • Hemochorial: Primates and rodents