Yolk sac placenta

The yolk sac placenta is an organ that is formed in many vertebrates during embryonic development and that supplies nutrients to the developing embryos in the uterus . The yolk sac placenta is formed from the yolk sac of the embryos and the uterine lining , whereby there are different types in terms of their shape and development (complete, circular, discoidal, row-shaped).

Live birthing sharks , reptiles and mammals usually also form placentas , which in the course of further embryonic development more or less ensure complete nutrition via the maternal bloodstream. In some mammals (e.g. horses , dogs , cats ), however, a real yolk sac placenta also temporarily forms.

literature

• Leonard Compagno , Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press , Princeton / Oxford 2005, ISBN 978-0-691-12072-0 , p. 335.
• Bertram Schnorr, Monika Kressin: Embryology of Pets. 5th edition, Enke, 2006, ISBN 3-8304-1061-1 .