Related Experiment Video
Updated: Jun 3, 2026

Dissection and Explant Culture of Murine Allantois for the In Vitro Analysis of Allantoic Attachment
Published on: January 13, 2018
Evolution and development of fetal membranes and placentation in amniote vertebrates
1Department of Research, Museum für Naturkunde Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University Berlin, Berlin, Germany. kirsten.ferner@mfn-berlin.de
Abstract:
We review aspects of fetal membrane evolution and patterns of placentation within amniotes, the most successful land vertebrates. Special reference is given to embryonic gas supply. The evolution of fetal membranes is a prerequisite for reproduction independent from aquatic environments. Starting from a basically similar repertoire of fetal membranes - the amnion, chorion, allantois and yolk sac, which form the cleidoic egg - different structural solutions for embryonic development have evolved. In oviparous amniotes the chorioallantoic membrane is the major site for the exchange of respiratory gases between fetus and outer environment. The richly vascularised yolk sac and allantois in concert with the chorion play an important role in the evolution of placentation in various viviparous amniotes. Highly complex placentas have evolved independently among squamate sauropsids and in marsupial and placental mammals. In conclusion, there seems to be a natural force to improve gas exchange processes in intrauterine environments by reducing the barrier between the blood systems and optimising the exchange areas.
Related Concept Videos
Development of Blood Vessels
The initial formation of this system is facilitated by the small amount of yolk present in the ovum and yolk sac. Blood vessels originate from...
Fetal Circulation
Two umbilical arteries transport blood from the fetus to the placenta. At the placenta, the blood absorbs oxygen and nutrients while simultaneously eliminating waste products. This oxygen-enriched and nutrient-rich blood then returns to the fetus through one...
Development of the Sexual Organs in the Embryo and Fetus
Near the gonadal ridges, two duct systems are present: the mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts). These ducts form the basis for the male...
Cleavage and Blastulation
Development of the Heart
As the embryo undergoes lateral folding, these paired tubes approach each other, merging into a single primitive heart tube by...
Embryonic Connective Tissues
The mesenchyme is the first connective tissue that emerges in the developing embryo. It consists of loosely arranged multipotent mesenchymal cells and reticular fibers in the extracellular matrix. This loose arrangement allows easy migration of cells, which is essential for germ layer positioning, patterning, and organ morphogenesis during embryonic development. Mesenchyme is...

