What is the Difference Between Amnion and Allantois?
🆚 Go to Comparative Table 🆚The amnion and allantois are two of the four fetal membranes that protect and nourish the developing embryo. They have distinct functions and structures:
Amnion:
- Thin, innermost layer that directly contacts the developing embryo.
- Forms a fluid-filled cavity that encloses the embryo.
- Does not contain blood vessels and obtains nutrients from nearby chorionic and amniotic fluid, and fetal surface vessels.
- Composed of cuboidal and columnar epithelial layers.
- Helps control embryonic body temperature and allows the fetus to move freely, aiding in skeletomuscular development.
Allantois:
- Extra-embryonic layer located between the amnion and chorion.
- Present in birds, reptiles, and mammals (except some marsupials) as a vascular structure.
- Expands greatly between the amnion and chorion to serve as a temporary respiratory organ for the fetus.
- Stores all the fetal excretions in its cavity and is filled with clear liquid.
- Composed of blood vessels that allow exchange of gases from the developing embryo.
- Eventually fuses with the chorion and umbilical cord and becomes a part of it.
- After birth, the allantois forms a unique structure called the urachus, which connects the bladder to the umbilical cord.
In summary, the amnion is the thin, innermost membrane that directly contacts the developing embryo and provides a protective environment, while the allantois is an extra-embryonic layer located between the amnion and chorion that helps with gas exchange and waste removal for the fetus.
Comparative Table: Amnion vs Allantois
Here is a table summarizing the differences between the amnion and allantois:
Feature | Amnion | Allantois |
---|---|---|
Location | Innermost layer, in direct contact with the developing embryo | Layer situated between the amnion and chorion |
Function | Forms a fluid-filled cavity that encloses the embryo | Helps with gas exchange and takes up nitrogenous waste of the fetus |
Structure | Thin, membranous layer | Sac-like structure, non-vascular |
Growth | Expands to form the amniotic sac | Ceases to grow once fused with the chorion and umbilical cord |
Blood Vessels | No blood vessels | Composed of blood vessels that allow exchange of gases from the developing embryo |
Fate | No specific post-birth fate mentioned | Fuses with the umbilical cord and becomes a part of it |
The amnion is a thin, membranous layer that forms a fluid-filled cavity enclosing the embryo, while the allantois is a sac-like structure located between the amnion and chorion that helps with gas exchange and nitrogenous waste disposal.
- Amnion vs Chorion
- Amniotes vs Anamniotes
- Discharge vs Amniotic Fluid
- Amniocentesis vs Cordocentesis
- Amniotic Fluid vs Urine
- Chorion vs Placenta
- Placenta vs Umbilical Cord
- NIPT vs Amniocentesis
- Blastula vs Gastrula
- Archenteron vs Blastocoel
- Morula vs Blastula
- Yolk Sac vs Gestational Sac
- Amniocentesis vs Chorionic Villus Sampling
- Blastocyst vs Embryo
- Mammals vs Amphibians
- Acrania vs Anencephaly
- Tetrapods vs Amphibians
- Embryo vs Fetus
- Umbilical Cord Stem Cells vs Embryonic Stem Cells