allantois

 
Pronunciation: /əˈlantəʊɪs/

noun (plural allantoides /-ɪdiːz/)

  • the fetal membrane lying below the chorion in many vertebrates, formed as an outgrowth of the embryo’s gut. In birds and reptiles it grows to surround the embryo; in eutherian mammals it forms part of the placenta.

Derivatives

allantoic

Pronunciation: /alənˈtəʊɪk/
adjective

allantoid

Pronunciation: /əˈlantɔɪd/
adjective

Origin:

mid 17th century: modern Latin, based on Greek allantoeidēs 'sausage-shaped'