Definition of allantois in English:

allantois

noun

  • 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.

    • ‘Inside the egg are a series of fluid-filled membranes which permit the embryo to survive: the amnion, allantois, yolk sac, and chorion.’
    • ‘In the fetus, the urachus connects the bladder with the allantois.’
    • ‘The urachus is a remnant of allantoic origin, connecting the embryonal cloaca to the allantois during early intrauterine life.’
    • ‘Initially, the bladder is continuous with the allantois.’
    • ‘The allantois is a structure that collects the waste that the embryo produces before it hatches.’

Origin

Mid 17th century: modern Latin, based on Greek allantoeidēs sausage-shaped.

Pronunciation:

allantois

/əˈlantəʊɪs/