Dictionary > Allantois

Allantois

Definition
noun, plural: allantoises or allantoides
An embryonic diverticulum of the hindgut of reptiles, birds, and mammals; in man its blood vessels give rise to those of the umbilical cord
Supplement
Allantois is one of the extraembryonic membranes essential during embryonic and fetal development of birds, reptiles, and certain mammals . It is sac-like or diverticulum from the ventral wall of the hindgut. It forms a part of conceptus (i.e. the embryo and its appendages or adjunct parts or associated membranes) of amniotes. The allantois helps in gas exchange and movement of liquid waste.
Amniotes are characterized by forming extraembryonic membranes during the development of embryo. Apart from allantois, the other membranes are chorion, amnion, and umbilical vesicle. In humans, the allantois becomes the urachus, i.e. a fibrous cord. In other mammals, it is associated with the formation of the umbilical cord and the placenta. In birds and reptiles, the allantois is located beneath the shell and is involved in respiration.1
Word origin: Greek allantoeidḗs (“sausage-shaped”)
Synonym(s):

  • allantoid (membrane)
  • allantoic sac

See also:

  • amnion
  • chorion
  • embryo
  • embryo
  • fetus
  • foetal membranes
  • Reference(s):

    1 allantois. (n.d.) Farlex Partner Medical Dictionary. (2012). Retrieved from ://medical-dictionary.thefreedictionary.com/allantois.


    You will also like...

    Early Earth
    The Origins of Life

    This tutorial digs into the past to investigate the origins of life. The section is split into geological periods in the..

    Still Water Community Plants
    Still Water Community Plants

    This tutorial looks at the adaptations of freshwater plants for them to thrive in still water habitats. Familiarize your..

    Biological Cell schematic diagram
    Biological Cell Introduction

    It only takes one biological cell to create an organism. A single cell is able to keep itself functional through its 'mi..

    Human gastrointestinal tract
    Human Biology – Food and Digestion

    This tutorial recognizes the importance of food as a source of energy that will fuel many biological processes. A good d..

    Selective Breeding
    Selective Breeding

    Gregor Mendel's studies into Monohybrid and Dihybrid crossing and Charles Darwin's study of evolution and natural select..

    New Zealand - Biodiversity fauna
    New Zealand’s Biodiversity

    Find out more about New Zealand's unique biodiversity by exploring a range of different ecosystems and the key role of s..