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...

    Selective Breeding
    Selective Breeding

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

    Structural depiction of catalase, an enzyme
    Protein Activity and Cellular Metabolism

    Proteins have a crucial role in various biological activities. Get to know how proteins are able to perform as enzymes, ..

    The process of photosynthesis
    Photosynthesis – Photolysis and Carbon Fixation

    Photosynthesis is the process that plants undertake to create organic materials from carbon dioxide and water, with the ..

    An artistic depiction of a human embryo
    Growth and Development of a Human Baby

    Upon fertilization, a zygote forms and develops into an embryo. This tutorial elaborates on the growth and development f..

    Psychiatry and mental disorders
    Psychiatry & Mental Disorders

    Different mental disorders are described here. Read this tutorial to get an overview of schizophrenia, affective mood di..

    Gibberellins and Gibberellic Acid
    Gibberellins and Gibberellic Acid

    This tutorial describes the role of gibberellin family in plants. Find out the effects of gibberellin on plant growth an..