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...

    Bryophytes
    Bryophytes

    Bryophytes (nonvascular plants) are a plant group characterized by lacking vascular tissues. They include the mosses, th..

    Homeostatic Mechanisms and Cellular Communication
    Homeostatic Mechanisms and Cellular Communication

    Homeostasis is the relatively stable conditions of the internal environment that result from compensatory regulatory res..

    Balanced Diet
    A Balanced Diet – Minerals and Proteins

    Proteins and minerals can be derived from various dietary sources. They are essential for the proper growth and developm..

    Disturbance on a still water
    Abiotic Factors – Water Conditions

    A still body of water may be disturbed by a variety of factors. One of them is wind. In fact, it is considered as the pr..

    Community Patterns

    Learn about community patterns and the ecological factors influencing these patterns. Revisit some of the ecosystems you..

    Nephrolepis exaltata
    Vascular Plants: Ferns and Relatives

    Ferns and their relatives are vascular plants, meaning they have xylem and phloem tissues. Because of the presence of va..

    Related Articles...

    No related articles found

    See all Related Topics