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Allantois (plural allantoides or allantoises) is a part of a developing animal conceptus
Conceptus

Conceptus denotes the embryo and its adnexa or associated membranes The conceptus includes all structures that develop from the zygote, both embryonic and extraembryonic....
 (which consists of all embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
nic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste.

The allantois, along with the amnion
Amnion

The amnion is a membranous sac that surrounds and protects an embryo. It is developed in reptiles, birds, and mammals, which are hence called ?Amniote?; but not in amphibians and fish, which are consequently termed ?Anamniota?....
 and chorion
Chorion

The chorion is one of the membranes that exists during pregnancy between the developing fetus and mother. It develops from the syncytiotrophoblast and surrounds the embryo and other membranes....
 (other embryonic membranes), identify humans as amniote
Amniote

The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include the Synapsida and Sauropsida . Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes....
s, along with reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s, dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
s, bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s, and other mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s.

sac-like structure is primarily involved in nutrition
Nutrition

Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with good nutrition....
 and excretion
Excretion

Excretion is the process of eliminating waste products of metabolism and other non-useful materials. It is an essential process in all forms of life....
, and is webbed with blood vessel
Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
s.

The function of the allantois is to collect liquid waste from the embryo, as well as to exchange gases used by the embryo.

structure first evolved in reptiles and birds as a reservoir for nitrogenous waste, but also as a means for oxygenation of the embryo.

Oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 is absorbed by the allantois through the egg shell.






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Allantois (plural allantoides or allantoises) is a part of a developing animal conceptus
Conceptus

Conceptus denotes the embryo and its adnexa or associated membranes The conceptus includes all structures that develop from the zygote, both embryonic and extraembryonic....
 (which consists of all embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
nic and extra-embryonic tissues). It helps the embryo exchange gases and handle liquid waste.

The allantois, along with the amnion
Amnion

The amnion is a membranous sac that surrounds and protects an embryo. It is developed in reptiles, birds, and mammals, which are hence called ?Amniote?; but not in amphibians and fish, which are consequently termed ?Anamniota?....
 and chorion
Chorion

The chorion is one of the membranes that exists during pregnancy between the developing fetus and mother. It develops from the syncytiotrophoblast and surrounds the embryo and other membranes....
 (other embryonic membranes), identify humans as amniote
Amniote

The amniotes are a group of tetrapod vertebrates that have a terrestrially adapted egg. They include the Synapsida and Sauropsida . Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes....
s, along with reptile
Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s, dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
s, bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s, and other mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s.

Function

This sac-like structure is primarily involved in nutrition
Nutrition

Nutrition is the provision, to cells and organisms, of the materials necessary to support life. Many common health problems can be prevented or alleviated with good nutrition....
 and excretion
Excretion

Excretion is the process of eliminating waste products of metabolism and other non-useful materials. It is an essential process in all forms of life....
, and is webbed with blood vessel
Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
s.

The function of the allantois is to collect liquid waste from the embryo, as well as to exchange gases used by the embryo.

In reptiles, birds, and monotremes

The structure first evolved in reptiles and birds as a reservoir for nitrogenous waste, but also as a means for oxygenation of the embryo.

Oxygen
Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
 is absorbed by the allantois through the egg shell. The allantois functions similarly in monotremes, which are egg-laying mammals.

In most marsupials

In most marsupials, the allantois is avascular, having no blood vessels, but still serves the purpose of storing nitrogenous (N2) waste.

Also, most marsupial allantoises do not fuse with the chorion
Chorion

The chorion is one of the membranes that exists during pregnancy between the developing fetus and mother. It develops from the syncytiotrophoblast and surrounds the embryo and other membranes....
. An exception is the allantois of the bandicoot
Bandicoot

A bandicoot is any of about 20 species of small to medium-sized, terrestrial marsupial omnivores in the order Peramelemorphia. The word bandicoot is an anglicised form of the Telugu language word pandi-kokku, which originally referred to the unrelated Indian Bandicoot Rat....
, which has a vasculature, and fuses with the chorion.

In placental mammals (Eutheria)

In placental mammals, the allantois is part of and forms an axis for the development of the umbilical cord
Umbilical cord

In placental mammals, the umbilical cord is the connecting cord from the developing embryo or fetus to the placenta. During prenatal development, the umbilical cord comes from the same zygote as the fetus and normally contains two arteries and one vein , buried within Wharton's jelly....
.

  • The mouse
    Mouse

    A mouse is a small animal that belongs to one of numerous species of rodents. The best known mouse species is the House Mouse . It is also a popular pet....
     allantois consists of mesoderm
    Mesoderm

    One of the three germ layers found in the embryos of animals more complex than cnidarians, making them triploblastic. Mesoderm forms in the embryo during gastrulation when some of the cells migrating inward to form the endoderm, produce an additional layer that lies between the endoderm and the ectoderm....
    al tissue, which undergoes vasculogenesis to form the mature umbilical artery and vein.


  • The human
    Human

    A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
     allantois is an endoderm
    Endoderm

    Endoderm, is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron from the inner layer of the gastrula, which develops into the endoderm....
    al evagination of the developing hindgut
    Hindgut

    The hindgut is the posterior part of the alimentary canal. It includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon, rectum and upper part of the anal canal....
     which becomes surrounded by the mesodermal connecting stalk. The connecting stalk forms the umbilical vasculature. These endodermal and mesodermal tissues together form the human umbilical cord. The allantois later becomes the urachus
    Urachus

    The urachus is an embryological canal connecting the urinary bladder of the fetus with the allantois, a structure that contributes to the formation of the umbilical cord....
    , which removes nitrogenous waste from the fetal bladder.


Pathology

A patent allantois can result in urachal cyst
Urachal cyst

A urachal cyst is a Sinus remaining from the allantois during embryogenesis.See also* urachus* cystExternal links...
.

Etymology

The word comes from the Greek word for sausage
Sausage

A sausage is a prepared food, usually made from ground meat, animal fat, salt, and spices , typically packed in a casing . Sausage making is a traditional food preservation technique....
, which the allantois resembles.

Additional images


External links