A blastopore is an opening into the archenteron

Archenteron

The primitive gut that forms during gastrulation in the developing blastula is known as the archenteron. It develops into the digestive tract of an animal....

 during the embryonic

Embryonic

Embryonic received general acclaim from critics upon release, garnering a 81/100 critic score on Metacritic. The New Musical Express noted that "ten years after their last masterpiece, The Flaming Lips have finally produced another one," while Paste Magazine described the record as "a wonderfully...

 stages of an organism. The distinction between

Embryological origins of the mouth and anus

This article needs to be clarified and may contain errors.The embryological origin of the mouth and anus is an important characteristic, and forms the morphological basis for separating bilaterian animals into two natural groupings: the protostomes and deuterostomes.In animals at least as complex...

 protostome

Protostome

Protostomia are a clade of animals. Together with the deuterostomes and a few smaller phyla, they make up the Bilateria, mostly comprising animals with bilateral symmetry and three germ layers...

s and deuterostome

Deuterostome

Deuterostomes are a superphylum of animals. They are a subtaxon of the Bilateria branch of the subregnum Eumetazoa, and are opposed to the protostomes...

s is based on the direction in which the mouth (stoma) develops in relation to the blastopore. Protostome derives from the Greek word protostoma meaning "first mouth"(πρώτος + στόμα) whereas Deuterostome's etymology is "second mouth" from the words second and mouth (δεύτερος + στόμα).

The major distinctions between deuterostomes and protostomes are found in embryonic development:

• Mouth/anus
  • In protostome development, the first opening in development, the blastopore, becomes the animal's mouth
    Mouth
    The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
    
    .
  • In deuterostome development, the blastopore becomes the animal's anus
    Anus
    The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
    
    .

• Cleavage
  Cleavage (embryo)
  In embryology, cleavage is the division of cells in the early embryo. The zygotes of many species undergo rapid cell cycles with no significant growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a...
  
  
  • Protostomes have what is known as spiral cleavage which is determinate, this meaning that the fate of the cells is determined as they are formed.
  • Deuterostomes have what is known as radial cleavage that is indeterminate.