restriction. n. 1. something that restricts; a restrictive measure, law, etc. 2. the act of restricting or the state of being restricted. 3. (Logic) logic maths a condition that imposes a constraint on the possible values of a variable or on the domain of arguments of a function.
The primitive gut that forms during gastrulation in the developing embryo is known as the archenteron or the digestive tube.It develops into the digestive tract of an animal.ach is controlled by the dorsal blastopore, and primitive node (also known as Hensen's node), respectively. During Gastrulation, the Archenteron develops into the digestive tube, with the blastopore developing into either the mouth (Protostome) or the anus (Deuterostome).
In some primitive species, the slits are used to filter food out of the water. In other species, like fish, the pharyngeal slits have gills. In other species, like mammals, the pharyngeal slits are only present during the embryonic stage. Chordates also have a dorsal nerve cord that runs down the length of the organism.The dorsal nerve cord has pairs of nerves that connect to the organism's muscles. In some organisms, the dorsal nerve cord expands into a brain at the top. All chordates have a post-anal tail.A post-anal tail is an extension of the body that runs past the anal opening.n some primitive species, the slits are used to filter food out of the water. In other species, like fish, the pharyngeal slits have gills. In other species, like mammals, the pharyngeal slits are only present during the embryonic stage. Chordates also have a dorsal nerve cord that runs down the length of the organism.