The ribs and vertebrae are repeated structures, and somites have a similar repeated structure in the early embryo, with dozens of them forming in a typical mammal. They form in a head-to-tail ...

Those discs that form the spine originate in embryonic blueprint segments called somites. As the embryo body elongates in all vertebrate species, it is cut into somites by a "biological clock knife." ...

They also compared the snake embryo to a lizard, because, said Pourquié, “lizards are like snakes in that they develop very slowly, but they produce many fewer somites than snakes.” ...

Once the embryo has reached the 8-cell stage ... Stage 9: Twenty-five days after ovulation, the mesoderm condenses into somites that form on either side of the neural groove.

At an early stage in vertebrates' embryonic development somites form: these are primitive segments from which the spine, ribs, back muscles, cartilage, tendons and part of the skin develop.

Those discs that form the spine originate in embryonic blueprint segments called somites. As the embryo body elongates in all vertebrate species, it is cut into somites by a "biological clock knife." ...

Vertebrates have a pretty diverse array of body plans, and one of the reasons for this is some evolutionary flexibility in the length of their primary body axis, the one that runs from head to tail.

Adding just the right mixture of signaling molecules — proteins involved in development — to human stem cells can coax them to resemble somites, which are groups of cells that give rise to skeletal ...