the protective fluid surrounding an embryo in mammals. 

the region where cells are mainly localized - the opposite pole is the vegetal pole, where the yolk is mainly localized.

one of the body axis running from the head of the organism down to the lower limbs.

an invertebrate without an internal skeleton, instead the organism is protected by an external case - an exoskeleton.

 a hole in the embryo which opens on to the primitive gut.

the early embryo simply consisting of a ball of cells.

a cell adhesion molecule.

 Cell adhesion molecules - molecules which allow cell-cell and cell-extra cellular matrix binding.

  the specialization of a cell’s fate into a certain pathway - e.g. neural, muscle etc.

 the dorsal or back of the organism. The dorsal-ventral axis is one of the body axis, others are the anterior (head) to posterior (feet) axis. 

non neuronal cells present in the nervous system, which support neurons and play important roles in signaling.

a secreted signaling molecule that can induces growth in receptive cells. 

see homologous.

two proteins in different species with very similar DNA sequences.

one of the body axis running from the midline of the body across to the outer side.

a cell type that can migrate through tissues and does not have regular tissue boundaries or cell-cell adhesion.

an imaginary line running down the middle of an organism.

a secreted signaling molecule which causes different effects on cells in a concentration-dependent way. 

a partially differentiated cell who will either differentiate into a neuron or glia cell.

a group of cells which secrete morphogens and induce cell fate throughout the embryo.

the process where, after Gastrulation, the three germ layers begin to create the major internal organs.

a non-differentiated cell which can develop into any cell in the adult body. 

a cell, which hasn’t fully transitioned into it’s final state.

cell division and growth - vital in the embryo as a single cell creates an entire organism.

groups of mesodermal cell distributed along either side of the neural tube. They form vertebrae amongst other things.

a DNA binding protein which increases transcription of certain genes.

 the pole at which mostly yolk is localized. See dorsal pole.

 the front side of the embryo - see dorsal.

nutrient-rich fluid attached to embryos who are not able to get nutrients from their mother via a sack. Found in amphibians, reptiles and birds.