A Mechanistic Model of Gastrulation in the Chick Embryo
As Lewis Wolpert once remarked, "It is not birth, marriage, or death, but gastrulation which is truly the most important time in your life." Gastrulation is a process during which germ layers are formed in an embryo and results in the body plan of adult organisms. Large scale movements during gastrulation are responsible for cells that start out in very simple form to create some complexity. When gastrulation is kicked off, there is massive cell movement and reorganisation that causes the formation of the germ layers starting with the formation of the Primitive Streak and displacement of cells in all directions in symmetrical circular motions called Polonaise Movements . The Primitive Streak is also the point where an axes of growth is introduced and it causes the embryo to become bilaterally symmetrical. Since the embryo goes so quickly from being a plain single layer disc of cells to the stage of the primitive streak and subsequent three layers, it has been difficult to establish what the trigger for these movements is and what causes these particular structures to be formed. This dissertation discusses whether a simple force directed mechanism with some additional directional elements can explain the observed dynamics of the chicken embryo.