In the course of the sixth week, close to each of the first two pharyngeal arches, three auricular hillocks develop 15. They delimit the external auditory canal 17.
The mesonephrogenic prominence 16 forms and indicates the location of the future uro-genital system.
During the sixth week a small intestinal loop invades the extraembryonic coelom and into the proximal section of the umbilical cord, because the abdominal cavity is still too small to contain all of it. A physiologic umbilical hernia (stage 16) occurs. This is a normal phenomenon that is due to the rapid growth of the intestines.
The cranial 17 and spinal ganglia arise from neural crest cells 9 .
The cerebral vesicle 14 bends forwards and downwards. The rostral pole of the embryo rests on the cardiac prominence.
The liver makes its appearance between the pericardium region and the umbilical cord as the liver prominence.