Fig. 1. Embryo, crown-rump length 9 mm. Limb primordia are taken for examination. The cervical flexure is ratherr distinctly marked. Thee head is lokated at a right angle to the trunk. The face is closely adjacent to the cardiohepatic prominence. Division of anteriorr brain vesicle into two vesicle of hemispheres is indicated. The mesencephalon anf diencephalon shown the appearence of an abruptly arched tube. The large cavity of hind-brain is closed by a transparent dorsal wall. In optic primordia a smoll lens lying at the entrance to the optic cup is seen. Pigment is almost absent and therefore the eyes are faintly seen/ Branchial arches and hyoid arch a smoll otic vesicle is seen. Primitive segments are distinctly manifested.
1 - telencephalon, 2 - diencephalon, 3 - mesencephalon, 4 - metencephalon, 5 - myelencephalon, 6 - stomodeum, 7 - spinal cord, 8 - oesophagus, 9 - trachea, 10 - stomach, 11 - primitive kidney, 12 - primordium of definitive kidney, 13 - liver, 14 - heart, 15 - Rathke's pouch
Вторая бранхиальная дуга увеличивается и нависает над третьей и четвертой дугой . В результате формирутеся эктодермальное углубление или карман, известный как шейный синус (cervical sinus) (Рис.3.Б).
По Theiler's (1989)17 стадия развития. 10,5-й день