8.1 The Carnegie stages

Synoptic table of the Carnegie stages 20 - 23

Stage 20

Approx. 49th day

18 - 22 mm

1 2 3 4 5 6 7 8 9 10 Liver prominence Primordium of the eyelid Eye Auditory canal Elbow Fingers Toes being formed Straightening of the trunk Subcutaneous vessel network of the head Cervical flexure

Characteristic signs:Arms in pronation Separated fingers Gonadal gender determinable in female embryos

Stage 21

Approx. 51rst day

22 - 24 mm

1 2 3 4 5 6 7 8 9 Umbilical cord with physiologic hernia Nose Subcutaneous vessel network of the head Ear Elbow Pronation of the hands (pink arrow) Knee Supination of the feet (blue arrow) Toes

Characteristic signs:Subcutaneous vessel network of the head spreads out Hands and feet come closer and touch each other

Stage 22

Approx. 53rd day

23 - 28 mm

1 2 3 4 5 6 7 8 9 10 Umbilical cord with physiologic hernia Nose Subcutaneous vessel network of the head Ear Elbow Pronation of the hands Knee Supination of the feet Well-developed toes Remainder of the embryonic tail

Characteristic signs:Development of the eyelids and the external ear canal Tragus and antitragus Nasal septum Secondary palate

Stage 23

Approx. 56th day

27 - 31 mm

1 2 3 4 5 6 7 8 9 10 Umbilcal cord with hernia Nose Eye Eyelid Ear (a: tragus, b: antitragus ) Mouth Elbow Finger Toes Atrophied embryonic tail bud Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon Spinal cord

Characteristic signs:Angle between the head and trunk amounts to 30° The head makes 50% of the embryo's size The head is rounded, the extremities lengthened and stand out from the body Chin Nasal pit Development of the external genital primordium

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