External: the rostral neuropore is in the process of closing; the optic invagination is shallow or still widely open; pharyngeal arches 1 and 2 are evident.

Internal: the sinus venosus develops; the oropharyngeal membrane ruptures; the mesonephric duct and nephric tubules appear; the optic vesicle and optic pit develop.

• Length: 2.5 - 4.5mm
• The anterior neoropore is in the process of closing
• The optic invagination is either shallow or still widely open.
• The embryo has two bronchial bars ( mandibular and hyoid)
• Ovulation age: 23 - 26 days

Question: What are the names of the two bronchial bars?

Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.  Published by Carnegie Institution of Washington, Publication 637. 1987. Stage 11 (PDF)

Stage 10

Stage 12 Stage 11 Internal