B3: Aortic sac with emerging 3rd arch artery. Thyroid cords. Arches l- 4. 4th arch arteries.
B3: Rudimentary thyroid ventral to aortic sac (also seen in B2, ventral to the hypopharyngeal eminence).
Development of Respiratory
B1,B2: Pharynx. Crest in ventral floor of pharynx formed by fusion of 3rd pharyngeal arches = hypopharyngeal eminence (precursor of root of tongue). Rathke's pouch = rudimentary adenohypophysis.
B2: Optic cup with optic ventricle. Note unequal thickness of walls of optic cup (inner wall; sensory retina: outer wall; pigment epithelium). Lens pit. Note position of eye with respect to maxillary arch. Hyaloid vessels near ventral margin of optic cup.
The Carnegie stage 13/14 Pig Embryo is 6mm in size and approximately equal to day 42 Human Embryo. Use the serial images to identify internal features and relationships that exist within the embryo at this stage. Then compare these images with the external appearance of the embryo at this stage and the later internal features of the stage 22 embryo.
Note that the nomenclature "stage 13/14" is not an actual Carnegie stage but indicates that the embryo stage lies between or has features of both stage 13 and stage 14 embryos.
Levels shown on whole embryo are only approximate.
Note that not all embryo features are labelled.
Hint: clicking on each section image above will also step you through the whole embryo in sequence.