Al-7: Midbrain and hindbrain. The isthmus can be observed on A3-4 as a constriction between the mid- and hind-brain. The hindbrain is already subdivided into two parts, the slim myelencephalon and the wider metencephalon. The boundary between these two parts is roughly at the level of the otic vesicles A3-4. identify the optic cup and stalk, which are derived from the forebrain B2-6. Caudally one can identify the spinal cord along the entire length of the embryo.
A3: Otocyst; surrounding mesenchyme = otic capsule. Note proximity of otocyst to wall of rhombencephalon. Superior glossopharyngealganglion. Vestibulo-cochlear-facial ganglion complex (R). Trigeminal ganglion.
A2,A3: Otocyst, otic capsule, rhombencephalon and rhombomeres.
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.