Muscles of the pharyngeal arches
The pharyngeal arches and pouches arise in the ventro-lateral head region (stages 10-13) and are separated from one another by thoracic folds. In general 5, possibly 6 pharyngeal arches are engendered.
The mesenchyma stems from a central accumulation of paraxial mesoderm that comes from the four unsegmented occipital somitomeres. These are the uppermost somites that form post-otic. Later, material of the neural ridge and the epipharynx disk also gets into the pharyngeal arches. From this the skeletal portion as well as the musculature of the pharynx and the face derives. The innervation, though, still indicates the occipital origin of the mesenchyma in that the associated pharyngeal arches are innervated by nerves from the uppermost 4 occipital (post-otic) myotome, i.e., from brain nerves. In contrast to the innervation of the extremities, the nerves are already present before the formation of the muscles.
|Origin of the pharyngeal arch musculature|
|1st pharyngeal arches||Mm. masseter, temporalis, pterygoideus||Mandibular nerve from the trigeminals nerve
(HN V 3)
|2nd pharyngeal arches||Mimic musculature: Mm. Stylohyoideus, digastricus (venter posterior) and stapedius||Facial nerve
|3rd pharyngeal arches||M. stylopharyngeus||N. glossopharyngeus
|4th pharyngeal arches||Almost the entire pharynx and larynx musculature||N. vagus and accessorius
(HN X and XI)
|5th pharyngeal arches and cervical somites||M. sternocleidomastoideus and trapezius||N. accessorius