what is pharyngeal gill slits?? please explain
tell their structure in vertebrates

Pharyngeal gill slits refer to paired openings that leads from the pharynx (lateral sides) to the exterior. They are involved in the respiration (in aquatic vertebrates) and suspension feeding (in invertebrate chordates). They are also found in the embryos of tetrapods.

The structure of the pharyngeal gill slits in vertebrates is shown in the following image: