Swallowing is the reflex in the human body that makes something pass from the mouth, through the esophagus, and to the stomach. If this fails and the object goes through the trachea, then choking occurs.
... would be "I pervade all this universe...".
"mat-sthaani" in the second line is a compound
of "mat" (me) and "stha" (standing, staying at) and
means "they are in ...