<P> The philtrum ( Latin : philtrum , Greek : φίλτρον philtron , lit . `` love charm '' ) , or medial cleft , is a vertical indentation in the middle area of the upper lip , common to many mammals , extending in humans from the nasal septum to the tubercle of the upper lip . Together with a glandular rhinarium and slit - like nostrils , it is believed to constitute the primitive condition for at least therian mammals . Monotremes lack a philtrum , though this could be due to the specialised , beak - like jaws in living species . </P>
<P> The philtrum ( Latin : philtrum , Greek : φίλτρον philtron , lit . `` love charm '' ) , or medial cleft , is a vertical indentation in the middle area of the upper lip , common to many mammals , extending in humans from the nasal septum to the tubercle of the upper lip . Together with a glandular rhinarium and slit - like nostrils , it is believed to constitute the primitive condition for at least therian mammals . Monotremes lack a philtrum , though this could be due to the specialised , beak - like jaws in living species . </P>
the vertical groove in the upper lip is the
the vertical groove in the upper lip is the
philtrum
philtrum