A histological study of the philtrum.

This is a detailed histological study of the philtrum of the upper lip. The aims of the study are to explain the unique configuration of the philtrum and to offer a new definition to it. The materials for the study are taken from human foetuses, operative specimens and cadavers. The upper lip is sectioned transversely and stained to show muscle, connective tissue and elastic fibres. The histological results show that there is no specific condensation of connective tissue in the midline to account for the central philtral groove. The significant histological finding is the pattern of insertion of the orbicularis oris muscle into the skin of the philtral area. The muscle fibres decussate in the midline and vertical as well as oblique muscle fibre extensions insert into the dermis in the region of the midline philtral groove and the philtral ridges. A dynamic role is postulated of the role of orbicularis oris muscle in giving rise to the unique configuration of the philtrum. It is redefined in the light of our present knowledge of the histological basis of the philtral morphology.