[Comparative ultrasonographic and histomorphologic examination of the lips]. 
High-resolution ultrasonography of the lips offers the opportunity to investigate the orbicularis oris muscle (OOM) and evaluate its morphology and function.  The goals of this paper are verification of the lip structures visible on ultrasound images by using histological section preparations and recommendation of uniform standards for sonographic examinations of the lips.  The lips of 78 healthy volunteers (age 4-77 years) where scanned with a Hitachi Hi Vision Avius ultrasound device equipped with a linear transducer (L75, variable frequency range 5.0-18.0 MHz).  Systematic B-mode examination was performed at five defined points, and the lips where also scanned dynamically in multiple directions.  The ultrasonography findings were verified by using histologic samples from five male body donors (age 72-83 years).  All parts of the OOM could be well distinguished from one another both histologically and ultrasonographically.  Sonographically visible lip structures could be verified histologically.  Labial glands and blood vessels of the mucosa could be identified with both methods.  Ultrasonography allows identification of lip structures and all parts of the OOM.  Scars, injuries and atrophy of the lip musculature are well detectable.  Functional examinations can visualize muscular dysfunctions and may support the diagnosis of dystonic or hypotonic functional deficits.  The following parameters are mandatory for a standardized examination of the lips: sagittal and transverse images of upper and lower lips; use of anatomical "landmarks"; functional diagnostics in tensed and relaxed conditions.