les articles définis avec les characteristiques physiques

The definite article (le, la, l', les) is often used with parts of the body instead of a possessive determiner (mon, ma, mes , etc.). Sentences with this  structure always use the verb avoir  to  indicate  that the possessor is the subject of the sentence. 

The definite article is also always used when pronominal verbs (se brosser, se peigner…) refer to parts of the body. (English uses possessive adjectives like my, your, their).