Semantics

Кирпич упал ей прямо на ступню. The brick fell right on her foot.
This entry is concerned with the use of the word ступня to refer to human foot. This word does not refer to animals. For the difference between ступня1 and нога see Lexical Relationships: Synonyms. The word ступня is also used to refer to the sole of a foot. This meaning is described in a separate entry.