The sartorius is your longest muscle. It runs from your pelvis to your knee. It helps you cross your legs. It gets its name from the Latin word sartor meaning "tailor". In olden times, tailors often sat cross-legged to sew. The muscle with the longest name is the levator labii superioris alaeque nasi. It curls your lip. of even finer threads, called myofibrils. Muscles also contain tiny nerves and blood vessels. Covering them is a stretchy "skin", called the epimysium.