Complex sentence: The ear canal stretches for a distance of about 1 inch (2.5 cm), and consists of an initial part surrounded by cartilage which changes to being surrounded by bone as it meets the eardrum.
Split into simpler sentences: The ear canal stretches for a distance of about 1 inch (2.5 cm). The first part of it is surrounded by cartilage which changes to being surrounded by bone as it meets the eardrum.