Complex sentence: Blood is supplied to the skin by two networks of blood vessels, the deep network that lies between the dermis and the subcutaneous tissue, and the shallow network that lies within the papillary layer of the dermis.
Split into simpler sentences: Blood is supplied to the skin mainly by two networks of blood vessels. The deep network lies between the dermis and the subcutaneous tissue, while the shallow network lies within the papillary layer of the dermis.