Complex sentence: The terminal lactiferous ducts drain the milk from TDLUs into 4--18 lactiferous ducts, which drain to the nipple; the milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman.
Split into simpler sentences: The terminal lactiferous ducts drain the milk from TDLUs into 4--18 lactiferous ducts, which drain to the nipple. The milk-glands-to-fat ratio is 2:1 in a lactating woman, and 1:1 in a non-lactating woman.