Final answer:
The breast shell, or nipple shell, is an external feature of the breast involved in lactation. It consists of the nipple and areola, and functions as the opening for milk release during breastfeeding.
Step-by-step explanation:
The breast shell, also known as the nipple shell, is a part of the female reproductive system that is involved in lactation. It is an external feature of the breast, consisting of a nipple surrounded by a pigmented areola. The nipple is the opening through which milk is released when a baby sucks during breastfeeding. The areola has small areolar glands that secrete lubricating fluid to protect the nipple.