Anatomy of the Breasts
These photographs reveal how important
breast-feeding is to our children.
Despite the amount of attention the female breasts receive, it is interesting that there is so little information available on their anatomy and functionality. I had to search through several references to find one that went into any detail when addressing these topics. Surprisingly, books you would expect to cover these topics had little to offer. A book about breast-feeding contained little, and several books on breast cancer did not address these topics at all. This is perhaps because the female breasts have come to serve a purpose in American society other than what they are intended, which is, providing nourishment, emotional and physical contentment, and protection from disease for our children. Unfortunately, the most detailed reference appeared to be in a book discussing plastic surgery of the breast!
Each breast is made up of fifteen to twenty lobes of glandular tissue. The number of lobes is not related to the size of the breast. Each lobe is made up of thousands of tiny glands called alveoli or acini. These glands are connected together by a series of ducts, much like grapes on a vine. The alveoli (alveolus and acinus singular) produce milk and other substances during lactation. Each lobe feeds into a single lactiferous duct that travels out through the nipple. As a result there are fifteen to twenty passages through the nipple, resulting in just as many openings in the nipple. Behind the nipple the lactiferous ducts enlarge slightly to form small reservoirs called lactiferous sinuses. Each sinus is 2-4mm (0.08-0.16in) in diameter. Fatty and connective tissues surround the lobes of glandular tissue. The amount of fatty tissue is depended on many factors including age, percentage of body fat, and heredity. Cooper's ligaments connect the chest wall to the skin of the breast, giving the breast its shape and elasticity.
The nipple and areola are located near the center of each breast. They most often have a color and texture that is different from that of the surrounding skin. Their color varies from very pale pink to black, and darkens during pregnancy and lactation. Their texture can vary between very smooth to wrinkled and bumpy. The nipple usually projects outward from the surface of the breast. The areola is the like pigmented area surrounding the nipple. The size of both varies considerably from woman to woman, and some size variation is normal from breast to breast on the same women. The nipple and areola are composed of smooth muscle fibers and a dense network of nerve endings. The nipples become erect as the result of muscular contractions, not blood engorgement. Erect nipples are not by themselves an indication of sexual arousal. The nipples may become erect as a result of many forms of stimulation that are not sexual in nature, and a woman's nipples may not be erect when she is sexually aroused. The area of the areola is populated by several oil producing Montgomery's glands. These glands may form raised bumps and be sensitive to a woman's menstrual cycle. These glands act to protect and lubricate the nipple during lactation. Some nipples project inward or are flat with the surface of the breast. The later are referred to as inverted nipples and neither condition appears to negatively impact a woman's ability to breast-feed.
While pregnancy prepares the breasts for lactation it does not trigger the production of milk. During pregnancy the breasts usually become larger as the number and size of the alveoli glands increases, as a result of increased estrogen levels. It is not until an infant has been nursing for a couple days that actual milk production begins. For the first couple of days the breasts release colostrum, which is important to a baby's health. When a baby starts suckling on a woman's nipple the resulting physical stimulation causes nerve impulses to be sent to the hypothalamus gland in the brain, which in turn tells the pituitary gland, also located in the brain, to release two hormones called oxytocin and prolactin. Prolactin causes milk to be produced and oxytocin causes muscle fibers that surround the alveoli to constrict, as well as the muscles of the uterus. When the muscle fibers around the alveoli constrict causing milk to be secreted it is referred to as "let-down" and can result in intense sensations within the breasts and the squirting of milk from the nipples. The sound of a crying baby can also trigger let-down, indicating how milk production is influenced by psychological and environmental conditions as well as actual nursing. Between feedings some milk, foremilk, is stored in the alveoli and lactiferous sinuses but the majority of the milk, hindmilk, is produced on demand. The breasts do not store milk, but rather produce it based on demand. The greater the demand, the more they produce. The breasts should never be compared to milk bottles!
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