Lactation 101
Biologists believe the evolutionary origins of lactation may go back some 200 million years. And although mammals are named for the glands that are central to lactation, the physiology of lactation involves the entire body, including the digestive, neurological, and endocrine systems.

“The mammary gland is made up of a variety of cells,” explains Sharon Donovan, “including fat, blood vessels, lymph vessels, ligaments, and nerves. Most of the mammary gland size is related to the amount of fat in the breast. What you have embedded within the fat are basically the milk-synthesizing units,” says Donovan, who adds, “The perception that small-breasted women can’t make enough milk is not true; breast size has very little to do with the amount of milk produced.”

In terms of architecture, each breast is made of multiple lobes arrayed around the areola like petals of a flower. Ducts from the lobes drain into the nipple. According to Susan Tucker Blackburn in Maternal, Fetal, & Neonatal Physiology, each lobe consists of 4-18 lobules and each lobule contains 10-100 alveoli with their respective ductules, smaller branches that lead into the larger ducts. The alveolus is the site of milk production and consists of clusters of specialized epithelial cells called lactocytes.

Picture it this way, suggests Donovan. “The alveoli are round, balloon-type structures surrounded by the epithelial cells, or lactocytes, which are the cells that make the milk. So these lactocytes are taking various components from the blood and converting them into specific milk components.”

Some of these components, such as vitamins and minerals, as well as certain infection-fighting immune factors, can be extracted basically intact from the mother’s blood. Other components, however, such as casein proteins or the carbohydrate lactose, must undergo assembly in the lactocytes.

“These components,” says Donovan, “are then secreted into the inside of the balloon, the alveolus.” The mixture of all these components is what constitutes milk. “As milk synthesis increases and the balloon gets bigger, the signal is sent back, ‘OK, there’s enough milk here, stop making milk.’” The alveoli are surrounded by specialized bands of cells (a type of smooth muscle) that are responsible for squeezing milk from the alveoli into the ducts.

“The milk stays in the alveoli until the body secretes oxytocin,” explains Donovan, “which signals that the milk be released into the mammary ducts.” During lactation, milk synthesis constantly occurs at low levels, but is most active when the infant’s sucking stimulates nerves in the nipple. These nerves carry a message to the brain, which then releases the hormones that regulate milk production.

Breastfeeding Science Through the Ages
Given lactation’s universal importance, it’s no surprise that human cultures throughout history have tried to understand the process of milk production as well as devise solutions to breastfeeding problems. In virtually all cultures, this has included special diets or herbal preparations. The earliest medical writings on breastfeeding go back to ancient Egypt. The Greeks also weighed in, including the physician Hippocrates nearly 2,500 years ago, who believed that there was a link between human milk and menstrual blood. Aristotle, a scientist as well as a philosopher, also considered the biological origins of breast milk.

By far the most detailed and sophisticated ancient account of breastfeeding, however, was written by Soranus, a Greek physician who practiced and wrote about gynecology. Soranus lived in Alexandria and Rome in the first and second century AD. His perspectives on women’s health live on because of the major work he wrote on the subject, titled The Gynecology. His treatise included sections on wellness and pathology, including abnormal pregnancies; the care of newborns, and a long discussion on breastfeeding, problems of nursing, and weaning. Remarkably ahead of his time, Soranus held sway over such matters in Europe until the Renaissance.

It was the Industrial Revolution, however, that really provided the impetus to understand human milk and infant nutrition as economic and social upheaval resulted in large numbers of women not breastfeeding. The pace of scientific knowledge rapidly advanced in the 20th century with the development of modern nutrition research. The result has been a deeper understanding and appreciation of the marvel of mother’s milk.

More on this topic

Mother's Milk (VIDEO)
The Best Start
The Ultimate Homemade Meal
Baby's Nutrition Begins with You
Local & Imported Ingredients
Meals Made to Order
Ingredients May Vary
Feeding Cycle
Designed for Growth
Recipe to Develop
The Closest Bond


Related Health Centers:

Infant Nutrition Health Center, Mother-Baby Bond Health Center, Mother’s Milk Health Center, Monthly Infant Development Calendar Health Center,Weekly Pregnancy Calendar Health Center