Anatomy of the human breast
Anatomy of the human breast - click to enlargeThe inside of a breast looks like a bush - with the nipple being the base or stump and the milk duct 'branches' and alveoli 'leaves' fanning out inside.
It is composed of essentially four parts: alveoli or glands, milk ducts and fat, plus connective tissue. The alveoli group together into larger units called lobes.
There will be around nine to twelve main milk lobes in each breast. Each lobe has a main duct, leading from the nipple back into the breast to the lobe - like a main branch of the bush. Multiple smaller ducts branch off, forming the milk lobe itself.
The 'leaves' of this bush are the alveoli - sac-like round glands, lined with milk-producing cells, lactocytes. It is inside each alveolus that the milk is produced, travelling down the ducts and out of the nipple.
(Click on the image to the right for a closer look.)
How breast milk is made
The process of making breast milk (lactogenisis) is heavily dependent on two hormones - prolactin and oxytocin. Each hormone needs an equivalent receptor located wherever the hormone’s influence is required, and must be an exact match to the hormone. In addition, there needs to be enough receptors for the amount of hormone. Both prolactin and oxytocin are secreted by the pituitary gland (a pea-sized gland at the base of the brain).
One
The hormone prolactin is needed for milk to be produced. Prolactin receptors are on the walls of the lactocytes (the milk-producing cells of the alveoli). The receptors allow the prolactin in the bloodstream to move into the lactocytes and stimulate milk production.
Two
As the alveoli fill up with milk two things happen:
1. They stretch, which changes the shape of the lactocytes so they cannot absorb any more prolactin, therefore slowing the rate of milk production.
2. The breast milk itself contains a protein called Feedback Inhibitor of Laction (FIL). When the breast is full of milk, and so there is an increased amount of FIL present, the FIL gives the message to the lactocytes to stop producing milk.
Three
The baby’s suckling stimulates the hormone to be released - oxytocin. (At the same time, the pituitary gland also releases more prolactin too.) Oxytocin causes the muscles around the alveoli to contract, squeezing the milk into the ducts, which swell behind the nipple, full of milk. The motion of the baby’s tongue as they suck, draws the milk into their mouth - though they must have a good mouthful of breast to be able to reach the ducts and feed effectively.
Four
As the milk empties out of the alveoli, the prolactin receptors return to their normal shape, so the prolactin flows back into the lactocytes and milk production starts again. The milk that is produced as the baby feeds is higher in fat and more satisfying.
Prolactin Receptor Theory proposes that frequent milk removal in the first several weeks of feeding increases the number of receptor sites. With more receptors, more prolactin can flow into the lactocytes, and milk production capacity increases.
Prolactin levels in the body start to rise around half-way through pregnancy, surging to their highest levels at the time of birth. However, during pregnancy high levels of progesterone, produced by the placenta, interact with the prolactin receptors on the walls of the lactocytes to inhibit milk production. But these progesterone levels fall dramatically once the placenta is delivered, and the prolactin is able to start having an effect.
The level of prolactin drops continuously until it plateaus around three months after birth. However the more frequent the prolactin surge, experienced during feeding, in the first several weeks, the higher the baseline for on-going milk supply levels. The more successful breastfeeding is in the first few weeks, the more successful it is likely to be going forward.
So if you're breastfeeding and need support, it is really is key to get it in the first few weeks. For more information, please visit our Breastfeeding Support page: www.contentedcalf.com/products/recipe-book/breastfeeding-support
(Bonyata, 2010)
(Chen, 2008)
(Evens, 2009)
(Kimball, 2009)
(West & Marasco, 2009)
It is composed of essentially four parts: alveoli or glands, milk ducts and fat, plus connective tissue. The alveoli group together into larger units called lobes.
There will be around nine to twelve main milk lobes in each breast. Each lobe has a main duct, leading from the nipple back into the breast to the lobe - like a main branch of the bush. Multiple smaller ducts branch off, forming the milk lobe itself.
The 'leaves' of this bush are the alveoli - sac-like round glands, lined with milk-producing cells, lactocytes. It is inside each alveolus that the milk is produced, travelling down the ducts and out of the nipple.
(Click on the image to the right for a closer look.)
How breast milk is made
The process of making breast milk (lactogenisis) is heavily dependent on two hormones - prolactin and oxytocin. Each hormone needs an equivalent receptor located wherever the hormone’s influence is required, and must be an exact match to the hormone. In addition, there needs to be enough receptors for the amount of hormone. Both prolactin and oxytocin are secreted by the pituitary gland (a pea-sized gland at the base of the brain).
One
The hormone prolactin is needed for milk to be produced. Prolactin receptors are on the walls of the lactocytes (the milk-producing cells of the alveoli). The receptors allow the prolactin in the bloodstream to move into the lactocytes and stimulate milk production.
Two
As the alveoli fill up with milk two things happen:
1. They stretch, which changes the shape of the lactocytes so they cannot absorb any more prolactin, therefore slowing the rate of milk production.
2. The breast milk itself contains a protein called Feedback Inhibitor of Laction (FIL). When the breast is full of milk, and so there is an increased amount of FIL present, the FIL gives the message to the lactocytes to stop producing milk.
Three
The baby’s suckling stimulates the hormone to be released - oxytocin. (At the same time, the pituitary gland also releases more prolactin too.) Oxytocin causes the muscles around the alveoli to contract, squeezing the milk into the ducts, which swell behind the nipple, full of milk. The motion of the baby’s tongue as they suck, draws the milk into their mouth - though they must have a good mouthful of breast to be able to reach the ducts and feed effectively.
Four
As the milk empties out of the alveoli, the prolactin receptors return to their normal shape, so the prolactin flows back into the lactocytes and milk production starts again. The milk that is produced as the baby feeds is higher in fat and more satisfying.
Prolactin Receptor Theory proposes that frequent milk removal in the first several weeks of feeding increases the number of receptor sites. With more receptors, more prolactin can flow into the lactocytes, and milk production capacity increases.
Prolactin levels in the body start to rise around half-way through pregnancy, surging to their highest levels at the time of birth. However, during pregnancy high levels of progesterone, produced by the placenta, interact with the prolactin receptors on the walls of the lactocytes to inhibit milk production. But these progesterone levels fall dramatically once the placenta is delivered, and the prolactin is able to start having an effect.
The level of prolactin drops continuously until it plateaus around three months after birth. However the more frequent the prolactin surge, experienced during feeding, in the first several weeks, the higher the baseline for on-going milk supply levels. The more successful breastfeeding is in the first few weeks, the more successful it is likely to be going forward.
So if you're breastfeeding and need support, it is really is key to get it in the first few weeks. For more information, please visit our Breastfeeding Support page: www.contentedcalf.com/products/recipe-book/breastfeeding-support
(Bonyata, 2010)
(Chen, 2008)
(Evens, 2009)
(Kimball, 2009)
(West & Marasco, 2009)