This Is What Happens After Your Baby Sucks Breastmilk

We all know that breast milk is best milk. But just how much do we know or understand the way a baby’s mouth and other internal organs coordinate to transport the sucked milk into his stomach? Here we attempt to explain how your baby derives milk from your breast and then what happens to it.

The mechanism of breastfeeding

Feeding in babies has its mechanism involving a well-coordinated baby’s tongue, jaw bone and mother’s breast. There must be maximum contact between the infant’s tongue and the breast of the mother. Therefore, the tongue of an infant is large when compared to the size of its mouth. Also, the cheeks contain fat pads for the good positioning of the tongue for sucking and preventing the cheeks from collapsing. This reduces the negative pressure and the size of the mouth to derive milk from the breast into the oral cavity.


Whenever a baby draws the breast nipple, it does so by suctioning the surrounding and underlying breast tissue into a teat shape. The teat is thrice as long as the breast nipple when at rest and it could go as far as the junction between the soft and hard palates. The teat is held between the upper gum and the tongue which forms a spoon shape around the nipple in a way that it lies in the central trough.

Suckling happens when the jaw is raised, and the front tip of the tongue presses up into the neck of the nipple. This is followed by a backward movement of the tongue under the nipple. This movement squeezes milk from the nipple.

The average volume of milk suckled in each cycle in newborns is about 0.6ml.

Pushing down the oropharynx

The palate muscles contract and rise to seal off the nasal cavity. Once an adequate amount of milk is collected, it is pushed down the oropharynx and swallowed.

The epiglottis, which is a tissue-flap at the tongue’s base that prevents the food from entering the windpipe, touches the soft tissue at the back of the roof of the mouth. This mechanism ensures that the milk goes straight down into the stomach and prevents it from entering the windpipe. It also enables the baby to stretch the neck to bring the lower jaw forward and maximize contact with the breast.

Apart from the oral cavity of the infant, there is also a coordinated action from his upper airway through which the lungs inhale and exhale to facilitate breastfeeding. The upper airway in newborns is very short.

Negative and positive pressure

The hind portion of the tongue creates a negative pressure to draw the nipple and milk into the mouth once again. Alongside, the jaw lowers for the milk to flow back into the nipple. The cycle might last about 1 to 1.5 seconds.

The role of negative pressure has not been ascertained, but it most likely helps in retaining the nipple and breast in position.

The positive pressure, on the other hand, happens when there is pressure on the nipple caused by the surface of the tongue. It essentially helps in evacuating milk from the nipple and allowing it to go down the esophagus.

And there is no friction

Breast suckling does not involve any frictional movement. Also, not much oral movement is required if the teat is adequately sucked into the mouth for the unidirectional exchange of milk from the breast into the body of the nipple and into the baby’s mouth.

This contradicts the past belief that a back and forth movement of the tongue on the underside of the nipple creates friction. Instead, it is a wave-like movement of the tongue that helps the aforesaid rolling motion.

Nipple elasticity

The shape of the nipple is determined by the internal geometry of the mouth. The nipple once drawn in must occupy the entire space to fill the free nipple tissue completely. The human nipple is highly elastic horizontally. Therefore, it can elongate to twice its resting length during active feeding.

The height of the nipple can also be reduced by half when it is compressed between the tongue and the plate. Maximum compression facilitates milk ejection at once.

(Source: Dr Peter P W Weiss; A report written for MAM Babyartikel GesmbH, International Children Medical Research Association)

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