Anatomy of the lactating breast

Key findings

The research performed at The University of Western Australia led to some groundbreaking discoveries that overturned most of the prior understanding of the anatomy of the lactating breast.

The key findings were:

• The number of ductal openings is 4 –18 (previously 15 – 20)
• The ducts branch closer to the nipple
• The conventionally described lactiferous sinuses do not exist
• Ducts can reside close to the skin surface making them easily compressible
• The majority of the glandular tissue is found within 30 mm of the nipple

Medela produced an image to demonstrate the new findings and many textbooks and internet sites now use this image as a resource.

Relevance to practice

There are three main considerations in relation to lactation practice:

1. A rapid first milk ejection is important for efficient milk removal
2. Breast shields need to be the correct size for each individual mother
3. Hand positioning is important when supporting the breast during expression

1. A rapid, efficient first milk ejection is important for optimal milk removal

Large volumes of milk are not stored in the ducts as no lactiferous sinuses were observed, therefore very little milk can be removed prior to milk ejection. It is known that a baby will initially utilise a rapid sucking action, which stimulates milk ejection ('let down'). Research shows that a rapid first milk ejection will then lead to more subsequent milk ejections. In fact, 80 per cent  of the breast milk is removed in the first seven minutes when using a 2-Phase breast pump at maximum comfort vacuum (Kent et al 2008).

It is therefore important to ensure a good latch to help initiate milk ejection during breastfeeding, as well as using a breast pump that can stimulate the milk ejection efficiently.

2. Breast shields need to be the correct size for an individual mother

A correctly fitting breastshield will avoid compression of the superficial milk ducts, supporting effective breast drainage.

3. Hand positioning: when supporting the breast or expressing

As 65 per cent of the glandular tissue is situated within the first 30mm of the nipple and the ducts are quite superficial, it is important to consider position of hands and fingers when feeding or pumping. Pressure on the ducts and tissue  can prevent milk from flowing freely and this can lead to blockages and in turn to engorgement and then a reduction in milk supply. When milk is not removed from the breast, a protein called feedback inhibitor of lactation (FIL) is produced. When the amount of FIL increases, a signal is sent to the hypothalamus to reduce prolactin and hence milk production is reduced. To avoid this happening, mothers should be advised on how to position the baby so that they do not have to put too much pressure on the breast during a feed or whilst pumping.