Asynchronous milk ejection in human lactating breast: case series.

Area of Science:

• Lactation physiology
• Human mammary gland function

Background:

• Autocrine control regulates milk synthesis, decreasing as the breast fills.
• Effective milk removal via the milk ejection reflex stimulates increased milk synthesis.
• Previous animal studies suggested heterogeneous mammary gland emptying, contrary to the assumption of simultaneous milk ejection in all alveoli.

Purpose of the Study:

• To investigate whether milk ejection occurs asynchronously in the human lactating breast.
• To determine if the timing of milk flow differs between different main milk ducts.

Main Methods:

• Retrospective analysis of ultrasound videos monitoring milk ducts during pumping.
• Simultaneous measurement of duct diameter every second in two separate ducts draining different mammary gland lobes.
• Observation of milk flow timing differences between ducts.

Main Results:

• Five out of six ultrasound monitoring sessions showed differences in duct dilation and milk flow timing between 2 to 8 seconds in separate main milk ducts.
• In one case, milk ejected from one part of a lobe and flowed retrogradely into another part when not removed.
• Observed asynchronous milk ejection in the human lactating breast.

Conclusions:

• Milk ejection occurs asynchronously in the human lactating breast.
• This asynchrony suggests differing timing in myoepithelial cell responses.
• Leads to heterogeneous emptying of the mammary gland.