Contractions of the seminiferous tubules propel immobile immature sperm
Travelling 5 millimetres in one minute sounds slow. But if you’re a human sperm, it’s pretty speedy. While mature sperm can whizz about, immature sperm are immobile. So how do they move through the tubes in the testicles (seminiferous tubules) where they’re made? Researchers investigated in mice using live cell imaging of the tubules to measure the flow of fluid through them. They found the flow matched the contractions of muscle-like cells in the tubule walls, pictured here (red) in a 3D reconstruction of mouse testes compiled using fluorescence confocal microscopy. Contractions were detected by fluorescently tagging and imaging calcium levels in these cells, which rise when they contract. It’s these coordinated contractions that propel the immature sperm through the tubules. This builds a clearer picture of how immobile sperm get moving.
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