Uma
Central channel (Skt. avadhūtī)
Uma (dbu ma) — the central channel, running along the front of the spinal axis from the secret-place cakra at the perineal floor up to the crown aperture. In Tsongkhapa's presentation it is described as deep blue or indigo, hollow, four-fingers-wide internally, and ordinarily empty of wind and drops in unrealized practitioners. The completion-stage yogas of Naropa work to dissolve the winds of roma and kyangma into uma, an inner event whose phenomenology (the four blisses, the eight signs of dissolution) is the heart of the Six Yogas curriculum.
Point 1 of 17 in Tibetan Tsa Lung — Three Channels
Cross-tradition overlaps
No overlapping points are registered for this point.
Sources
Tsongkhapa, A Book of Three Inspirations (primary_canonical)
In A Book of Three Inspirations, the section on the three channels in the Six Yogas of Nāropa places uma (dbu ma; Skt. avadhūtī) on the central axis, extending from the secret-place region through the cakras toward the crown. The source presents this as subtle-body visualization in completion-stage practice, not as gross anatomy.
Geshe Kelsang Gyatso, Clear Light of Bliss (secondary)