Śivasaṃhitā 5.70

The seven dhātu—literally “the sustainers” (dhṛ, to sustain)—of the Āyurvedic body are: rasa (plasma/chyle), rakta (blood), māṃsa (muscle), meda (fat), asthi (bone), majjā (marrow/nerves), and śukra (semen/reproductive fluid). Each dhātu is nourished by the previous one in a chain of progressive refinement. The piṇḍa—“the body,” literally “the ball” or “the conglomerate”—formed by these seven tissues is the material seat of jīva (the living being) in its present incarnation.

That the first two food essences—the most subtle (at the liṅga śarīra level) and the middle (at the sthūla śarīra level)—“reside in the nāḍī” establishes continuity between the physical and subtle circulation systems. The nāḍī are not only prāṇa channels but also channels of the most subtle nutritional essence: they are literally the vessels through which life distributes from the kanda (root) to the body’s periphery. This understanding integrates the perspectives of Āyurveda and yoga.

The image of the body nourished from head to foot (mūrdhataḥ pādaparyantam) by rasa transported by the nāḍī is an image of completeness and organic unity: the yogin’s body is a perfectly integrated living system where no part fails to receive prāṇa nourishment. Practices of āsana and prāṇāyāma optimize this distribution, eliminating blockages in the nāḍī and ensuring each cell of the body is uniformly irrigated.