THE FALCIFORM LIGAMENT AS A HEPATIC DELIVERY CONDUIT: ANATOMICAL DIMENSIONS, VASCULAR CONNECTIVITY, AND PHARMACOKINETICIMPLICATIONS FOR NABHI-APPLIED MEDICINES

Background and Purpose: The falciform ligament - the double peritoneal fold connecting the anterior abdominal wall to the superior hepatic surface - contains in its free inferior border the round ligament of the liver (ligamentum teres hepatis), the obliterated remnant of the foetal umbilical vein. This anatomical structure creates a direct, continuous connective tissue and vascular pathway from the umbilical scar (Nabhi) to the liver, traversing a distance of approximately 8-12 cm in the average adult. The pharmacokinetic significance of this pathway for Nabhi-applied medicines has never been systematically characterised. This review synthesises evidence from hepatic anatomy, portal vascular physiology, lymphatic biology, and pharmacokinetics to construct the first comprehensive framework for the falciform ligament as a hepatic delivery conduit for Nabhi Chikitsa. Anatomical Findings: The adult falciform ligament is a triangular peritoneal fold measuring approximately 12-18 cm in craniocaudal extent and 2-5 cm in width at its broadest point. Its free inferior border contains the round ligament, which ranges from 3 to 8 mm in diameter and traverses 8-12 cm from the umbilicus to the hepatic hilum. The round ligament sheath contains: para-umbilical veins (veins of Sappey) that may remain patent in 30-68% of adults, providing a direct venous connection from the peri-umbilical dermal plexus to the left branch of the portal vein; sympathetic and parasympathetic nerve fibres from the hepatic plexus and the anterior vagal trunk; lymphatic channels draining the anterior hepatic surface to the hepatic hilar and para-aortic nodes; and connective tissue with a thermal conductivity substantially higher than the surrounding subcutaneous fat, facilitating preferential heat transmission from the Nabhi surface toward the liver. Pharmacokinetic Framework: Three pharmacokinetically distinct delivery pathways from Nabhi to the liver are characterised: (i) the venous portal pathway via para-umbilical veins (direct hepatic first-pass delivery of absorbed molecules to hepatic sinusoids, identical in pharmacokinetic consequence to portal vein infusion); (ii) the connective tissue diffusion pathway (interstitial diffusion of molecules along the low-resistance connective tissue corridor of the round ligament sheath, bypassing the systemic circulation and delivering molecules to the periportal space); and (iii) the thermal conduction pathway (preferential heat transmission along the falciform ligament activating TRPV4 channels on hepatic stellate cells and periportal sensory afferents, generating non-pharmacological hepatic responses). A physiologically based pharmacokinetic (PBPK) model is developed for withanolide A and jatamansone delivery via these three pathways, predicting hepatic tissue concentrations following standard Nabhi oil application. Conclusions: The falciform ligament-round ligament axis constitutes a uniquely privileged anatomical conduit from the Nabhi skin surface to the liver that has no equivalent at any other anterior body surface site. The three delivery pathways it enables - venous portal, connective tissue interstitial, and thermal conductive - collectively explain the remarkable hepatic and systemic pharmacological effects attributed to Nabhi Chikitsa in classical Ayurvedic medicine. The Charaka Samhita description of the Nabhi as Yakrit srotasa mula - root of the liver channel - is an anatomically precise clinical observation whose molecular and vascular basis is now fully explicable.