This paper investigates the mass structure of spiral galaxies using a homogeneous sample of approximately 1100 optical and radio rotation curves (RCs) and surface photometry. The authors confirm the strong dependence of RC profiles and amplitudes on luminosity, revealing a Universal Rotation Curve (URC) that is consistent with a single global parameter, such as luminosity, dictating the rotation velocity at any radius. At high luminosities, there is a slight discrepancy between RC profiles and those predicted from luminous matter (LM) distributions, indicating the presence of dark matter (DM). At low luminosities, the failure of LM predictions is more severe, with DM being the dominant mass component. The URC implies scaling properties between DM and LM mass parameters, including an inverse relationship between the DM/LM mass ratio and luminosity, a scaling of the central halo density with luminosity, and a scaling of the total halo mass with luminosity. These scaling properties are represented in a curve in the (luminosity)-(DM/LM mass ratio)-(DM core radius)-(DM central density) space, providing a geometric description of the tight coupling between dark and luminous matter in spiral galaxies. The study also discusses the implications of these findings for current theories of galaxy formation and the nature of dark matter.This paper investigates the mass structure of spiral galaxies using a homogeneous sample of approximately 1100 optical and radio rotation curves (RCs) and surface photometry. The authors confirm the strong dependence of RC profiles and amplitudes on luminosity, revealing a Universal Rotation Curve (URC) that is consistent with a single global parameter, such as luminosity, dictating the rotation velocity at any radius. At high luminosities, there is a slight discrepancy between RC profiles and those predicted from luminous matter (LM) distributions, indicating the presence of dark matter (DM). At low luminosities, the failure of LM predictions is more severe, with DM being the dominant mass component. The URC implies scaling properties between DM and LM mass parameters, including an inverse relationship between the DM/LM mass ratio and luminosity, a scaling of the central halo density with luminosity, and a scaling of the total halo mass with luminosity. These scaling properties are represented in a curve in the (luminosity)-(DM/LM mass ratio)-(DM core radius)-(DM central density) space, providing a geometric description of the tight coupling between dark and luminous matter in spiral galaxies. The study also discusses the implications of these findings for current theories of galaxy formation and the nature of dark matter.