In the catagen (resting) stage of the hair cycle, the hair strand disconnects from the dermal papillae, leading to degeneration of the dermal papillae and their capillary networks.

“in the 1960s there was a lot of histological research done scalp biopsies trying to track what hair follicles were doing during each stage of the hair cycle and they showed that there was a really strong connection between the dermal papillai the hair follicle and then the micro capillary networks that support that dermal papillae in the anagen stage or the growth stage of the hair follicle but then in the catagen stage where that hair rests what they showed in late catagen is that what ends up happening is that the hair strand itself disconnects from its hair follicle base and the dermal papillae first and then that dermal papillai and its subsequent capillary networks degenerate so because of this ordered process people presumed that okay if the hair sheds first if male pattern hair loss is related to hair shedding then technically speaking that's why hair loss or low blood flow is a is a consequence of hair loss because it's a consequence of hair shedding the hair disconnects first and then the blood capillary networks uh dissolve second or degenerate second”