"Connective tissue" in the sense of ki tends to refer in the micro sense to the skin, the tendons, the ligaments, the muscles, including in the macro sense also the bones as they all work together in a connected body to assist in managing the balance forces of ground/gravity and any other forces brought to bear. This kind of ki can be conditioned in terms of thickness and elasticity to better convey receiving and issuance of force even as skill is built to more ably generate and receive power. To maximize this connected type of movement the body tends to primarily open or close as a single unit. There's more (how the forces are explicitly managed/generated, how sophisticated and articulated the middle is engaged as the controller, etc.) but that's a starting point.