The lubrication system and the cooling system.
cartilage
Reduces friction between moving parts.
catrilage covers the ends of bone and reduces the friction between them.
A substance or material that reduces friction is called a lubricant. Lubricants are applied between surfaces in motion to decrease friction and wear, allowing for smoother movement and reduced heat generation.
use lubricants it smoothens the surface and reduces the irregularity between both the surfaces resulting in reduction of friction
Airtrack reduces friction by creating a cushion of air that separates the object from the surface it is moving on. This cushion of air effectively reduces the contact area between the object and the surface, minimizing friction and allowing for smoother movement.
It reduces friction between the bottom of the ski and the top of the snow.
Bursa
Synovial fluid reduces friction between bones at joints. It is a lubricating fluid secreted by the synovial membrane and contains hyaluronic acid and lubricin to facilitate smooth movement between bones.
Serous fluid reduces friction between the layers of tissue in body cavities such as the pericardial, peritoneal, and pleural cavities. It is a clear, watery fluid produced by serous membranes that serves to lubricate the surfaces and allow for smooth movement between them.
because the water reduces friction between the surface you are standing on, and your feet.
Bursa