Skeletal--->Urinary
The skeletal system and urinary system are connected in many ways. For example, the pelvic bone protects some parts of the urinary system such as the bladder. These parts need protection because otherwise they'll break, (and then they won't work) and the pelvis provides this protection. The bone has a hole-like shape in the middle that fits the bladder perfectly. The urinary system is a very important part of your body, because it gets rid of wastes that MUST leave the body. In addition, the bone marrow in bones is helpful to the urinary system. What does bone marrow do again? It makes white blood cells, which are a KEY part of your body's blood. And what does they blood do? It carries things like glucose and oxygen to cells. Where am I going with this? Well, wouldn't you think that these urinary system cells would need a lot of these molecules? Your body is constantly taking in nutrients to survive, and going through cell respiration to turn those nutrients into energy- and this process creates waste products. If these wastes don't leave the body, you could die from waste overload. You need energy for your urinary system cells to do this and many other jobs. Your cells can make their own energy (in a process called cell respiration), but they need glucose and oxygen to do so. The equation for for this process is shown here:

glucose + oxygen --> energy + water + carbon dioxide

Since urinary system cells are doing so much, they must need a lot of energy, and to make a lot of energy they'd need a lot of glucose and oxygen to do that. SO, the cells would have to have a lot of capillaries going by them with blood in them and white blood cells in the blood. And what make those cells? Bone marrow. In addition, white blood cells have many immune functions, meaning they play a large role in protecting the body form viruses. The muscular systems' parts would also be protected by the white blood cells.sci_thing_mira.jpg