Hi. Does skin and muscular cells do mitosis? If so, why they stem cells? Why heart muscles cant regenerate? 

They do. Thats how skin and muscles grow and replace damaged cells. Did you maybe mean meiosis? If you meant meiosis then the answer is no.

On 9/23/2019 at 4:56 PM, Scientist_Supreme said:

They do. Thats how skin and muscles grow and replace damaged cells. Did you maybe mean meiosis? If you meant meiosis then the answer is no.

That is only part of the story. In muscle, for example only specialized cells in skeletal muscles (located beneath the lamina) divide, once stimulated. Smooth muscle cells on the other hand, can de-differentiate from a contractile version (i.e. acting as muscle) to become a more motile, dividing cell type. Cardiac muscle cells as another example, generally do not divide anymore.

Similarly in skin there are specialized layers containing cells that are still able to divide. During regeneration of damages for example, they become more differentiated and lose their ability to divide. That control is quite relevant to avoid continuous growth and formation of tumours. Regarding OP, in most cases you do not have true (embryonic) stem cells that do repairs or division, but rather at least somewhat differentiated cells.