I have two questions:
1) Are adult stem cells somatic cells?
2) Can differentiated cells proliferate in vivo? I mean once blood cells, nerve cells, muscle cells are differentiated do they actually proliferate if they are not cancerous? Or can only stem cells proliferate? I find the concept of adult stem cells, differentiated cells, post-mitotic cells and somatic cells very confusing. And I’ll be very happy if anybody could help me to find some definitions.
1) Yes they are Somatic cells, the definition of a somatic cell is – Any cell in a multicellular organism except gametes and their precursors.
As to your second set of questions if you are talking about replicating, then yes differentiated cells do proliferate in vivo, generally via mitosis. Cancerous cells proliferate excessively, with no control from the cell cycle. Due to these facts stem cells aren’t the only cell type to proliferate. With regards to the potency of the cells, zygotic cells are totipotent – meaning they can differentiate into any of the somatic cells of the organism. Adult stem cells however have lost some of their potency and are Pluripotent- They can only differentiate into the three germ layers, Ectoderm, mesoderm (if present) and Endoderm.
I suggest you look up the Cell cycle as it will help you understand somatic cell replication and cancerous cell formation.