Somatic

The term somatic (from the Greek σωματικός) means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes (ovum or sperm). These somatic cells are diploid containing two copies of each chromosome, whereas the germ cells are haploid as they only contain one copy of each chromosome. Although under normal circumstances all somatic cells contain identical DNA, they develop a variety of tissue-specific characteristics. This process is called differentiation, through epigenetic and regulatory alterations. The grouping of like cells and tissues creates the foundation for organs.

Somatic mutations are changes to the genetics of a multicellular organism which are not passed on to its offspring through the germline. Many cancers are somatic mutations.

Somatic is also defined as relating to the wall of the body cavity, particularly as distinguished from the head, limbs or viscera.

It is also used in the term somatic nervous system which is the portion of the vertebrate nervous system which regulates voluntary movements of the body.