Human body as multicellular organisms which reside in the gastrointestinal tract and on the skin. Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen, surrounded by extracellular fluids. Of the 70 kg weight of an average human body, nearly 25 kg is non-human cells or non-cellular material such as bone and connective tissue. Cells in the body function because of DNA. DNA sits within the nucleus of a cell. Here, parts of DNA are copied and sent to the body of the cell via RNA. The RNA is
Dermal equivalent Dermal equivalent The dermal equivalent is an in vitro model of the dermal layer of skin. It is constructed by seeding dermal fibroblasts into a collagen gel. This gel may then be allowed to contract as a model of wound contraction. This collagen gel contraction assay may be used to screen for treatments which promote or inhibit contraction and thus affect the development of a scar. Other cell types may be incorporated into the dermal equivalent to increase the complexity of the model. For example, keratinocytes may be seeded on the surface to create a skin equivalent, or macrophages may