The subcutis is the deepest layer of the integument, sandwiched between the dermis and skeletal muscle. The hypodermis serves as physical protection, as well as an energy reserve and source of insulation and thermal regulation. It is composed primarily of adipose tissue, the amount of which varies based on species, anatomic site, and nutritional status. Adipose tissue is composed of clusters or sheets of lipid-filled cells, called adipocytes. On histology, the lipid in adipocytes appears empty, as the fat-soluble lipid is washed out during processing.
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