The hypodermis is the innermost and thickest layer of the skin. It invaginates into the dermis and is attached to the latter, immediately above it, by collagen and elastin fibres. It is essentially composed of a type of cells specialised in accumulating and storing fats, known as adipocytes.
Fatal familial insomnia Fatal familial insomnia (FFI) is a very rare, autosomal dominant inherited, disease of the brain. It is caused by a mutation in a protein called prion protein (PrP): asparagine-178 is replaced by aspartic acid.
Most adults have experienced insomnia or sleeplessness at one time or another in their lives. However, some of the general population have chronic insomnia. Insomnia is a symptom, not a stand-alone diagnosis or a disease. By definition, insomnia is difficulty initiating or maintaining sleep, or both or the perception of poor quality sleep. Insomnia may therefore be due to inadequate quality or quantity of sleep.