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.
Fabricated or induced illness. Fabricated or induced illness (FII) is a rare form of child abuse. It occurs when a parent or carer, usually the child's biological mother, exaggerates or deliberately causes symptoms of illness in the child. FII is also known as 'Munchausen's syndrome by proxy' (not to be confused with Munchausen's syndrome, where a person pretends to be ill or causes illness or injury to themselves).