See a picture of the spine. Upper and middle back pain is not as common as low back pain or neck pain, because the bones in this area of the back don't flex or move as much as the bones in your lower back or neck.
Fats are a class of lipids containing two kinds of monomers, fatty acids and glycerol. Glycerol is a three carbon biomolecule containing three hydroxyl groups, one bonded to each carbon atom. Dehydration synthesis creates an ester linkage between the carboxyl group of fatty acids and a hydroxyl group in glycerol.
The structure of the lipid bilayer explains its function as a barrier. Lipids are fats, like oil, that are insoluble in water. There are two important regions of a lipid that provide the structure of the lipid bilayer. Each lipid molecule contains a hydrophilic region, also called a polar head region, and a hydrophobic, or nonpolar tail region.