title: Theories of ageing: extracellular aspects.
mesh_terms: D000375:Aging; D001798:Blood Proteins; D002468:Cell Physiological Phenomena; D003094:Collagen; D003238:Connective Tissue / Q000502:physiology; D004549:Elastin; D004798:Enzymes; D006728:Hormones; D006801:Humans
chemical_list: D001798:Blood Proteins; D004798:Enzymes; D006728:Hormones; D003094:Collagen; D004549:Elastin