Entity
         Physical Object
             Organism
                 Plant
                     Alga
                 Fungus
                 Virus
                 Rickettsia or Chlamydia
                 Bacterium
                 Animal
                     Invertebrate
                     Vertebrate
                         Amphibian
                         Bird
                         Fish
                         Reptile
                         Mammal
                             Human
                 Archaeon
             Anatomical Structure
                 Embryonic Structure
                 Fully Formed Anatomical Structure
                     Body Part, Organ, or Organ Component
                     Tissue
                     Cell
                     Cell Component
                     Gene or Genome
                 Anatomical Abnormality
                     Congenital Abnormality
                     Acquired Abnormality
             Manufactured Object
                 Medical Device
                     Drug Delivery Device
                 Research Device
                 Clinical Drug
             Substance
                 Body Substance
                 Chemical
                     Chemical Viewed Structurally
                         Organic Chemical
                             Nucleic Acid, Nucleoside, or Nucleotide
                             Organophosphorus Compound
                             Amino Acid, Peptide, or Protein
                             Carbohydrate
                             Lipid
                                 Steroid
                                 Eicosanoid
                         Element, Ion, or Isotope
                         Inorganic Chemical
                     Chemical Viewed Functionally
                         Pharmacologic Substance
                             Antibiotic
                         Biomedical or Dental Material
                         Biologically Active Substance
                             Neuroreactive Substance or Biogenic Amine
                             Hormone
                             Enzyme
                             Vitamin
                             Immunologic Factor
                             Receptor
                         Indicator, Reagent, or Diagnostic Aid
                         Hazardous or Poisonous Substance
                 Food
         Conceptual Entity
             Organism Attribute
                 Clinical Attribute
             Finding
                 Laboratory or Test Result
                 Sign or Symptom
             Idea or Concept
                 Temporal Concept
                 Qualitative Concept
                 Quantitative Concept
                 Spatial Concept
                     Body Location or Region
                     Body Space or Junction
                     Geographic Area
                     Molecular Sequence
                         Nucleotide Sequence
                         Amino Acid Sequence
                         Carbohydrate Sequence
                 Functional Concept
                     Body System
             Occupation or Discipline
                 Biomedical Occupation or Discipline
             Organization
                 Health Care Related Organization
                 Professional Society
                 Self-help or Relief Organization
             Group
                 Professional or Occupational Group
                 Population Group
                 Family Group
                 Age Group
                 Patient or Disabled Group
             Group Attribute
             Intellectual Product
                 Regulation or Law
                 Classification
             Language
   Event
         Activity
             Behavior
                 Social Behavior
                 Individual Behavior
             Daily or Recreational Activity
             Occupational Activity
                 Health Care Activity
                     Laboratory Procedure
                     Diagnostic Procedure
                     Therapeutic or Preventive Procedure
                 Research Activity
                     Molecular Biology Research Technique
                 Governmental or Regulatory Activity
                 Educational Activity
             Machine Activity
         Phenomenon or Process
             Injury or Poisoning
             Human-caused Phenomenon or Process
                 Environmental Effect of Humans
             Natural Phenomenon or Process
                 Biologic Function
                     Physiologic Function
                         Organism Function
                             Mental Process
                         Organ or Tissue Function
                         Cell Function
                         Molecular Function
                             Genetic Function
                     Pathologic Function
                         Disease or Syndrome
                             Mental or Behavioral Dysfunction
                             Neoplastic Process
                         Cell or Molecular Dysfunction
                         Experimental Model of Disease