| Amino Acids, Peptides, and Proteins (4 sub-categories) |
| Anesthesia and Analgesia (8 sub-categories) |
| Animal Diseases (45 sub-categories) |
| Animal Structures (50 sub-categories) |
| Archaea (4 sub-categories) |
| Bacteria (17 sub-categories) |
| Bacterial Structures (10 sub-categories) |
| Behavior and Behavior Mechanisms (15 sub-categories) |
| Behavioral Disciplines and Activities (10 sub-categories) |
| Biological Factors (15 sub-categories) |
| Biological Phenomena (23 sub-categories) |
| Biomedical and Dental Materials (12 sub-categories) |
| Body Regions (12 sub-categories) |
| Carbohydrates (13 sub-categories) |
| Cardiovascular Diseases (5 sub-categories) |
| Cardiovascular System (10 sub-categories) |
| Cell Physiological Phenomena (41 sub-categories) |
| Cells (36 sub-categories) |
| Chemical Actions and Uses (3 sub-categories) |
| Chemical Phenomena (40 sub-categories) |
| Chemically-Induced Disorders (2 sub-categories) |
| Circulatory and Respiratory Physiological Phenomena (3 sub-categories) |
| Complex Mixtures (19 sub-categories) |
| Congenital, Hereditary, and Neonatal Diseases and Abnormalities (4 sub-categories) |
| Dentistry (33 sub-categories) |
| Diagnosis (12 sub-categories) |
| Digestive System (4 sub-categories) |
| Digestive System and Oral Physiological Phenomena (2 sub-categories) |
| Digestive System Diseases (8 sub-categories) |
| Disorders of Environmental Origin (2 sub-categories) |
| Education (17 sub-categories) |
| Embryonic Structures (29 sub-categories) |
| Endocrine System (3 sub-categories) |
| Endocrine System Diseases (11 sub-categories) |
| Environment and Public Health (3 sub-categories) |
| Enzymes and Coenzymes (4 sub-categories) |
| Equipment and Supplies (58 sub-categories) |
| Eukaryota (19 sub-categories) |
| Eye Diseases (26 sub-categories) |
| Fluids and Secretions (9 sub-categories) |
| Food and Beverages (4 sub-categories) |
| Fungal Structures (5 sub-categories) |
| Genetic Phenomena (47 sub-categories) |
| Geographic Locations (11 sub-categories) |
| Health Care Economics and Organizations (10 sub-categories) |
| Health Care Facilities Workforce and Services (9 sub-categories) |
| Health Care Quality, Access, and Evaluation (6 sub-categories) |
| Health Occupations (26 sub-categories) |
| Health Services Administration (5 sub-categories) |
| Hemic and Immune Systems (3 sub-categories) |
| Hemic and Lymphatic Diseases (2 sub-categories) |
| Heterocyclic Compounds (7 sub-categories) |
| Hormones, Hormone Substitutes, and Hormone Antagonists (2 sub-categories) |
| Human Activities (17 sub-categories) |
| Humanities (13 sub-categories) |
| Immune System Diseases (11 sub-categories) |
| Immune System Phenomena (34 sub-categories) |
| Infections (36 sub-categories) |
