What are the major MeSH (Medical Subject Headings) classes?
QS: Human Anatomy QT: Physiology QU: Biochemistry QV: Pharmacology QW: Bacteriology & Immunology QX: Parasitology QY: Clinical Pathology QZ: Pathology W: Medical Profession WA: Public Health WB: Practice of Medicine WC: Infectious Diseases WD 100: Deficiency Diseases WD 200: Metabolic Diseases WD 300: Diseases of Allergy WD 400: Animal Poisoning WD 500: Plant Poisoning WD 600: Diseases Caused by Physical agents WE: Musculoskeletal System WF: Respiratory System WG: Cardiovascular System WH: Lymphatic Systems WI: Gastrointestinal System WJ: Urogenital System WK: Endocrine System WL: Nervous System WM: Psychiatry WN: Radiology WO: Surgery WP: Gynecology WQ: Obstetrics WR: Dermatology WS: Pediatrics WT: Geriatrics. Chronic Disease WU: Dentistry.