| B0 | Central Nervous System |
| B2 | Heart |
| B3 | Upper Arteries |
| B4 | Lower Arteries |
| B5 | Veins |
| B7 | Lymphatic System |
| B8 | Eye |
| B9 | Ear, Nose, Mouth and Throat |
| BB | Respiratory System |
| BD | Gastrointestinal System |
| BF | Hepatobiliary System and Pancreas |
| BG | Endocrine System |
| BH | Skin, Subcutaneous Tissue and Breast |
| BL | Connective Tissue |
| BN | Skull and Facial Bones |
| BP | Non-Axial Upper Bones |
| BQ | Non-Axial Lower Bones |
| BR | Axial Skeleton, Except Skull and Facial Bones |
| BT | Urinary System |
| BU | Female Reproductive System |
| BV | Male Reproductive System |
| BW | Anatomical Regions |
| BY | Fetus and Obstetrical |