The paired terms
Each term of location has an opposite, and each pair describes position along one axis of the body.
| Term | Meaning | Example |
|---|---|---|
| Anterior (ventral) | Nearer the front | The sternum is anterior to the heart |
| Posterior (dorsal) | Nearer the back | The oesophagus is posterior to the trachea |
| Superior (cranial) | Nearer the head | The thyroid gland is superior to the sternum |
| Inferior (caudal) | Nearer the feet | The bladder is inferior to the umbilicus |
| Medial | Nearer the median plane | The ulna is medial to the radius |
| Lateral | Further from the median plane | The eyes are lateral to the nose |
| Proximal | Nearer the root of a limb or origin of a structure | The elbow is proximal to the wrist |
| Distal | Further from the root or origin | The fingers are distal to the carpus |
| Superficial | Nearer the surface | Skin is superficial to muscle |
| Deep | Further from the surface | Bone is deep to muscle |
Terms combine to give intermediate positions: the axilla is superolateral to the umbilicus, and a structure lying anterior and to the side is anterolateral. Intermediate describes a structure between two others, such as the middle finger between the index and ring fingers.
Terms for specific regions
Some regions use their own terms because the general ones would be ambiguous.
- Hand: palmar (front) and dorsal (back). Volar is a common clinical synonym for palmar.
- Foot: plantar (sole) and dorsal (top). The dorsum of the foot faces upwards in the anatomical position.
- Forearm: radial (lateral) and ulnar (medial). These stay correct when the forearm pronates, whereas lateral and medial would swap.
- Leg: tibial (medial) and fibular (lateral). Fibular replaces the older term peroneal.
- Hollow organs and cavities: internal (inside) and external (outside), as in the internal and external surfaces of the skull.
- Vessels and nerves: proximal means nearer the heart or the origin of the nerve, and distal further along it.
Terms of laterality and the midline
Laterality terms describe which side of the body a structure or lesion is on relative to another.
- Ipsilateral: on the same side. The right hand is ipsilateral to the right foot.
- Contralateral: on the opposite side. A stroke in the left motor cortex weakens the contralateral, right, side of the body.
- Bilateral: on both sides, as with the kidneys.
- Unilateral: on one side only.
- Median: lying in the midline, as with the median sagittal plane or the median umbilical ligament. Medial is a relative term; median is an absolute position.
- Paramedian: alongside the midline, as with a paramedian abdominal incision.
Terms in the nervous system
Direction terms change meaning in the brain because the neuraxis bends. In the spinal cord and brainstem, dorsal means posterior and ventral means anterior, as elsewhere in the body. At the junction of the midbrain and diencephalon the long axis of the central nervous system turns forwards, so in the cerebrum dorsal points upwards and ventral points downwards. Rostral means towards the front of the head in the brain and towards the head in the cord; caudal is the opposite.
Clinical relevance
Precise direction terms make clinical notes, operation notes and imaging reports unambiguous. Surgeons write cephalad and caudad for directions towards the head and feet. Using medial and lateral in the forearm or hand can mislead if the forearm is pronated, which is why hand surgeons use radial, ulnar, palmar and dorsal. The side of a lesion is always recorded as the patient's right or left.