Say "above the wrist" and a doctor has learned almost nothing. The scar could be several inches up the forearm, or it could be on the base of the hand, on the palm or on the back of it. Every one of those is "above the wrist" in ordinary speech, and two of them are on opposite sides of the same limb.
Anatomical directional terms exist to close that gap. They are not hard because the words are strange. They are hard because each one is measured against a fixed posture that is almost never the posture the patient is actually in. Once that is clear, the rest follows.
Everything Is Measured Against One Posture
The standard anatomical position is a person standing upright, arms at the sides, palms facing forward. That is the reference. Every directional term describes where something sits in that body, not where it sits in the body on the table in front of you.
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| Standing, arms at the side, palms forward. This is the posture every term below assumes — Image: Connexions, CC BY 3.0, via Wikimedia Commons |
The reason is obvious once stated. A body can change its orientation to match its environment, and limbs can move relative to the trunk. If "up" and "down" tracked the room, two people describing the same patient from opposite ends of the bed would contradict each other. Fixing the posture removes that failure mode entirely.
So if a patient lies flat with one arm raised above their head, the term for that hand does not change. It stays superior to the hip and proximal to nothing in particular. The words describe the body, not the world.
The Terms Describe Three Planes and Three Axes
Directional terms are not free-floating adjectives. They count distance from a small number of fixed reference surfaces and lines.
Planes
- Sagittal planes divide the body into left and right. The central one of these is the median plane, also called the midsagittal plane, and it passes through the head, the spinal cord and the navel.
- Coronal, or frontal, planes divide the body into front and back. In quadrupeds this is called the dorsal plane.
- Transverse, also axial or horizontal, planes sit at right angles to the other two.
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| Every directional term is really a statement about position relative to one of these surfaces — Image: Connexions, CC BY 4.0, via Wikimedia Commons |
Axes
The three axes run at right angles to each other: left-right, craniocaudal, and anteroposterior. They are named for the directions of the embryo during gastrulation, before any of the structures they will describe have formed. The body plan is laid down first, and the vocabulary follows it.
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| The axes are the same in any vertebrate, but a fish lies belly down with neutral appendages, so up and down mean something else — Image: public domain, via Wikimedia Commons |
The Pairs, and What Each One Counts
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| Most of the vocabulary on one figure — Image: Blausen Medical 2014, CC BY 3.0, via Wikimedia Commons |
| Term pair | The question it answers | Example |
| Superior / inferior | nearer the head or nearer the feet? | the head is superior to the neck |
| Anterior / posterior | in front of or behind? | the chest is anterior to the spine |
| Medial / lateral | nearer the median plane or further from it? | the arms are lateral to the trunk |
| Proximal / distal | nearer the main mass of the body, or further? | the hand is distal to the upper arm |
| Superficial / deep | nearer the body surface, or further in? | the epidermis is superficial to the subcutis |
| Ipsilateral / contralateral | on the same side, or the other one? | the left arm is ipsilateral to the left leg |
| Central / peripheral | towards or away from the center? | the great vessels run centrally |
Most of these come straight from Latin, and the roots are worth learning as words because they recur in every structure name built on them. Superius is above, inferus below, ante before and post after, medius in the middle, lateralis to the side, proximus nearest, superficies surface, contrarium against and ipse the same.
Left and right are the subject's, not yours
This is worth separating out because it is the most common real mistake. In anatomical description, left and right always refer to the subject's own left and right, never the observer's. Standing at the foot of a bed facing a patient, their left hand is on your right. You say "left hemithorax" because it is their left, and everyone in the room knows it.
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| Anterior is defined from the body facing you, not from the viewer — Image: Mikael Häggström, CC0, via Wikimedia Commons |
Proximal and distal are relative, not fixed
These two get taught as if they were absolute. Closer to the point of attachment, or further from it, as though that settled it. It does not, because the point of reference has to be named each time.
The elbow is distal to a wound on the upper arm, and the same elbow is proximal to a wound on the forearm. Both statements are true. Which one you need depends on what you are comparing the elbow to.
In practice the reference point is usually the main mass of the body, taken as the center, the chest, or the heart. The upper arm is proximal and the hand is distal. For limbs, fins and tentacles the word describes distance from the point where the appendage joins the body. The same two words turn up in molecular biology, where they describe position along a molecule rather than along an arm.
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| Proximal and distal describe a line from the body outwards, not a fixed place — Image: OpenStax College, CC BY 3.0, via Wikimedia Commons |
Why Animals Need a Different Set of Words
Every term in the table above assumes a person standing on two legs. Change the body plan and the same word points somewhere else. A horse is not facing up; its head end is forward and its back end is behind, but neither is "superior".
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| The planes match, but the orientation does not, so the vocabulary has to change — Image: CNX OpenStax, CC BY 4.0, via Wikimedia Commons |
This is not a preference. In humans standing upright, the front-to-back direction and the up-to-down direction happen to line up with anterior and dorsal on the one hand, and superior and inferior on the other. In a quadruped the spine is horizontal, so those pairings break. Veterinary anatomy so uses dorsal and ventral through the body, and reserves anterior and posterior for structures of the head. Superior and inferior survive only for the eye, the eyelids, the lips and the inner ear.
For the same reason, a brain is described using dorsal and ventral rather than anterior and posterior. The neuraxis runs at an angle, so "front" and "top" no longer coincide. That is why the frontal lobe has a dorsolateral part and a dorsomedial part, and why the anterior cingulate cortex gets both words at once.
Invertebrates are harder still. Something roughly spherical has no front at all, and nothing distinguishes one line through its center from any other. In those organisms only superficial and deep stay useful, with proximal and distal sometimes doing duty.
Where the Vocabulary Breaks: Hands, Feet and Teeth
Some parts of the body need their own words because the general ones genuinely fail.
- Hands and feet. The forearm pronates and supinates, which flips the hand over without the rest of the body moving. Saying "anterior surface of the hand" could then mean the palm or the back of the hand depending on which way the forearm is turned. So palmar means the palm and dorsal means the back, and neither word can be wrong. Volar is a synonym for palmar, and plantar means the sole of the foot.
- Forearm and lower leg. In the forearm, structures near the radius are radial, structures near the ulna are ulnar, and both are radioulnar. In the lower leg, structures near the tibia are tibial and structures near the fibula are fibular. The bones supply the words.
- Teeth. Teeth can be rotated in the jaw, which makes anterior and lateral ambiguous. Dentists use mesial and distal for surfaces relative to the midpoint of the dental arch, and buccal for the cheek side and palatal for the palate.
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| Because the hand can rotate, it gets its own pair of words — Image: Esseh, CC BY-SA 3.0, via Wikimedia Commons |
Combined terms
Terms also combine, and the combination is not decorative. Anterolateral means anterior and lateral at once, as in the bulk of the pectoralis major. Anteromedial means nearer the midline and further forward at the same time. Prefix forms do the same job. Sub means beneath, as in subcutaneous. Infra means below or within, as in the infraorbital nerve. Hypo means under, as in the hypoglossal nerve supplying the muscles beneath the tongue. Supra means above, as in the supraorbital ridges.
Why Any of This Was Fixed in the First Place
The terminology is not old. It is recent, and it exists because without it communication failed.
In the late nineteenth century around 30,000 terms for body parts were in use. The same structures went under different names depending on the anatomist's school and national tradition. Latin and Greek were being translated into vernaculars that pulled in different directions. Structures were also named after the people who had first described them, so an international conversation depended on whether you had read the same paper. The result was disagreement among the people best placed to resolve it.
The Nomina Anatomica was agreed as the international standard in 1895 and held that position until 1998, when it was replaced by Terminologia Anatomica. That list is still maintained by the Federative International Programme on Anatomical Terminology, a programme of the International Federation of Associations of Anatomists. Separate standards exist for the nervous system and for embryology, and a further one, Nomina Anatomica Veterinaria, covers animals.
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| Surface terms in everyday clinical use, all built on the same directional logic — Image: OpenStax, CC BY 3.0, via Wikimedia Commons |
There is a second reason the language is kept rigid, which is that the everyday version drifts. These terms are not in common use, so their meanings do not shift the way ordinary words do. A word used constantly by everyone slowly stops meaning one thing, and a term used by a few specialists does not.
Where these words are actually used
- Describing an examination. Where the tenderness sits, how far it extends, and whether it crosses the midline.
- Naming imaging views. Radiology uses the same logic. An anteroposterior view sends the beam from front to back, a posteroanterior view from back to front, and a lateral view from the side.
- Locating structures. Vertebrae are used as landmarks, so a site can be given as the level of the fourth cervical vertebra, written C4, or the third lumbar vertebra, L3.
- Describing movement. Abduction moves a limb away from the midline and adduction brings it back, and those two words depend entirely on the median plane having been agreed in advance.
- Sorting out which side. Ipsilateral, contralateral, bilateral and unilateral remove the need to say left or right out loud, which is where verbal errors get made.
Key Terms in Plain English
These are the words in this article that would send you to a dictionary. Each one is given here the way it is actually used above.
| Term | What it means here |
| Anatomical position | the agreed reference posture every description starts from: standing, arms at the sides, palms facing forward, facing the observer |
| Superior / inferior | nearer the head, or nearer the feet. Not "better" and "worse" |
| Anterior / posterior | in front of, or behind. The whole vocabulary can be reversed for animals, which is why dorsal and ventral also appear |
| Ventral / dorsal | towards the belly, or towards the back. In veterinary and embryology usage these replace anterior and posterior |
| Medial / lateral | nearer the midline of the body, or further from it. The midline is the median plane running down the center |
| Proximal / distal | nearer the main mass of the body, or further out along a limb. The two swap places depending on which structure you are measuring from |
| Superficial / deep | nearer the body surface, or further inside. A root word meaning "of the surface", which is where the word comes from |
| Ipsilateral / contralateral | on the same side of the body, or on the opposite one. Used mostly in neurology, when a lesion and a symptom are compared |
| Sagittal plane | a plane dividing the body into left and right. The one down the middle is the median, or midsagittal, plane |
| Coronal plane | a plane dividing the body into front and back. Called the dorsal plane in four-legged animals |
| Transverse plane | a plane at right angles to the other two, cutting the body into upper and lower parts. Also called axial or horizontal |
| Axis | one of the three lines the planes run along: left-right, craniocaudal, and anteroposterior. They meet at right angles |
| Nomina Anatomica | the international list of anatomical names agreed in 1895, which held the official standard until 1998 |
| Terminologia Anatomica | the list that replaced Nomina Anatomica in 1998, still maintained internationally and still open to occasional revision |
These are the terms that carry the argument above. Every one of them is used here in the sense given here, and nowhere else.
Key Takeaways
- Every directional term is defined against the standard anatomical position: standing, arms at the sides, palms facing forward.
- The terms describe the body, not the room. Raising an arm over the head does not make the hand inferior to anything.
- Left and right always mean the subject's own left and right, never the observer's.
- The terms count distance from three planes and three axes. Medial and lateral are counted from the median plane in particular.
- Proximal and distal need a second term to mean anything. The elbow is distal to the upper arm and proximal to the forearm.
- Superficial and deep measure from the body surface. Deep is one of very few location terms that is not Latin or Greek.
- The vocabulary changes with the body plan. A quadruped uses dorsal and ventral, and the brain uses dorsal and ventral because its neuraxis runs at an angle.
- Hands, feet and teeth get their own words, because pronation and rotation make the general ones ambiguous.
- Around 30,000 terms were in circulation before Nomina Anatomica was agreed in 1895, and Terminologia Anatomica replaced it in 1998.
- The words are kept rigid precisely because ordinary language drifts.
Frequently Asked Questions
What is the standard anatomical position?
A person standing upright with the arms at the sides and the palms facing forward. Every anatomical directional term describes position in that posture, regardless of the posture the person is actually in at the time.
Is "anterior" the same as "front"?
In a standing person, yes. The word is defined from the body itself, so it keeps its meaning when the body is lying down or upside down. A patient lying supine is still described as having a lesion on the anterior chest.
Is left the patient's left or mine?
The patient's, always. Anatomical left and right never refer to the observer. Standing facing someone, their left hand is on your right, but you still say left hand.
Why is a wrist not simply "proximal to the hand"?
Proximal and distal are relative, so they need something to be measured against. A structure can be proximal to one thing and distal to another at the same time. The elbow is distal to a wound on the upper arm and proximal to a wound on the forearm.
What is the difference between anterior and ventral?
In human anatomy they usually mean the same thing. Ventral is kept mainly for the brain, the spinal cord and embryology, where the neuraxis runs at an angle and anterior would be misleading. In veterinary anatomy ventral is the standard word, and anterior is reserved for structures of the head.
What are the three body planes?
The sagittal plane divides the body into left and right, with the median or midsagittal plane running down the center. The coronal, or frontal, plane divides it into front and back. The transverse, axial or horizontal, plane sits at right angles to both.
Why do we say palmar instead of anterior for the palm?
Because the forearm turns. Pronation and supination flip the hand over without the rest of the body moving. "Anterior surface of the hand" could then mean either side. Palmar and dorsal cannot be wrong.
Is "deep" a Latin word?
No. It is one of very few anatomical location terms that comes from Old English rather than Latin. The Latin equivalent would have been profundus.
Who decides these terms?
They are set by international bodies rather than left to people. Terminologia Anatomica is the current international standard for human anatomy, maintained by the Federative International Programme on Anatomical Terminology. It replaced Nomina Anatomica in 1998.
What if a patient cannot stand?
Nothing changes. The position is a reference, not a need. The terms describe where structures are in the body, so they work identically whether the person is standing, lying or unconscious.
Sources: Wikipedia articles on anatomical terminology, superior and inferior, anatomical position, human anatomy, Terminologia Anatomica, Basle Nomina Anatomica and median plane. Images: Wikimedia Commons, with authors and licenses noted in each caption.
