biology

Standard anatomical position

Standard anatomical position is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Standard anatomical position rather than just read about it. In short: The standard anatomical position, or standard anatomical model, is the scientifically agreed upon reference position for anatomical location terms. Standard anatomical positions are used to standardise the position of appendages of animals with respect to the main body of the organism.

Key takeaways

Standard anatomical position belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Standard anatomical position to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Standard anatomical position from memory before moving on to harder problems.

Reference excerpt

The standard anatomical position, or standard anatomical model, is the scientifically agreed upon reference position for anatomical location terms. Standard anatomical positions are used to standardise the position of appendages of animals with respect to the main body of the organism. In medical disciplines, all references to a location on or in the body are made based upon the standard anatomical position. A straight position is assumed when describing a proximo-distal axis (towards or away from a point of attachment). This helps avoid confusion in terminology when referring to the same organism in different postures. For example, if the elbow is flexed, the hand remains distal to the shoulder even if it approaches the shoulder.

Human anatomy

In standard anatomical position, the human body is standing erect and at rest. Unlike the situation in other vertebrates, the limbs are placed in positions reminiscent of the supine position imposed on cadavers during autopsy. Therefore, the body has its feet together (or slightly separated), and its arms are rotated outward so that the palms are forward, and the thumbs are pointed away from the body (forearms supine). As well, the arms are usually moved slightly out from the body, so that the hands do not touch the sides. The positions of the limbs (and the arms in particular) have important implications for directional terms in those appendages. The penis in the anatomical position is described in its erect position and therefore lies against the abdomen, hence the dorsal surface of the penis is actually anterior when the penis is flaccid.

Skull In humans, the anatomical position of the skull has been agreed by international convention to be the Frankfurt plane (also known as the Frankfort plane), a position in which the lower margins of the orbits, the orbitales, and the upper margins of the ear canals, the porions, all lie in the same horizontal plane. This is a good approximation to the position in which the skull would be if the subject were standing upright and facing forward normally.

History

Frankfurt plane The Frankfurt plane was established at the World Congress on Anthropology in Frankfurt am Main, Germany in 1884, and decreed as the anatomical position of the human skull. It was decided that a plane passing through the inferior margin of the left orbit (the point called the left orbitale) and the superior margin of each ear canal or external auditory meatus, a point called the porion, was most nearly parallel to the surface of the earth at the position in which the head is normally carried in the living subject. The alternate spelling Frankfort plane is also widely used, and found in several medical dictionaries, although Frankfurt is the modern standard spelling of the city it is named for. Another name for the plane is the auriculo-orbital plane. Note that in the normal subject, both orbitales and both porions lie in a single plane. However, due to pathology, this is not always the case. The formal definition specifies only the three points listed above, sufficient to describe a plane in three-dimensional space. For purposes of comparison of human skulls with those of some other species, notably hominids and primates, the skulls may be studied in the Frankfurt plane; nonetheless, the Frankfurt plane is not horizontal in the anatomical position for most non-primate species. The Frankfurt plane may also be used as a reference point in related fields. For example, in prosthodontics, the Frankfurt-Mandibular plane Angle (FMA) is the angle formed at the intersection of the Frankfurt plane with the mandibular plane.

Other animals

In quadrupeds the standard anatomical position is the animal standing upright with all four feet on the ground and the head facing forward. For a fish this is belly down with neutral appendages.

See also Reid's base line Anatomical terms of location

References

Illustrations

Worked examples

Example 1 — a first encounter with Standard anatomical position

Start with the simplest possible case. Write down what Standard anatomical position claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Standard anatomical position before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Standard anatomical position ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Standard anatomical position

In research: Standard anatomical position appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Standard anatomical position in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Standard anatomical position is common in secondary-school and first-year university syllabi. It links to neighbouring topics Anatomical terminology, so understanding it makes those chapters shorter.
In everyday life: Look for Standard anatomical position outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Standard anatomical position in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Standard anatomical position means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Standard anatomical position out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Standard anatomical position in simple terms?

Why does Standard anatomical position matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Standard anatomical position?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Standard anatomical position.