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

appendage An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface app ...

s 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

cadaver A cadaver, often known as a corpse, is a Death, dead human body. Cadavers are used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue (biology), tissue to ...

s 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.Marieb, E.N. Human Anatomy and Physiology pub: Benjamin/Cummings, Tortora, G.J. and Derrickson, B. Principles of Anatomy and Physiology. Wiley 2006 The positions of the limbs (and the arms in particular) have important implications for directional terms in those appendages. The

penis A penis (; : penises or penes) is a sex organ through which male and hermaphrodite animals expel semen during copulation (zoology), copulation, and through which male placental mammals and marsupials also Urination, urinate. The term ''pen ...

in the anatomical position is described in its erect position and therefore lies against the abdomen, hence the

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

surface of the penis is actually

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

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 or Frankfort plane, a position in which the lower margins of the

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

, the orbitales, and the upper margins of the ear canals, the poria, 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 Anthropology is the scientific study of humanity, concerned with human behavior, human biology, cultures, society, societies, and linguistics, in both the present and past, including archaic humans. Social anthropology studies patterns of behav ...

Frankfurt Frankfurt am Main () is the most populous city in the States of Germany, German state of Hesse. Its 773,068 inhabitants as of 2022 make it the List of cities in Germany by population, fifth-most populous city in Germany. Located in the forela ...

am Main,

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

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 In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

(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 Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

at the position 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 considered to be 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 A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

this is belly down with neutral appendages.

References