Anatomical terms of location

Standard anatomical terms of location are used to describe unambiguously the anatomy of animals, including humans.

The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position.

The meaning of terms that are used can change depending on whether an animal is bipedal or quadrupedal.

Standard anatomical and zoological terms of location have been developed, usually based on Latin and Greek words, to enable all biological and medical scientists, veterinarians, doctors and anatomists to precisely delineate and communicate information about animal bodies and their organs, even though the meaning of some of the terms often is context-sensitive.

[1] Different terms are used for those vertebrates with different body layouts, such as bipeds, including humans that stand on two feet, and quadrupeds.

[1] The reasoning is that the neuraxis is different between the two groups, and so is what is considered the standard anatomical position, such as how humans tend to be standing upright and with their arms reaching forward.

[2] Unique terms are also used to describe invertebrates, because of their wider variety of shapes and symmetries.

[6] Anatomical planes are useful in a number of fields including medical imaging, embryology, and the study of movement.

[16] The terms are used in other contexts, for example in dorsal and ventral gun turrets on a bomber aircraft.

"Proximal and distal" are frequently used when describing appendages, such as fins, tentacles, and limbs.

[20] This terminology is also employed in molecular biology and therefore by extension is also used in chemistry, specifically referring to the atomic loci of molecules from the overall moiety of a given compound.

Specific terms exist to describe how close or far something is to the head or tail of an animal.

The term "rostral" is rarely used in human anatomy, apart from embryology, and refers more to the front of the face than the superior aspect of the organism.

[27] Many anatomical terms can be combined, either to indicate a position in two axes simultaneously or to indicate the direction of a movement relative to the body.

[32] In the more internal brain and spinal cord of the central nervous system the terms dorsal and ventral and their combinations are often used in place of anterior and posterior.

References may also take origin from surface anatomy, made to landmarks that are on the skin or visible underneath.

For example, the mid-clavicular line is used as part of the cardiac exam in medicine to feel the apex beat of the heart.

[2] Fields such as osteology, paleontology and dentistry apply special terms of location to describe the mouth and teeth.

For example, as humans are approximately bilaterally symmetrical organisms, anatomical descriptions usually use the same terms as those for other vertebrates.

[59] In invertebrates, the large variety of body shapes presents a difficult problem when attempting to apply standard directional terms.

Some such borrowed terms are widely applicable in most invertebrates; for example proximal, meaning "near" refers to the part of an appendage nearest to where it joins the body, and distal, meaning "standing away from" is used for the part furthest from the point of attachment.

In such organisms, only terms such as superficial and deep, or sometimes proximal and distal, are usefully descriptive.

In organisms that maintain a constant shape and have one dimension longer than the other, at least two directional terms can be used.

Similarly, a perpendicular transverse axis can be defined by points on opposite sides of the organism.

Usually such organisms are planktonic (free-swimming) protists, and are nearly always viewed on microscope slides, where they appear essentially two-dimensional.

Radially symmetrical organisms include those in the group Radiata – primarily jellyfish, sea anemones and corals and the comb jellies.

Two such terms are useful in describing views of the legs and pedipalps of spiders, and other arachnids.

Prolateral refers to the surface of a leg that is closest to the anterior end of an arachnid's body.

Retrolateral refers to the surface of a leg that is closest to the posterior end of an arachnid's body.

All the eyes are on the carapace of the prosoma, and their sizes, shapes and locations are characteristic of various spider families and other taxa.