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Anatomical terms of location
Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans.
All vertebrates (including humans) have the same basic body plan – they are strictly bilaterally symmetrical in early embryonic stages and largely bilaterally symmetrical in adulthood. That is, they have mirror-image left and right halves if divided down the centre. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other (invertebrate) organisms as well.
While these terms are standardized within specific fields of biology, there are unavoidable, sometimes dramatic, differences between some disciplines. For example, differences in terminology remain a problem that, to some extent, still separates the terminology of human anatomy from that used in the study of various other zoological categories.
Standardized anatomical and zoological terms of location have been developed, usually based on Latin and Greek words, to enable all biological and medical scientists to precisely delineate and communicate information about animal bodies and their component organs, even though the meaning of some of the terms often is context-sensitive.
The vertebrates and Craniata share a substantial heritage and common structure, so many of the same terms are used to describe location. To avoid ambiguities this terminology is based on the anatomy of each animal in a standard way.
For humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. For one reason, this is because humans have a different neuraxis and, unlike animals that rest on four limbs, humans are considered when describing anatomy as being in the standard anatomical position. Thus what is on "top" of a human is the head, whereas the "top" of a dog may be its back, and the "top" of a flounder could refer to either its left or its right side.
Defined axes in vertebrate zoology
|Anteroposterior (rostrocaudal1,craniocaudal1, cephalocaudal2)
||Back, spinal column
|Left-right (dextro-sinister2, sinistro-dexter2)
||Left and right
||Point at which appendage joins the body
||Extremity of appendage
(1) Fairly common use.
(2) Uncommon use.
(3) Equivalent to one-half of the left-right axis.
(The terms "intermediate", "ipsilateral", "contralateral", "superficial", and "deep", while indicating directions, are relative terms and thus do not properly define fixed anatomical axes. Also, while the "rostrocaudal" and anteroposterior directionality are equivalent in a significant portion of the human body, they are different directions in other parts of the body.)
- In human anatomy
- Latin convention
- The sagittal plane is a plane parallel to the sagittal suture. All other sagittal planes (referred to as parasagittal planes) are parallel to it. It is also known as a "longitudinal plane". The plane is a Y-Z plane, perpendicular to the ground.
- The median plane or midsagittal plane is in the midline of the body, and divides the body into left and right (sinister and dexter) portions. This passes through the head, spinal cord, navel and, in animals, the tail. The median plane can also refer to the midsagittal plane of other structures, such as a digit.
- The frontal plane or coronal plane divides the body into dorsal and ventral (back and front, or posterior and anterior) portions. For post-embryonic humans a coronal plane is vertical and a transverse plane is horizontal, but for embryos and quadrupeds a coronal plane is horizontal and a transverse plane is vertical. A longitudinal plane is any plane perpendicular to the transverse plane. The coronal plane and the sagittal plane are examples of longitudinal planes.
- A transverse plane, also known as a cross-section, divides the body into cranial and caudal (head and tail) portions.
- A transverse (also known as horizontal) plane is an X-Y plane, parallel to the ground, which (in humans) separates the superior from the inferior or, put another way, the head from the feet.
- A coronal (also known as frontal) plane is a X-Z plane, perpendicular to the ground, which (in humans) separates the anterior from the posterior, the front from the back, the ventral from the dorsal.
Contralateral (from Latin contra, meaning "against"): on the side opposite to another structure. For example, the left arm is contralateral to the right arm, or the right leg.
Ipsilateral (from Latin ipse, meaning "same"): on the same side as another structure. For example, the left arm is ipsilateral to the left leg.
Bilateral (from Latin bi, meaning "two"): on both sides of the body. For example, bilateral orchiectomy (removal of testes on both sides of the body's axis) is surgical castration.
Unilateral (from Latin uni, meaning "one"): on one side of the body. For example, unilateral paresis is hemiparesis.
Rostral, from Latin ("beak, nose"): situated toward the oral or nasal region, or in the case of the brain, toward the tip of the frontal lobe.
Cranial, from Greek (kranion, "skull") or cephalic ( (kephalē, "head").
Anteversion refers to an anatomical structure being tilted further forward than normal, whether pathologically or incidentally. For example, there may be a need to measure the anteversion of the neck of a bone such as a femur. For example, a woman's uterus typically is anteverted, tilted slightly forward. A misaligned pelvis may be anteverted, that is to say tilted forward to some relevant degree.
Retroversion is rotation around the same axis as that of anteversion, but in the opposite sense, that is to say, tilting back. A structure so affected is described as being retroverted. As with anteversion, retroversion is a completely general term and can apply to a backward tilting of such hard structures as bones, soft organs such as uteri, or surgical implants.
Axial (from Latin axōn, meaning "axle"): around the central axis of the organism or the extremity. Two related terms, "abaxial" and "adaxial", refer to locations away and toward the central axis of an organism, respectively.
Intermediate (from Latin inter, meaning "between", and Latin medius, meaning "middle"): between two other structures. For example, the navel is intermediate to the left arm and the contralateral (right) leg.
Parietal (from Latin paries, meaning "wall"): pertaining to the wall of a body cavity. For example, the parietal peritoneum is the lining on the inside of the abdominal cavity. Parietal can also refer specifically to the parietal bone of the skull or associated structures.
Visceral (from Latin viscus, meaning "internal organs"): associated with organs within the body's cavities. For example, the stomach is covered with a lining called the visceral peritoneum. Viscus can also be used to mean "organ". For example, the stomach is a viscus within the abdominal cavity.
Figure 10: Aurelia aurita, another species of jellyfish, showing multiple radial and medio-peripheral axes
The sea star Porania pulvillus, aboral and oral surfaces
Aspects of spider anatomy; This aspect shows the mainly prolateral surface of the anterior femora, plus the typical horizontal eye pattern of the Sparassidae
Typical arrangement of eyes in the Lycosidae, with PME being the largest
Wake, ed. by Marvale H. (1992). Hyman's comparative vertebrate anatomy. (3d ed.). Chicago: University of Chicago Press. ISBN .
"GeneOntology". GeneOntology. The Gene Ontology Consortium.
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