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An anatomical plane is a hypothetical
plane Plane(s) most often refers to: * Aero- or airplane, a powered, fixed-wing aircraft * Plane (geometry), a flat, 2-dimensional surface Plane or planes may also refer to: Biology * Plane (tree) or ''Platanus'', wetland native plant * ''Planes' ...
used to transect the body, in order to describe the location of structures or the direction of movements. In human and animal anatomy, three principal planes are used: * The sagittal plane or lateral plane (''longitudinal, anteroposterior'') is a plane parallel to the sagittal suture. It divides the body into left and right. * The
coronal plane The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes. Details The coronal plane is an example of a longitud ...
or frontal plane (''vertical'') divides the body into dorsal and ventral (back and front, or posterior and anterior) portions. * The
transverse plane The transverse plane (also known as the horizontal plane, axial plane and transaxial plane) is an anatomical plane that divides the body into Anatomical terms of location#Superior and inferior, superior and inferior sections. It is perpendicula ...
or axial plane (''horizontal'') divides the body into cranial and caudal (head and tail) portions.


Terminology

There could be any number of sagittal planes; however, there is only one cardinal sagittal plane. The term ''cardinal'' refers to the one plane that divides the body into equal segments, with exactly one half of the body on either side of the cardinal plane. The term ''cardinal plane'' appears in some texts as the ''principal plane''. The terms are interchangeable.


Human anatomy

In human anatomy, the anatomical planes are defined in reference to the anatomical model being in the upright, or standing, orientation. * A transverse plane (also known as axial or horizontal plane) is parallel to the ground; it separates the
superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...
from the inferior, or the head from the feet. The transverse planes identified in '' Terminologia Anatomica'' are the
transpyloric plane The transpyloric plane, also known as Addison's plane, is an imaginary horizontal plane, located halfway between the suprasternal notch of the manubrium and the upper border of the symphysis pubis at the level of the first lumbar vertebrae, L1. It ...
, the
subcostal plane The subcostal plane is a transverse plane which bisects the body at the level of the 10th costal margin and the vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily los ...
, the transumbilical (or umbilical) plane, the
supracristal plane Supracristal plane (''Planum supracristale'') (or supracrestal plane) is an anatomical transverse plane lying at the upper most part of the pelvis, the iliac crest. This is usually at the level of the L4 vertebrae. It passes through the umbilical re ...
, the intertubercular plane, and the interspinous plane. * A coronal plane (also known as frontal plane) is perpendicular to the ground; it separates the anterior from the posterior, the front from the back, the ventral from the dorsal. * A sagittal plane (also known as anteroposterior plane) is perpendicular to the ground, separating left from right. The median (or midsagittal) plane is the sagittal plane that is exactly in the middle of the body; it passes through midline structures such as the navel and the
spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolo ...
. All other sagittal planes (also known as parasagittal planes) are parallel to it. The axes and sagittal plane are the same for bipeds and quadrupeds, but the orientation of the coronal and transverse planes switch. The axes on particular pieces of equipment may or may not correspond to axes of the body, especially since the body and the equipment may be in different relative orientations. File:Sobo 1909 623.png, Brain viewed from below. This is an example of a ''transverse plane''. File:Sobo 1909 624.png, Brain cut in half through the midsection. This is an example of a ''sagittal plane''.


Uses


Motion

When describing anatomical motion, these planes describe the axis along which an action is performed. So by moving through the transverse plane, movement travels from head to toe. For example, if a person jumped directly up and then down, their body would be moving through the transverse plane in the coronal and sagittal planes. A ''longitudinal plane'' is any plane perpendicular to the transverse plane. The
coronal plane The coronal plane (also known as the frontal plane) is an anatomical plane that divides the body into dorsal and ventral sections. It is perpendicular to the sagittal and transverse planes. Details The coronal plane is an example of a longitud ...
and the sagittal plane are examples of longitudinal planes.


Medical imaging

Sometimes the orientation of certain planes needs to be distinguished, for instance in
medical imaging Medical imaging is the technique and process of imaging the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to rev ...
techniques such as
sonography Medical ultrasound includes diagnostic techniques (mainly medical imaging, imaging techniques) using ultrasound, as well as therapeutic ultrasound, therapeutic applications of ultrasound. In diagnosis, it is used to create an image of internal ...
, CT scans, MRI scans, or PET scans. There are a variety of different standardized coordinate systems. For the
DICOM Digital Imaging and Communications in Medicine (DICOM) is the standard for the communication and management of medical imaging information and related data. DICOM is most commonly used for storing and transmitting medical images enabling the integ ...
format, the one imagines a human in the anatomical position, and an X-Y-Z
coordinate system In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space. The order of the coordinates is sign ...
with the x-axis going from front to back, the y-axis going from right to left, and the z-axis going from toe to head. The
right-hand rule In mathematics and physics, the right-hand rule is a common mnemonic for understanding orientation of axes in three-dimensional space. It is also a convenient method for quickly finding the direction of a cross-product of 2 vectors. Most of t ...
applies.


Finding anatomical landmarks

In humans, reference may take origin from
superficial anatomy Surface anatomy (also called superficial anatomy and visual anatomy) is the study of the external features of the body of an animal.Seeley (2003) chap.1 p.2 In birds this is termed ''topography''. Surface anatomy deals with anatomical features th ...
, made to
anatomical landmark Anatomical terminology is a form of scientific terminology used by anatomists, zoologists, and health professionals such as doctors. Anatomical terminology uses many unique terms, suffixes, and prefixes deriving from Ancient Greek and Latin. T ...
s that are on the skin or visible underneath. As with planes, lines and points are imaginary. Examples include: * The midaxillary line, a line running vertically down the surface of the body passing through the apex of the
axilla The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded super ...
(armpit). Parallel are the anterior axillary line, which passes through the anterior axillary skinfold, and the posterior axillary line, which passes through the posterior axillary skinfold. * The mid-clavicular line, a line running vertically down the surface of the body passing through the midpoint of the
clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the right ...
. In addition, reference may be made to structures at specific levels of the
spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolo ...
(e.g. the 4th
cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sau ...
, abbreviated "C4"), or the rib cage (e.g., the 5th
intercostal space The intercostal space (ICS) is the anatomic space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it. Structures in intercostal space * several kinds ...
). Occasionally, in medicine,
abdominal The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
organs may be described with reference to the trans-pyloric plane, which is a transverse plane passing through the
pylorus The pylorus ( or ), or pyloric part, connects the stomach to the duodenum. The pylorus is considered as having two parts, the ''pyloric antrum'' (opening to the body of the stomach) and the ''pyloric canal'' (opening to the duodenum). The ''pylori ...
.


Comparative embryology

In discussing the
neuroanatomy Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defi ...
of animals, particularly rodents used in neuroscience research, a simplistic convention has been to name the sections of the brain according to the homologous human sections. Hence, what is technically a ''transverse'' (orthogonal) section with respect to the body length axis of a rat (dividing anterior from posterior) may often be referred to in rat neuroanatomical coordinates as a ''coronal'' section, and likewise a ''coronal'' section with respect to the body (i.e. dividing ventral from dorsal) in a rat brain is referred to as ''transverse''. This preserves the comparison with the human brain, whose length axis in rough approximation is rotated with respect to the body axis by 90 degrees in the ventral direction. It implies that the planes of the brain are not necessarily the same as those of the body. However, the situation is more complex, since comparative embryology shows that the length axis of the neural tube (the primordium of the brain) has three internal bending points, namely two ventral bendings at the
cervical In anatomy, cervical is an adjective that has two meanings: # of or pertaining to any neck. # of or pertaining to the female cervix: i.e., the ''neck'' of the uterus. *Commonly used medical phrases involving the neck are **cervical collar **cervic ...
and
cephalic flexure Three flexures form in the part of the embryonic neural tube that develops into the brain. At four weeks gestational age in the human embryo the neural tube has developed at the cranial end into three swellings – the primary brain vesicles. The ...
s (cervical flexure roughly between the medulla oblongata and the spinal cord, and cephalic flexure between the diencephalon and the
midbrain The midbrain or mesencephalon is the forward-most portion of the brainstem and is associated with vision, hearing, motor control, sleep and wakefulness, arousal (alertness), and temperature regulation. The name comes from the Greek ''mesos'', "m ...
), and a dorsal ( pontine or rhombic flexure) at the midst of the hindbrain, behind the
cerebellum The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cerebe ...
. The latter flexure mainly appears in mammals and sauropsids (reptiles and birds), whereas the other two, and principally the cephalic flexure, appear in all vertebrates (the sum of the cervical and cephalic ventral flexures is the cause of the 90 degree angle mentioned above in humans between body axis and brain axis). This more realistic concept of the longitudinal structure of vertebrate brains implies that any section plane, except the sagittal plane, will intersect variably different parts of the same brain as the section series proceeds across it (relativity of actual sections with regard to topological morphological status in the ideal unbent neural tube). Any precise description of a brain section plane therefore has to make reference to the anteroposterior part of the brain to which the description refers (e.g., transverse to the midbrain, or horizontal to the diencephalon). A necessary note of caution is that modern embryologic orthodoxy indicates that the brain's true length axis finishes rostrally somewhere in the hypothalamus where basal and alar zones interconnect from left to right across the median line; therefore, the axis does not enter the telencephalic area, although various authors, both recent and classic, have assumed a telencephalic end of the axis. The causal argument for this lies in the end of the axial mesoderm -mainly the notochord, but also the prechordal plate- under the hypothalamus. Early inductive effects of the axial mesoderm upon the overlying neural ectoderm is the mechanism that establishes the length dimension upon the brain primordium, jointly with establishing what is ventral in the brain (close to the axial mesoderm) in contrast with what is dorsal (distant from the axial mesoderm). Apart from the lack of a causal argument for introducing the axis in the telencephalon, there is the obvious difficulty that there is a pair of telencephalic vesicles, so that a bifid axis is actually implied in these outdated versions.


History

Some of these terms come from Latin. ''Sagittal'' means "like an arrow", a reference to the position of the spine that naturally divides the body into right and left equal halves, the exact meaning of the term "midsagittal", or to the shape of the sagittal suture, which defines the sagittal plane and is shaped like an arrow.


See also

*
Anatomical terms of location Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
*
Horizontal plane In astronomy, geography, and related sciences and contexts, a '' direction'' or '' plane'' passing by a given point is said to be vertical if it contains the local gravity direction at that point. Conversely, a direction or plane is said to be ho ...


References

{{Anatomical planes, state=collapsed Anatomical planes planes Anatomy Human surface anatomy