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 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 techniques such as
sonography,
CT scans,
MRI scans, or
PET scans. There are a variety of different standardized coordinate systems. For the
DICOM format, the one imagines a human in the anatomical position, and an X-Y-Z
coordinate system 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 applies.
Finding anatomical landmarks . In humans, reference may take origin from
superficial anatomy, made to
anatomical landmarks 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 (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. In addition, reference may be made to structures at specific levels of the
spine (e.g. the 4th
cervical vertebra, abbreviated "C4"), or the rib cage (e.g., the 5th
intercostal space). Occasionally, in medicine,
abdominal organs may be described with reference to the
trans-pyloric plane, which is a transverse plane passing through the
pylorus.
Comparative embryology In discussing the
neuroanatomy 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 and
cephalic flexures (cervical flexure roughly between the
medulla oblongata and the
spinal cord, and cephalic flexure between the
diencephalon and the
midbrain), and a dorsal (
pontine or rhombic flexure) at the midst of the hindbrain, behind the
cerebellum. 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. ==Other animals==