Anatomical Position
Ø All anatomical descriptions are expressed in relation to one consistent position, ensuring that descriptions are not ambiguous. One must visualize this position in the mind when describing patients (or cadavers), whether they are lying on their sides, supine (recumbent, lying on the back, face upward), or prone (lying on the abdomen, face downward). The anatomical position refers to the body position as if the person were standing upright with the:
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Head, gaze (eyes), and toes directed anteriorly (forward).
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Arms adjacent to the sides with the palms facing anteriorly.
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Lower limbs close together with the feet parallel.
Ø This position is adopted globally for anatomicomedical descriptions. By using this position and appropriate terminology, you can relate any part of the body precisely to any other part. It should also be kept in mind, however, that gravity causes a downward shift of internal organs (viscera) when the upright position is assumed. Since people are typically examined in the supine position, it is often necessary to describe the position of the affected organs when supine, making specific note of this exception to the anatomical position.
Anatomical Planes
Ø Anatomical descriptions are based on four imaginary planes (median, sagittal, frontal, and transverse) that intersect the body in the anatomical position:
A. The median plane (median sagittal plane), the vertical anteroposterior plane passing longitudinally through the midlines of the head, neck, and trunk where it intersects the surface of the body, dividing it into right and left halves. Midline is often erroneously used as a synonym for the median plane.
B. Sagittal planes are vertical planes passing through the body parallel to the median plane. “Parasagittal” is commonly used but is unnecessary because any plane parallel to and on either side of the median plane is sagittal by definition. However, a plane parallel and near to the median plane may be referred to as a paramedian plane.
C. Frontal (coronal) planes are vertical planes passing through the body at right angles to the median plane, dividing the body into anterior (front) and posterior (back) parts.
D. Transverse planes are horizontal planes passing through the body at right angles to the median and frontal planes, dividing the body into superior (upper) and inferior (lower) parts. Radiologists refer to transverse planes as transaxial, which is commonly shortened to axial planes. Since the number of sagittal, frontal, and transverse planes is unlimited, a reference point (usually a visible or palpable landmark or vertebral level) is necessary to identify the location or level of the plane, such as a “transverse plane through the umbilicus”. Sections of the head, neck, and trunk in precise frontal and transverse planes are symmetrical, passing through both the right and left members of paired structures, allowing some comparison.
E. Longitudinal sections run lengthwise or parallel to the long axis of the body or of any of its parts, and the term applies regardless of the position of the body. Although median, sagittal, and frontal planes are the standard (most commonly used) longitudinal sections, there is a 180° range of possible longitudinal sections.
F. Transverse sections, or cross sections, are slices of the body or its parts that are cut at right angles to the longitudinal axis of the body or of any of its parts. Because the long axis of the foot runs horizontally, a transverse section of the foot lies in the frontal plane.
G. Oblique sections are slices of the body or any of its parts that are not cut along the previously listed anatomical planes. In practice, many radiographic images and anatomical sections do not lie precisely in sagittal, frontal, or transverse planes; often, they are slightly oblique.
Ø Anatomists create sections of the body and its parts anatomically, and clinicians create them by planar imaging technologies, such as computerized tomography (CT), to describe and display internal structures.