Anatomical position
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The anatomical position is a schematic convention for describing the relative morphology of the human body. The person is oriented in an erect standing position, with eyes and head facing forward, feet forward and perpendicular to the body, arms close to the sides, and palms of the hands facing forward with fingers extended. It should be noted that this is not the normal position for the arms, which in a relaxed subject would be rotated more or less medially (with the palms of the hands facing the body).
The body in anatomical position may be divided conceptually by planes. The median plane passes through the long axis of the body and separates the left side from the right side of the body in equal halves; positions toward the median plane are called medial, and positions away from the median plane are called lateral. A sagittal plane is any plane parallel to the median, hence the median plane is also called the midsagittal plane. A sagittal slice or section that is not on the median plane is also referred to as a parasagittal section.
The frontal or coronal plane passes through the long axis of the body, is perpendicular to the median plane, and separates the front, or venter (from Latin venter, genitive ventris), from the back, or dorsum. Positions in front of the coronal plane are called anterior or ventral, and positions behind the coronal plane are called posterior or dorsal.
The horizontal or transverse plane is perpendicular to both of these planes and passes through the waist (just above the points of the hips). Positions above the transverse plane are called superior, and positions below the transverse plane are called inferior. In comparative anatomy, these may be called the rostral or cranial (head) or caudal (tail) ends respectively.
Since the foot is discontiguous with the coronal plane, it is described by analogy with the hand. The ventrum (palm) of the hand corresponds to the ventrum (sole) of the foot, and the dorsum (back) of the hand corresponds to the dorsum (top) of the foot. In an earlier scheme, the foot was flattened such that it was placed along the coronal plane, and flexion of the foot strictly described approximation of the heel toward the leg, with the foot proper producing a larger angle of the foot to the leg. Conversely, flexion in general produces a smaller angle of a part to an adjacent part, for example of the hand to the arm, thus certain analogies with the hand were lost. Terminology developed to address this possible ambiguity is dorsiflexion for strict extension of the foot (approximation of the toes toward the leg) and plantarflexion for strict flexion as described above.
The position of the hand in anatomical position is considered supine, such that rotation of the hand so that the palm faces backwards is called pronation and the reverse action, supination.
For the penis, the terms "ventral" and "dorsal" are used as if the penis were erect and pointing upwards, i.e. the dorsal side of the penis is what one would normally call its top side.
Other relative positions, directions and motions are discussed in the article Anatomical terms of location.