When a person is standing in the anatomical position, the head is pointed forward, the arms are at the sides with the palms facing forward, and the toes are pointed forward with the feet slightly separated. The anatomical position is used as a frame of reference for scientists and doctors.
Because humans are capable of moving their limbs in many directions, it is essential to have a specific position in mind when discussing the relative placement of body parts. The use of the anatomical position as a reference allowed for the development of directional terms. The word anterior, for instance, refers to a structure that is in front of another when a person is standing in the anatomical position. The word is used in statements such as "the belly button is anterior to the spine." The word inferior means below, such as in the statement "the ankles are inferior to the knees." Because a person can contort his or her body in such a way that the ankles are above the knees, directional statements like these only make sense in light of the anatomical position.
Several body planes are defined relative to the anatomical position. A median plane divides the body into equal left and right halves. A frontal plane runs vertical through the center of the body, dividing it into front and back, or anterior and posterior sides.