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The movement of body structures is accomplished by the contraction of muscles. Muscles may move parts of the skeleton relatively to each other, or may move parts of internal organs relatively to each other. All such movements are classified by the directions in which the affected structures are moved. In human anatomy, all descriptions of position and movement are based on the assumption that the body is in anatomical position.
The prefix hyper- is sometimes added to emphasize movement beyond the normal position, such as in hyperflexion or hyperextension. Such movements can put significant stress on the joints involved.
All motions are considered to be a mixture of or a single contribution by the following types of movement.
General Motion
- Adjusting angle between two parts
- Flexion - Bending movement that decreases the angle between two parts. Bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed. Flexion of the hip or shoulder moves the limb forward (towards the anterior side of the body).
- Extension - The opposite of flexion; a straightening movement that increases the angle between body parts. In a conventional handshake, the fingers are fully extended. When standing up, the knees are extended. Extension of the hip or shoulder moves the limb backward (towards the posterior side of the body).
- Adjusting relation to midline of body
- Adduction - A motion that pulls a structure or part towards the midline of the body, or towards the midline of a limb. Dropping the arms to the sides, or bringing the knees together, are examples of adduction. In the case of the fingers or toes, adduction is closing the digits together. Adduction of the wrist is called ulnar deviation.
- Abduction - A motion that pulls a structure or part away from the midline of the body (or, in the case of fingers and toes, spreading the digits apart, away from the centerline of the hand or foot). Abduction of the wrist is called radial deviation. Raising the arms to the sides is an example of abduction.
- Adjusting elevation
- Elevation - Movement in a superior direction. This term is often applied to the shoulders (eg shrugging shoulders is elevation).
- Depression - Movement in an inferior direction, the opposite of elevation.
Special motions of the hands and feet
| A flexed arm in the pronated position. Note the hand position, and that the biceps brachii muscle is not fully contracted. | A flexed arm in the supinated position. Note the hand position, and that the biceps brachii muscle is fully contracted. |
- sides of the hands and feet
- The palm (adj palmar) of the hand corresponds to the sole (adj plantar) of the foot. The term volar, used mainly in orthopaedics, is synonymous with palmar and plantar.
- The dorsum (back) of the hand corresponds to the dorsum (top) of the foot.
- rotation of the forearm
- Pronation - A rotation of the forearm that moves the palm from an anterior-facing position to a posterior-facing position. This is not medial rotation as this must be performed when the arm is half flexed.
- Supination - The opposite of pronation, the rotation of the forearm so that the palm faces anteriorly. The hand is supine (facing anteriorly) in the anatomical position.
- flexion of the entire foot
- Dorsiflexion - flexion of the entire foot superiorly, or upwards.
- Plantarflexion - Flexion of the entire foot inferiorly, or downwards.
- movement of the sole of the foot
- Eversion - the movement of the sole of the foot away from the median plane.
- Inversion - the movement of the sole towards the median plane. (same as when an ankle is twisted).
Other special motions
- anterior/posterior movement
- Protrusion - The anterior movement of an object. This term is often applied to the jaw.
- Retraction - The opposite of protrusion, moving a part posteriorly.
- motion in an arc
- Rotation - A motion that occurs when a part turns on its axis. The upper arm rotates on the shoulder socket, and the head rotates on the neck.
- Circumduction - The circular (or, more precisely, conical) movement of a body part, such as a ball-and-socket joint or the eye. It consists of a combination of flexion, extension, adduction, and abduction. "Windmilling" the arms or rotating the hand from the wrist are examples of circumductive movement.
- motion within body (such as in blood vessels or the digestive system)
- anterograde motion is in the normal direction of flow. (For example, passage of food from the mouth to the stomach.)
- retrograde motion means reversed flow. (For example, gastric reflux.)
- Opposition - A motion in which body parts are brought together. Most commonly used to describe the grasping motion of the thumb and fingers.
See also
External links
- Gross movements at the joints of the body
- Guidance on normal range of muscle movements.
- Relative motions
- Movement
- Control of Human Movement I
- Hypermuscle: Muscles in Action
External references
- White, T. D. & P. A. Folkens. Human Osteology. 1991. Academic Press, Inc. San Diego.
"Anatomical terms of motion"