Anatomical terms of motion

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 its complete medial and abduction stage 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. See: Medical terminology

All motions are considered to be a mixture of or a single contribution by the following types of movement.

Most terms of a motion have clear opposites, and as such, are treated below in pairs.

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). Good examples of hip flexors are the rectus femoris, sartorius, iliacus, and psoas. Some knee flexors are the biceps femoris, semitendinosus, and semimembranosus. A couple elbow flexors are the brachialis, biceps brachii, and brachioradialis.	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). Elbow extensors include the triceps brachii and anconeus. The main muscles that extends the hip is the gluteus maximus. The muscles that extend the knee are the quadriceps. They are the rectus femoris, vastus lateralis, vastus medalis, and vastus intermedius.
Adjusting relation to mid-line of body	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 laterally, to the sides, is an example of abduction. A good example for the arm is the deltoid. Some leg abductors are the gluteus medius and the gluteus minimus.	Adduction – A motion that pulls a structure or part toward 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. The inner thigh houses some adductors, including the adductor brevis, adductor longus, adductor magnus, and pectineus. The latissimus dorsi is a good example for the arm.
Rotating body parts	Internal rotation (or medial rotation) of the shoulder or hip would point the toes or the flexed forearm inwards (towards the midline). The pectoralis major and subscapularis both medially rotate the humerus. The adductor longus and adductor brevis both medially rotate the thigh.	External rotation (or lateral rotation) is the opposite of Internal Rotation. It would turn the toes or the flexed forearm outwards (away from the midline). The sartorius laterally rotates the femur. The infraspinatus and teres minor both laterally rotate the humerus.
Adjusting elevation	Elevation – Movement in a superior direction. The upper muscle fibers of the trapezius aid in elevating the apex of the shoulder.	Depression – Movement in an inferior direction, the opposite of elevation. Opposite to the upper fibers, the lower half of the trapezius aids in depressing the apex of the shoulder.

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Special motions of the hands and feet

surfaces of the hands and feet	The palm (adj palmar) of the hand corresponds to the sole (adj plantar) of the foot. The adjective 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, or palm facing down. This is not medial rotation as this must be performed when the arm is half flexed. (See also Pronator quadratus and Pronator teres muscle.)	Supination – The opposite of pronation, the rotation of the forearm so that the palm faces anteriorly, or palm facing up. The hand is supine (facing anteriorly) in the anatomical position. (See also Supinator muscle.)
bending of the entire foot	Dorsiflexion – Extension of the entire foot superiorly, as if taking one's foot off an automobile pedal.	Plantarflexion – Flexion of the entire foot inferiorly, as if pressing an automobile pedal. Occurs at ankle.
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 – general	Protrusion – The anterior movement of an object. This term is often applied to the jaw.	Retrusion – The opposite of protrusion, moving a part posteriorly.
anterior/posterior movement – shoulders	Protraction – Anterior movement of the arms at the shoulders.	Retraction – Posterior movement of the arms at the shoulders.
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.)

Some additional motions without clear opposites are as follows:

• Rotation – A motion that occurs when a part turns on its axis. The head rotates on the neck, as in shaking the head 'no'.
• 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.

• Opposition – A motion involving a grasping of the thumb and fingers.
• Reposition – To release an object by spreading the fingers and thumb.

• Reciprocal motion of a joint – Alternating motion in opposing directions, such as the elbow alternating between flexion and extension.

See also

• Anatomical terms of location
• Medical terminology

References

Saladin, K.S. 2010. Anatomy & Physiology: 5th edition. McGraw-Hill.

Grants Atlas of Anatomy: 12th edition. Lippincott Williams & Wilkins.

External references

• White, T. D. & P. A. Folkens. Human Osteology. 1991. Academic Press, Inc. San Diego.

External links

• Hypermuscle: Muscles in Action at med.umich.edu