Protraction: Effect, Uses & Risks

In anatomy, protraction corresponds to a forward movement of individual body structures. The opposite movement is retraction. The increased protraction of the chin, for example, can promote a herniated disc in the long term.

What is protraction?

In anatomy, protraction plays a role as a movement term, especially in connection with the scapula, for example. Anatomy uses different motion terms for motion sequences close to the joints. One of these terms is protraction. The term corresponds to a loanword from Latin and derives from the verb ‘protrahere’ for ‘to draw forth’ or ‘to extend’. In anatomy, protraction thus refers to the forward movement of extremities and otherwise movable body structures. The opposite direction of motion corresponds to retraction. The term protraction does not necessarily have to be used in an anatomical context within medicine. The word can just as well be used in the context of pharmacology. Unlike anatomists, pharmacologists understand protraction as the deliberate delay in the action of a drug. Interrelationships of this kind are dealt with primarily by pharmacokinetics, which, in addition to the uptake of drugs (absorption), studies the distribution of substances in the body (distribution), the biochemical conversion and degradation processes (metabolization), and the excretion processes (excretion).

Function and task

The joints of the human body connect two or more bones in a mobile manner. In different joints, different motion sequences are conceivable for the connected bones. The respective motion sequences are based on the specific requirements that extremities and bones must fulfill in the human body. For this reason, for example, not every joint enables the connected bones to perform movements such as protraction. Protraction is a forward movement. In anatomy, protraction as a movement term plays a role primarily in connection with the jaw and the scapula. The scapula is the upper part of the bony shoulder girdle and is in articulated connection with the upper arm bone (humerus) and the clavicle. The mandible, in turn, is a bone of the facial skull that corresponds to the more mobile portion of the masticatory apparatus. The scapula can undergo protraction and retraction by moving forward and backward in a ventral (abdominal) or dorsal (dorsal) direction. This movement is an important type of movement for the entire arm. As soon as people extend their arms toward something, a protraction of the scapula connected to the humerus is required. The arm is thus extended and purposefully stretched toward the object. Both protraction and retraction of the scapula are performed by muscles of the shoulder girdle. Efferent motor nerves connect these muscles to the central nervous system and transmit the contraction command in the form of bioelectric excitation via the motor end plate to the effector muscle. Retraction is similar in itself, but is performed by a different muscle. The pro- and retraction ability of the mandible is in turn relevant for food intake. The maxillary bone is static and cannot be moved purposefully. The movable mandible compensates for this static. A completely different definition for the expression of protraction exists in pharmacokinetics. In this context, the principle of the retard drug plays an important role. Retard drugs develop their effect in the organism only after a delay, since the active ingredients are released only slowly. This slow release is intentional and is mostly used for peroral drugs. Short-term high blood levels of the drugs are thus prevented. The effect of sustained-release drugs also lasts longer and is more controlled, as is the case, for example, with some hormones taken perorally and drugs that regulate blood pressure.

Diseases and medical conditions

Herniated discs are often due to excessive protratcion movements. For example, those who habitually move their chin in protraction, pushing it forward while their head rests on the neck, risk cervical spine impairments. Modern lifestyle contributes to disc herniations based on increased protraction movements of the chin area.For example, in the 21st century, the computer is an irreplaceably important tool in both leisure and work. In front of the computer screen, however, the chin performs more protraction movements. The anterior structures of the cervical spine are brought to length by the protraction. This elongation of the anterior structures is opposed by the simultaneous compression of the posterior structures. Thus, the continuous protraction of the chin in front of the computer simultaneously stresses both the posterior and anterior structures of the cervical spine. The result is permanent postural damage and pain symptoms. There is a slowly increasing displacement in the area of the intervertebral discs, which can be accompanied by compression of the spinal cord or nerve compression. These processes correspond to a herniated disc of the cervical spine, the leading symptom of which is pain radiating into the arms or as far as the occipital region. Depending on the compression of the surrounding nerves, sensory disturbances or even paralysis of the arm and hand muscles may occur. Disc protrusion can also be a symptom of increased protraction of the chin structures. This is not directly a herniated disc, but an isolated protrusion of the disc’s gelatinous nucleus. The outer fibrous ring of the disc is not yet ruptured in this phenomenon. In a manifest herniated disc of the cervical spine, the fibrous ring ruptures and allows the gelatinous nucleus to protrude to the sides, downward and upward. Not only excessive protraction, but also decreased protraction capacity may indicate pathological changes. This is true, for example, when structures that are physiologically actually capable of protraction can no longer be moved in protraction. Usually, this phenomenon is neuromuscular in origin.