lateral pterygoid muscle

lateral pterygoid muscle

n.

A muscle whose inferior head has origin from the pterygoid process, and whose superior head has origin from the sphenoid bone, with insertion into the mandible and the articular disk, with nerve supply from the lateral pterygoid branch of the trigeminal nerve, and whose action brings the jaw forward and opens it.

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muscle(s),

n an organ that, by cellular contraction, produces the movements of life. The two varieties of muscle structure are striated, which includes all the muscles in which contraction is voluntary and the heart muscle (in which contraction is involuntary), and unstriated, smooth, or organic, which includes all the involuntary muscles (except the heart), such as the muscular layer of the intestines, bladder, and blood vessels. See also each of the individual muscles of the head and neck as they are listed.

muscle, buccinator

(buk´sinātr),
n the muscle consisting of three bands and composing the wall of the cheek between the mandible and the maxilla; it causes the cheek to stay tight to the teeth and the lip corners to pull inward. It is often known as the “cheek muscle.”

muscle, ciliary

(sil´ēer´ē),
n a tiny smooth muscle at the junction of the cornea and sclera, consisting of two groups of fibers: circular fibers, which exert parasympathetic control through the oculomotor nerve and the ciliary ganglion, and radial fibers, which exert sympathetic control. Ciliary muscles are responsible for accommodation for far vision through flattening of the lens.

muscle, concentric, contraction,

n See contraction, muscle, concentric.

muscle contraction,

n See contraction, muscle.

muscle, digastric

n suprahyoid muscle that helps activate the jaw for mastication and swallowing. It has both an anterior and a posterior belly. See also deglutition; mastication; muscle, hyoid.

muscle, eccentric, contraction,

n See contraction, muscle, eccentric.

muscle, elasticity of, physical,

n the physical quality of being elastic, of yielding to passive physical stretch.

muscle, elasticity of, physiologic,

n the biologic quality, unique for muscle, of being able to change and resume size under neuromuscular control.

muscle fatigue,

n the depletion of the metabolites necessary to sustain or repeat a muscle contraction.

muscle fiber,

n the cell of muscle tissue. The three types of muscle fibers are striated (voluntary), cardiac, and smooth (involuntary).

muscle, functional changes of,

n.pl asymmetric modifications in length, diameter, and bulk of muscle fibers as a result of variations in function. Muscle responds to normal function by maintenance of bulk. An increase in bulk is caused by an increase in the number of capillaries and in the mean diameter of individual muscle fibers. The response to function accounts for the asymmetry of the musculature, which is frequently found when the growth patterns have been influenced by a traumatogenic agent such as disease, injury, or surgery, and also by the functional processes of the body itself, such as posture and habit. Asymmetry is not necessarily pathologic; i.e., it may be the result of differences in habits of chewing, incision, speech sounds, and facial gestures.

muscle, genioglossus

(jē´nēōglôs´us),
n an extrinsic tongue muscle that originates from the genial tubercles of the mandible and extends inside the tongue. It aids in tongue extension and prevents respiratory obstruction.

muscle, geniohyoid

(jē´nēōhī´oid),
n suprahyoid muscle attached to the superior surface of the hyoid bone. This muscle, which is used for mastication and swallowing, originates on the genial tubercles of the mandible and extends along the floor of the oral cavity. See also deglutition; mastication; muscle, hyoid.

muscle, hyoglossus

(hī´ōglôs´s),
n an extrinsic tongue muscle that originates from the hyoid bone and extends on the lateral surface of the body of the tongue. It depresses the tongue during mastication and speech.

muscle, hypertenseness,

n an increased muscular tension that is not easily released but that does not prevent normal lengthening of the muscle. Hypertenseness is found in patients with general nervousness.

muscle, innervation of, reciprocal,

n a phenomenon of antagonistic muscles demonstrated during a concentric contraction such as that of the temporal muscle. Innervation of the antagonist, the external pterygoid muscle, is partially inhibited, so that freedom of action in flexing the temporomandibular joint is possible. This phenomenon demonstrates inhibition of antagonistic skeletal muscles in a reflex arc brought about automatically by a reduction of the motor discharges from the central nervous system. One of the two muscles in the reflex arc is activated, and the activity of the other is depressed.

muscle, isometric, contraction,

n See contraction, muscle, isometric.

muscle, isotonic, contraction,

n See contraction, muscle, isotonic.

muscle, lateral pterygoid

(lat´rl ter´igoid),
n the muscle whose superior head attaches to the sphenoid bone and whose inferior head attaches to the pterygoid plate. This muscle moves the jaw from side to side. Also known as the
external pterygoid muscle.

muscle, masseter

(msē´tr),
n one of the four muscles of mastication. The thick rectangular muscle in the cheek that functions to close the jaw. The masseter muscle arises from the zygomatic arch and inserts into the mandible at the corner of the jaw.

Palpation of the masseter muscle.

muscle memory,

n a kinesthetic phenomenon by which a muscle or set of muscles may involuntarily produce movement that follows a pattern that has become established by frequent repetition over a long period.

muscle, mentalis

(mental´s),
n the muscle in the chin that originates in the incisive fossa and is inserted into the skin of the chin; it lifts the lower lip and wrinkles the skin of chin.

muscle, mylohyoid,

n suprahyoid muscle originating from the mandible. It helps to raise the tongue and lower the mandible for mastication and swallowing and also forms the floor of the oral cavity. See also deglutition; mastication; muscles, hyoid.

muscle, omohyoid

n infrahyoid muscle with both inferior and superior bellies. It is used for chewing and swallowing. See also muscles, hyoid.

muscle, orbicularis oris

(orbik´ylar´s or´is),
n the muscle that encircles the oral cavity; it encompasses both fibers proper to the lips as well as the adjacent facial muscles. Also known as the “kissing muscle” for its puckering role, it is intimately involved in the opening and closing of the oral cavity.

muscle, palatoglossal

(pal´tōglos´l),
n the interior palate muscle that serves to raise and lower the posterior part of the tongue.

muscle, palatopharyngeus

(pal´tōferin´jēs),
n the muscle that extends from the soft palate to the walls of the laryngopharynx and the thyroid cartilage to form the posterior facial pillars; it is used during swallowing to cover the opening of the nasopharynx by moving the palate and the posterior pharyngeal wall.

muscle, physical characteristics of primary, elasticity,

n.pl a muscle is an elastic body. Its individual fibers follow Hooke's law of elastic bodies: that is, the amount of elongation is proportional to the stretching force. The muscle organs contain tissue other than muscle fibers and thus deviate slightly from this law. The human muscle fiber can contract to about half its total length.

muscle, platysma

(pltiz´m),
n the muscle that extends from the clavicle and shoulder, along the neck, to the mandible and the muscles surrounding the oral cavity; it allows the corners of the oral cavity to be pulled down in a grimace and the skin of the neck to be raised into ridges and depressions.

muscle, regeneration of reproduction or repair of muscle fiber,

n a sequela to many types of muscle damage. Reparation is always associated with the proliferation of sarcolemmic nuclei. Connective tissue elements do not participate in this process except to bridge the gap and offer support for the regenerative fibers. The regenerative process takes place in two forms: regeneration by budding from the surviving parts of the muscle fibers, which occurs when segments of the muscle fiber and its sheath are destroyed, and regeneration by proliferation of cellular bands, which occurs when the sarcolemmic nuclei are spared and can form a sarcoplasmic band by linkage of the cytoplasmic processes.

muscle relaxation,

n the resting state of a muscle fiber or a group of muscle fibers.

muscle reposition,

n surgical replacement of a muscle attachment into a more acceptable functional position.

muscle, sequence of, development,

n the pattern of embryologic muscular development. The muscles of the neck and trunk are the first to develop; they are followed by the lingual and facial musculature and then by the distal and proximal appendicular musculature.

muscle, smooth,

n the simplest of the three types of muscle (smooth, striated, and cardiac). It is the muscle of the lining of the digestive tract, ducts of glands, and viscera associated with the gut. It also supplies the muscles for the genitourinary tract, structures of the blood vessels, connective tissues of the mucous membranes, and skin with its appendages. A typical fiber is a slender, spindle-shaped body averaging a few tenths of a millimeter in length. There is a single, centrally striated nucleus. The cytoplasm appears homogeneous. The cells are arranged in bands, or bundles, with interspersed connective tissue fibers uniting them into an effective common mass. They are innervated in part by nerve fibers and in part by the contraction of adjacent muscle tissues. The digestive tract, particularly, demonstrates waves of contraction that pass along a band of smooth muscle.

muscle, spasticity of,

n increased muscular tension of antagonists that prevents normal movement; caused by an inability to relax (a loss of reciprocal inhibition) resulting from a lesion of the upper motor neuron.

muscle, sternocleidomastoid (SCM),

n a muscle of the neck that is attached to the mastoid process and superior nuchal line and by separate heads to the sternum and clavicle. It functions with other muscles to turn the head from side to side and tilt the head to one side or the other. It separates the neck region into triangles.

muscle, sternothyroid

(stur´nōthī´roid),
n infrahyoid mus-cle that runs from the sternum to the thyroid cartilage and depresses the larynx and the thyroid cartilage for mastication and swallowing. See also deglutition; mastication; muscle, hyoid.

muscle, striated

n skeletal muscles forming the bulk of the body; the voluntary muscles derived from the myotomes of the embryo. Generally, they are organized as formed muscles that attach to and move the skeletal structures. The cells are large, elongated, and cylindric, with lengths ranging from 1 mm to several centimeters. The cells have multiple nuclei that are peripherally situated and scattered along the length of the fiber. The fiber contains a large number of elongated fibers that, under the microscope, appear as the alternating light and dark bands that give the characteristic striated appearance of striated muscle. The dimensional relationships between these light and dark bands are altered during contraction of the muscle fiber. The potential interaction between these bands permits the wide range of selective purposeful and rapid activity of the skeletal muscles.