Systema musculare
Muscoli scheletrici, tendini e fasce.
Zygomaticus major may be absent or doubled. Zygomaticus minor may be absent or it may be fused with zygomaticus major. In addition, the muscle may be doubled throughout or only at one end. Syn.: m. zygomaticus.
See Thyroarytenoideus .
See Quadriceps .
See Articularis genus .
See Pronator quadratus .
See Pronator quadratus .
See Flexor digiti minimi brevis .
See Extensor carpi ulnaris .
See Hyoglossus .
Variations in the triceps are neither numerous or common. Each of the heads may be fused, in varying degrees, with neighboring muscles. The fibers of the long head may be found extending to the capsule of the shoulder joint above or distally, for a greater extent than usual on the axillary border of the scapula. Macalister (1875) described the variations of triceps extensor cubiti (triceps brachii) as follows: 1.
Like the sternocleidomastoid, the trapezius is a compound muscle consisting of three distinct parts, as indicated by a more or less clear separation of the clavicular portion of the muscle from the rest and, less frequently, by the separation of the lower from the middle portion. The three parts consist of 1) a dorsoscapularis superior, 2) a dorsoscapularis inferior, and 3) a cleidooccipitalis division.
Transversus thoracis arises from the posterior surface of the sternum and xiphoid (to the level of the third costal cartilage) and extends onto the internal surface of the second (third) to sixth costal cartilages. Transversus thoracis may extend to the first rib. Absence on one or both sides has been recorded. It is sometimes divided into separate fasciculi which may number from two to six, and its division into two lamellae has also been observed. This muscle was Hyrtl's candidate for the most variable in the body.
This muscle is frequently absent or poorly developed. Sometimes it consists of several separate fasciculi, and it may be inserted wholly or in large part into the bulbocavernosus or external anal sphincter. A muscular slip is occasionally found arising from the fascia at the lower border of gluteus maximus or upper fascia lata and inserts under the origin of bulbocavernosus in the albuginea of the bulbous (penile) urethra in males. This variation is not found in females.
This muscle, variable in its development, may be absent. This very rare variation occurs more frequently in females.
See Adductor hallucis, caput transversum .
See Obliquus superior .
See Occipitalis minor .
See Depressor anguli oris .
See Adductor pollicis brevis .
See Orbicularis oculi .
See Transversus abdominus .
The number of costal slips varies: it may be reduced to five or increased to seven. The muscle has been fused with internal oblique; it has also been reported absent. Absence of the inguinal bundles has been reported; on the other hand, extension of the transversus to the pubic crest has also been noted, and the spermatic cord has been seen piercing its lower border. The insertion onto the seventh rib may be absent, but in some cases there may be a supernumerary digitation for the sixth rib.
See Longissimus .
See Longissimus .
See Longissimus .
See Scaleneus anterior .
Muscular bands have been reported in the oblique fissure of the right lung, which originate from the sixth rib and extend to the central part of the diaphragm just behind the caval opening. Reference Allen, L. (1950) Transpleural muscles. J. Thoracic Surg. 19:290-291.
See Trapezius .
See Tibialis posterior .
See Tibialis posterior .
See Tibialis posterior .
See Tibialis posterior .
Variations of this muscle are few and rare. At least two cases have been reported in which the muscle consisted of two parts; the accessory part was inserted separately in the sole of the foot. The insertion onto the first cuneiform may be absent. Macalister reported the variations of the tibialis posterior as follows: 1. It may have a trifurcated tendon, one slip going to the usual site of insertion, the second to the tendon of peroneus longus, and the third to the heads of the third and fourth metatarsal bones; 2.
The tendon may be found divided, for a variable distance proximally, into a cuneal (reference os cuneiform) and metatarsal slip; in very rare instances, this division may involve the whole muscle. In some cases, a deep division of the tendon has been found inserted onto the talus (m. tibioastragalus of Gruber) , and the tendon may also supply a slip to the head of the first metatarsal or base of the first phalanx. A separate muscular slip, tibiofascialis anticus , sometimes occurs.
See Cricothyroideus .
See Constrictor pharyngeus inferior .
See Omohyoideus .
A superior thyroarytenoideus muscle, in the form of a thin band, arises from the inner, anterior superior surface of the thyroid cartilage and crosses the cartilage and thyroarytenoideus, inserting on the inferior lateral aspect of the arytenoid cartilage of the larynx. The portion of vocalis that inserts onto the the vocal ligament has been designated the aryvocalis (Ludwig) muscle.
Absence of teres minor has been reported. Teres minor may be absent in 4% of individuals (Mori, 1964). The partial separation into two parts has also been reported; one inserted onto the the greater tubercle and the other onto the neck of the humerus (teres minimus scapulae [Gruber]). The origin of the muscle may be expanded so that it covers the infraspinatus entirely replacing the fascial sheet (deep fascia) usually covering that muscle. Teres minor may fuse with infraspinatus in 20% of cases studied (Mori).
See Teres minor .
It is believed that this muscle is closely related developmentally with latissimus dorsi. It is part of the same muscle sheet and it is often fused with a slip of latissimus dorsi at the inferior angle of the scapula. A muscular slip has been found joining the scapular head of the triceps, as well as one joining the fascia of the (upper) arm on its lateral aspect. An accessory slip originating from the vertebral border of the scapula just below the spine has also been described. The tendon of insertion is variable.
See Levator palpebrae superioris .
Three bifurcated tensor tympani muscles have been reported. Middle ear muscle variations have a reported incidence of about 5.6% (Wright and Eitholm). See also m. Stapedius .
See Pectoralis major .
See Trapezius .
See Trapezius .
See Biceps femoris .
See Gastrocnemius .
This muscle is occasionally found doubled longitudinally, partially or completely. Accessory slips have been reported proceeding from the iliac crest, inguinal ligament, or aponeurosis of the abdominal wall. Union with gluteus maximus has been observed. This muscle is considered by some authors to be an atrophied relic of a "deltoid" of the hip. The muscle may be absent. The tensor fasciae latae and the gluteus maximus represent separated portions of a muscle known as the ilio-tibialis in reptilia (Iguana).
See Tibialis posterior .