Musa \'mii-sa\ or Mousa (d. 1332/37?) Emperor ( mansa ) of the West African Mali empire from 1307 (or 1312). Musa left a realm notable for its extent and riches (he built the Great Mosque at Timbuktu), but he is best remembered for the splendour of his pilgrimage to Mecca (1324), which awakened the world to Mali’s stupendous wealth and stimulated a desire among North Africans and Europeans to locate its source. Under Musa, Mali became one of the largest empires in the world and Timbuktu grew to be a major commercial city.
Musandam \m9-'san-d9m\ Peninsula Northeastern extension of the Arabian Peninsula. It partially separates the Gulf of Oman from the Per¬ sian Gulf to form the Strait of Hormuz to the north. Part of Oman, it is divided from the rest of the country by the United Arab Emirates. It is a mountainous region with a rocky coast that is hazardous to passing ships. Fishing is the main industry, and there are reserves of petroleum and natural gas off the western coast. The port town of Dlba al-Hisn is on the southeastern coast.
Musavi, Ruhollah See Ruhollah Khomeini
Muscat or Masqat Vmos-.kaA City (pop., 2003: city, 24,769; urban agglom., 638,000), capital of Oman, located on the Gulf of Oman. Situ¬ ated on a cove surrounded by volcanic mountains, it came under Persian control in the 6th century bc, and Islam was introduced into the region in the 7th century ad. The Portuguese gained control in 1508 and made Muscat a trading post and naval base until they were expelled in 1650. Held again by the Persians (1650-1741), it later became part of the sul¬ tanate of Oman. Two 16th-century Portuguese forts overlook the city; the sultan’s Indian-style palace is built at the edge of the sea.
Muscat and Oman See Oman
muscle Contractile tissue that produces motion for functions, including body movements, digestion, focusing, circulation, and body warmth. It can be classified as striated, cardiac, and smooth or as phasic and tonic (responding quickly or gradually to stimulation, respectively). Striated muscle, whose fibres appeal' striped under a microscope, is responsible
for voluntary movement. Most of these muscles are phasic. They are attached to the skeleton and move the body by contracting in response to signals from the central nervous system; contraction is achieved by the sliding of thin filaments (of actin) between thick ones (of myosin); stretch receptors in the tissue provide feedback, allowing smooth motion and fine motor control. The branched fibres of cardiac muscle give it a netlike structure; contraction originates in the heart’s muscle tissue itself with a signal from the natural pacemaker; vagus and sympathetic nerves control heart rate. Smooth muscle, the muscle of internal organs and blood ves¬ sels, is generally involuntary and tonic; its cells can operate either col¬ lectively or individually (in response to separate nerve endings) and have different shapes. Disorders of voluntary muscle cause weakening, atro¬ phy, pain, and twitching. Some systemic diseases (e.g., dermatomyositis, polymyositis) can cause muscle inflammation. See also abdominal muscle; muscle tumour; muscular dystrophy; myasthenia gravis.
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Major muscles of the human body. (1) frontalis, (2) occipitalis, (3) temporalis, (4) orbicularis of eye, (5) nasalis, (6) orbicularis of mouth, (7) mentalis, (8) masseter,
(9) platysma, (10) sternocleidomastoid, (11) trapezius, (12) pectoralis major, (13) deltoid, (14) latissimus dorsi, (15) anterior serratus, (16) external oblique, (17) rec¬ tus abdominis, (18) internal oblique, (19) infraspinatus, (20) teres minor, (21) teres major, (22) biceps, (23) triceps, (24) brachialis, (25) long radial extensor of wrist, (26) short palmaris, (27) pronator quadratus, (28) annular ligament of the carpus, (29) common extensor of digits, (30) ulnar extensor of wrist, (31) tendons of exten¬ sors of digits and wrists, (32) palmar aponeurosis, (33) gluteus medius, (34) tensor of the fascia lata, (35) rectus femoris, (36) pectineus, (37) sartorius, (38) long adductor of thigh, (39) gracilis, (40) vastus lateralis, (41) vastus medialis, (42) patella, (43) anterior tibialis, (44) medial head of gastrocnemius, (45) soleus, (46) annular ligament of ankle, (47) short extensor, (48) gluteus maximus, (49) biceps of thigh, (50) semitendinosus, (51) plantaris, (52) lateral head of gastrocnemius, (53) Achilles' tendon.
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Muscle Shoals Former rapids, Tennessee River, northwestern Alabama, U.S. At about 37 mi (60 km) long, it was a navigation hazard but is now submerged under at least 9 ft (3 m) of water by the Wilson, Wheeler, and Pickwick Landing dams, which completely eliminated the rapids. Manu¬ facturing plants and hydroelectric power facilities are administered by the
Common murres (Uria aalge), ringed phase at left
RJ. TULLOCH-BRUCE COLEMAN INC./EB INC.
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© 2006 Encyclopaedia Britannica, Inc.
1314 I muscle tumour ► Musial
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Tennessee Valley Authority (TVA). The city of Muscle Shoals (pop., 2000: 11,924) developed from the TVA complex in the Wilson Dam area.
muscle tumour Abnormal tissue growth in or originating from muscle tissue. There are three major types. Leiomyomas are tumours of smooth muscles, seen most often in the uterus but also in the digestive, urinary, and female genital systems. Part of the tumour may become malignant, but it usually does not spread or recur. Rhabdomyomas occur most often in cardiac muscle. Some forms spread, and it may remain contained in tissue or become diffuse and hard to remove. Rhabdomyomas involving both smooth and striated muscle are often malignant and may grow very large. The several types of rhabdomyosarcoma are rare; they arise in skel¬ etal muscle, usually in the leg or arm, and are extremely malignant.
muscovite Vmos-ko-.vitV or common mica or potash mica or isinglass Abundant silicate mineral that contains potassium and alumi¬ num and has a layered atomic structure. It is the most common member of the mica group. Because it occurs in thin, transparent sheets, it was used in Russia for window panes and became known as Muscovy glass (isin¬ glass), hence its name. Muscovite is usually colourless but may be light gray, brown, pale green, or rose red. Its low iron content makes it a good electrical and thermal insulator.
muscular dystrophy \'dis-tra-fe\ Inherited disease that causes pro¬ gressive weakness in the skeletal (and occasionally heart) muscle. Muscle tissue degenerates and regenerates randomly and is replaced by scar tis¬ sue and fat. There is no specific treatment. Physical therapy, braces, and corrective surgery may help. Duchenne muscular dystrophy, the most common, strikes only males. Symptoms, including frequent falls and dif¬ ficulty in standing up, start in boys 3-7 years old; muscle wasting progresses from the legs to the arms and then the diaphragm. Pulmonary infection or respiratory failure usually causes death before age 20. The gene can now be detected in female carriers and male fetuses. Becker dystrophy, also sex-linked, is less severe and begins later. Patients remain able to walk and usually survive into their 30s and 40s. Myotonic mus¬ cular dystrophy affects adults of both sexes, with myotonia and degenera¬ tion two to three years later, along with cataracts, baldness, and gonadal atrophy. Limb-girdle dystrophy affects the pelvic or shoulder muscles in both sexes. Facioscapulohumeral (face, shoulder-blade, and upper-arm) dystrophy starts in childhood or adolescence and affects both sexes; after initial symptoms of difficulty raising the arms, the legs and pelvic muscles can be affected; the main facial effect is difficulty in closing the eyes. Life expectancy is normal.
Muse In Greco-Roman religion and myth, any of a group of sister god¬ desses, daughters of Zeus and Mnemosyne (Memory). A festival was held in their honour every four years near Mount Helicon, the centre of their cult in Greece. They probably began as the patron goddesses of poets, though later their range was extended to include all the liberal arts and sciences. Nine Muses are usually named: Calliope (heroic or epic poetry), Clio (history), Erato (lyric or love poetry), Euterpe (music or flutes), Mel¬ pomene (tragedy), Polyhymnia (sacred poetry or mime), Terpsichore (dancing and choral song), Thalia (comedy), and Urania (astronomy).