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top 10 words in brain distribution (in article): muscle bone human animal structure nerve contain branch join limb |
top 10 words in brain distribution (in article): time type form state world century require term refer provide |
top 10 words in brain distribution (not in article): cell body form brain tissue organism wear function organ horse |
top 10 words in brain distribution (not in article): plant produce light fruit water drink grow seed lamp species |
times more probable under arm 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under arch (words not in the model) | |
In anatomy, an arm'" is one of the upper limbs of an animal. The term "arm" can also be used for analogous structures, such as one of the paired upper limbs of a four-legged animal, or the arms of cephalopods. In the lexicon of human anatomy, the term "arm" refers specifically to the segment between the shoulder and the elbow. The segment between the elbow and wrist is the forearm. However, in colloquial speech the term "arm" often refers to the entire upper limb from shoulder to wrist. In primates the arms are richly adapted for both climbing and for more skilled, manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the presence of two forearm bones which can rotate around each other allows for additional range of motion at this level. Anatomy of the human arm. The human arm contains 30 bones, joints, muscles, nerves, and blood vessels. Many of these muscles are used for everyday tasks. Bony structure and joints. The humerus is the (upper) arm bone. It joins with the scapula above at the shoulder joint (or glenohumeral joint) and with the ulna and radius below at the elbow joint. Elbow joint. The elbow joint is the hinge joint between the distal end of the humerus and the proximal ends of the radius and ulna. The humerus cannot be broken easily. Its strength allows it to handle loading up to 300lbs. Osteofascial compartments. The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two "osteofascial compartments": The fascia merges with the periosteum (outer bone layer) of the humerus. The compartments contain muscles which are innervated by the same nerve and perform the same action. Two other muscles are considered to be partially in the arm: Cubital fossa. The cubital fossa is clinically important for venepuncture and for blood pressure measurement. It is an imaginary triangle with borders being: The structures which pass through the cubital fossa are vital. The order from which they pass into the forearm are as follows, from medial to lateral: Nerve supply. The musculocutaneous nerve, from C5, C6, C7, is the main supplier of muscles of the anterior compartment. It originates from the lateral cord of the brachial plexus of nerves. It pierces the coracobrachialis muscle and gives off branches to the muscle, as well as to brachialis and biceps brachii. It terminates as the anterior cutaneous nerve of the forearm. The radial nerve, which is from the fifth cervical spinal nerve to the first thoracic spinal nerve, originates as the continuation of the posterior cord of the brachial plexus. This nerve enters the lower triangular space (an imaginary space bounded by, amongst others, the shaft of the humerus and the triceps brachii) of the arm and lies deep to the triceps brachii. Here it travels with a deep artery of the arm (the profunda brachii), which sits in the radial groove of the humerus. This fact is very important clinically as a fracture of the bone at the shaft of the bone here can cause lesions or even transections in the nerve. Other nerves passing through give no supply to the arm. These include: Arteries. The main artery in the arm is the brachial artery. This artery is a continuation of the axillary artery. The point at which the axillary becomes the brachial is distal to the lower border of teres major. The brachial artery gives off an important branch, the profunda brachii (deep artery of the arm). This branching occurs just below the lower border of teres major. The brachial artery continues to the cubital fossa in the anterior compartment of the arm. It travels in a plane between the biceps and triceps muscles, the same as the median nerve and basilic vein. It is accompanied by venae comitantes (accompanying veins). It gives branches to the muscles of the anterior compartment. The artery is in between the median nerve and the tendon of the biceps muscle in the cubital fossa. It then continues into the forearm. The profunda brachii travels through the lower triangular space with the radial nerve. From here onwards it has an intimate relationship with the radial nerve. They are both found deep to the triceps muscle and are located on the spiral groove of the humerus. Therefore fracture of the bone may not only lead to lesion of the radial nerve, but also haematoma of the internal structures of the arm. The artery then continues on to anastamose with the recurrent radial branch of the brachial artery, providing a diffuse blood supply for the elbow joint. Veins. The veins of the arm carry blood from the extremities of the limb, as well as drain the arm itself. The two main veins are the basilic and the cephalic veins. There is a connecting vein between the two, the median cubital vein, which passes through the cubital fossa and is clinically important for venepuncture (withdrawing blood). The basilic vein travels on the medial side of the arm and terminates at the level of the seventh rib. The cephalic vein travels on the lateral side of the arm and terminates as the axillary vein. It passes through the deltopectoral triangle, a space between the deltoid and the pectoralis major muscles. Fractures. Clavicle · Humerus · Monteggia · Galeazzi · Colles' · Smith's · Barton's · Scaphoid · Rolando · Bennett's · Boxer's. Distal Radius · Scapular | An arch'" is a structure that spans a space while supporting weight (e.g. a doorway in a stone wall). Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture, but their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures. History. Arches were known by the Mesopotamian, Urartian, Harappan, Egyptian, Babylonian, Greek and Assyrian civilizations, but their use was infrequent and mostly confined to underground structures such as drains where the problem of lateral thrust is greatly diminished. The ancient Romans learned the arch from the Etruscans, refined it and were the first builders to tap its full potential for above ground buildings: "The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome." Throughout the Roman empire, their engineers erected arch structures such as bridges, aqueducts, and gates. They also introduced the triumphal arch as a military monument. Vaults began to be used for roofing large interior spaces such as halls and temples, a function which was also assumed by domed structures from the 1st century BC onwards. The Roman arch is semicircular, and built from an odd number of arch bricks (called "voussoirs"). An odd number of bricks is required for there to be a "capstone" or "keystone", the topmost stone in the arch. The Roman arch's shape is the simplest to build, but not the strongest. There is a tendency for the sides to bulge outwards, which must be counteracted by an added weight of masonry to push them inwards. The Romans used this type of semicircular arch freely in many of their secular structures such as aqueducts, palaces and amphitheaters. The semicircular arch was followed in Europe by the pointed Gothic arch or ogive (derived from the Islamic pointed arch in Moorish Spain), whose centreline more closely followed the forces of compression and which was therefore stronger. The semicircular arch can be flattened to make an elliptical arch as in the Ponte Santa Trinita. The parabolic and catenary arches are now known to be the theoretically strongest forms. Parabolic arches were introduced in construction by the Spanish architect Antoni Gaudí, who admired the structural system of Gothic style, but for the buttresses, which he termed “architectural crutches”. The catenary and parabolic arches carry all horizontal thrust to the foundation and so do not need additional elements. The horseshoe arch is based on the semicircular arch, but its lower ends are extended further round the circle until they start to converge. The first examples known are carved into rock in India in the first century AD, while the first known built horseshoe arches are known from Aksum (modern day Ethiopia and Eritrea) from around the 3rd–4th century, around the same time as the earliest contemporary examples in Syria, suggesting either an Aksumite or Syrian origin for the type of arch. It was used in Spanish Visigothic architecture, Islamic architecture and mudéjar architecture, as in the Great Mosque of Damascus and in later Moorish buildings. It was used for decoration rather than for strength. Across the ocean in Mexico and Central America, Mesoamerican civilizations created various types of corbelled arches, such as with the interior tunnels in the Great Pyramid of Cholula and the many styles of corbelled arches built by the Mayan civilization. In Peru, the Inca civilization used a trapezoidal arch in their architecture. The arch is still used today in some modern structures such as bridges. Construction. An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would in any case be required by the builders, so the scaffolding can be combined with the arch support. Occasionally arches would fall down when the frame was removed if construction or planning had been incorrect. (The A85 bridge at Dalmally, Scotland suffered this fate on its first attempt, in the 1940s). The interior and lower line or curve of an arch is known as the "intrados". Old arches sometimes need reinforcement due to decay of the keystones, known as bald arch. The gallery shows arch forms displayed in roughly the order in which they were developed. Technical aspects. The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning an open space. All the forces are resolved into compressive stresses. This is useful because several of the available building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them. By using the arch configuration, significant spans can be achieved. This is because all the compressive forces hold it together in a state of equilibrium. This even applies to frictionless surfaces. However, one downside is that an arch pushes outward at the base, and this needs to be restrained in some way, either with heavy sides and friction or angled cuts into bedrock or similar. This same principle holds when the force acting on the arch is not vertical such as in spanning a doorway, but horizontal, such as in arched retaining walls or dams. Even when using concrete, where the structure may be monolithic, the principle of the arch is used so as to benefit from the concrete's strength in resisting compressive stress. Where any other form of stress is raised, it has to be resisted by carefully placed reinforcement rods or fibres. (See Arch bridge.) Other types. The Delicate Arch, a natural arch in Moab, UtahA blind arch is an arch infilled with solid construction so it cannot function as a window, door, or passageway. A dome is a three-dimensional application of the arch, rotated about the center axis. Igloos are notable vernacular structures making use of domes. Natural rock formations may also be referred to as arches. These natural arches are formed by erosion rather than being carved or constructed by man. See Arches National Park for examples. A special form of the arch is the triumphal arch, usually built to celebrate a victory in war. A famous example is the Arc de Triomphe in Paris, France. A vault is an application of the arch extended horizontally in two dimensions; the groin vault is the intersection of two vaults. |