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| Arm | |
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| The human arm | |
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| Cross-section through the middle of upper arm. | |
| Latin | bracchium
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| MeSH | Arm |
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods. In anatomical usage, the term arm refers specifically to the segment between the shoulder and the elbow,[1][2] while the segment between the elbow and wrist is the forearm. However, in common, literary, and historical usage, arm refers to the entire upper limb from shoulder to wrist. This article uses the former definition; see upper limb for the wider definition.
In primates the arm is adapted for precise positioning of the hand and thus assist in the hand's manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the structure of the two forearm bones which can rotate around each other allows for additional range of motion at that level.
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Skeleton [link]
The humerus is the bone of the arm. It joins with the scapula above in the shoulder at the glenohumeral joint and with the ulna and radius below at the elbow. 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 300 pounds (140 kg).
Muscles [link]
The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two osteofascial compartments: the anterior and the posterior compartments of the arm. 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:
- The large deltoid muscle is considered to have part of its body in the anterior compartment. This muscle is the main abductor muscle of the upper limb and extends over the shoulder.
- The brachioradialis muscle originates in the arm but inserts into the forearm. This muscle is responsible for rotating the hand so its palm faces forward (supination).
Nerve and blood supply [link]
The cubital fossa (colloquially known as the elbow pit) is clinically important for venepuncture and for blood pressure measurement.
Innervation [link]
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:
- The median nerve, nerve origin C5-T1, which is a branch of the lateral and medial cords of the brachial plexus. This nerve continues in the arm, travelling in a plane between the biceps and triceps muscles. At the cubital fossa, this nerve is deep to the pronator teres muscle and is the most medial structure in the fossa. The nerve passes into the forearm.
- The ulnar nerve, origin C8-T1, is a continuation of the medial cord of the brachial plexus. This nerve passes in the same plane as the median nerve, between the biceps and triceps muscles. At the elbow, this nerve travels posterior to the medial epicondyle of the humerus. This means that condylar fractures can cause lesion to this nerve.
Arteries [link]
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 [link]
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.
Additional images [link]
See also [link]
References [link]
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Wikimedia Commons has media related to: Arm |
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Look up arm in Wiktionary, the free dictionary. |
- ^ "arm" at Dorland's Medical Dictionary[dead link]
- ^ Arm at the US National Library of Medicine Medical Subject Headings (MeSH)
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Tor (anonymity network)
Tor is free software for enabling anonymous communication. The name is an acronym derived from the original software project name The Onion Router, however the correct spelling is "Tor", capitalizing only the first letter. Tor directs Internet traffic through a free, worldwide, volunteer network consisting of more than seven thousand relays to conceal a user's location and usage from anyone conducting network surveillance or traffic analysis. Using Tor makes it more difficult for Internet activity to be traced back to the user: this includes "visits to Web sites, online posts, instant messages, and other communication forms". Tor's use is intended to protect the personal privacy of users, as well as their freedom and ability to conduct confidential communication by keeping their Internet activities from being monitored.
Onion routing is implemented by encryption in the application layer of a communication protocol stack, nested like the layers of an onion. Tor encrypts the data, including the destination IP address, multiple times and sends it through a virtual circuit comprising successive, randomly selected Tor relays. Each relay decrypts a layer of encryption to reveal only the next relay in the circuit in order to pass the remaining encrypted data on to it. The final relay decrypts the innermost layer of encryption and sends the original data to its destination without revealing, or even knowing, the source IP address. Because the routing of the communication is partly concealed at every hop in the Tor circuit, this method eliminates any single point at which the communicating peers can be determined through network surveillance that relies upon knowing its source and destination.
Arm (disambiguation)
An arm is an upper limb of the body.
Arm or ARM may also refer to:
Geography
- Distributary or arm, a subsidiary branch of a river
Science and medicine
Technology
Computing
- ARM Holdings, a British company that designs the ARM computer processors
ARM (novella)
ARM is a science fiction novella by American author Larry Niven. Set in the Known Space cycle, it is the third of five Gil Hamilton detective stories.
Hamilton is called to the scene of a murder. The victim is Dr. Raymond Sinclair, a brilliant scientist who has invented a mysterious device that creates a bubble of accelerated time. The murder scene is a locked apartment at the top of a high-rise, where the prime suspect is a beautiful young woman whom Gil refuses to believe is the killer.
One of the themes running throughout the story, and in fact a vital element in the solution of the mystery, is the loss of an arm. Gil himself lost an arm and had a new one grafted on, using parts from an organ bank which is supplied by the bodies of criminals and "corpsicles", people who underwent cryogenic suspension. At the scene of the crime, a beautiful young woman is discovered unconscious in an "autodoc" (a device for fixing minor injuries or preserving life until help arrives) recovering from the loss of one of her arms. Another character in the story also lost an arm previously, but regards grafts as immoral and wears an advanced prosthetic arm instead. The "accelerated time bubble" has the effect of amputating the arm of anyone who reaches into it, since the arm's metabolism speeds up to the point where the rest of the body cannot supply it with blood.
Arm (geography)
In geography, an arm is a narrow extension, inlet, or smaller reach, of water flowing out from a much larger body of water, such as an ocean, a sea, or a lake. Although different geographically, a sound or bay may also be called an arm.
By extension, a canal arm is a subsidiary branch of a canal or inland waterway.
See also
Edward Armitage
Edward Armitage RA (May 20, 1817 – May 24, 1896) was an English Victorian-era painter whose work focused on historical, classical and biblical subjects.
Family background
Armitage was born in London to a family of wealthy Yorkshire industrialists, the eldest of seven sons of James Armitage (1793–1872) and Anne Elizabeth Armitage née Rhodes (1788–1833), of Farnley Hall, just south of Leeds, Yorkshire. His great-grandfather James (1730–1803) bought Farnley Hall from Sir Thomas Danby in 1799 and in 1844 four Armitage brothers, including his father James, founded the Farnley Ironworks, utilising the coal, iron and fireclay on their estate. His brother Thomas Rhodes Armitage (1824–1890) founded the Royal National Institute of the Blind.
Armitage was the uncle of Robert Armitage (MP), the great-uncle of Robert Selby Armitage, and first cousin twice removed of Edward Leathley Armitage.
Art Training
Armitage's art training was undertaken in Paris, where he enrolled at the École des Beaux-Arts in October 1837. He studied under the history painter, Paul Delaroche, who at that time was at the height of his fame. Armitage was one of four students selected to assist Delaroche with the fresco Hemicycle in the amphitheatre of the Palais des Beaux-Arts, when he reputedly modelled for the head of Masaccio. Whilst still in Paris, he exhibited Prometheus Bound in 1842, which a contemporary critic described as 'well drawn but brutally energetic'.
