In anatomy, an arm is one of the upper limbs of an animal. Anatomy (from the Greek anatomia, from ana separate apart from and temnein, to cut up cut open is a branch of Biology that is the consideration In Human anatomy, the upper limb (also upper extremity) refers to what in common English is known as the arm, that is the region of the shoulder 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 an octopus. The In the lexicon of human anatomy, the term arm refers specifically to the segment between the shoulder and the elbow. In Human anatomy, the shoulder joint comprises the part of the body where the Humerus attaches to the Scapula. The elbow is the region surrounding the elbow-joint&mdashthe ginglymus or Hinge joint in the middle of the Arm. The segment between the elbow and wrist is the forearm. In Human anatomy, the wrist is the flexible and narrower connection between the Forearm and the palm. The forearm is the structure on the Upper limb, between the elbow and the Wrist. 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.
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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. The humerus is a Long bone in the Arm or Forelimb that runs from the Shoulder to the Elbow. It joins with the scapula above at the shoulder joint (or glenohumeral joint) and with the ulna and radius below at the elbow joint. In Anatomy, the scapula, omo, or shoulder blade, is the Bone that connects the Humerus (arm bone with the Clavicle (collar In Human anatomy, the shoulder joint comprises the part of the body where the Humerus attaches to the Scapula. The ulna ( elbow bone) is a long bone prismatic in form placed at the medial side of the Forearm, parallel with the radius. The radius is the Bone of the Forearm that extends from the lateral side of the elbow to the Thumb side of the Wrist. The elbow is the region surrounding the elbow-joint&mdashthe ginglymus or Hinge joint in the middle of the Arm.
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 elbow is the region surrounding the elbow-joint&mdashthe ginglymus or Hinge joint in the middle of the Arm. In the hinge joint ( ginglymus) the articular surfaces are moulded to each other in such a manner as to permit motion only in one plane forward and backward the extent of motion 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. Fascia (făsh'ē-ə pl fas·ci·ae (făsh'ē-ē adj fascial (făsh'ē-əl (from Latin: a band is the Soft tissue component of The anterior compartment of the arm is known as the "flexor compartment" as Flexion is its main action The posterior compartment of the arm is an Anatomic compartment which contains muscles which are all supplied by the Radial nerve. Periosteum is a Membrane that lines the outer surface of all bones, except at the joints of Long bones. 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. In Human anatomy, the deltoid muscle is the Muscle forming the rounded contour of the Shoulder. This muscle is the main abductor muscle of the upper limb and extends over the shoulder. Abduction, in functional anatomy is a movement which draws a limb away from the median ( Sagittal) plane of the body
- The brachioradialis muscle originates in the arm but inserts into the forearm. Brachioradialis is a Muscle of the Forearm that acts to flex the forearm at the Elbow. This muscle is responsible for rotating the hand so its palm faces forward (supination). Supination is a position of either the Forearm or foot in the forearm when the palm faces anteriorly or faces up (when the arms are unbent and at the sides
Cubital fossa
The cubital fossa is clinically important for venepuncture and for blood pressure measurement. The cubital fossa is the triangular area on the anterior view of the Elbow joint of the Arm. In medicine venipuncture or venepuncture (also known as phlebotomy, venesection, blood draw, drawing blood or taking blood Blood pressure is also the title of a short story by Damon Runyan in Guys and Dolls and Other Stories It is an imaginary triangle with borders being:
- Laterally, the medial border of brachioradialis muscle
- Medially, the lateral border of pronator teres muscle
- Superiorly, the intercondylar line, an imaginary line between the two condyles of the humerus
- The floor is the brachialis muscle
- The roof is the skin and fascia of the arm and forearm
The structures which smell through the cubital fossa are vital. Brachioradialis is a Muscle of the Forearm that acts to flex the forearm at the Elbow. The pronator teres is a Muscle of the Human body (located mainly in the Forearm) that along with the Pronator quadratus, serves to pronate The humerus is a Long bone in the Arm or Forelimb that runs from the Shoulder to the Elbow. The brachialis ( brachialis anticus) is a Muscle in the upper Arm that flexes the elbow joint. The skin is the outer covering of living tissue of an animal (or plant Fascia (făsh'ē-ə pl fas·ci·ae (făsh'ē-ē adj fascial (făsh'ē-əl (from Latin: a band is the Soft tissue component of The order from which they pass into the forearm are as follows, from medial to lateral:
- Median nerve, which starts to branch
- Brachial artery
- Tendon of the biceps brachii muscle
- Radial nerve
- Median cubital vein - this important vein is where venepuncture occurs. The median nerve is a Nerve that runs down the Arm and Forearm. The brachial artery is the major Blood vessel of the upper arm In Human anatomy, the biceps brachii is a Muscle located on the upper Arm. The radial nerve is a Nerve in the human body that supplies the Triceps brachii muscle of the arm as well as all 12 muscles in the Posterior osteofascial compartment In Human anatomy, the median cubital vein (or median basilic vein) a Superficial vein of the Upper limb. It connects the basilic and cephalic veins. In Human anatomy, the basilic vein is a large Superficial vein of the Upper limb that helps drain parts of hand and Forearm. In Human anatomy, the cephalic vein is a Superficial vein of the Upper limb.
- lymph nodes
Nervous supply
The musculocutaneous nerve, from C5, C6, C7, is the main supplier of muscles of the anterior compartment. The musculocutaneous nerve arises from the Lateral cord of the Brachial plexus, opposite the lower border of the Pectoralis minor, its fibers being derived It originates from the lateral cord of the brachial plexus of nerves. The brachial Plexus is an arrangement of nerve fibers running from the spine formed by the Ventral rami of the lower cervical and upper thoracic nerve roots specifically It pierces the coracobrachialis muscle and gives off branches to the muscle, as well as to brachialis and biceps brachii. The Coracobrachialis is the smallest of the three muscles that attach to the Coracoid process of the Scapula. The brachialis ( brachialis anticus) is a Muscle in the upper Arm that flexes the elbow joint. In Human anatomy, the biceps brachii is a Muscle located on the upper Arm. It terminates as the anterior cutaneous nerve of the forearm. The lateral antebrachial cutaneous nerve (or lateral cutaneous nerve of forearm) (branch of Musculocutaneous nerve, also sometimes spelled "antebrachial"
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. The radial nerve is a Nerve in the human body that supplies the Triceps brachii muscle of the arm as well as all 12 muscles in the Posterior osteofascial compartment 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. Anatomists use the term triangles of the neck to describe the divisions created by the major muscles in the region Here it travels with a deep artery of the arm (the profunda brachii), which sits in the radial groove of the humerus. The arteria profunda brachii (also known as deep artery of the arm) is a large vessel which arises from the Medial and back part of the Brachial, just below The radial sulcus ( also known as the musculospiral groove, radial groove, or spiral groove) is a broad but shallow oblique depression for the Radial 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. A lesion is any abnormal tissue found on or in an organism usually damaged by disease or trauma
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. The median nerve is a Nerve that runs down the Arm and Forearm. The brachial Plexus is an arrangement of nerve fibers running from the spine formed by the Ventral rami of the lower cervical and upper thoracic nerve roots specifically 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 pronator teres is a Muscle of the Human body (located mainly in the Forearm) that along with the Pronator quadratus, serves to pronate The nerve passes into the forearm. The forearm is the structure on the Upper limb, between the elbow and the Wrist.
- The ulnar nerve, origin C7-T1, is a continuation of the medial cord of the brachial plexus. In Human anatomy, the ulnar nerve is a nerve which runs near the Ulna bone The brachial Plexus is an arrangement of nerve fibers running from the spine formed by the Ventral rami of the lower cervical and upper thoracic nerve roots specifically This nerve passes in the same plane as the median nerve, between the biceps and triceps muscles. The median nerve is a Nerve that runs down the Arm and Forearm. 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. A fracture is the (local separation of an object or material into two or more pieces under the action of stress.
Blood supply and venous drainage
Arteries
The main artery in the arm is the brachial artery. The brachial artery is the major Blood vessel of the upper arm This artery is a continuation of the axillary artery. In Human anatomy, the axillary artery is a large Blood vessel that conveys oxygenated Blood to the lateral aspect of the Thorax, the Axilla 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). The brachial artery is the major Blood vessel of the upper arm The arteria profunda brachii (also known as deep artery of the arm) is a large vessel which arises from the Medial and back part of the Brachial, just below 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. The cubital fossa is the triangular area on the anterior view of the Elbow joint of the Arm. It travels in a plane between the biceps and triceps muscles, the same as the median nerve and basilic vein. The median nerve is a Nerve that runs down the Arm and Forearm. In Human anatomy, the basilic vein is a large Superficial vein of the Upper limb that helps drain parts of hand and Forearm. It is accompanied by venae comitantes (accompanying veins). Vena comitans is Latin for accompanying vein. It refers to a vein that is usually paired with both veins lying on the sides of an artery 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. The median nerve is a Nerve that runs down the Arm and Forearm. In Human anatomy, the biceps brachii is a Muscle located on the upper Arm. It then continues into the forearm. The forearm is the structure on the Upper limb, between the elbow and the Wrist.
The profunda brachii travels through the lower triangular space with the radial nerve. Anatomists use the term triangles of the neck to describe the divisions created by the major muscles in the region The radial nerve is a Nerve in the human body that supplies the Triceps brachii muscle of the arm as well as all 12 muscles in the Posterior osteofascial compartment 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. The humerus is a Long bone in the Arm or Forelimb that runs from the Shoulder to the Elbow. 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. A fracture is the (local separation of an object or material into two or more pieces under the action of stress. The radial nerve is a Nerve in the human body that supplies the Triceps brachii muscle of the arm as well as all 12 muscles in the Posterior osteofascial compartment A hematoma, or haematoma, is a collection of Blood outside the blood vessels generally the result of Hemorrhage, or more specifically Internal bleeding 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. An anastomosis (plural anastomoses, from gr ἀναστόμωσις communicating opening) is a Network of streams that both branch out and reconnect The radial recurrent artery arises from the Radial artery immediately below the elbow. The brachial artery is the major Blood vessel of the upper arm The elbow is the region surrounding the elbow-joint&mdashthe ginglymus or Hinge joint in the middle of the Arm.
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. In Human anatomy, the basilic vein is a large Superficial vein of the Upper limb that helps drain parts of hand and Forearm. In Human anatomy, the cephalic vein is a Superficial vein of the Upper limb. 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). In Human anatomy, the median cubital vein (or median basilic vein) a Superficial vein of the Upper limb. The cubital fossa is the triangular area on the anterior view of the Elbow joint of the Arm. In medicine venipuncture or venepuncture (also known as phlebotomy, venesection, blood draw, drawing blood or taking 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.
See also
Additional images
 Cross-section through the middle of upper arm. In fields of Anatomy, anatomical terms of location are descriptive terms to help identify relative positions or directions within a species |
External links
- Neuro-controlled bionic arm.
- Arm fractures
- MeSH Arm
- Arm at eMedicine Dictionary
RVC
Medical Subject Headings ( MeSH) is a huge Controlled vocabulary (or metadata system for the purpose of indexing journal articles and books eMedicine is an online clinical medical knowledge base that was founded in 1996 by Scott Plantz and Richard Lavely two medical doctorsDapyx Software network: MP3 Explorer | Ebook Manager | Zenithic