human anatomy The human body is the structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body. It comprises a hea ...

, the arm refers to the

upper limb The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shou ...

in common usage, although academically the term specifically means the upper arm between the

glenohumeral joint The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...

(shoulder joint) and the elbow joint. The distal part of the upper limb between the elbow and the radiocarpal joint (

wrist joint In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

) is known as the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...

or "lower" arm, and the extremity beyond the wrist is the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...

. By anatomical definitions, the

bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, ...

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal l ...

s and

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

s of the

shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists ...

, as well as the

axilla The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...

between them, is considered parts of the upper limb, and thus also components of the arm. The

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

term ''brachium'', which serves as a

root word A root (or root word) is the core of a word that is irreducible into more meaningful elements. In morphology, a root is a morphologically simple unit which can be left bare or to which a prefix or a suffix can attach. The root word is the prima ...

for naming many anatomical structures, may refer to either the upper limb as a whole or to the upper arm on its own.

Anatomy

Bones

The

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...

is one of the three

long bone The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities ...

s of the arm. It joins with the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

at the

shoulder joint The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...

and with the other long bones of the arm, the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

and

radius In classical geometry, a radius (plural, : radii) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', ...

at the elbow joint. The elbow is a complex

hinge joint A hinge joint (ginglymus or ginglymoid) is a bone joint in which the articular surfaces are molded to each other in such a manner as to permit motion only in one plane. According to one classification system they are said to be uniaxial (having ...

between the end of the humerus and the ends of the radius and ulna.

Muscles

The arm is divided by a

fascia A fascia (; plural fasciae or fascias; adjective fascial; from Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches to, stabilizes, encloses, and separates muscles and other internal organs ...

l layer (known as lateral and medial intermuscular septa) separating the muscles into two ''osteofascial compartments'': the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...

and the posterior compartments of the arm. The fascia merges with the

periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. Endosteum lines the inner surface of the medullary cavity of all long bones. Structu ...

(outer bone layer) of the humerus. The anterior compartment contains three muscles:

biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join ...

brachialis The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow ...

and

coracobrachialis The coracobrachialis muscle is the smallest of the three muscles that attach to the coracoid process of the scapula. (The other two muscles are pectoralis minor and the short head of the biceps brachii.) It is situated at the upper and medial part ...

muscles. They are all innervated by the musculocutaneous nerve. The posterior compartment contains only the

triceps brachii muscle The triceps, or triceps brachii (Latin for "three-headed muscle of the arm"), is a large muscle on the back of the upper limb of many vertebrates. It consists of 3 parts: the medial, lateral, and long head. It is the muscle principally respon ...

, supplied by the

radial nerve The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial comp ...

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 The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in t ...

of nerves. It pierces the

muscle and gives off branches to the muscle, as well as to

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 The triangular interval (also known as the lateral triangular space, lower triangular space, and triceps hiatus) is a space found in the axilla. It is one of the three intermuscular spaces found in the axillary space. The other two spaces are: q ...

(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 the

deep artery of the arm The deep artery of arm (also known as arteria profunda brachii and the deep brachial artery) is a large vessel which arises from the lateral and posterior part of the brachial artery, just below the lower border of the teres major. Structure It ...

, which sits in the radial groove of the humerus. This fact is very important clinically as a fracture of the shaft of the bone here can cause

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classif ...

s or even transections in the nerve. Other nerves passing through give no supply to the arm. These include: * The

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

, nerve origin C5-T1, which is a branch of the lateral and medial cords of the

. 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 The pronator teres is a muscle (located mainly in the forearm) that, along with the pronator quadratus, serves to pronate the forearm (turning it so that the palm faces posteriorly when from the anatomical position). It has two attachments, to t ...

muscle and is the most medial structure in the fossa. The nerve passes into the

. * The

ulnar nerve In human anatomy, the ulnar nerve is a nerve that runs near the ulna bone. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is ...

, origin C8-T1, is a continuation of the medial cord of the

. This nerve passes in the same plane as the

, between the biceps and triceps muscles. At the elbow, this nerve travels posterior to the

medial epicondyle of the humerus The medial epicondyle of the humerus is an epicondyle of the humerus bone of the upper arm in humans. It is larger and more prominent than the lateral epicondyle and is directed slightly more posteriorly in the anatomical position. In birds, whe ...

. This means that

condylar A condyle (;Entry "condyle"
in
fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displ ...

s can cause lesion to this nerve.

Blood supply

The main artery in the arm is the

brachial artery The brachial artery is the major blood vessel of the (upper) arm. It is the continuation of the axillary artery beyond the lower margin of teres major muscle. It continues down the ventral surface of the arm until it reaches the cubital foss ...

. 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

gives off an unimportant branch, the

deep artery of arm The deep artery of arm (also known as arteria profunda brachii and the deep brachial artery) is a large vessel which arises from the lateral and posterior part of the brachial artery, just below the lower border of the teres major. Structure It ...

. This branching occurs just below the lower border of

teres major The teres major muscle is a muscle of the upper limb. It attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles. It is a thick but somewhat flattened muscle. The teres major muscle (from Latin ''teres'', meaning ...

. The brachial artery continues to the

cubital fossa The cubital fossa, chelidon, or elbow pit, is the triangular area on the anterior side of the upper limb between the arm and forearm of a human or other hominid animals. It lies anteriorly to the elbow (Latin ) when in standard anatomical position ...

in the anterior compartment of the arm. It travels in a plane between the

biceps The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...

and triceps muscles, the same as the

and

basilic vein The basilic vein is a large superficial vein of the upper limb that helps drain parts of the hand and forearm. It originates on the medial ( ulnar) side of the dorsal venous network of the hand and travels up the base of the forearm, where its ...

. It is accompanied by

venae comitantes 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. They are found in close proximity to arteries so that the pulsations of the artery aid venous return. B ...

(accompanying veins). It gives branches to the muscles of the anterior compartment. The artery is in between the

and the tendon of the

muscle in the

. It then continues into the

. The deep artery of the arm travels through the

with the

. 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

. Therefore,

fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displ ...

of the bone may not only lead to lesion of the

, but also

haematoma A hematoma, also spelled haematoma, or blood suffusion is a localized bleeding outside of blood vessels, due to either disease or trauma including injury or surgery and may involve blood continuing to seep from broken capillaries. A hematoma is b ...

of the internal structures of the arm. The artery then continues on to anastamose with the recurrent radial branch of the

, 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 vein In human anatomy, the cephalic vein is a superficial vein in the arm. It originates from the radial end of the dorsal venous network of hand, and ascends along the radial (lateral) side of the arm before emptying into the axillary vein. At the e ...

s. There is a connecting vein between the two, the median cubital vein, which passes through the

and is clinically important for

venepuncture In medicine, venipuncture or venepuncture is the process of obtaining intravenous access for the purpose of venous blood sampling (also called ''phlebotomy'') or intravenous therapy. In healthcare, this procedure is performed by medical labor ...

(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.

Society and culture

In Hindu, Buddhist and Egyptian iconography the symbol of the arm is used to illustrate the power of the sovereign. In Hindu tradition gods are depicted with several arms which carry specific symbols of their powers. It is believed that several arms depict omnipotence of gods. In popular culture Thakur did not have arms in the movie Sholay. In West Africa, the Bambara use forearm to symbolize the spirit, which is a link between God and man. Symbolic gestures of raising both hands signal surrender, appeals for mercy, and justice.

Clinical significance

The

is clinically important for

and for

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure ...

measurement. When the arm is fractured this may refer to a fracture of the humerus bone. Veins on the arm may be taken when a coronary artery bypass graft is needed.

Other animals

In other animals, the term ''arm'' can also be used for homologous or analogous structures (such as one of the paired

forelimb A forelimb or front limb is one of the paired articulated appendages (limbs) attached on the cranial ( anterior) end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used inste ...

s of a four-legged animal or the arms of cephalopods, respectively). In anatomical usage, the term ''arm'' may sometimes refer specifically to the segment between the shoulder and the elbow, while the segment between the elbow and

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carp ...

is the

. 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

for the wider definition. In primates the arm is adapted for precise positioning of the

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.

Additional images

File:Arm Bones.png, Gross anatomy of the upper arm and

elbow The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the me ...

References

{{Authority control Upper limb anatomy