The humerus (; : humeri) is a

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 ...

in the

arm In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between ...

that runs from the

shoulder The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder m ...

to the

elbow The elbow is the region between the upper 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 t ...

. It connects the

scapula The scapula (: 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 either side ...

and the two bones of the lower arm, the

radius In classical geometry, a radius (: radii or radiuses) 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 radius of a regular polygon is th ...

and

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

, and consists of three sections. The humeral

upper extremity The upper Limb (anatomy), limbs or upper extremities are the forelimbs of an upright posture, upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digit (anatomy), digits, including all the musc ...

consists of a rounded head, a narrow neck, and two short processes (

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projectio ...

s, sometimes called tuberosities). The

body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of anim ...

is cylindrical in its upper portion, and more

prism PRISM is a code name for a program under which the United States National Security Agency (NSA) collects internet communications from various U.S. internet companies. The program is also known by the SIGAD . PRISM collects stored internet ...

atic below. The lower extremity consists of 2

epicondyle An epicondyle () is a rounded eminence on a bone that lies upon a condyle ('' epi-'', "upon" + ''condyle'', from a root meaning "knuckle" or "rounded articular area"). There are various epicondyles in the human skeleton The human skeleton is ...

s, 2 processes (

trochlea {{wiktionary Trochlea (Latin for pulley) is a term in anatomy. It refers to a grooved structure reminiscent of a pulley's wheel. Related to joints Most commonly, trochleae bear the articular surface of saddle and other joints: * Trochlea of humeru ...

and

capitulum capitulum (plural capitula) may refer to: *the Latin word for chapter ** an index or list of chapters at the head of a gospel manuscript ** a short reading in the Liturgy of the Hours *** derived from which, it is the Latin for the assembly known ...

), and 3 fossae (

radial fossa The radial fossa is a slight depression found on the humerus above the front part of the capitulum. It receives the anterior border of the head of the radius when the forearm is flexed. Structure The joint capsule of the elbow attaches to the h ...

coronoid fossa Superior to the anterior portion of the trochlea is a small depression, the coronoid fossa, which receives the coronoid process of the ulna during flexion of the forearm. It is directly adjacent to the radial fossa of the humerus The humerus ...

, and

olecranon fossa The olecranon fossa is a deep triangular depression on the posterior side of the humerus, superior to the trochlea. It provides space for the olecranon of the ulna during extension of the forearm. Structure The olecranon fossa is located ...

). As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.

Etymology

The word "humerus" is derived from

Late Latin Late Latin is the scholarly name for the form of Literary Latin of late antiquity.Roberts (1996), p. 537. English dictionary definitions of Late Latin date this period from the 3rd to 6th centuries CE, and continuing into the 7th century in ...

, from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, meaning upper arm, shoulder, and is linguistically related to

Gothic Gothic or Gothics may refer to: People and languages *Goths or Gothic people, a Germanic people **Gothic language, an extinct East Germanic language spoken by the Goths **Gothic alphabet, an alphabet used to write the Gothic language ** Gothic ( ...

(shoulder) and

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

Structure

Upper extremity

The upper or proximal extremity of the humerus consists of the bone's large rounded head joined to the body by a constricted portion called the neck, and two eminences, the greater and lesser tubercles.

Head

The head (''caput humeri''), is nearly hemispherical in form. It is directed upward, medialward, and a little backward, and articulates with the

glenoid cavity The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from , "socket", reflecting the shoulder joint's ball-and-socket form. It is a shallow, pyri ...

of the scapula to form the glenohumeral joint (shoulder joint). The circumference of its articular surface is slightly constricted and is termed the anatomical neck, in contradistinction to a constriction below the tubercles called the surgical neck which is frequently the seat of fracture. Fracture of the anatomical neck rarely occurs.''

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter and first published in London in 1858. It has had multiple revised editions, and the current edition, the 42nd (October 2020 ...

'', see infobox The diameter of the humeral head is generally larger in men than in women.

Anatomical neck

The anatomical neck (''collum anatomicum'') is obliquely directed, forming an obtuse angle with the body. It is most prominent in the lower half of its circumference, while in the upper half, it is represented by a narrow groove separating the head from the tubercles. The line separating the head from the rest of the upper end is called the ''anatomical neck.'' It affords attachment to the articular capsule of the shoulder-joint, and is perforated by numerous vascular

foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...

s. Fracture of the anatomical neck rarely occurs. The anatomical neck of the humerus is an indentation distal to the head of the humerus on which the articular capsule attaches. Neck-of-Humerus

Surgical neck

The surgical neck is a narrow area distal to the tubercles that is a common site of fracture. It makes contact with the

axillary nerve The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus ( upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. ...

and the

posterior humeral circumflex artery The posterior humeral circumflex artery (posterior circumflex artery or posterior circumflex humeral artery) arises from the third part of the axillary artery at the distal border of the subscapularis. Anatomy Course and relations It passes p ...

Greater tubercle

The greater tubercle (''tuberculum majus''; greater tuberosity) is a large, posteriorly placed projection that is placed laterally. The greater tubercle is where ''supraspinatus'', ''infraspinatus'' and ''teres minor'' muscles are attached. The crest of the greater tubercle forms the lateral lip of the bicipital groove and is the site for insertion of ''pectoralis major''. The greater tubercle is just lateral to the anatomical neck. Its upper surface is rounded and marked by three flat impressions: the highest of these gives insertion to the

supraspinatus muscle The supraspinatus (: supraspinati) is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus. It is one of the four rotator cuff mus ...

; the middle to the

infraspinatus muscle In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa.''Gray's Anatomy'', see infobox. As one of the four muscles of the rotator cuff, the main function of the infraspin ...

; the lowest one, and the body of the bone for about 2.5 cm. below it, to the

teres minor muscle The teres minor (Latin ''teres'' meaning 'rounded') is a narrow, elongated muscle of the rotator cuff. The muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the ...

. The lateral surface of the greater tubercle is convex, rough, and continuous with the lateral surface of the body. Greater-Tubercle-of-Right-Humerus

Lesser tubercle

The lesser tubercle (''tuberculum minus''; lesser tuberosity) is smaller, anterolaterally placed to the head of the humerus. The lesser tubercle provides insertion to ''subscapularis'' muscle. Both these tubercles are found in the proximal part of the shaft. The crest of the lesser tubercle forms the medial lip of the bicipital groove and is the site for insertion of ''teres major'' and ''latissimus dorsi'' muscles. The lesser tuberosity, is more prominent than the greater: it is situated in front, and is directed medialward and forward. Above and in front it presents an impression for the insertion of the tendon of the

subscapularis muscle The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint. Structure The subscapularis is covered by a dense fasci ...

Bicipital groove

The tubercles are separated from each other by a deep groove, the

bicipital groove The bicipital groove (intertubercular groove, sulcus intertubercularis) is a deep groove on the humerus that separates the greater tubercle from the lesser tubercle. It allows for the long tendon of the biceps brachii muscle to pass. Structure ...

(intertubercular groove; bicipital sulcus), which lodges the long tendon of the

biceps brachii muscle The biceps or 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 Muscle head, heads of the muscle arise on the scapula and join to form a single ...

and transmits a branch of the

anterior humeral circumflex artery The anterior humeral circumflex artery (anterior circumflex artery, anterior circumflex humeral artery) is an artery in the arm. It is one of two circumflexing arteries that branch from the axillary artery, the other being the posterior humeral cir ...

to the shoulder-joint. It runs obliquely downward, and ends near the junction of the upper with the middle third of the bone. In the fresh state its upper part is covered with a thin layer of cartilage, lined by a prolongation of the

synovial membrane Synovial () may refer to: * Synovial fluid * Synovial joint A synovial joint, also known as diarthrosis, joins bones or cartilage with a fibrous joint capsule that is continuous with the periosteum of the joined bones, constitutes the outer bou ...

of the shoulder-joint; its lower portion gives insertion to the tendon of the

latissimus dorsi muscle The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsi'') comes from ...

. It is deep and narrow above, and becomes shallow and a little broader as it descends. Its lips are called, respectively, the crests of the greater and lesser tubercles (''bicipital ridges''), and form the upper parts of the anterior and medial borders of the body of the bone. Bicipital-groove

Shaft

The body or shaft of the humerus is triangular to cylindrical in cut section and is compressed anteroposteriorly. It has 3 surfaces, namely: *Anterolateral surface: the area between the lateral border of the humerus to the line drawn as a continuation of the crest of the greater tubercle. The antero-lateral surface is directed lateralward above, where it is smooth, rounded, and covered by the

deltoid muscle The deltoid muscle is the muscle forming the rounded contour of the shoulder, human shoulder. It is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat. Anatomically, the deltoid muscle is made up o ...

; forward and lateralward below, where it is slightly concave from above downward, and gives origin to part of the

brachialis The brachialis (brachialis anticus) is a muscle in the upper arm that flexes the elbow. It lies beneath the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow pit). It originates from the anterior aspec ...

. About the middle of this surface is a rough, rectangular elevation, the

deltoid tuberosity In human anatomy, the deltoid tuberosity is a rough, triangular area on the anterolateral (front-side) surface of the middle of the humerus. It is a site of attachment of deltoid muscle. Structure Variation The deltoid tuberosity has been r ...

for the insertion of the

; below this is the

radial sulcus The radial groove (also known as the musculospiral groove, radial sulcus, or spiral groove) is a broad but shallow oblique depression for the radial nerve and deep brachial artery. It is located on the center of the lateral border of the humerus b ...

, directed obliquely from behind, forward, and downward, and transmitting 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 compartment of the ...

and profunda artery. *Anteromedial surface: the area between the medial border of the humerus to the line drawn as a continuation of the crest of the greater tubercle. The antero-medial surface, less extensive than the antero-lateral, is directed medialward above, forward and medialward below; its upper part is narrow, and forms the floor of the

intertubercular groove The bicipital groove (intertubercular groove, sulcus intertubercularis) is a deep groove on the humerus that separates the greater tubercle from the lesser tubercle. It allows for the long tendon of the biceps brachii muscle to pass. Structure ...

which gives insertion to the tendon of the

; its middle part is slightly rough for the attachment of some of the fibers of the tendon of insertion of the

coracobrachialis muscle The coracobrachialis muscle muscle in the upper medial part of the arm. It is located within the anterior compartment of the arm. It originates from the coracoid process of the scapula; it inserts onto the middle of the medial aspect of the body ...

; its lower part is smooth, concave from above downward, and gives origin to the

brachialis muscle The brachialis (brachialis anticus) is a muscle in the upper arm that flexes the elbow. It lies beneath the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow pit). It originates from the anterior aspe ...

. *Posterior surface: the area between the medial and lateral borders. The posterior surface appears somewhat twisted, so that its upper part is directed a little medialward, its lower part backward and a little lateralward. Nearly the whole of this surface is covered by the lateral and medial heads of the Triceps brachii, the former arising above, the latter below the radial sulcus. Its three borders are: *Anterior: the anterior border runs from the front of the greater tubercle above to the

below, separating the antero-medial from the antero-lateral surface. Its upper part is a prominent ridge, the crest of the greater tubercle; it serves for the insertion of the tendon of the pectoralis major muscle. About its center it forms the anterior boundary of the

, on which the

attaches; below, it is smooth and rounded, affording attachment to the

. *Lateral: the lateral border runs from the back part of the greater tubercle to the lateral

, and separates the anterolateral from the posterior surface. Its upper half is rounded and indistinctly marked, serving for the attachment of the lower part of the insertion of the

, and below this giving origin to the lateral head of 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 three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

; its center is traversed by a broad but shallow oblique depression, the

spiral groove The radial groove (also known as the musculospiral groove, radial sulcus, or spiral groove) is a broad but shallow oblique depression for the radial nerve and deep brachial artery. It is located on the center of the lateral border of the humerus b ...

(''musculospiral groove''). The

runs in the spiral groove. Its lower part forms a prominent, rough margin, a little curved from backward, forward the

lateral supracondylar ridge The lateral supracondylar ridge is a prominent, rough margin on the lower part of the lateral border of the humerus. It presents an anterior lip for the origin of forearm extensors, including the brachioradialis muscle above, and the extensor ca ...

, which presents an anterior lip for the origin of the

brachioradialis muscle The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...

two-thirds above, and

extensor carpi radialis longus muscle The extensor carpi radialis longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone (metacarpal of ...

one-third below, a posterior lip for the

, and an intermediate ridge for the attachment of the lateral intermuscular septum. *Medial: the medial border extends from the lesser tubercle to the medial epicondyle. Its upper third consists of a prominent ridge, the crest of the lesser tubercle, which gives insertion to the tendon of the

teres major muscle 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'', meanin ...

. About its center is a slight impression for the insertion of the

, and just below this is the entrance of the nutrient canal, directed downward; sometimes there is a second nutrient canal at the commencement of the

. The inferior third of this border is raised into a slight ridge, the

medial supracondylar ridge The inferior third of the medial border of the humerus is raised into a slight ridge, the medial supracondylar ridge (or medial supracondylar line), which becomes very prominent below; it presents an anterior lip for the origins of the Brachiali ...

, which became very prominent below; it presents an anterior lip for the origins of the

and the

pronator teres muscle 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 origins, at the ...

, a posterior lip for the medial head of the

, and an intermediate ridge for the attachment of the medial intermuscular septum. Anterior-view-of-the-humerus-showing-borders-and-surfaces

Posterior-view-of-the-humerus-showing-borders-and-surfaces

The deltoid tuberosity is a roughened surface on the lateral surface of the shaft of the humerus and acts as the site of insertion of ''deltoideus'' muscle. The posterorsuperior part of the shaft has a crest, beginning just below the surgical neck of the humerus and extends till the superior tip of the deltoid tuberosity. This is where the lateral head of ''triceps brachii'' is attached. Deltoid-Tuberosity

The radial sulcus, also known as the spiral groove, is found on the posterior surface of the shaft and is a shallow oblique groove through which the radial nerve passes along with deep vessels. This is located posteroinferior to the deltoid tuberosity. The inferior boundary of the spiral groove is continuous distally with the lateral border of the shaft. Radial-groove-continuing-as-lateral-border-of-shaft

Radial-groove-continuing-as-lateral-border-of-shaft

The nutrient foramen of the humerus is located in the anteromedial surface of the humerus. The nutrient arteries enter the humerus through this foramen. Nutrient-Foramen

Distal humerus

The distal or lower extremity of the humerus is flattened from before backward, and curved slightly forward; it ends below in a broad, articular surface, which is divided into two parts by a slight ridge. Projecting on either side are the lateral and medial

Articular surface

The articular surface extends a little lower than the epicondyles, and is curved slightly forward; its medial extremity occupies a lower level than the lateral. The ''lateral'' portion of this surface consists of a smooth, rounded eminence, named the

capitulum of the humerus In human anatomy of the arm, the capitulum of the humerus is a smooth, rounded eminence on the lateral portion of the distal articular surface of the humerus. It articulates with the cup-shaped depression on the head of the radius, and is limi ...

; it articulates with the cup-shaped depression on the head of the radius, and is limited to the front and lower part of the bone.

Fossae

Above the front part of the trochlea is a small depression, the

, which receives the coronoid process of the ulna during

flexion Motion, the process of movement, is described using specific anatomical terminology, anatomical terms. Motion includes movement of Organ (anatomy), organs, joints, Limb (anatomy), limbs, and specific sections of the body. The terminology used de ...

of the forearm. Above the back part of the trochlea is a deep triangular depression, the

, in which the summit of the

olecranon The olecranon (, ), is a large, thick, curved bony process on the proximal, posterior end of the ulna. It forms the protruding part of the elbow and is opposite to the cubital fossa or elbow pit (trochlear notch). The olecranon serves as a lever ...

is received in

extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (proof theory) * Extension (predicate logic), the set of tuples of values that ...

of the forearm. Olecranon-fossa

The coronoid fossa is the medial hollow part on the anterior surface of the distal humerus. The coronoid fossa is smaller than the olecranon fossa and receives the coronoid process of the ulna during maximum flexion of the elbow. Coronoid-Fossa

Above the front part of the

is a slight depression, the

, which receives the anterior border of the head of the radius, when the forearm is flexed. Radial-Fossa

These fossæ are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a

supratrochlear foramen The supratrochlear foramen is a small hole located above the trochlea of the humerus of several mammals, it is found frequently in dogs and sometimes in humans, especially women and in the left humerus. It is covered by a layer of connective tissu ...

; they are lined in the fresh state by the synovial membrane of the

elbow-joint The elbow is the region between the arm, upper 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 epic ...

, and their margins afford attachment to the anterior and posterior ligaments of this articulation. The

is a rounded eminence forming the lateral part of the distal humerus. The head of the radius articulates with the capitulum. Capitulum-and-trochlea

The

is spool-shaped medial portion of the distal humerus and articulates with the ulna. Trochlea

Epicondyles

The epicondyles are continuous above with the supracondylar ridges. * The lateral epicondyle is a small, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow-joint, and to a tendon common to the origin of the

supinator In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius (bone), radius. Its function is to supination, supinate the forearm. Structure The supinator consists of tw ...

and some of the extensor muscles. * The medial epicondyle, larger and more prominent than the lateral, is directed a little backward; it gives attachment to the ulnar collateral ligament of the elbow-joint, 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 origins, at th ...

, and to a common tendon of origin of some of the flexor muscles of the forearm; the

ulnar nerve The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. 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 ...

runs in a groove on the back of this epicondyle. Medial-epicondyle-and-lateral-epicondyle

Medial-supracondylar-crest-and-lateral-supracondylar-crest

The medial supracondylar crest forms the sharp medial border of the distal humerus continuing superiorly from the medial epicondyle. The lateral supracondylar crest forms the sharp lateral border of the distal humerus continuing superiorly from the lateral epicondyle.

Borders

The medial portion of the articular surface is named the

, and presents a deep depression between two well-marked borders; it is convex from before backward, concave from side to side, and occupies the anterior, lower, and posterior parts of the extremity. * The ''lateral border'' separates it from the groove which articulates with the margin of the head of the radius. * The ''medial border'' is thicker, of greater length, and consequently more prominent, than the lateral. The grooved portion of the articular surface fits accurately within the

semilunar notch The trochlear notch (), also known as semilunar notch and greater sigmoid cavity, is a large depression in the upper extremity of the ulna that fits the trochlea of the humerus (the bone directly above the ulna in the arm) as part of the elbow ...

of the ulna; it is broader and deeper on the posterior than on the anterior aspect of the bone, and is inclined obliquely downward and forward toward the medial side.

Articulations

At the shoulder, the head of the humerus articulates with the glenoid fossa of the

. More distally, at the elbow, the capitulum of the humerus articulates with the head of the

, and the

trochlea of the humerus In the human arm, the humeral trochlea is the medial portion of the articular surface of the elbow joint which articulates with the trochlear notch on the ulna in the forearm. Structure In humans and other apes, it is trochleariform (or trochlei ...

articulates with the trochlear notch of the

Nerves

The

is located at the proximal end, against the shoulder girdle. Dislocation of the humerus's

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 ...

has the potential to injure the axillary nerve or 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 (armpit) and the upper limb. Its origin is at the lateral margin of the first rib, before which it is c ...

. Signs and symptoms of this dislocation include a loss of the normal shoulder contour and a palpable depression under the acromion. The

follows the humerus closely. At the midshaft of the humerus, the radial nerve travels from the posterior to the anterior aspect of the bone in the ''spiral groove''. A fracture of the humerus in this region can result in radial nerve injury. The

lies at the distal end of the humerus near the elbow. When struck, it can cause a distinct tingling sensation, and sometimes a significant amount of pain. It is sometimes popularly referred to as 'the funny bone', possibly due to this sensation (a "funny" feeling), as well as the fact that the bone's name is a homophone of 'humorous'. It lies posterior to the medial epicondyle, and is easily damaged in elbow injuries.

Function

Muscular attachment

The

deltoid Deltoid (delta-shaped) can refer to: * The deltoid muscle, a muscle in the shoulder * Kite (geometry), also known as a deltoid, a type of quadrilateral * A deltoid curve, a three-cusped hypocycloid * A leaf shape * The deltoid tuberosity, a part o ...

originates on the lateral third of the

clavicle The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately long that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body. The clavic ...

acromion In human anatomy, the acromion (from Greek: ''akros'', "highest", ''ōmos'', "shoulder", : acromia) or summit of the shoulder is a bony process on the scapula (shoulder blade). Together with the coracoid process, it extends laterally over the sh ...

and the crest of the

spine Spine or spinal may refer to: Science Biology * Spinal column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoology), ...

of the scapula. It is inserted on the

of the humerus and has several actions including abduction, extension, and circumduction of the shoulder. The

supraspinatus The supraspinatus (: supraspinati) is a relatively small muscle of the upper back that runs from the supraspinous fossa superior portion of the scapula (shoulder blade) to the greater tubercle of the humerus. It is one of the four rotator cuff m ...

also originates on the spine of the scapula. It inserts on the greater tubercle of the humerus, and assists in abduction of the shoulder. The pectoralis major,

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'', meanin ...

, and

latissimus dorsi The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsi'') comes from L ...

insert at the ''intertubercular groove'' of the humerus. They work to adduct and medially, or internally, rotate the humerus. The

infraspinatus In human anatomy, the infraspinatus muscle is a thick triangular muscle, which occupies the chief part of the infraspinatous fossa.''Gray's Anatomy'', see infobox. As one of the four muscles of the rotator cuff, the main function of the infraspin ...

and

teres minor The teres minor (Latin ''teres'' meaning 'rounded') is a narrow, elongated muscle of the rotator cuff. The muscle originates from the lateral border and adjacent posterior surface of the corresponding right or left scapula and inserts at both the ...

insert on the greater tubercle, and work to laterally, or externally, rotate the humerus. In contrast, the

subscapularis The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the Glenohumeral joint, shoulder-joint. Structure The subscapularis is covere ...

muscle inserts onto the lesser tubercle and works to medially, or internally, rotate the humerus. The

biceps brachii The biceps or 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 to form a single muscle bell ...

, and

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...

(which attaches distally) act to flex the elbow. (The biceps do not attach to the humerus.) The

triceps brachii 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 three parts: the medial, lateral, and long head. All three heads cross the elbow jo ...

and

anconeus The anconeus muscle (or anconaeus/anconæus) is a small muscle on the posterior aspect of the elbow joint. Some consider anconeus to be a continuation of the triceps brachii muscle. Some sources consider it to be part of the posterior compartment ...

extend the elbow, and attach to the posterior side of the humerus. The four muscles of supraspinatus, infraspinatus, teres minor and subscapularis form a musculo-ligamentous girdle called the

rotator cuff The rotator cuff (SITS muscles) is a group of muscles and their tendons that act to stabilize the human shoulder and allow for its extensive range of motion. Of the seven scapulohumeral muscles, four make up the rotator cuff. The four muscles a ...

. This cuff stabilizes the very mobile but inherently unstable

. The other muscles are used as counterbalances for the actions of lifting/pulling and pressing/pushing.

Other animals

Primitive fossils of

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

s had little, if any, shaft connecting the upper and lower extremities, making their limbs very short. In most living

tetrapod A tetrapod (; from Ancient Greek :wiktionary:τετρα-#Ancient Greek, τετρα- ''(tetra-)'' 'four' and :wiktionary:πούς#Ancient Greek, πούς ''(poús)'' 'foot') is any four-Limb (anatomy), limbed vertebrate animal of the clade Tetr ...

s, however, the humerus has a similar form to that of humans. In many

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s and some

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

s (where it is the primitive state), the lower extremity includes a large opening called the

entepicondylar foramen The entepicondylar foramen is an opening in the distal (far) end of the humerus (upper arm bone) present in some mammals. It is often present in primitive placentals, such as the enigmatic Madagascan '' Plesiorycteropus''. In most Neotominae and a ...

to allow the passage of nerves and blood vessels.

Additional images

File:Humerus animation.gif, Position of humerus (shown in red). Animation. File:Left humerus - close-up - animation.gif, Left humerus. Animation. File:Human humerus 2.stl, 3D image File:Human arm bones diagram.svg, Human arm bones diagram. File:Inferior epiphysis of humerus.jpg, Humerus - inferior epiphysis. Anterior view. File:Slide10DEN.JPG, Trochlea. Posterior view. File:LeftHumanPosteriorDistalHumerusFlexed.jpg, Humerus - inferior epiphysis. Posterior view. File:AnteroMedialHeadofLeftHumerus.jpg, Humerus - superior epiphysis. Anterior view. File:Superior epiphysis.jpg, Humerus - superior epiphysis. Posterior view. File:Elbow joint - deep dissection (anterior view, human cadaver).jpg, Elbow joint. Deep dissection. Anterior view. File:Slide1bgbg.JPG, Elbow joint. Deep dissection. Posterior view. File:Slide3bgbg.JPG, Elbow joint. Deep dissection. Posterior view. File:Gray326.png, The left shoulder and acromioclavicular joints, and the proper ligaments of the scapula File:Gray207.png, Left humerus. Anterior view. File:Gray208.png, Left humerus. Posterior view. File:AnteriorHeadOfLeftHumerus.jpg, Left humerus. Anteriolateral view. File:MedialHeadOfLeftHumerus.jpg, Left humerus. Medial view. File:ProxHumeralFracture.png, Fracture of the proximal humerus File:Gray329.png, Left elbow-joint, showing anterior and ulnar collateral ligaments. File:Gray332.png, Capsule of elbow-joint (distended). Posterior aspect. File:Humerus Anatomy by Jason Christian.webm, Humerus anatomy

Ossification

During embryonic development, the humerus is one of the first structures to ossify, beginning with the first

ossification center An ossification center is a point where ossification of the hyaline cartilage begins. The first step in ossification is that the chondrocytes at this point become hypertrophic and arrange themselves in rows. The matrix in which they are imbedd ...

in the shaft of the bone. Ossification of the humerus occurs predictably in the embryo and fetus, and is therefore used as a fetal biometric measurement when determining gestational age of a fetus. At birth, the neonatal humerus is only ossified in the shaft. The epiphyses are cartilaginous at birth. The medial humeral head develops an ossification center around 4 months of age and the greater tuberosity around 10 months of age. These ossification centers begin to fuse at 3 years of age. The process of ossification is complete by 13 years of age, though the

epiphyseal plate The epiphyseal plate, epiphysial plate, physis, or growth plate is a hyaline cartilage plate in the metaphysis at each end of a long bone. It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, with ma ...

(growth plate) persists until skeletal maturity, usually around 17 years of age.

References

External links

*
Humerus
- BlueLink Anatomy, University of Michigan Medical School {{Authority control Bones of the upper limb Long bones

Etymology

Structure

Upper extremity

Head

Anatomical neck

Surgical neck

Greater tubercle

Lesser tubercle

Bicipital groove

Shaft

Distal humerus

Articular surface

Fossae

Epicondyles

Borders

Articulations

Nerves

Function

Muscular attachment

Other animals

Additional images

Ossification

See also

References

External links