Humerus

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"Humeral" redirects here. Humerus_sentence_0

It is not to be confused with humoral immunity. Humerus_sentence_1

Humerus_table_infobox_0

HumerusHumerus_header_cell_0_0_0
DetailsHumerus_header_cell_0_1_0
IdentifiersHumerus_header_cell_0_2_0
LatinHumerus_header_cell_0_3_0 humerusHumerus_cell_0_3_1
MeSHHumerus_header_cell_0_4_0 Humerus_cell_0_4_1
TA98Humerus_header_cell_0_5_0 Humerus_cell_0_5_1
TA2Humerus_header_cell_0_6_0 Humerus_cell_0_6_1
FMAHumerus_header_cell_0_7_0 Humerus_cell_0_7_1

The humerus (/ˈhjuːmərəs/, plural: humeri) is a long bone in the arm that runs from the shoulder to the elbow. Humerus_sentence_2

It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. Humerus_sentence_3

The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes (tubercles, sometimes called tuberosities). Humerus_sentence_4

The body is cylindrical in its upper portion, and more prismatic below. Humerus_sentence_5

The lower extremity consists of 2 epicondyles, 2 processes (trochlea & capitulum), and 3 fossae (radial fossa, coronoid fossa, and olecranon fossa). Humerus_sentence_6

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. Humerus_sentence_7

Etymology Humerus_section_0

The word "humerus" is derived from Latin: humerus, umerus meaning upper arm, shoulder, and is linguistically related to Gothic ams shoulder and Greek ōmos. Humerus_sentence_8

Structure Humerus_section_1

Upper extremity Humerus_section_2

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. Humerus_sentence_9

Head Humerus_section_3

The head (caput humeri), is nearly hemispherical in form. Humerus_sentence_10

It is directed upward, medialward, and a little backward, and articulates with the glenoid cavity of the scapula to form the glenohumeral joint (shoulder joint). Humerus_sentence_11

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. Humerus_sentence_12

Fracture of the anatomical neck rarely occurs. Humerus_sentence_13

The diameter of the humeral head is generally larger in men than in women. Humerus_sentence_14

Anatomical neck Humerus_section_4

Main article: Anatomical neck of the humerus Humerus_sentence_15

The anatomical neck (collum anatomicum) is obliquely directed, forming an obtuse angle with the body. Humerus_sentence_16

It is best marked in the lower half of its circumference; in the upper half it is represented by a narrow groove separating the head from the tubercles. Humerus_sentence_17

It affords attachment to the articular capsule of the shoulder-joint, and is perforated by numerous vascular foramina. Humerus_sentence_18

Fracture of the anatomical neck rarely occurs. Humerus_sentence_19

The anatomical neck of the humerus is an indentation distal to the head of the humerus on which the articular capsule attaches. Humerus_sentence_20

Surgical neck Humerus_section_5

Main article: Surgical neck of the humerus Humerus_sentence_21

The surgical neck is a narrow area distal to the tubercles that is a common site of fracture. Humerus_sentence_22

It makes contact with the axillary nerve and the posterior humeral circumflex artery. Humerus_sentence_23

Greater tubercle Humerus_section_6

Main article: Greater tubercle Humerus_sentence_24

The greater tubercle (tuberculum majus; greater tuberosity) is a large, posteriorly placed projection that is placed laterally. Humerus_sentence_25

The greater tubercle is where supraspinatus, infraspinatus and teres minor muscles are attached. Humerus_sentence_26

The crest of the greater tubercle forms the lateral lip of the bicipital groove and is the site for insertion of pectoralis major. Humerus_sentence_27

The greater tubercle is just lateral to the anatomical neck. Humerus_sentence_28

Its upper surface is rounded and marked by three flat impressions: the highest of these gives insertion to the supraspinatus muscle; the middle to the infraspinatus muscle; the lowest one, and the body of the bone for about 2.5 cm. Humerus_sentence_29

below it, to the teres minor muscle. Humerus_sentence_30

The lateral surface of the greater tubercle is convex, rough, and continuous with the lateral surface of the body. Humerus_sentence_31

Lesser tubercle Humerus_section_7

Main article: Lesser tubercle Humerus_sentence_32

The lesser tubercle (tuberculum minus; lesser tuberosity) is smaller, anterolaterally placed to the head of the humerus. Humerus_sentence_33

The lesser tubercle provides insertion to subscapularis muscle. Humerus_sentence_34

Both these tubercles are found in the proximal part of the shaft. Humerus_sentence_35

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. Humerus_sentence_36

The lesser tuberosity, is more prominent than the greater: it is situated in front, and is directed medialward and forward. Humerus_sentence_37

Above and in front it presents an impression for the insertion of the tendon of the subscapularis muscle. Humerus_sentence_38

Bicipital groove Humerus_section_8

The tubercles are separated from each other by a deep groove, the bicipital groove (intertubercular groove; bicipital sulcus), which lodges the long tendon of the biceps brachii muscle and transmits a branch of the anterior humeral circumflex artery to the shoulder-joint. Humerus_sentence_39

It runs obliquely downward, and ends near the junction of the upper with the middle third of the bone. Humerus_sentence_40

In the fresh state its upper part is covered with a thin layer of cartilage, lined by a prolongation of the synovial membrane of the shoulder-joint; its lower portion gives insertion to the tendon of the latissimus dorsi muscle. Humerus_sentence_41

It is deep and narrow above, and becomes shallow and a little broader as it descends. Humerus_sentence_42

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. Humerus_sentence_43

Shaft Humerus_section_9

Humerus_table_infobox_1

Body of humerusHumerus_header_cell_1_0_0
DetailsHumerus_header_cell_1_1_0
IdentifiersHumerus_header_cell_1_2_0
LatinHumerus_header_cell_1_3_0 corpus humeriHumerus_cell_1_3_1
MeSHHumerus_header_cell_1_4_0 Humerus_cell_1_4_1
TA98Humerus_header_cell_1_5_0 Humerus_cell_1_5_1
TA2Humerus_header_cell_1_6_0 Humerus_cell_1_6_1
FMAHumerus_header_cell_1_7_0 Humerus_cell_1_7_1

The body or shaft of the humerus is triangular to cylindrical in cut section and is compressed anteroposteriorly. Humerus_sentence_44

It has 3 surfaces, namely: Humerus_sentence_45

Humerus_unordered_list_0

  • 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; forward and lateralward below, where it is slightly concave from above downward, and gives origin to part of the Brachialis. About the middle of this surface is a rough, rectangular elevation, the deltoid tuberosity for the insertion of the deltoid muscle; below this is the radial sulcus, directed obliquely from behind, forward, and downward, and transmitting the radial nerve and profunda artery.Humerus_item_0_0
  • 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 which gives insertion to the tendon of the latissimus dorsi muscle; its middle part is slightly rough for the attachment of some of the fibers of the tendon of insertion of the coracobrachialis muscle; its lower part is smooth, concave from above downward, and gives origin to the brachialis muscle.Humerus_item_0_1
  • 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.Humerus_item_0_2

Its three borders are: Humerus_sentence_46

Humerus_unordered_list_1

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. Humerus_sentence_47

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. Humerus_sentence_48

This is where the lateral head of triceps brachii is attached. Humerus_sentence_49

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. Humerus_sentence_50

This is located posteroinferior to the deltoid tuberosity. Humerus_sentence_51

The inferior boundary of the spiral groove is continuous distally with the lateral border of the shaft. Humerus_sentence_52

The nutrient foramen of the humerus is located in the anteromedial surface of the humerus. Humerus_sentence_53

The nutrient arteries enter the humerus through this foramen. Humerus_sentence_54

Distal humerus Humerus_section_10

Humerus_table_infobox_2

Lower extremity of humerusHumerus_header_cell_2_0_0
DetailsHumerus_header_cell_2_1_0
IdentifiersHumerus_header_cell_2_2_0
LatinHumerus_header_cell_2_3_0 Extremitas distalis humeriHumerus_cell_2_3_1
MeSHHumerus_header_cell_2_4_0 Humerus_cell_2_4_1
TA98Humerus_header_cell_2_5_0 Humerus_cell_2_5_1
TA2Humerus_header_cell_2_6_0 Humerus_cell_2_6_1
FMAHumerus_header_cell_2_7_0 Humerus_cell_2_7_1

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. Humerus_sentence_55

Projecting on either side are the lateral and medial epicondyles. Humerus_sentence_56

Articular surface Humerus_section_11

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. Humerus_sentence_57

The lateral portion of this surface consists of a smooth, rounded eminence, named the capitulum of the humerus; 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. Humerus_sentence_58

Fossae Humerus_section_12

Above the front part of the trochlea is a small depression, the coronoid fossa, which receives the coronoid process of the ulna during flexion of the forearm. Humerus_sentence_59

Above the back part of the trochlea is a deep triangular depression, the olecranon fossa, in which the summit of the olecranon is received in extension of the forearm. Humerus_sentence_60

The coronoid fossa is the medial hollow part on the anterior surface of the distal humerus. Humerus_sentence_61

The coronoid fossa is smaller than the olecranon fossa and receives the coronoid process of the ulna during maximum flexion of the elbow. Humerus_sentence_62

Above the front part of the capitulum is a slight depression, the radial fossa, which receives the anterior border of the head of the radius, when the forearm is flexed. Humerus_sentence_63

These fossæ are separated from one another by a thin, transparent lamina of bone, which is sometimes perforated by a supratrochlear foramen; they are lined in the fresh state by the synovial membrane of the elbow-joint, and their margins afford attachment to the anterior and posterior ligaments of this articulation. Humerus_sentence_64

The Capitulum is a rounded eminence forming the lateral part of the distal humerus. Humerus_sentence_65

The head of the radius articulates with the capitulum. Humerus_sentence_66

The trochlea is spool-shaped medial portion of the distal humerus and articulates with the ulna. Humerus_sentence_67

Epicondyles Humerus_section_13

The epicondyles are continuous above with the supracondylar ridges. Humerus_sentence_68

Humerus_unordered_list_2

  • 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 and some of the Extensor muscles.Humerus_item_2_6
  • 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, and to a common tendon of origin of some of the Flexor muscles of the forearm; the ulnar nerve runs in a groove on the back of this epicondyle.Humerus_item_2_7

The Medial supracondylar crest forms the sharp medial border of the distal humerus continuing superiorly from the medial epicondyle. Humerus_sentence_69

The Lateral Supracondylar crest forms the sharp lateral border of the distal humerus continuing superiorly from the lateral epicondyle. Humerus_sentence_70

Borders Humerus_section_14

The medial portion of the articular surface is named the trochlea, 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. Humerus_sentence_71

Humerus_unordered_list_3

  • The lateral border separates it from the groove which articulates with the margin of the head of the radius.Humerus_item_3_8
  • The medial border is thicker, of greater length, and consequently more prominent, than the lateral.Humerus_item_3_9

The grooved portion of the articular surface fits accurately within the semilunar notch 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. Humerus_sentence_72

Articulations Humerus_section_15

At the shoulder, the head of the humerus articulates with the glenoid fossa of the scapula. Humerus_sentence_73

More distally, at the elbow, the capitulum of the humerus articulates with the head of the radius, and the trochlea of the humerus articulates with the trochlear notch of the ulna. Humerus_sentence_74

Nerves Humerus_section_16

The axillary nerve is located at the proximal end, against the shoulder girdle. Humerus_sentence_75

Dislocation of the humerus's glenohumeral joint has the potential to injure the axillary nerve or the axillary artery. Humerus_sentence_76

Signs and symptoms of this dislocation include a loss of the normal shoulder contour and a palpable depression under the acromion. Humerus_sentence_77

The radial nerve follows the humerus closely. Humerus_sentence_78

At the midshaft of the humerus, the radial nerve travels from the posterior to the anterior aspect of the bone in the spiral groove. Humerus_sentence_79

A fracture of the humerus in this region can result in radial nerve injury. Humerus_sentence_80

The ulnar nerve lies at the distal end of the humerus near the elbow. Humerus_sentence_81

When struck, it can cause a distinct tingling sensation, and sometimes a significant amount of pain. Humerus_sentence_82

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'. Humerus_sentence_83

It lies posterior to the medial epicondyle, and is easily damaged in elbow injuries. Humerus_sentence_84

Function Humerus_section_17

Muscular attachment Humerus_section_18

The deltoid originates on the lateral third of the clavicle, acromion and the crest of the spine of the scapula. Humerus_sentence_85

It is inserted on the deltoid tuberosity of the humerus and has several actions including abduction, extension, and circumduction of the shoulder. Humerus_sentence_86

The supraspinatus also originates on the spine of the scapula. Humerus_sentence_87

It inserts on the greater tubercle of the humerus, and assists in abduction of the shoulder. Humerus_sentence_88

The pectoralis major, teres major, and latissimus dorsi insert at the intertubercular groove of the humerus. Humerus_sentence_89

They work to adduct and medially, or internally, rotate the humerus. Humerus_sentence_90

The infraspinatus and teres minor insert on the greater tubercle, and work to laterally, or externally, rotate the humerus. Humerus_sentence_91

In contrast, the subscapularis muscle inserts onto the lesser tubercle and works to medially, or internally, rotate the humerus. Humerus_sentence_92

The biceps brachii, brachialis, and brachioradialis (which attaches distally) act to flex the elbow. Humerus_sentence_93

(The biceps do not attach to the humerus.) Humerus_sentence_94

The triceps brachii and anconeus extend the elbow, and attach to the posterior side of the humerus. Humerus_sentence_95

The four muscles of supraspinatus, infraspinatus, teres minor and subscapularis form a musculo-ligamentous girdle called the rotator cuff. Humerus_sentence_96

This cuff stabilizes the very mobile but inherently unstable glenohumeral joint. Humerus_sentence_97

The other muscles are used as counterbalances for the actions of lifting/pulling and pressing/pushing. Humerus_sentence_98

Humerus_table_general_3

Left humerus. Anterior view.Humerus_table_caption_3
Humerus_cell_3_0_0 Humerus_cell_3_0_1 Humerus_cell_3_0_2 Humerus_cell_3_0_3 Humerus_cell_3_0_4 Humerus_cell_3_0_5

Humerus_table_general_4

Left humerus. Posterior view.Humerus_table_caption_4
Humerus_cell_4_0_0 Humerus_cell_4_0_1 Humerus_cell_4_0_2 Humerus_cell_4_0_3 Humerus_cell_4_0_4

Other animals Humerus_section_19

Primitive fossils of amphibians had little, if any, shaft connecting the upper and lower extremities, making their limbs very short. Humerus_sentence_99

In most living tetrapods, however, the humerus has a similar form to that of humans. Humerus_sentence_100

In many reptiles and some primitive mammals, the lower extremity includes a large foramen, or opening, which allows nerves and blood vessels pass through. Humerus_sentence_101

Additional images Humerus_section_20

Humerus_unordered_list_4

  • Humerus_item_4_10
  • Humerus_item_4_11
  • Humerus_item_4_12
  • Humerus_item_4_13
  • Humerus_item_4_14
  • Humerus_item_4_15
  • Humerus_item_4_16
  • Humerus_item_4_17
  • Humerus_item_4_18
  • Humerus_item_4_19
  • Humerus_item_4_20
  • Humerus_item_4_21
  • Humerus_item_4_22
  • Humerus_item_4_23
  • Humerus_item_4_24
  • Humerus_item_4_25
  • Humerus_item_4_26
  • Humerus_item_4_27
  • Humerus_item_4_28
  • Humerus_item_4_29

Ossification Humerus_section_21

Further information: ossification Humerus_sentence_102

During embryonic development, the humerus is one of the first structures to ossify, beginning with the first ossification center in the shaft of the bone. Humerus_sentence_103

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. Humerus_sentence_104

At birth, the neonatal humerus is only ossified in the shaft. Humerus_sentence_105

The epiphyses are cartilaginous at birth. Humerus_sentence_106

The medial humeral head develops an ossification center around 4 months of age and the greater tuberosity around 10 months of age. Humerus_sentence_107

These ossification centers begin to fuse at 3 years of age. Humerus_sentence_108

The process of ossification is complete by 13 years of age, though the epiphyseal plate (growth plate) persists until skeletal maturity, usually around 17 years of age. Humerus_sentence_109

See also Humerus_section_22

Humerus_unordered_list_5


Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Humerus.