The humerus or arm-bone (french : humérus), the largest bone of the upper extremity, extends from the scapula to the bones of the fore-arm, with each of which it is articulated. Its direction is vertical, with an inclination inwards towards the lower end. Long and irregularly cylindrical in form, the humerus is divisible into a body and two extremities.

Bone of the arm, type of the long bone, formed of a body (diapyse) and two ends (epiphysis), it is articulated:

proximal with the scapula
distal with the radius and the ulna

The diaphyse of the humerus

All the long bones of the members are triangular with the cut, the cut of a segment of member always represents the section of section of the segment proximal:

Three surfaces:

anterio-medial suface
anterio-lateral surface
dorsal surface

Three borders :

anterior border
lateral border
medial border

(the bones structures take the name of the area that they look at)

Anterior surface

Give insertions give to muscles which come from the shoulder or which go to the elbow.

Dorsal surface

Presents at its middle part an oblic gutter into distal and side; furrow of torsion of the humerus; it contains the radial nerve, (furrow of the radial nerve). Lesion attends radial nerve during the fractures of the diaphyse of the humerus.

Borders

Only the ventral border is quite marked. It begins at the the upper epiphysis level of the humerus. It contributes at its middle part to the insertion of the deltoïd muscle, the deltoid tuberosity overflows at the anterior-side surface. It forks with its distal part.

The other border are less marked (foams).

Humeral epiphysis

They carry articular surfaces.

Proximal epiphisis

Divided into three parts:

The head
The neck : anatomical and surgical
The tuberosities : two.

Humeral head

Covered with cartilage, of spherical form (1/3 of sphere), it articulates with the glenoidal cavity of the scapula. The head is larger than the cavity which receives it, luxations of the shoulder are frequent.

It looks in crânial, medial and dorsal. Angle of inclination of 130°.

The neck

Narrowed part which gives fastener to the articular capsule, anatomical neck.

Tuberosities

They prolong the neck.

The lateral major tuberosity is the greater tuberosity

The medial minor tuberosity is the lesser tuberosity

Between the two tuberosities; the gutter gives passage to a tendon of the biceps muscle (the long portion) : bicipital gutter.

The Surgical neck

Union zone of the proximal epiphysis and the diaphyse, circumvented by the axillary nerve.

Distal epiphysis

Widened transversely, to buckle anteriorly

Made of two principal parts:

- Central Part: Articular, humeral condyle.

- Peripheral Part: Muscular insertions, epicondyles.

Articular part (condyle), divided the side one into medial in three parts: Into side and ventral -> The capitulum (capitelum) spherical surface which is articulated with the radial head.

Then -> Furrow capitulo-trochleaire (conoide zone) it is articulated with the radial head.

In medial -> Hmeral trochlee (pulley)

The slope medial goes down low than the side slope, it is asymmetrical, it is articulated with the ulna. Be rolled up around the distal edge of the epiphysis.

Peripheral part: There exists in crânial articular surfaces two surfaces of muscular insertions; one in medial, one into side.

Into side -> articular condyle, side epicondyle

(epicondyle), (insertion gives to the side muscles epicondyliens, they move into dorsal, extensors).

In medial -> articular condyle, the medial epicondyle (epitrochlee), (insertion gives to the muscles mediaux epicondyliens, they move into ventral, flexors). Into dorsal of the epicondyle medial presence of a gutter: furrow of the ulnar nerve.

With the top -> articular condyle, presence of small cavities in which come to place the bones of before arm at the time of the movements from inflection or extension, these small cavities are mechanical stop units.

Small cavities into ventral

- Pit coronoïdienne, known-trochleenne (thrust for the coronoïde of the ulna at the time of the inflection)

- Radial Pit, in crânial of the capitulum

(thrust for the head of the radius at the time of the inflection).

Small cavity into dorsal

- Pit olecranienne, (known trochleenne)
(thrust for the olecrane of the ulna during the extension).