The subclavian triangle (or supraclavicular triangle, omoclavicular triangle, Ho's triangle), the smaller division of the posterior triangle, is bounded, above, by the inferior belly of the
omohyoideus; below, by the
clavicle; its base is formed by the posterior border of the
sternocleidomastoideus.
Its floor is formed by the first rib with the first digitation of the
serratus anterior.
The size of the subclavian triangle varies with the extent of attachment of the clavicular portions of the
Sternocleidomastoideus and
Trapezius, and also with the height at which the
Omohyoideus crosses the neck.
Its height also varies according to the position of the arm, being diminished by raising the limb, on account of the ascent of the clavicle, and increased by drawing the arm downward, when that bone is depressed.
This space is covered by the integument, the superficial and deep fasciæ and the
platysma
The platysma muscle is a superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the neck, and a "bowstring" eff ...
, and crossed by the supraclavicular nerves.
Just above the level of the clavicle, the third portion of the
subclavian artery curves lateralward and downward from the lateral margin of the
scalenus anterior, across the first
rib, to 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 supe ...
, and this is the situation most commonly chosen for
ligaturing the vessel.
Sometimes this vessel rises as high as 4 cm. above the clavicle; occasionally, it passes in front of the Scalenus anterior, or pierces the fibers of that muscle.
The subclavian vein lies behind the clavicle, and is not usually seen in this space; but in some cases it rises as high as the artery, and has even been seen to pass with that vessel behind the Scalenus anterior.
The
brachial plexus of nerves lies above the artery, and in close contact with it. Passing transversely behind the clavicle are the
transverse scapular vessels; and traversing its upper angle in the same direction, the
transverse cervical artery
The transverse cervical artery (transverse artery of neck or transversa colli artery) is an artery in the neck and a branch of the thyrocervical trunk, running at a higher level than the suprascapular artery.
Structure
It passes transversely b ...
and vein.
The
external jugular vein runs vertically downward behind the posterior border of the Sternocleidomastoideus, to terminate in the
subclavian vein; it receives the transverse cervical and transverse scapular veins, which form a plexus in front of the artery, and occasionally a small vein which crosses the
clavicle from the
cephalic.
The small nerve to the subclavius also crosses this triangle about its middle, and some
lymph glands are usually found in the space.
Enlarged nodes in this triangle irrespective of size are categorized at N3 in the TNM classification for nasopharyngeal carcinoma.
Gallery
File:Musculussternocleidomastodieus.png, Sternocleidomastoid muscle
File:Gray386.png, Muscles of the neck. Anterior view.
File:Posterior triangle of the neck.PNG, Posterior triangle of the neck labeled. (Anterior triangles to the left. Occipital triangle labeled at center left.) )
See also
*
Posterior triangle of the neck
References
External links
*
{{Authority control
Human head and neck
Triangles of the neck