Triangles Of The Neck

Front 1

Ant. Triangles

Muscular triangle

Back 1

The inferior carotid triangle (or muscular triangle), is bounded, in front, by the median line of the neck from the hyoid bone to the sternum; behind, by the anterior margin of the Sternocleidomastoideus; above, by the superior belly of the Omohyoideus.

It is covered by the integument, superficial fascia, Platysma, and deep fascia, ramifying in which are some of the branches of the supraclavicular nerves.

Beneath these superficial structures are the Sternohyoideus and Sternothyreoideus, which, together with the anterior margin of the Sternocleidomastoideus, conceal the lower part of the common carotid artery.

This vessel is enclosed within its sheath, together with the internal jugular vein and vagus nerve; the vein lies lateral to the artery on the right side of the neck, but overlaps it below on the left side; the nerve lies between the artery and vein, on a plane posterior to both.

In front of the sheath are a few descending filaments from the ansa hypoglossi; behind the sheath are the inferior thyroid artery, the recurrent nerve, and the sympathetic trunk; and on its medial side, the esophagus, the trachea, the thyroid gland, and the lower part of the larynx.

By cutting into the upper part of this space, and slightly displacing the Sternocleidomastoideus, the common carotid artery may be tied below the Omohyoideus.

Front 2

Ant. Triangles

Carotid Triangle

Back 2

It is bounded:

* behind by the Sternocleidomastoideus;
* below, by the superior belly of the Omohyoideus
* above, by the Stylohyoideus and the posterior belly of the Digastricus.

Arteries:
Common carotid arteries

* the superior thyroid artery, running forward and downward;
* the lingual artery, directly forward;
* the facial artery , forward and upward;
* the occipital artery , backward;
* the ascending pharyngeal artery, directly upward on the medial side of the internal carotid.

Veins:
* the internal jugular, which lies on the lateral side of the common and internal carotid arteries;
* and veins corresponding to the above-mentioned branches of the external carotid—viz.,
o the superior thyroid,
o the lingual,
o common facial,
o ascending pharyngeal,
o and sometimes the occipital

...all of which end in the internal jugular

The nerves in this space are the following.

In front of the sheath of the common carotid is the ramus descendens hypoglossi.

The hypoglossal nerve crosses both the internal and external carotids above, curving around the origin of the occipital artery.

Within the sheath, between the artery and vein, and behind both, is the vagus nerve; behind the sheath, the sympathetic trunk.

On the lateral side of the vessels, the accessory nerve runs for a short distance before it pierces the Sternocleidomastoideus; and on the medial side of the external carotid, just below the hyoid bone, may be seen the internal branch of the superior laryngeal nerve; and, still more inferiorly, the external branch of the same nerve.

Front 3

Ant. Triangles

Submandibular Triangle

Back 3

It is bounded:

* above, by the lower border of the body of the mandible, and a line drawn from its angle to the mastoid process;
* below, by the posterior belly of the Digastricus and the Stylohyoideus; in front, by the anterior belly of the Digastricus.

It is covered by the integument, superficial fascia, Platysma, and deep fascia, ramifying in which are branches of the facial nerve and ascending filaments of the cutaneous cervical nerve.

Its floor is formed by the Mylohyoideus, Hyoglossus, and Constrictor pharyngis superior

It`s divided into two:

Anterior part

The anterior part contains the submaxillary gland, superficial to which is the anterior facial vein, while imbedded in the gland is the external maxillary artery and its glandular branches.

Beneath the gland, on the surface of the Mylohyoideus, are the submental artery and the mylohyoid artery and nerve.

[edit] Posterior part

The posterior part of this triangle contains the external carotid artery, ascending deeply in the substance of the parotid gland

This vessel lies here in front of, and superficial to, the internal carotid, being crossed by the facial nerve, and gives off in its course the posterior auricular, superficial temporal, and internal maxillary branches: more deeply are the internal carotid, the internal jugular vein, and the vagus nerve, separated from the external carotid by the Styloglossus and Stylopharyngeus, and the glossopharyngeal nerve

Front 4

Ant. Triangles

Submental Triangle

Back 4

Boundaries:
* behind by the anterior belly of the Digastricus,
* in front by the middle line of the neck between the mandible and the hyoid bone;
* below, by the body of the hyoid bone;
* its floor is formed by the Mylohyoideus.

It contains:

* one or two lymph glands, the submental lymph nodes
* some small veins; the latter unite to form the anterior jugular vein

Front 5

Post. Triangles

Occipital Triangle

Back 5

The occipital triangle, the larger division of the posterior triangle, is bounded, in front, by the Sternocleidomastoideus; behind, by the Trapezius; below, by the Omohyoideus.

Its floor is formed from above downward by the Splenius capitis, Levator scapulæ, and the Scaleni medius and posterior.

It is covered by the skin, the superficial and deep fasciæ, and by the Platysma below.

The accessory nerve is directed obliquely across the space from the Sternocleidomastoideus, which it pierces, to the under surface of the Trapezius; below, the supraclavicular nerves and the transverse cervical vessels and the upper part of the brachial plexus cross the space.

A chain of lymph glands is also found running along the posterior border of the Sternocleidomastoideus, from the mastoid process to the root of the neck.

Front 6

Post. Triangles

Subclavian triangle

Back 6

The subclavian 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, 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, 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 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.

Front 7

Post. Triangles

Suboccipital triangle

Back 7

The suboccipital triangle is a region of the neck bounded by the following three muscles:

* Rectus capitis posterior major - above and medially
* Obliquus capitis superior - above and laterally
* Obliquus capitis inferior - below and laterally

It is covered by a layer of dense fibro-fatty tissue, situated beneath the Semispinalis capitis.

The floor is formed by the posterior occipito-atlantal membrane, and the posterior arch of the atlas.

In the deep groove on the upper surface of the posterior arch of the atlas are the vertebral artery and the first cervical or suboccipital nerve.