By Prof. Saeed Abuel Makarem

ByProf. Saeed Abuel Makarem

Prof. MakaremProf. Makarem 22

STERNOCLEIDOMASTOIDSternocleidomastoid is a strap muscle.It descends obliquely across the side of the neck. It forms a prominent surface landmark.It divides the side of the neck into anterior & posterior triangles


The neck is divided into anterior and posterior triangles by sternocleidomastoid

Anterior triangle lies in front of the muscle

Posterior triangle lies behind it.

TRIANGLES OF THE NECK


Boundaries of the Posterior triangle:

Anteriorly: posterior border of sternomastoid

Posteriorly: anterior border of trapezius

Inferiorly: middle third of the clavicle.


OMOHYOID MUSCLEThe omohyoid

muscle has:

Inferior belly Intermediate

tendon

Superior belly.


The inferior belly of omohyoid subdivides the posterior triangle into:

a large occipital triangle above

a small supraclavicular triangle below.


The roof of the triangle is covered by:

Skin. superficial fascia, which

contains: platysma, cutaneous branches of

cervical plexus External jugular vein Investing layer of deep

cervical fascia.


Running across the triangle in its covering: the cutaneous branches of cervical plexus


The floor of the triangle is covered by the prevertebral layer of deep cervical fascia. It is formed from below upward by the:

– Scalenus medius. – Levator scapulae– Splenius capitis, &

Semispinalis capitis, A small part of the Scalenus anterior may be present, but it is usually overlapped and hidden by the sternocleidomastoid.

Parts of Deep cervical fascia:

Investing layer.Prevertebral layer.Pretracheal layer.Carotid sheath.

Notice:

The cutaneous branches of cervical plexus & the external jugular vein are contents and in the same time they run in the roof of the triangle


PLATYSMA MUSCLEThe platysma can be seen as a sheet of muscle by asking the patient to clench the jaws firmly. It extends from the body of the mandible downward over the clavicle onto the anterior thoracic wall.

Contents of Posterior triangle

Nerves: The main contents are nerves: - 3 trunks of the brachial plexus. - (4)cutaneous branches of cervical plexus. (lesser occipital, great auricular, transverse cervical & supraclavicular nerves. - Spinal accessory. Arteries: - 3rd part of subclavian artery. - Suprascapular artery. - Transverse cervical artery. - Occipital artery. Veins: - Subclavian vein. - External jugular vein. + Muscle: Inferior belly of omohyoid muscle.


BRACHIAL PLEXUSThe brachial plexus is formed from the anterior rami of the C 5th, 6th, 7th,& 8th &T 1st . It lies in the anteroinferior angle of the posterior triangle.


The roots of the brachial plexus enter the posterior triangle of the neck through the interval between the scalenus anterior and the scalenus medius muscles.


ACCESSORY NERVE (SPINAL PART)

The spinal part of the accessory nerve enters the posterior triangle by emerging from beneath the middle of the posterior border of sternomastoid.It runs downward and laterally across the posterior triangle on the levator scapulae muscle, (dangerous position)


BRANCHES OF THE CERVICAL PLEXUS

The cervical plexus is formed by the anterior rami of C1,C2,C3 & C4.Several cutaneous nerves emerge from under the middle of the posterior border of the sternomastoid muscle.They innervate parts of the skin in the head and neck region.N.B.: Block anesthesia


LESSER OCCIPITAL NERVEThe lesser occipital nerve is a branch of C2.It hooks around the accessory nerve and ascends along the posterior border of the sternomastoid muscle It supply the skin over the lateral part of the occipital region and the medial surface of the auricle.


GREAT AURICULAR NERVEThe great auricular nerve is a branch of C2 & C3.It ascends across the sternomastoid where it divides into branches that supply the skin over the angle of the mandible, the parotid gland, and the auricle.


TRANSVERSE CERVICAL NERVETransverse cervical nerve of the neck is a branch of C2 and C3. It emerges from behind the middle of the posterior border of the sternomastoid.It passes forward across that muscle and divides into branches that supply the skin on the anterior and lateral surfaces of the neck, from the body of the mandible to the sternum.


SUPRACLAVICULAR NERVESThe supraclavicular nerves are branches of C3 and C4. They emerge from beneath the posterior border of the sternocleidomastoid muscle and descend across the side of the neck. They pass onto the chest wall and shoulder region, down to the level of the second rib.


THIRD PART OF THE SUBCLAVIAN ARTERYThe subclavian artery is divided into three parts by the scalenus anterior muscle, which crosses in front of the artery. First part medial to

scalenus anterior. Second part lies

behind the muscle. Third part extends

from the lateral border of the muscle to the outer border of the first rib; where, it is continuous as the axillary artery.


The third part of the subclavian artery enters the anteroinferior angle of the posterior triangle and disappears behind the middle of the clavicle.


SUPERFICIAL CERVICAL ARTERY

It is a branch of the thyrocervical trunk, of the first part of the subclavian artery. It runs across the lower part of the posterior triangle and disappears deep to the trapezius muscle.


SUPASCAPULAR ARTERYThe suprascapular artery is also a branch of the thyrocervical trunk. It runs across the lower part of the posterior triangle. It follows the suprascapular nerve into the supraspinous fossa and takes part in the anastomosis around the scapula.


OCCIPITAL ARTERYIt is a branch of the external carotid artery. It enters the posterior triangle at its superior angle, appearing between the sternomastoid & trapezius muscles. Then, it ascends in a tortuous course over the back of the scalp, accompanied by the greater occipital nerve.


EXTERNAL JUGULAR VEINThe External jugular vein begins just behind the angle of the mandible by the union of the posterior auricular vein with the posterior division of the retromandibular vein.


TRIBUTARIES Posterior auricular vein.Posterior division of the retromandibular vein.Transverse cervical vein.Suprascapular vein.Anterior jugular vein. Posterior external jugular vein, a small vein that drains the posterior part of the scalp and neck and joins the external jugular vein about halfway along its course.

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By Prof. Saeed Abuel Makarem