THE Neck

The Neck

Narrow & flexible portion between the head above & the chest below. Functionally the neck can be divided into four areas or units:


1- Vertebral unit : includes the cervical portion of vertebral column & its musculature , pass through the vertebral canal the cervical portion of the spinal cord , give rise to 8 pairs of spinal cervical nerves.

2- Visceral unit : Contain the air & food passages. The larynx & pharynx above vertebral level C6. The thyroid gland found lateral to the larynx & trachea ( two lateral lobes ) joined by an isthmus.


3- Carotid unit : Lateral to the visceral unit bilateral tube of fascia ( the carotid sheaths ) contain : A- Common carotid artery . B- Internal jugular vein. C- Vagus nerve.


4- Muscular unit : A- The lateral group : Sternoclidomastoid muscle & Trapezius muscle. B- The anterior group : The group of infrahyoid muscles , between the hyoid bone above & the manubrium of sternum below.

DIVISION OF THE NECK

The neck divided into two major & a number of small triangles by several key muscles: 1- Sternomastoid m. 2- Trapezius m. 3- The anterior & posterior bellies of digastrics m. 4- Inferior & superior bellies of omohyoid m.

The major triangles:

1- The posterior triangle. 2- The anterior triangle.



The posterior triangle includes: 1- Occipital. 2- Supraclavicular triangles. The anterior triangles includes : 1- Submandibular , 2- Submental , 3-Carotid , & 4- Muscular triangles.

The posterior triangle :

The posterior triangle occupies the lateral aspect of the neck, its apex toward the skull & its base toward the clavicle. Boundaries : The anterior boundary : Posterior border of the sternomastoid m. The posterior boundary: Anterior border of Trapezius m. The inferior boundary: middle third of clavicle.

Sternomatoid muscle :

Arise as two heads , the manubrium of sternum & the superior aspect of the medial third of the clavicle. The two heads blend as they pass obliquely upward & backward to insert into the mastoid process & the lateral half of the superior nuchal line of the skull.


Action: Bilaterally : Flex the neck. Singly : Flex the head & rotate the head to opposite side. Nerve supply : Spinal accessory nerve & anterior rami of C2 & C3.

Trapezius muscle :

A superficial muscle of the back, a muscle of upper limb girdle & a cervical muscle. Arises : From the external occipital protuberance & the medial half of superior nuchal line, the ligamentum nuchae of the lower cervical & all thoracic spine.

Insertion:

The fibers originate from the head insert into the lateral third of the clavicle. The remaining fibers insert into the acromion & spine of scapula. Action : Elevate & rotate the scapula. Nerve supply : Spinal accessory nerve & anterior rami of C3 & C4.



Roof of the posterior triangle :
1- Skin. 2- Superficial fascia & platysma muscle. 3- Deep investing fascia of the neck.

Platysma muscle :

Its thin wide sheet of muscle , covers the anterior & lateral aspects of the neck. It’s a superficial muscle related to the muscles of facial expression . It lie within the superficial fascia of the neck. Origine : from the pectoral fascia & pass upward to inserts in the inferior border of the mandible.Some fibers inserts into the angle of the mouth

Nerve supply: The cervical branches of the facial nerve.

The floor of posterior triangle: Formed by series of five muscles & their overlying prevertebral deep fascia. From the top downward in triangle , the muscles are : 1- Splenius Capitis muscle. 2- Levator scapulae muscle. 3- Scalenus posterior & medius muscles. 4- Scalenus anterior muscle.

Contents of the posterior triangle :

1- External jugular vein. 2- Cutaneous nerves of the posterior triangle. 3- Accessory nerve. 4- The brachial plexus. 5- Subclavian artery. 6- Subclavian vein.

The external jugular vein:

Pass obliquely downward over the sternomastoid muscle, to inter the posterior triangle & receives 3 tributaries : 1- Transverse cervical vein : drain to posterolateral aspect of the neck. 2- Supra scapular vein : drain the suprascapulae region of the neck. 3- The anterior jugular vein :

The anterior jugular vein drain the anterior aspect of the neck & descends on either side of the midline to a point above the jugular notch of the manubrium , deep to origin of sternomastoid muscle to inter the posterior triangle & empties to external jugular vein. E.J.V. ends by passing deep to the clavicle to inter the subclavian vein .



Cutaneous nerves of the posterior triangle :
Four branches of cervical plexus called cutaneous nerves of the cervical plexus , arise from the posterior triangle deep to the posterior border of the sternomastoid muscle. All the nerves radiate from a single area at the midpoint of the posterior border of the sternomastoid muscle.


1- Lesser occipital nerve ( C2 + C3 ). Carry sensation from the skin of occipital region behind the ear. 2- Greater auricular nerve (C2 + C3). Cross the lateral surface of the muscle obliquely & directed upward toward the auricle & the angle of the mandible & divided into two branches :


A- Posterior branch : Supply skin on both surface on the mastoid process. B- Anterior branch : Supply skin over the angle of mandible & parotid gland. 3- Transverse cervical nerve ( C2 + C3 ). Supply skin on the side & front of the neck.

4- Supraclavicular nerve ( C3 + C4 ).

Descends along the posterior border of the sternomastoid m.,near the clavicle it divided into three branches : 1- Medial supraclavicular nerve .To skin in base of neck. 2- Intermediate supraclavicular nerve.Cross clavicle to skin over the pectoralis region tell 3rd rib. 3- Lateral supraclavicular nerve.To skin over the lateral part of the clavicle.

Accessory nerve :

The accessory nerve ( cranial nerve 11 ) appears in posterior triangle as it emerges from under the posterior border of the sternomastoid m. It runs obliquely downwards along the surface of levator scapulae m. & disappears under the anterior border of Trapezius m. The accessory nerve has two parts:


The spinal part : Originate as rootlets of spinal nervesC1-C6 form up as a nerve trunk on either side of the spinal cord & inter the cranial cavity through the foramen magnum. The cranial part : Originate from the medulla oblongate & joins the spinal part. The two portions travel together within the cranium to the jugular foramen.


At the jugular foramen the cranial part join the vagus nerve & distributed with it. The spinal fibers pass through the jugular foramen to enter the neck below. The spinal accessory nerve passes through the sternomastoid m. & supply it, then crosses the posterior triangle to enter the Trapezius m. & supply it.


The brachial plexus :
The brachial plexus lie in the lower part of the posterior triangle behind the clavicle & in the axilla. Roots : Anterior rami of spinal nerve C5, C6, C7, C8 & T1. Trunks: The root of C5+C6 unite to form the upper trunk. C7 continues as middle trunk. C8 +T1 unite to form lower trunk.


Divisions : After passing over the 1st rib to the axilla below, each trunk divided into anterior & posterior divisions. Cords: The three posterior divisions unite to form the posterior cord. The upper two anterior divisions unite to form the lateral coed . The lower anterior division form the medial cord


The lateral cord gives a portion of median nerve. The medial cord gives part of median & ulnar nerves. The posterior cord gives radial & axillary nerves.

Branches of the brachial plexus in the neck :

1- Drsal scapular nerve. C5. 2- Nerve to subclavius m. .C5 +C6. 3- Supra scapular nerve. C5 +C6. 4- Long thoracic nerve C5 +C6 +C7.

Subclavian artery:

The right subclavian artery arises from the brachiocephalic artery. The left subclavian artery arises from the arch of aorta. The arteries arch upward & over the 1st rib are separated from the subclavian vein by the insertion of the scalenus anterior m. On crossing the 1st rib subclavian artery becomes the axillary artery.

The branches of the subclavian artery in the posterior triangle:

1- Transverse cervical artery: Run laterally to the anterior border of the levator scapulae m. crossing scalenus anterior m. & phrenic nerve. It divided into: A- Superficial br.to Trapezius m. B- Deep br. To levator scapulae m. 2- Suprascapular artery : Descends to scapula with suprascapular nerve.



Subclavian vein:
As continuation of the axillary vein at the outer border of the 1st rib , passes medially & forms the brachiocephalic vein by uniting with the internal jugular vein (I.J.V.). External jugular vein & vertebral vein drain to subclavian vein . The transverse cervical v. & the suprascapular v. drain to external jugular v.