Anatomy of the neck

By Dr. Rasha Sabry

الرحمن الله بسمالرحيم

”” تبصرون أفال أنفسكم تبصرون وفي أفال أنفسكم ““وفي

• The anterolateral part of the neck is quadrilateral area which is divided by sternomastoid muscle into 2 large triangular areas ( anterior and posterior ) .

• The investing layer of deep fascia roofs both triangles .

• Sternomastoid muscle :• 1- action :when one muscle acts alone , it bends the

head to its same side and rotates it to the opposite side ( the face looks to the opposite side

• As you want to approximate the mastoid process to the manubrium of the sternum ).

• When the two muscles act together , they flex the head .

• 2-Nerve supply : 1- the spinal root of the accessory nerve (motor )

• 2- the cervical nerves C2&C3 (proprioceptive )

Omohyoidmuscle Sternomastoid

muscle

Relations of the sternomastoid

• 1- superficial relations :• 1- the lower end of the parotid gland .• 2- the great auricular nerve .• 3- anterior cutaneous nerve of the neck .• 4- external jugular vein .

Great auricular nerve

Transverse cutaneous nerve of the neck

External jugular vein

Parotid gland

• Deep relations :• A- Deep relations to its upper half : • 1- posterior belly of digastric muscle .• 2- spinal accessory nerve .• 3- splenius capitis • 4- occipital artery

• B- Deep relations to its lower half :• 1- intermediate tendon of omohyoid muscle .• 2- transverse cervical artery .• 3- suprascapular artery • 4- anterior jugular vein• 5- scalenous anterior • 6- phrenic nerve • 7- carotid sheath and its contents

• Stucture emerging from its posterior border (they appear in the posterior triangle )

• 1- branches of the cervical plexus • 2- trunks of brachial plexus • 3- spinal accessory nerve • 4- transverse cervical artery &suprascapular

arteries • 5- the 3rd part of subclavian artery • 6- deep cervical lymph nodes

• Clinical importance of the sternomastoid muscle :

• 1- congenital torticollis : (wry neck ), it is a fibrous tissue tumour or injuiry of the muscle during birth .

• 2- spasmodic torticollis : abnormal tonicity in the muscle .

apex

trapeziusmuscle

Investing layer of deep fascia roof

Sternomastoid muscle

Middle 1/3 of clavicle – base

The posterior triangle

• the posterior triangle lies behind the sternomastoid muscle , it has an apex , base and 2 borders .

• The outlines of the posterior triangle :• 1- the posterior border of the sternomastoid muscle .

(infront )• 2- the anterior border of trapezius muscle(behind )• 3- the middle one third of the clavicle forms the base

of the triangle .• 4- the meeting of the sternomastoid muscle and

trapezius muscle forms the apex of the triangle .

• Roof :• It consists of the following layers (from outwards

inwards )• 1-the skin • 2- the superficial fascia containing :• 1- the platysma muscle (very thin sheet of muscle

layer )• 2- the external jugular vein • 3- the deep fascia of the roof ( part of the general

investing layerof the deep fascia of the neck ) .

• Floor :• The deep fascia of the floor ( prevertebral fascia )

which cover the muscles of the floor .• The muscles of the floor ( arranged from below

upwards ) • 1- scalenus medius • 2- levator scapulae • 3- splenius capitis • 4- semi- spinalis capitis ( at the apex of the

triangle )

• The posterior triangle is subdivided by the inferior belly of omohyoid into 2 smaller triangles :

• 1- the occipital triangle ( above )• 2- the subclavian triangle ( below )

Contents of the posterior triangle

• 1- nerves, remember that the main contents of the posterior triangle are nerves .

• 2- vessels ( arteries and veins )• 3- the inferior belly of the omohyoid muscle

Nerves in posterior triangle

1-Cervical plexus 2-Brachial plexus 3- spinal root of accessory nerve (11th cranial nerve )

1- four muscular branches

2- four cutaneous branches

Roots , trunks and their branches1- dorsal scapular nerve –c5(nerve to rhomboids )2- nerve to subclavius – c5 &c63- nerve to serratus anterior –c5,6 &7Suprascapular nerve –c5&6

It is the most important structure in the occipital triangle

Spinal part of accessory nerve

• Cervical plexus :• It is formed by the anterior 1ry rami of the upper

4 cervical nerves .• It gives off 4 muscular branches :• 1- nerve to sternomastoid muscle ( C2&C3

proprioceptive)• 2- nerve to trapezius muscle ( C3&C4

proprioceptive)• 3- nerve to levator scapulae muscle ( C3&C4)• 4- roots to the phrenic nerve . (C3&C4 & C5)

• Cutaneous branches of the cervical plexus :• 1- lesser occipital nerve (C2)• 2- great auricular nerve (C2&C3).• 3- transverse cervical nerve (C2&C3)• 4- supraclavicular nerves (C3&C4)

• Arteries :• 1- 3rd part of subclavian artery .• 2- two branches which come from the 1st part of

the subclavian artery ( transverse cervical artery and suprascapular artery )

• Veins :• 1- subclavian vein • 2- transverse cervical vein • 3- suprascapular vein

The anterior triangle of the neck • It lies in front of the sternomastoid muscle .• It is bounded by :• 1- anterior border of sternomastoid muscle .

(behind)• 2- anterior midline of the neck ( in front )• 3- lower border of the mandible (base )• It is subdivided into 4 triangles by means of the

superior belly of omohyoid muscle , the anterior and posterior bellies of digastric muscle as follows :

• 1- Digastric triangle • 2- carotid triangle • 3- Muscular triangle • 4- Submental triangle

Anterior belly of digastric muscle

Posterior belly of digastric

Stylohyoid

Sternohyoid muscle

Digastric triangle

• Outlines :• Above : the lower border of the mandible • Below & infront : the anterior belly of Digastric

muscle • Below & behind : the posterior belly of Digastric

and stylohyoid muscles . • Floor : • Anteriorly : the mylohyoid muscle • Posteriorly : part of hyoglossus muscle

Contents of the Digastric triangle

• 1- submandibular salivary gland • 2- the submandibular lymph nodes lie on the

surface of the gland • 3- facial artery deep to posterior end of

submandibular salivary gland • 4- facial vein lies superficial to submandibular

salivary gland • 5- hypoglossal nerve • 6- nerve to mylohyoid muscle

• dDigastric triangle

Carotid triangle

Muscular triangle

Anterior belly of digastric

Posterior belly of digastric

Mylohyoid muscle forms the floor of the mouth

Carotid triangle • Outlines :• Behind : the sternomastoid muscle • Infront and above : the posterior belly of digastric

muscle • Infront and below : the superior belly of omohyoid

muscle • Floor : infont : the hyoglossus muscle ( above ) and the

thyrohyoid muscle (below) • Behind: the middle constrictor muscle of the pharynx

(above ) and the inferior constrictor muscle of the pharynx (below )

External carotid artery

Common carotid artery

Internal carotid artery

Contents of the Carotid triangle

• 1- The carotid sheath and its contents : • - common carotid artery : in the lower part of

the triangle .• - internal carotid artery : in the upper part of

the triangle .• Internal jugular vein : lateral • Vagus nerve : between the artery and the vein

but in a more posterior plane .

• 2- the external carotid artery : gives most of its branches in the carotid triangle ( superior thyroid artery ,lingual artery ,facial artery , ascending pharyngeal artery and occipital artery )

• 3- hypoglossal nerve • 4- Descendes cervicalis (C2,3) anterior to carotid

sheath.• 5- sympathetic trunk adherent to the posterior

wall of carotid sheath

Muscular triangle

• Outlines :• Infront : midline of the neck • Behind and above :superior belly of omohyoid

muscle • Behind and below : the sternomastoid muscle

Contents of the Muscular triangle

• It contains the infrahyoid muscle

Submental triangle

• Outlines : • Infront : symphysis menti of the mandible • On each side : the anterior belly of digastric

muscle • Behind ( base ) : the hyoid bone • Floor : parts of the mylohyoid muscles as they

meet each other in the median plane

Contents of the Submental triangle

• 1- submental lymph nodes • 2- beginning of the anterior jugular vein

The infrahyoid muscles

• They are strap like muscles occupy each side of the midline of the neck , from the hyoid bone to the manubrium sterni .

• They consist of 4 muscles arranged into 2 layers : • 1- superficial layer : a- sternohyoid • B- omohyoid • 2- deep layer: a- sternothyroid • B- thyrohyoid

The Hyoid Bone

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• The only bone that does not articulate with another bone

• Serves as a moveable base for the tongue

The infrahyoid muscles

• Nerve supply : • All The infrahyoid muscles are supplied by

• Ansa cervicalis except thyrohyoid muscle supplied by fibres from C1 through hypoglossal nerve .

Ansa cervicalis

• Ansa = loop • It is a loop of cervical nerve fibres derived from

C1,2,3 which lies below the carotid sheath below the middle of the neck .

• It consists of 2 roots :• 1- descendes hypoglossi C1: derived from

hypoglossal nerve • 2- descendes cervicalis : C2,3 : from the cervical

plexus

Action of the infrahyoid muscles

• 1- superficial layer : a- sternohyoid : depress the hyoid bone after it has been elevated during swallowing .

• B- omohyoid : depresses , retracts and steadies the hyoid bone .

• 2- deep layer: a- sternothyroid : depress the hyoid bone and the larynx

• B- thyrohyoid : depress the hyoid bone and elevate the larynx

Suprahyoid muscles

• 1- digastric muscle • 2- mylohyoid muscle • 3- hyoglossus muscle • 4- geniohyoid muscle • 5- stylohyoid muscle

Geniohyoid muscle

Hyoglossus

Digastric muscle • It consists of 2 bellies anterior and posterior , that

connected together by an intermediate tendon .• Nerve supply :• 1- anterior belly : from nerve to mylohyoid which is a

branch of mandibular nerve .• 2- posterior belly : the facial nerve • Action : • When the mandible is fixed , it raises the hyoid bone

during swallowing .• When the hyoid bone is fixed , the anterior belly can

depress the mandible

• mylohyoid muscle :• Formed of superoir and inferior bellies .• Nerve supply : nerve to mylohyoid , which is a

branch of the mandibular nerve .• Action :• When the 2 bellies contract they elevate the

hyoid bone and the floor of the mouth as well as the root of the tongue during swallowing .

• If the hyoid bone is fixed , the 2 bellies depress the mandible and open the mouth .

Hyoglossus muscle

• Nerve supply :• Hypoglossal nerve ( 12th cranial nerve )• Action :• It draws the tongue downwards and thus help

suckling .

• Geniohyoid muscle :• Nerve supply :• Hypoglossal nerve ( via fibres from C1 )• Action : • It pulls the hyoid bone upwards and forwards ,

if the hyoid bone is fixed , it depresses the mandible .

• Stylohyoid muscle • Nerve supply :• Facial nerve • Action :• Raises the hyoid bone upwards