Anatomy of the neck By Dr. Rasha Sabry

”وفي أنفسكم أفلا تبصرون“ بسم الله الرحمن الرحيم ”وفي أنفسكم أفلا تبصرون“

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 .

Parotid gland Great auricular nerve Transverse cutaneous nerve of the neck External jugular vein

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 branches 1- dorsal scapular nerve –c5(nerve to rhomboids ) 2- nerve to subclavius – c5 &c6 3- nerve to serratus anterior –c5,6 &7 Suprascapular 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

Posterior belly of digastric Stylohyoid Anterior belly of digastric muscle 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

d Anterior belly of digastric Digastric triangle Posterior belly of digastric Carotid triangle Mylohyoid muscle forms the floor of the mouth Muscular triangle

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 )

Internal carotid artery External carotid artery Common 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 The only bone that does not articulate with another bone Serves as a moveable base for the tongue Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

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