Anatomy of Neck & itsMedicolegal importance.Presenter Dr Gopal G HargiPG in FM& T
Neck is a very prominent & vital part .Eventrivial injuries can cause death withoutshowing any signs. There are very vitalstructures in a relatively small & unprotectedanatomic region making it very vulnerable tofatal injuries. Moreover the Neck is an area which can beeasily grasped and immobilized
Lower border of mandible lies b/w C2 & C3. The front of the lower pharynx & upperoesophagus lie the larynx & trachea. On each side of the pharynx is the carotidsheath,containing the common & internalcarotid arteries & the IJV with the cervicalsympathetic trunk behind it. The Platysma –a broad flat sheet of musclelies superficial to the layers of fascia.
Coll’s fascia :The space among the structures ofneck are filled with loose areolar tissue.Thestructures of the neck are mostly supplied to moveup & down .This fascia is a laminar condensation of looseareolar tissue in neck produced by the movementsof these structures. These laminar condensations take different namesin different regions & are continuous with eachother or indirectly. These loose areolar tissue form sheaths whichenclose muscles and their moving structures
INVESTING LAYER ATTATCHMENTS ABOVE- EXTERNAL OCCIPITAL PROTUBERANCE,MASTOID PROCESS, EXTERNAL ACOUSTICMEATUS, BASE OF THE MANDIBLE BELOW- SPINE OF SCAPULA, ACROMION PROCESS, CLAVICLE, MANUBRIUM STERNI FRONT- HYOID BONE & CONTINUOUS WITH THE FASCIA OF THE FASCIA OF THE OPPOSITESIDE BEHIND- 7TH CERVICAL VERTEBRA, LIGAMENTUM NUCHAE
CCA ,arises from the left side of AOA. It lies in the medial part of carotid sheath . Upper border of C4 the CCA bifurcates. The carotid pulse can be felt by pressing againstthe anterior tubercle of the tranverse process ofC6 vertebra. ICA ,at its commencment there is a bulge , here the arterial wall is thin & contains thebaroreceptors which is supplied by the 9th & 10thnerves which control the CVS . carotid body is a small structure behind thebifurcation of CCA & contains baroreceptors whichmaintain oxygen saturation.
IJV forms a jugular arch in the suprasternalspace i.e between the sternal & clavicularhead of sternocleadomastoid tendon. Larynx lies below the hyoid bone in themidline of the neck at the level of C4-C6vertebra.
The AJV commences beneath the chin & passesdownwards ,side by side beneath the platysma tothe suprasternal region.Here they pierce the deepfascia & come to lie in the suprasternal space. Carotid sheath consists of a network of areolartissue that surrounds the carotidarteries(c&i),IJV,Vagus nerve & some deep cervicallymph nodes. It is thin where it overlies the IJV ,allowing thevein to dilate during increased blood flow.
The thyroid gland is situated low down at the frontof the neck.The 2 symmetrical lobes are connectedby isthmus which lie in front of 2nd,3rd & 4thtracheal rings. Trachea begins at the level of C6 vertebra incontinuity of the larynx,The cervical part lies inthe midline of the neck ,in contact with the frontof the oesophagus. Oesophagus commences in continuity with thepharynx at the level of lower border of the cricoidcartilage(C6).
Hyoid bone lies free ,suspended by muscles & sovery mobile .Above its attached to floor of mouth &tongue,larynx below,behind to epiglottis &pharynx.It lies at the level of C3 vertebra. Vertebral artery arises from subclavian artery &passes up to traverse the foramen of transverseprocess of upper 6 cervical vertebras.On emergingfrom foramen the artery enters the skull throughforamen magnum .It pierces the spinal dura mater & archnoid and atthe lower border of pons forms the basillar artery.
For judging the severity of the injuries to the neckits divided into 3 zones. Zone I• highest mortality Zone II• most frequent site of injury• lower mortality Zone III• neurological• distal carotids• pharyngeal injuries
(Zone 1)Thoracic inlet (clavicle)to cricoidcartilagesignificant injury in the zone I region may be hiddenfrom inspection of the chest or the mediastinum. subclavian vessels brachiocephalic veins common carotid artery jugular vein aortic arch Trachea esophagus Lung apices c spine spinal cord CN roots
Zone 2 Carotid and vertebralarteries jugular veins pharynx larynx trachea esophagus c spine spinal cordCricoid cartilage to angle of mandible
Zone 3 Salivary glands parotid gland esophagus trachea c spine Carotid arteries jugular veins CN IX - XIIAngle of mandible to base of skull
Injury above the level of C4 –rapid death Due to disruption of CV centre. Causes- Hyperextension & hyperflexionAtlanto-occipital injury---fatal: widening of spacewith some blood palpated as ‘loosening ‘Of the junction with widening.Severe form thearticulating condyles of atlas can be seen withinforaen magnum.C1-C2 injury-- neurogenic shock ,odontoin is #C2-C3 #( HANGMAN #) rapid
Injuries over the region of neck A) Homicidal: a)strangulation i)Ligature ii) Manual c)bansdola e)mugging f)penetrating injuries a) knife b) gunshot g)cut throat injuries h)blunt force impact i) homicidal ii) accidental
Blunt force impact to the side of neck Shearing excessive rotation/ hyperextension◦ distention and stretching Tearing of Vertebral Artery The carotids too get dissected ,veins damaged Blood tracks along upper part of vessel & entersthe cranial cavity producing massive SAH .
B) Suicidala)Hanging b)postural asphyxiation◦ children with neck over object and body weight producescompression C)Accidentali)carotid sleepers ii)bar arm control a)choking b)RTA : rapid deceleration hyperflexion,hyperextension, and rotation vascular structuresare stretched over the cervical spine shearingforces create intimal tears in the vessel wallc)toxic gas inhalation D)Judicial or justified hanging
Cause of death in hanging Asphyxia Venous congestion Cerebral oedema # vertebra Significant cervical spine and spinal cord damagecan occur in hangings that involve a fall from adistance greater than the body height.Cause of death in strangulation Vagal inhibition Asphyxia Cerebral anoxia & Venous congestion
Other consequences of Neck TraumaSubcutaneous emphysema Tension pneumothorax Traumatic asphyxia◦ Penetrating Trauma Esophagus or Trachea Vagus nerve disruption◦ Tachycardia & GI disturbances Thyroid & Parathyroid glands◦ High vascular
More than 95% of penetrating neck wounds resultfrom guns and knives, with the remainder resultingfrom motor vehicle accidents, householdinjuries, industrial accidents, and sporting events gun shot wound (GSW) sustain greater injury thanthose with stab wounds because of a bullets abilityto penetrate deeper and cause cavitation, thusdamaging structures lying outside the tract of themissile. Injury to the blood vessels can also result fromexternal compression or mural contusion. Thrombosis is the most common complication ofblood vessel injury, occurring in 25-40% ofpatients.
Blunt trauma to the neck typically results frommotor vehicle crashes but also occurs with sports-related injuries (eg, clothesline tackle),strangulation, blows from the fists or feet, andexcessive manipulation In motor vehicle crashes, thrusting forward withthe head extended, forcing the anterior neckagainst the steering column. Cerebral vessel andlaryngeal injuries secondary to shoulder strapcompression have occurred. Direct forces can shear the vasculature producingshearing damage and resultant thrombosis
Laryngotracheal Injuries in BNT Although not prevalent, it is second to onlyintracranial injury as the most common cause ofdeath among patients with head and neck traumaand is a clinically important injury.◦◦ 60% of all external laryngotracheal traumas are due toblunt neck trauma. The final common pathway of laryngotrachealinjury is compressive force on the larynx leads toinjury. This is modified by the degree of laryngealcalcification present;
Dissection of neck Before exploring the neck the thorax and theskuull should be opened and the viscera removed After cutting the skin ,the ant cervical strapmuscles are cut and examined Expose the thyroid cartilage & trachea Following this ,the tongue ,hyoid bone & the larynxare removed as unit. Examine the hyoid bone after separating fromthyroid cartilage & soft tissues removed See for periosteal haemorrhages & # .Palpate the sup horn of thyroid cartilage .Examinelamina of thyroid cartilage & cricoid cartilage forinjury. Open thyroid cartilage posteriorly & examinemucosa of larynx
Triticeous cartilage are little cartilaginousnodules embedded in the thyroidhyoidligsment .These may be confused with a # ofsuperior horn of thyroid cartilage Thank You