ANATOMY OF LARYNXAND ITS ANAESTHETICIMPORTANCE Presented by Dr Sindhu Sapru Moderator Dr. S.P Meena
Larynx An air passage, a sphincter and an organ of phonation. Upto puberty – Male and female larynx similar in Extends from root of tongue to trachea size after that male larynx enlarges considerably At Rest and continue until 40 years of age. – Lies opposite 3rd-6th cervical vertebra in adult male – Some what higher in children( 2nd and 3rd cervical vertebrae) and females
Difference between male andfemale larynx Male FemaleLength 44 mm 36 mmTransverse diameter 43 mm 41 mmSagittal diameter 36 mm 26 mm
Embryology Internal lining of larynx Endoderm Cartilage and muscle Mesenchyme of 4th and 6th Pharyngeal arches Rapid proliferation of mesenchyme Change in laryngeal orifice from sagittal slit to T-shaped opening Transforms into thyroid, cricoid and arytenoid cartilages Rapid proliferation of epithelium Temporary occlusion of lumen Vacuolization and recanalization Formation of laryngeal ventricles False and true vocal cords.
All laryngeal muscles innervated by 10 th cranial nerve Superior laryngeal N. innervate derivatives of 4 th pharyngeal arch Recurrent laryngeal N. innervate derivatives of 6 th pharyngeal arch
Skeleton of Larynx Series of cartilages interconnected by Corniculate, and fibrous membrane and moved by ligaments cuneiform, tritate, epiglottis and apices of arytenoid of muscles. of elastic fibrocartilage with little number are composed Laryngeal Cartilages tendancy to calcify. Thyroid, cricoid and greater part of arytenoid composed Single Paired of hyaline Cricoid Corniculate cartilage and may undergo mottled calcification with advancing age. Arytenoid Thyroid Epiglottis Cuneiform Tritate
Epiglottis Thin leaf like plate of elastic fibrocartilage projects obliquely upward behind the tongue and hyoid body and in front of laryngeal inlet Free end Attached part Broad and Long and narrow notched in Connected to elastic midline thyroepiglottic ligament Sides: Attached to arytenoids by aryepiglottic folds
Anterior surface : Covered by mucosa (non keratinised stratified squamous) reflect to tongue as median glossoepiglottic fold and pharynx as two lateral glossoepiglottic fold Post surface : Covered by ciliated respiratory mucosa. Tubercle of the epiglottis.
Valleculae : Depression on each side of median fold. Common sites for impaction of sharp swallowed objects. Pitted by small mucous glands Perforated by branches of internal laryngeal nerve and fibrous tissue, to be continue with pre – epiglottic space.
Function of epiglottis During Deglutition Hyoid bone move upward and forward Epiglottis is bent posteriorly on laryngeal inlet Food bolus slips over its ant surface to reach in piriform fossa which constitute lateral food passage Sense of taste Assist in phonation Gag reflex Prevent aspiration of food into the trachea
Thyroid cartilage Largest of laryngeal cartilage Consist of 2 quadrilateral laminae, fuse along their inferior two third anteriorly to form laryngeal prominence Above laminae separated by V shaped superior thyroid notch or incisure Posteriorly – Lamina diverge as slender horns Superior cornua Inferior cornua
Thyroid cont… Internal surface and lamina – Smooth Angle between laminae provide attachment to: Thyroepiglottic ligament paired (vestibular and vocal ligaments) Thyoarytenoid thyroepiglottic and vocal muscle Anteriorly – connected to cricoid cartilage by anterior (median) cricothyroid ligament (thickened portion of cricothyroid membrane)
Ant. Border of laminae fuse at angle of 90º in males and 120º in female. Shallower angle in men – Large laryngeal prominence( Adams apple) – Greater length of vocal cords – Deeper pitch
The oblique line provide the attachmentof the :1.Thyrohyoid2.Inferior constrictor of the pharynx
Cricoid cartilage Attached below to trachea and articulate with thyroid cartilage and two arytenoid cartilage by synovial joints. Only laryngeal cartilage to form a complete ring Smaller but thicker & stronger than thyroid
Arch Lamina• Ant. narrow, curved •Posteriorly broad flattened•Cricothyroid and deeper •Bears median vertical ridgecricopharyngeous attached to •Fasciculi of longitudinal layer ofext. aspect oesophageal muscle attached by a tendon to upper part of ridge
Joints Cricothyroid Cricoarytenoid ArytenocorniculateAll are synovial joints
Ligaments and MembranesExtrinsic ligament and membranes Thyrohyoid membrane – Extends from superior border and superior cornua of thyroid to superior margin of body and greater cornua of hyoid – Thicker part is median thyrohyoid ligament – Pierced by the internal laryngeal nerve and superior laryngeal vessels Hyoepiglottic ligament Cricotracheal ligament Thyroepiglottic ligament
Intrinsic ligaments and membranes Part of the fibroelastic membrane of the larynx :- Quadrate membrane- part above the sinus. From the arytenoid cartilage to epiglottis. lower free border – vestibular ligament which underlies the vestibular fold (false cord) upper border – aryepiglottic fold Conus elasticus(crico vocal membrane) : ant part – thick known as criothyroid ligament upper free border – vocal fold
Laryngeal cavity Extends from laryngeal inlet down to lower border of cricoid cartilage where it continues into trachea By paired upper and lower mucosal fold projecting into lumen laryngeal cavity is divided into Upper(Vestibule) Middle( sinus of larynx) Lower(infraglottic) Upper fold : Vestibular fold guarding rima vestibuli. Lower fold – Vocal fold guarding rima glottidis
Laryngeal inlet or aditius- looks backwards andupwards.Anterior- epiglottisPosterior- interarytenoid fold of mucous membraneEach side- aryepiglottic fold
Saccule of larynx- Anterior part of the sinus is prolonged upwards as a divericulum between the vestibular fold and lamina of thyroid cartilage. Vocal Cords and ligaments Free thickened upper edge of cricovocal membrane – vocal ligament When covered by mucosa – vocal fold ( true vocal cord )Reinke’s Edema Any tissue swelling below vocal cords exaggerates potential space deep to mucosa causing accumulation of ECF and flabby swelling of vocal cord.
Diff. position of vocal cords andarytenoid cartilages
Muscle of Larynx Extrinsic : Connect larynx to neighbouring structures Infrahyoid strap muscles i.e. thyrohyoid, sternothyroid, sternohyoid, inf. Constrictor of pharynx Intrinsic muscle – Oblique arytenoid and aryepiglottic muscle – Transverse (inter arytenoid) – Posterior cricorytenoid – Lateral cricoarytenoid – Cricothyroid
Infant Larynx 1/3 size of adult, though it is proportionately larger. Cavity – short and funnel shaped Lumen is disproportionately narrower Lies high in neck At rest – Upper border of epiglottis at 2nd / 3rd cervical vertebrae, on elevation – reach upto 1st cervical vertebrae This high position – Ability to use nasal airway to breathe and suckling
Epiglottis – X shaped with furled petiole laryngeal cartilages are softer and more pliable Predispose to airway collapse in inspiration Thyroid cartilage – Shorter and broader Cricoid cartilage – Same shape Vocal cords – 4-4.5 mm long, relatively short Narrowest part of larynx – Subglottis One size smaller ETtube should be ready along with the ETtube calculated for the age. Unlike adults, neonatal subglottic cavity extends posteriorly as well a inferiorly which is important to consider when passing ET tube.
Blood Supply – Mainly from Superior and Inferior laryngeal arteries.
Superior laryngeal A Branch of sup. Thyroid A – Br. Of ext. carotid artery In 15% cases directly from ext. carotid A. Run’s down towards larynx with internal branch of sup. laryngeal N. lying above it. Enter the larynx by penetrating thyrohyoid membrane. Supplies larynx above the vocal fold. Inferior laryngeal A Smaller than sup. Laryngeal A Br. Of inf. Thyroid A – Arises from thyrocervical trunk of subclavin A. Ascends on trachea with recurrent laryngeal N Enter larynx at lower border of inf. Constrictor muscles. Supplies larynx below vocal folds. Cricothyroid A – Arises from sup. Thyroid A.
Venous supply – Sup. and inf. Laryngeal vein – Sup. laryngeal vein – sup thyroid V – Int. Jugular V. – Inf. Laryngeal vein – Inf. Thyroid V – Lt. brachiocephalic vein
Lymphatic supply Above vocal cords Upper deep cervical lymph nodes Below vocal cords Some into Prelaryngeal (delphian) Pretrachial Other Lower deep cervical lymph nodes
Nerve Innervation Epiglottis Rest of larynx – Pharyngeal surface -: Glossopharyngeal Sensory nerve Above vocal cords – Internal branch of sup laryngeal N. – Below vocal cords - Recurrent laryngeal nerve Laryngeal surface -: Vagus nerve Motor Stimulation of laryngeal side of epiglottis during All muscles of larynx are supplied by recurrent laryngeal laryngoscopy with Miller’s blade may produce vagally nerve except cricothyroid which is supplied by external related reactions – branch of superior laryngeal nerve. Laryngospasm, Bradycardia, hypertension
Sup. Laryngeal N. : Arises form middle and inf. Vagal ganglion Int. laryngeal N. Ext. laryngeal N• Pierces thyrohyoid membrane • Continue downwad on lat. Surface of• Sup. Br. – Mucosa of piriform fossa inf. Constrictor• Middle Br – Musoca of ventricle • Close relationship to Sup. Thyroid• Inf. Br. Mucosa of subglottic cavity Artery where art is clamped during thyroid lobectomy
Recurrent laryngeal nerve Close and variable relationship to inf. thyroid artery May pass in front or behind or parallel to artery Ant. Br. – Motor Post Br. – Sensory
Rt. Side – Leaves the vagus, at level of Rt. Subclavian A. then loops under the art & ascend to larynx in trancheoesophageal groove Left side – Originates from vagus at level of aortic arch nerve passes under the arch to reach tracheoesphageal groove.Unusual anomaly Non recurrent laryngeal nerve Freg. 0.3 – 1% Only Rt. Side affected Always associated with abnormal origin of Rt. Subclavian A from aortic arch on left side.
Subglottic StenosisCongenital malformation of cricoid Other reasons cartilage resulting in severe Trauma narrowing of subglottic airway and Scarring after prolonged endotracheal respiratory obstruction. intubation (in premature babies and in I.C.U.)
LaryngocoeleObstruction of ventricular aditus by inflammation, scarring, tumor Mucous filled cavity (laryngocoele) Expansion Into paraglottic space Through thyrohyoid and aryepiglottic space membrane to present as a (internal laryngocoele) lump in neck (external laryngocoele)
Injuries of the laryngeal nerves Ext. br. of superior laryngeal nerve- descends over the inferior constrictor muscle of the pharynx immediately deep to the superior thyroid artery and vein as these pass to the superior pole of the gland; at this site the nerve may be damaged in securing these vessels. Paralysis of cricothyroid- hoarseness which is compensatory
Causes of rec. laryngeal nerve injury Close relation to the inferior thyroid artery. On the left side more likely to lie posterior to the artery. Thyroidectomy Malignant and benign enlargement of thyroid gland Enlarged lymph nodes Cervical traumaLeft RLN : May be involved in thoracic causes Malignant tumor of lung, oesophagus, malignant node Mitral stenosis Compression between Lt. pulmonary artery (pushed forward by greately enlarged Lt. Atrium) and aortic arch Following ligation of PDA
U/L complete paralysis of Rec. L.N. Asymptomatic or having hoarse voice Hoarseness may be permanent or become less severe with time as healthy cord hyper-adduct and appose paralysed cord. No risk of aspirationB/L R.L.N. Paralysis Complete loss of vocal power Vocal folds in cadaveric position (in btw adduction and abduction) Valve like obstruction(esp during inspiration) -dyspnea & marked inspiratory stridor.
Respiratory obstruction after thyroidectomy- direct trauma to the tracheal cartilages (especially in carcinoma of the thyroid) causing tracheomalacia. Haemorrhage into the neck deep to the investing fascia, causing external pressure on the trachea.Haemorrhage into an intact gland is more likely to obstruct the airway by producing laryngeal oedema than by direct compression. If the tracheal cartilages have not been damaged,very unusual for a benign enlarged thyroid to compress the trachea to an extent that prevents tracheal intubation. The trachea invariably straightens and dilates during intubation.Laryngoscopy within 24 h of thyroidectomy often reveals some degree of oedema of the false cords, presumably as a result of external laryngeal trauma during the operation and damage to venous and lymphatic drainage channels.
CRICOTHYROTOMY ‘ Surgical’ airway via the cricothyroid membrane in acute emergency when obsruction at or above the larynx not relieved. Patient positon: supine and the neck in the neutral position or (in the absence of cervical spine injury) in extension
Cricothyrotomy is relatively easy to perform andshould (in theory at least) be associated with minimalblood loss, as the cricothyroid membrane is thought tobe largely avascular
Laryngoscopic anatomy To view larynx – Mouth, oropharynx and larynx must be in one plane Flexion at the Extension at atlanto occipital joint joint atlantoaxial . sniffing position Like moving the head forward to take 1st sip from a glass of water full to the brim.
Structures Visible Base of tongue Valleculae Ant. Surface of epiglottis Laryngeal aditus Front - post. Aspect of epiglottis Aryepiglotic fold on each side post. Medially Vocal Cords Pale, glistening, ribbon, extending from angle of thyroid cartilage backwards to vocal process of arytenoids
AIRWAY BLOCKS General Indications : Before anesthetic induction in patients with airway compromise, trauma to the upper airway, or cervical instability. To abolish or blunt reflexes such as laryngospasm, coughing, and other undesirable cardiovascular reflexes that often occur during procedures that involve manipulation of the airway (awake laryngoscopy, nasal intubation, and fiberoptic intubation). To provide patient comfort and airway anesthesia during the performance of these procedures.
SUPERIOR LARYNGEAL NERVEBLOCK Indications: To block the internal (sensory) branch of the SLN, resulting in abolition of the gag reflex or hemodynamic responses to laryngoscopy or bronchoscopy. Drugs: 2-4 ml of Lidocaine 1% or 2% lidocaine, with or without epinephrine. Patient Position: Supine, with head slightly extended.
GLOSSOPHARYNGEAL NERVE BLOCK When topical techniques are not completely effective in obliterating the gag reflex. This block can be performed after the mouth and oropharynx are adequately anesthetized. Branches of this nerve are most easily accessed as they transverse the palatoglossal folds
A posterior approach (*often used for tonsillectomy), may be difficult, in visualizing the site for needle insertion, which is behind the palatopharyngeal arch (where the nerve is in close proximity to the carotid artery). There is risk for arterial injection and bleeding
RECURRENT LARYNGEALNERVEBLOCK( TRANSTRACHEAL/ Indications : Transtracheal injection performed to block theTRANSLARYNGEAL) laryngoscopy, fiberoptic recurrent laryngeal nerve for awake and/or retrograde intubation. Abolition of the gag reflex or hemodynamic responses to laryngoscopy or bronchoscopy. Used to help avoid Valsalva-like straining that may follow other "awake" intubations (patient is sedated and spontaneously ventilating). Drugs: Most often, 3-4 ml of Lidocaine 4 % is used. Also, 1% or 2% lidocaine, with or without epinephrine. Patient Position: Supine, with neck hyperextended (or Position pillow removed and extended).
Placement offingers toidentify themidline of thecricothyroidmembrane