ANATOMY OF LARYNX AND TRACHEOBRONCHIAL TREEGuide: Dr. Bhanu Chaudhary MD Presented by, Professor & Head of Department Dr. Ranjith kumar Dept of Anaesthesiology PG Resident G.R.Medical college Gwalior.
Descriptive Anatomy - LarynxSituation & Extent: – Lies in anterior midline of neck – Opp to C3 to C6 vertebra in men – Level is higher in female & children Infants b/w 6 and 12 months of age - the tip of the epiglottis lies little above the level of fibrocartilage b/w the odontoid process and body of the axis.
SIZEAccording to Sappey the average measurements of the adultlarynx are as follows: In Males In Females.Length 44 mm. 36 mm.Transverse diameter 43 mm. 41 mm.Antero-posterior diameter 36 mm 26 mm.Circumference 136 mm. 112 mm.Until puberty there is little difference b/w male & femalelarynx.After puberty - male larynx undergoes considerable increase;all the cartilages are enlarged and the thyroid cartilagebecomes prominent in the middle line of the neck.
General principles of developmentThe development of the larynx - prenatal and postnatal stages.At birth - larynx is located high in the neck b/w C1 and C4 vertebrae,allowing concurrent breathing or vocalization and deglutition.At 2 years - larynx descends inferiorly;At 6 years - reaches the adult position between C4 and C7 vertebrae.This new position provides a greater range of phonation (because of the widersupraglottic pharynx) at the expense of losing this separation of function, i.e.,deglutition and breathing.
Embryology• Larynx - develops from endodermal lining and the adjacent mesenchyme of the foregut b/w the 4 & 6th branchial arches.• At 20 days gestation - the foregut is first identifiable with a ventral laryngotracheal groove. It continues to deepen until its lateral edges fuse.• Trachea becomes separated from the esophagus by the tracheoesophageal septum with a persistent slit like opening into the pharynx• Fusion occurs in the caudal-to-cranial direction, and incomplete fusion results in development of persistent communication between the larynx or trachea and the esophagus(tracheoesophageal fistula)
The larynx grows rapidly during the first 3 years of life. The larynx elongates as the hyoid, thyroid, and cricoid cartilages separate from each other. The cricoid cartilage continues to develop during the first decade of life, gradually changing from a funnel shape to a wider adult lumen; therefore, it is no longer the narrowest portion of the upper airway. The main changes occurring in the larynx postnatally are a change in the axis, luminal shape, length, and proportional growth of the laryngeal elements.
Cartilages of Larynx 3 Unpaired cartilages 3 Paired cartilages • Thyroid • Arytenoid • Cricoid • Corniculate • Epiglottis • CuneiformHistology:Hyaline – Thyroid, Cricoid & base of Arytenoids are Hyaline. May ossify after 25 yrs of ageOther cartilages are Elastic & they do not ossify.
Thyroid Cartilage• Shield shaped, open posteriorly, angulated anteriorly.• Largest cartilage of larynx• Angulation more acute in males(90 ) & in females it is 120 .• Its function is to shield larynx from injury and provide an attachment to vocal cords
Cricoid Cartilage• Signet ring shaped• Stronger than thyroid cartilage.• Narrow ant part - arch• Broad post part - lamina
Important from structural & functional point of view – Base for entire larynx – Support to arytenoid – Attachment to intrinsic muscles – Only part of cartilagenous framework that forms continuous 360 degree ringThe narrowest portion of the airway in an infant.We use this fact when ventilating infants as infantET tubes do not have cuffs to seal the trachea
Epiglottis• Thin leaf shaped fibro-cartilage, situated in midline• Upper free end broad & rounded, projects up behind base of tongue• Spoon-shaped cartilage prevents aspiration by covering the opening of the larynx during swallowing.• ‡ The tongue and the epiglottis are connected by folds of mucous membranes which form a small space called the vallecula.
Arytenoids• Paired cartilages, pyramidal in shape• Base articulated with cricoid• PCA & LCA muscles attach on muscular process• Anterior angle elongated into vocal process which receives insertion of vocal ligament
Laryngeal compartments1. Glottis or superior vestibule2. Supraglottis or ventricle/sinus of larynx3. subglottis
Supraglottis• Consists of ventricles, false cords, laryngeal surface of epiglottis & aryepiglottic folds .• Vestibular folds- narrow band of fibrous tissue passing from anterolateral surface of arytenoid to angle of thyroid cartilage.• Separated from true vocal cords by larngeal sinus.
Glottis or superior vestibule • Consists of true cords, anterior commissure and posterior commissure. • Vocal cords – 2 pearly white folds of mucous membrane stretching from angle of thyroid cartilage to vocal process of arytenoid. • Narrow triangular space between the true cords is called rima glottis. • Anterior 2/3 is membranous • Posterior third consists of vocal processes of arytenoids. • Posterior 1/3 of cords and covering mucosa are called posterior commissurePearly white – since there is no true submucosa with usual network of blood vessels
Sub-glottis • Begins about 5mm below free margins of Vocal cord. • Extends from vocal folds to the lower border of cricoid cartilage. • Consists of a mobile upper and fixed lower part. • Narrowest part of laryngeal cavity in children under 10 years of age.Clinical significance – During intubation in small children an ET tube can pass between vocalcord may yet too large to pass beyond cricoid ring
Mucosa• Mucosa of glottic and Supraglottic regions is stratified squamous epithelium.• Mucosa of ventricles and sub-glottic regions is pseudo- stratified ciliated epithelium.• Supra and sub glottic regions particularly ventricles are rich in submucosal mucous or minor salivary glands while glottis is not.
Laryngeal LigamentsA series of intrinsic ligaments binds all 9 cartilagestogether to form the larynx.Extrinsic ligaments attach the thyroid cartilage to thehyoid bone and the cricoid cartilage to the trachea.The vestibular ligaments and the vocal ligaments extendbetween the thyroid cartilage and the arytenoids.The vestibular and vocal ligaments are covered by foldsof laryngeal epithelium that project into the glottis.
Ligaments Cont…The vestibular folds, which are relatively inelastic, helpprevent foreign objects from entering the glottis and provideprotection for the more delicate vocal folds.The vocal folds are highly elastic, because the vocal ligamentis a band of elastic tissue.The vocal folds are involved with the production of soundshence known as the true vocal cords.Because the vestibular folds play no part in sound production- called the false vocal cords.
Blood Supply Sup.laryngeal vein drains into Sup.Thyroid Vein Inf.laryngeal vein drains into Inf. Thyroid veinsThese vessels accompany superior and recurrent laryngeal nerves
Lymphatic drainageAbove vocal folds – Antero superior group of Deep cervicalnodes.Below Vocal folds – Postero inferior group of deep cervical nodesthrough prelaryngeal & pretracheal nodes.
Nerve Supply: Derived from the Vagus• Superior Laryngeal Nerve -It leaves the vagus nerve high in the neck – Internal - provides sensation of the glottis and supraglottis, which includes the pharynx, underside of the epiglottis and the larynx above the cords. – External -It supplies motor function to the cricothyroid muscle which tenses the vocal cords and could cause laryngopasm.
• Recurrent Laryngeal Nerve - provides sensation to the subglottic area which includes the larynx below the vocal cords and upper esophagus. Motor function to most of intrinsic muscles of the larynx • It branches from the vagus in the mediastinum and turns back up into the neck. On the right, it travels inferior to the subclavian and loops up, and on the left it travel inferior to the aorta and loops up.Motor nerves :All the muscles of larynx are supplied by therecurrent laryngeal nerve except cricothyroid which is supplied byexternal laryngeal nerve‡Sensory nerves :Internal laryngeal nerve-upto level of vocal fold Reccurent laryngeal nerve-below vocal fold
Position of vocal cord in health &disease Location of cord Situations inPositon of cord from midline health disease Median Midline Phonation RLN paralysis RLN paralysis Paramedian 1.5 mm Strong whisper 3.5 mm. (This is neutral position of Intermediate Combined paralysis cricoarytenoid joint. - (cadaveric) ( both RLN & SLN) Abduction and adduction takes place from this position.)Gentle abduction 7 mm Quiet respiration Paralysis of adductors Full abduction 9.5 mm Deep inspiration -
Vocal cordThe opening into trachea is maximum at the end of deep inspiration.In order to minimise the risk of trauma to voca cords Intubation and Extubation should be carried out during inspiration
RLN Paralysis• It carries fibres for both abductor and adductor muscles of larynx.• Injury – partial or complete• Abductor fibres - more vulnerable even for mild injuryModerate trauma produces only abductor paralysis.Severe injury or section of nerve produces both abductor and adductorparalysis.Semons law: This theory proposed by Rosenbach and Semon in 1881,depends on the concept that abductor fibres in the recurrent laryngeal nervesare more susceptible to pressure than the adductor fibers.Wagner and Grossman theory (1897).: most popular and widely acceptedtheory, states that in complete paralysis of RLN the cord lies in theparamedian position because the intact cricothyroid muscle adducts the cord.(Because the superior laryngeal nerve is intact). If the superior laryngeal nerve is also paralysed the cord will assume anintermediate position because of the loss of adductive force.
Unilateral Abductor Paralysis Paralysis of recurrent laryngeal nerve. Vocal cord lies in median or paramedian position, doesn’t move on deep inspiration. Initial hoarseness. No regurgitation. Vocal cord compensation occurs leading to improvement of voice.
Bilateral Abductor Paralysis Paralysis of both recurrent laryngeal nerves. Thyroid surgery - cause Both vocal cord lies in paramedian position due to unopposed action of cricothyroid. Severe dyspnoea and stridor. Voice is good and there is no regurgitation Vocal cord compensation may occurs leading to improvement Immediate tracheostomy & various procedures for Lateralisation of cord.
Unilateral Adductor Paralysis1.Paralysis of both superior and recurrent laryngeal nerves2. Vocal cord lies in Lateral (cadaveric) position3. Weak husky voice4. There is aspiration of food and fluid5. Vocal cord compensation occurs leading to improvement of voiceMedialization of vocal cord or reverse cordopexy ---- Treatment
Bilateral Adductor Paralysis1. Paralysis of combined both recurrent and superior laryngeal nerves2. Psychiatric Illness or widespread neurological lesion or neoplastic lesion in the base of skull, upper neck etc.3. Both vocal cord lies in lateral (cadaveric) position4. Severe regurgitation of food and fluid.5. Voice is breathy6. Vocal cord compensation may occurs leading to improvement7. If compensation does not occur than total laryngectomy and epiglottopexy --- - Treatment
TRACHEA It is a cartilaginous & membranous tube,10 - 11cm long & 2.5cm(1 inch) in diameter. Cartilages – deficit posteriorly. Extend from lower border of cricoid cartilage(C6) to carina(T5) where it bifurcates into right & left main bronchus. Lined by ciliated columnar epithelium Trachea moves upward during swallowing, & downward forward during inspiration.Extension of head & neck can increase the length of the tracheaby as much as 23 to 30 %.
TRACHEOBRONCHIAL TREE Bronchiole Terminal Bronchioles Respiratory Alveolar Pulmonary Alveolar sac & Pulmonary Bronchioles Ducts Atria AlveoliDichotomous division – starting with trachea & ending in alveolar sacs (23 generations)First 16 generation – only conductiveLast 7 generation – Respirative (involves in gas exchange)
Left main bronchus:Right main bronchus: • 5.5cm long,2-• 5 cm long, wider, 3mm narrower shorter & more then the Right vertical then the Lt main bronchus. main bronchus. • more horizontal &• It makes 25-300 with making an angle of 450 with carina tracheaRt main bronchus – since it is more vertical there is much greater tendency for ET tubes or Suction catheters to enter this lumen.In small children <3yrs of age - angulation of 2 main bronchi at the carina isequal on both sides.
Aspiration pneumonitis• Aspiration pneumonitis (Mendelson’s syndrome) is a chemical injury caused by the inhalation of sterile gastric contents.• A reduced level of consciousness can lead to an unprotected airway. If the patient vomits they can aspirate the vomitus contents into their lungs. This can set up lung inflammation with infection.• Also occur in spinal anaesthesia if the level of spinal block is too high, leading to paralysis or impairment of the vocal cords and respiratory impairment.• Most authors agree that a pH < 2.5 and a volume of gastric aspirate greater than 0.3 ml per kilogram of body weight (20 to 25 ml in adults) are required for the development of aspiration pneumonitis.• Aspiration of particulate food matter from the stomach may cause severe pulmonary damage, even if the pH of the aspirate is above 2.5.
LocationPatients who aspirate In a lateral position, the inhaled materials tends to gravitate into the lateral portion of posterior segment of upper lobe. In supine position, the material accumulates in the apical segment of lower lobe. When patient is propped up in post operative period, secretions tend to gravitate to the lower lobes.
Prevention• Use regional technique, awake intubation.• Ensure empty stomach.(Fasting)• Inhibit secretion of gastric acid .• Rapid sequence induction. (sellick maneuver)• Extubate when pt fully awake.
Fasting RecommendationsIngested Material Minimum Fasting Period• Clear liquids 2 h• Breast milk 4 h• Infant formula 6 h• Nonhuman milk 6 h• Light meal 6 hExamples of clear liquids include water, fruit juices without pulp,carbonated beverages, clear tea, and black coffee.
Brian A Sellick 1918-1996, London Anaesthetist"Cricoid pressure must be exerted by an assistant.Before induction, the cricoid is palpated and lightly held between thethumb and second finger.As anaesthesia begins, pressure is exerted on the cricoid cartilagemainly by the index finger. Even a conscious patient can toleratemoderate pressure without discomfort but as soon as consciousness islost, firm pressure can be applied without obstruction of the patientsairway.Pressure is maintained until intubation and inflation of the cuff of theendotracheal tube is complete.”
Essential Elements of Cricoid Pressure• Must apply force to the cricoid cartilage• Must apply force in correct direction• Must apply correct amount of force• Must apply force for correct duration of time
How Much Force?• A force of 30 N (3 kg) is recommended for an unconscious patient”Clayton TJ, Vanner RG. A novel method of measuring cricoid force.Anaesthesia. 2002;57:326-9.