Respiratory Anatomy - Extrapulmonary Airways (Lecture Outline) PDF

Respiratory Anatomy – Extrapulmonary Airways Lecture Outline I. Overview of airways II. Cranial bones III. Oral Cavity (Mouth) IV. Palate V. Nasal Cavity (Nose) VI. Pharynx VII. Larynx VIII. Trachea 1 Respiratory Anatomy – Extrapulmonary Airways Objectives 1.Define extrapulmonary, intrapulmonary...

Respiratory Anatomy – Extrapulmonary Airways Lecture Outline I. Overview of airways II. Cranial bones III. Oral Cavity (Mouth) IV. Palate V. Nasal Cavity (Nose) VI. Pharynx VII. Larynx VIII. Trachea 1 Respiratory Anatomy – Extrapulmonary Airways Objectives 1.Define extrapulmonary, intrapulmonary, conducting, and respiratory airways 2.Identify cranial bones involved in respiration 3.Describe the significance of Larson’s maneuver 4.Explain why thyromental distance and atlanto-occipital flexion and extension are part of an airway assessment 5.Explain the anatomy of the structures of the oral cavity including boundaries 6.Describe the structure and function of the hard and soft palates 7.Understand the structures of the nasal cavity and paranasal sinuses 8.Identify characteristics of nasal epithelium and nasal mucosa 9.Describe the anatomy and structures of the three divisions of the pharynx 10.Identify the boundaries of the fauces 11.Identify the function of Waldeyer’s tonsillar ring 12.Explain the anatomy of the upper esophageal sphincter 13.Identify the bone, cartilages, ligaments, and muscles of the larynx 14.Identify those structures visible during direct laryngoscopy 15.Identify boundaries of the laryngeal inlet 16.Describe areas within the laryngeal cavity 17.Identify the innervation of the structures of the airways and larynx 18.Describe the anatomy of the trachea including noted measurements 19.Identify the distance of the trachea and compare to endotracheal tube depth 20.Explain the anatomical site of both a tracheostomy and cricothyrotomy 2 References Assigned reading from your text: Selections from Moore Chapters 4,5, 8, 9 David Morton, Kurt Albertine, Bo Foreman The Big Picture: Gross Anatomy. 2011. The McGraw-Hill Companies Inc.: New York. Nagelhout Apex Anesthesia 3 I. Overview of Airways 4 Overview of airways q Extrapulmonary airways reside outside of lungs: – Extend from nose/mouth to main (primary) bronchus – Includes the nose, mouth, pharynx, larynx, trachea, bronchi – Function of conducting airways is to clean, warm, and moisten air – Have no alveoli- are conducting airways only q Intrapulmonary airways are both conducting and respiratory airways: – Located within lung structure – Secondary bronchi to alveoli q Conducting airways do not participate in gas exchange = anatomical dead space q Respiratory airways involve alveoli and function in gas exchange – Alveoli are present from respiratory bronchioles to alveoli to facilitate gas exchange 5 II. Cranial bones 6 Cranial Bones q Neurocranium - skull - 8 bones • 4 single bones • Frontal * • Ethmoid * • Sphenoid * • Occipital • 2 paired bones • Temporal * • Parietal q Viscerocranium – facial skeleton – 15 bones • 3 single bones: • Mandible – lower jaw – TMJ • Ethmoid * • Vomer • 6 paired bones: • Maxilla * – upper jaw • Inferior nasal conchae • Zygomatic • Palatine • Nasal • Lacrimal * Pneumatized – have air cells or sinuses 7 Laryngospasm Notch on the Mandible q Larson’s maneuver: • Applying a forcible jaw thrust with inward bilateral digital pressure on the body of the mandible just anterior to the mastoid process may relieve laryngospasm • “Laryngospasm notch” or “Larson’s point” • Opens airway and stimulates a sigh 8 Viscerocranium Related to Respiratory Anatomy q Bones of the viscerocranium and respiratory system include: • Ethmoid • Cribriform plate transmits olfactory nerves • Perpendicular plate • Descends from cribriform plate • Forms superior part of nasal septum • Superior and middle conchae • Conchae increase the surface area • Create turbulence for protection and conditioning • Inferior nasal conchae • A separate bone • Also increases SA and turbulence • Palatine bone • Posterior portion of hard palate • Found above uvula • Vomer • Inferior-posterior nasal septum 9 Airway Assessment- Viscerocranium q Bony structures of each patient are assessed in preparation for airway manipulation • Mandibular protrusion test measures the mobility of the temporomandibular joint • Ideal if patient can sublux the lower incisors above the vermillion of the upper lip • Inter-incisor gap is measured to determine mouth opening and the ability to align axes for laryngoscopy • Normal is ~ 4cm • Thyromental distance correlates to the submandibular space for tongue displacement during laryngoscopy- a large space allows the tongue to be moved out of the visual field • Normal > 6 cm 10 Atlanto-Occipital Joint Mobility and the Sniffing Position q Adequate atlanto-occipital (AO) joint mobility needed to obtain the sniffing position • AO flexion and extension is normally between 90-165 degrees • Adequate mobility allows for alignment of axis for laryngoscopy • Sniffing position improves laryngoscopy view by displacing tongue and aligning the oral, pharyngeal, and laryngeal axes • Reduced mobility is anticipated in some conditions- e.g. diabetes, rheumatoid arthritis, etc • Airway adjuncts • Fiberoptic bronchoscope • Video laryngoscopy FIGURE 22-11 Oral axis (OA), pharyngeal axis (PA), and laryngeal axis (LA) for intubation. A, Nonaligned position. B, Head resting on a pad causes flexion of the neck and aligns the PA and LA. C, Head resting on pad causes flexion of the neck, with neck extension into sniffing position aligns the OA, PA, and LA. D, Extension of the neck without head elevation aligns PA and LA, but not the OA. (From Miller RD, Pardo MC. Basics of Anesthesia. 6th ed. Philadelphia: Saunders; 2011.) 11 III. Oral Cavity (Mouth) 12 Boundaries of the Oral Cavity q Oral cavity extends from lips to the palatoglossal (anterior) arch • Two parts of the oral cavity: • Vestibule is the space between the lips/cheeks and gums /teeth • Oral cavity proper extends from inside teeth to palatoglossal arch q Oropharynx lies behind the oral cavity • Fauces (“throat”) is a subdivision of the oropharynx that begins at the palatoglossal arch Tongue q Tongue functions in speech, taste, and digestion – Tongue structures: • Body - Anterior 2/3 tongue (presulcal) - is in the oral cavity proper • Root – Posterior 1/3 tongue (postsulcal) – is the anterior wall of oropharynx • Dorsum: • Median sulcus- midline groove – divides tongue into left and right halves • Terminal sulcus- V-shaped groove on tongue dorsum • Foramen cecum- nonfunctional embryonic remnant from thyroid development • • Lingual tonsils- lymphoid nodules Inferior surface connected to floor of mouth by lingual frenulum 14 Tongue Muscle and Blood Supply q The tongue consists of intrinsic and extrinsic skeletal muscles • Extrinsic muscle support the tongue in the oral cavity by muscular connections to bones and the pharynx • Genioglossus (“genio”- chin) is the large fan-shaped muscle • Constitutes the bulk of the tongue mass and • Protrudes the tongue q Blood supply is from the lingual artery that branches from the external carotid 15 Innervation of the Tongue q The tongue is skeletal muscle covered by special and general sensory nerve endings • Body- anterior 2/3 tongue (oral) – – § § Taste sensations transmitted via chorda tympani branch of CN VII Pain, touch and temperature sensations transmitted by lingual branch of CN V Root – posterior 1/3 tongue (pharyngeal) – Taste sensations transmitted via CN IX (glossopharyngeal) – – Pain, touch, temperature sensations transmitted by both CN IX Afferent limb of the gag reflex is via CN IX- An awake patient will gag (oral airway) Motor innervation to all muscles is CN XII- except palatoglossus (CNX) 16 IV. Palate 17 The Palate q The palate separates the nasal and oral cavities and is composed of two regions: • Anteriorly, the hard palate serves as a vault for the tongue at rest and is composed of: – Palatine process of maxilla (anterior 2/3) – Palatine bone (posterior 1/3) • Posteriorly- the soft palate serves as a flap valve controlling access to and from the nasal passages – Soft palate is raised during deglutition to close isthmus of the pharynx between oral and nasal pharynx – Soft palate lowers to close isthmus of fauces for air to pass through nose or to maintain substance in oral cavity 18 Soft Palate q The soft palate is continuous with the palatoglossal and palatopharyngeal folds and consists of: – An aponeurosis (no bone) that connects to the palatine bone – Uvula – a conical process suspended from the midline of the free edge • Do not suction the uvula – Septal cartilage – Skeletal muscles tense or elevate soft palate • Tensor Veli Palatini- tenses and opens the nasopharynx – Relaxation of this muscle allows soft palate to occlude the airway • Levator Veli Palatini • Palatoglossal • Palatopharyngeus • Uvular muscles – CN V sensory innervation 19 V. Nose 20 Nasal Cavity q Nasal cavity extends from the nares to the choanae and is divided into two lateral compartments separated by the nasal septum §External nose: visible portion • Nose mainly composed of bones and cartilage • Dorsum extends from root to apex • Nares (openings) bound by alae (wings) • Sensory information sent via CN V §Internal nose = inside the nasal cavities § Divided by the nasal septum § Deviated septum is common § Can obstruct airflow if severe enough § Extends from external to internal nares § Includes the conchae § Components include the: § Perpendicular plate of ethmoid- superior portion § Vomer- Inferior and posterior portion § Septal cartilage – anterior portion 21 Structures of Nasal Cavities • External naris- bound laterally by alae • Nostrils or Anterior nasal apertures • Vestibule – hairy (vibrissae) entrance of nasal cavity thick skin with many sebaceous glands • Atrium – chamber posterior to vestibule • Conchae- turbinates- 3 thin bony plates • Project into the nasal cavity from lateral walls • Superior and middle conchae – ethmoid bone • Inferior concha is a separate bone • Meatuses – narrow passages beneath the concha • Each meatus associated with an opening for drainage from paranasal sinuses • Named according to respective concha • • • • Superior meatus- drains ethmoid/sphenoid sinuses Middle meatus- drains frontal sinus, maxillary sinus, and a portion of the ethmoid sinus Inferior meatus drains nasolacrimal duct and tears from eye into the nasal cavity Internal naris- connect the nasal cavities to the nasopharynx • Choanae or posterior nasal apertures 22 Paranasal Sinuses q The paranasal sinuses are hollow cavities within the pneumatized facial bones • • • • Their function is to resonate sounds of speech and produce mucus Air-filled, appear dark on x-ray Their cavities communicate with the nasal cavity via a meatus that drains mucus Paranasal sinuses can become infected if flow obstructed- further exacerbated by swollen mucous membranes q Transphenoidal hypophysectomy- In this surgical procedure, the pituitary gland can be accessed via the nasal cavity through the sphenoid sinus to reach the sella turcica 23 Blood Supply to Nasal Cavities q Nasal cavity vascular supply Is via the: • Sphenopalatine artery • Ethmoidal arteries • Greater palatine artery • Facial artery (labial artery is a branch of the facial) q Kiesselbach’s area (plexus) • A region of the anteroinferior nasal septum where branches of each of the above arteries anastamose • Common site of chronic epistaxis q The triangle from the upper lip to the bridge of the nose is the “danger area” of the face • A submucosal venous plexus deep to the nasal mucosa provides venous drainage of the nose and into the cavernous dural venous sinus 24 Innervation of Nose q Sensory innervation of nose: – Upper portion only is innervated by CN I- olfactory – Rest of nose and paranasal sinuses innervated by branches of CN V q – – – Motor innervation: CNVII- Parasympathetic stimulations increases mucous gland productions Sympathetic fibers innervate blood vessels Mucus-producing goblet cells are not innervatedà they respond intrinsically to irritants q Anosmia- lack of smell resulting from trauma or infection 25 Pterygopalatine ganglion q The pterygopalatine ganglion is also known as the sphenopalatine ganglion (SPG) – The SPG is located in the pterygopalatine fossa – Sphenopalatine nerve of nasal cavity connects to pterygopalatine ganglion – This ganglion lies inferior to CN V and receives preganglionic parasympathetic neurons from CN VII • Regional anesthesia placed here blocks the maxillary nerve – Cholinergic neurons from this ganglion innervate cerebral blood vessels • These vessels dilate with stimulation; blocking this ganglion may prevent associated headaches 26 Nasal Mucosa qMucosa- Three types of epithelial lining of the internal nose • Olfactory epithelium - Contains bodies of olfactory receptors (CNI) - CNI passes through cribriform plate - Covers the superior nasal conchae • Stratified squamous epithelium – Initial 1.5 cm of vestibule keratinized – Then transitions to non-keratinized – Lines the anterior 1/3 of internal nose • Pseudostratified ciliated columnar epithelium – Aka respiratory epithelium – Found throughout respiratory system – A single layer of cells – Nuclei occur at different heights • Nasal mucosa is vascular – Thickest on septum and conchae – Thinnest on floor of nasal cavity – Significant bleeding (eg nasal airways) 27 Cells in Respiratory Epithelium qCell types of the respiratory system • Ciliated cells (30%)– sweep sputum toward the oral cavity – Sputum (phlegm) is mucus + trapped material (pathogens) – Cilia serve as the mucociliary escalator • Basal (short) cells (30%) – undifferentiated stem cells that can replace other cell types • Metaplasia- eg A smoker’s basal cells may become goblet cells to é mucus production • Brush cells – tall columnar cells with a tuft of microvilli on surface – Afferent nerve endings on basal surface – May function as sensory receptors • Small granule cells - part of the diffuse neuroendocrine system – Basal cytoplasm filled with dense-core granules – Amines and peptides (eg serotonin) have paracrine function – Found in respiratory and gastrointestinal epithelium • Mucous goblet cells (30%)– secrete mucus onto luminal surface – Mucus traps inhaled particles – Moisturizes inspired air – Goblet cells are single-cell mucous glands of epithelium – Mucus glands lie in the submucosa 28 VI. Pharynx 29 Pharynx q A tube that extends from the cranial base to the inferior border of cricoid cartilage • Widest (~5 cm) opposite the hyoid • Narrowest (~1.5 cm) at its inferior end (C6) – becomes continuous with esophagus q Pharynx has 4 layers • Mucosal layer of epithelium • Nasopharynx – respiratory epithelium • Oropharynx – stratified squamous epithelium • Laryngopharynx – stratified squamous epithelium • • • q Thick fibrous layer Muscular coat of pharyngeal muscles Thin fascial layer Subdivisions of the pharynx and their functions: • Nasopharynx - Respiratory • Oropharynx- Respiratory and digestive • Laryngopharynx- Respiratory and digestive 30 Nasopharynx q Nasopharynx lies posterior to the nasal cavity- behind the choanae and includes: • • Pharyngotympanic (eustachian/auditory) tubes Pharyngeal tonsils – Adenoids q Mostly innervated by CN V 31 Oropharynx q Oropharynx lies posterior to the oral cavity behind the palatoglossal arches and includes: • Root of tongue and lingual tonsils form the anterior wall • Palatopharyngeal arch in lateral walls • Palatine tonsils located between pillars q Innervated by CN IX 32 Oropharynx - Fauces qFauces is a subdivision of the oropharynx bounded: • Superiorly by the soft palate, • Inferiorly by the root of the tongue, • and laterally by the pillars of the fauces (faucial pillars) qPillars of the Fauces – “faucial pillars” •Palatoglossal and palatopharyngeal arches: § Anterior faucial pillar- palatoglossal arch • Palatoglossal muscle covered by a fold of mucosa • Origin- Palatine aponeurosis; Insertion- tongue • Posterior faucial pillar- palatopharyngeal arch • Palatopharyngeal muscle covered by a fold of mucosa • Origin- palatine aponeurosis; insertion- wall of pharynx •Fossa for the Palatine tonsils is bounded by the faucial pillars •Oropharyngeal isthmus is the isthmus of the fauces -the space between the pillars 33 Oropharynx - Palatine Tonsils Posterior to the oral cavity -Root of tongue and lingual tonsils form the anterior wall -Palatopharyngeal arch in lateral walls -Palatine tonsils between pillars 34 Laryngopharynx q Posterior to the larynx – aka Hypopharynx – Inferior portion of pharynx – Bifurcates to trachea (through the larynx) and esophagus • Important structure- Piriform fossa- a recess on either side of the larynx – Aryepiglottic folds separate piriform fossa from laryngeal inlet – Site for impaction of bones/food lodged here – Anesthesia landmark to block internal laryngeal nerve • Lies just under the mucosa of the piriform fossa- easily blocked topically • Innervated by CN X 35 Waldeyer’s tonsilar ring q Lymphoid tissue forms an incomplete tonsillar ring around the pharynx • Pharyngeal tonsils -posterior/superior part • Palatine tonsils and tubal tonsils (if present) -lateral part • Lingual tonsils -anterior/inferior part 36 Pharyngeal Muscles q Two layers of skeletal muscle – an external circular and an internal longitudinal layer • External Circular Layer – fibers extend laterally and circle the pharyngeal wall – Function- Constrict walls of pharynx during swallowing – pharyngeal constrictors – Superior pharyngeal constrictor – Middle pharyngeal constrictor • Overlaps the superior pharyngeus; overlapped by the inferior pharyngeus – Inferior pharyngeal constrictor • Cricopharyngeus muscle located at C6 – tonically contracted • Upper esophageal sphincter 37 Internal Longitudinal Layer q Function - Elevates (shortens/widens) larynx and pharynx during swallowing and speaking • Lifts larynx against the base of tongueà epiglottis not essential to close inlet – Stylopharyngeus – Palatopharyngeus – Salpingopharyngeus – salpingo (trumpet) 38 Innervation of Pharyngeal Muscles q Innervation – the pharyngeal plexus supplies the motor and most sensory to pharynx • Motor fibers in plexus derived from CN X – except stylopharyngeus (CN IX) 39 Airway Assessment- Mallampati q A Mallampati score is determined for each patient based on the visibility of oral structures • Score is given based on the visibility of the faucial pillars, uvula, soft and hard palate • A score of “Class 1” indicates these structures are visible; higher scores indicate less visibility 40 Upper Airway Obstruction q Note three potential sites of upper airway obstruction when a patient is asleep/sedated q Nasopharyngeal and oropharyngeal airways maintain patency by extending into the pharynx • Poorly tolerated in an awake patient without local anesthetic 41 VII. Larynx 42 Larynx q The larynx is the organ of voice production that extends from the hyoid bone to the trachea q Characteristics – Guards the airway – Located in anterior neck – Bodies of C3-C6 vertebrae – Laryngeal prominence – “Adam’s apple” Cricoid Cartilage q Cricoid cartilage corresponds to the: – C6 vertebra - transverse and spinous processes palpable – Junction of larynx and trachea – Joining of pharynx and esophagus – Point where recurrent laryngeal nerve (RLN) enters the larynx Hyoid bone q The hyoid bone is the superior border of the larynx § Unique- the only bone that does not articulate with another bone – Suspended from the styloid processes of temporal bones by ligaments • Provides a moveable base for the tongue and attachment site for neck • Hyoid maintains patency of the pharynx • Is required for swallowing and respiration • Composed of body and greater and lesser horns Laryngeal Inlet q Bounded: • Anteriorly by the epiglottis • Laterally by the aryepiglottic folds • Posteriorly- cuneiform & corniculate cartilages 46 Direct Laryngoscopy q A laryngoscope is used to visualize the vocal cords for endotracheal tube placement Figure 50-8 Schematic view of the glottic opening during direct laryngoscopy when the epiglottis is elevated with a curved or straight laryngoscope blade. The glottic opening is recognized by its triangular shape and the pale, white vocal cords. (From Stoelting RK, Miller RD: Basics of Anesthesia, 3rd ed. New York, Churchill Livingstone, 1994.) 47 Laryngeal Assessment q Cormack-Lehane Score (one example of a common laryngeal assessment) • • • • Recorded on the anesthesia record - good data if available Assesses the visibility of the glottic opening during direct laryngoscopy The ability to obtain full visibility of the glottic opening = Grade 1 view The inability to see the glottic opening = Grade IV view 48 Laryngeal Cartilages qSkeleton of the larynx formed by 9 cartilages •3 unpaired cartilages: • • • Epiglottis Thyroid Cricoid •3 paired cartilages: • • • Arytenoid Corniculate Cuneiform 49 Unpaired cartilage- Epiglottis q Epiglottis • Leaf-shaped elastic cartilage posterior to root of tongue • Lower end attached to thyroid cartilage by thyroepiglottic ligament • Epiglottis is attached to tongue by median glossoepiglottic fold • Vallecula- depressions on each side of median glossoepiglottic fold that hold saliva – The “pill box” of the larynx • Aryepiglottic folds form lateral walls of epiglottis • During swallowing, tips posteriorly to cover inlet 50 Unpaired cartilage- Thyroid and Cricoid q Thyroid • Largest cartilage of the larynx – “V” shaped opening projects posteriorly q Cricoid • “Signet ring” with broad lamina facing posteriorly • Inferior border is at C6- lowermost part of the upper airway • The only cartilage that completely encircles the airway • The only non-expandable portion of the upper airway • In infants- the subglottic area inside the cricoid is the narrowest fixed part of the upper airway – Subglottic narrowing can result in difficulty passing an endotracheal tube 51 Paired Cartilages- Arytenoids q Arytenoid cartilages • Paired 3-sided pyramids in posterior larynx • Sit atop the superior border of the cricoid cartilage • 2 significant processes: – Muscular process-posterior/lateral cricoarytenoids attach (#5) – Vocal process- Site of posterior attachment of vocal ligament • “True vocal cords” attach here (#4) 52 Paired Cartilages- Corniculate and Cuneiform q Corniculate cartilages may be visible when vocal cords are not – Sit atop and articulate with arytenoids – Visible during laryngoscopy – Located in ary-epiglottic fold q Cuneiform cartilages do not directly communicate with other cartilages – Small cylinders – Lie lateral to corniculate cartilage – Under the cuneiform tubercle 53 Ligaments of the Larynx q Function of the ligaments is to hold the laryngeal cartilages together q Two types or ligaments/ membranes • Extrinsic-Attach laryngocartilages to hyoid bone or trachea • Cricotracheal ligament- joins cricoid to the first tracheal rings • Thyrohyoid ligament- joins thyroid cartilage to hyoid bone • Hyoepiglottic ligament- joins hyoid bone to epiglottis • Intrinsic- Connect laryngocartilages • Cricothyroid ligament- site for an emergency airway or intratracheal injections 54 Laryngeal Folds/ Cords qLaryngeal folds/ cords- 2 sets • Vestibular folds • False cords • Superior to true cords • Pink color • Vocal cords • True vocal cords • Lack submucosa- White appearance • Poor vascularityà • Less swelling in adults qStructures • Vocal ligament lies under the vocal cords • Rima glottidis – Opening between true cords and arytenoid cartilages • The narrowest part of the adult upper airway • Cricoid is the narrowest fixed part of the pediatric airway • Glottis- the vocal apparatus of the larynx à vocal folds and rima glottidis 55 Laryngeal Cavity q Laryngeal cavity extends from the laryngeal inlet to the inferior border of cricoid cartilage q Areas within the laryngeal cavity: • • • Laryngeal vestibule- cavity between the laryngeal inlet and vestibular folds Laryngeal ventricle- recesses extending laterally between vestibular and vocal folds Infraglottic/subglottic cavity- lies between the vocal folds and inferior border of cricoid 56 Positions of the Rima Glottidis Variations in shape of rima glottidis. A. The shape of the rima glottidis, the aperture between the vocal folds, varies according to the position of the vocal folds. During normal respiration, the laryngeal muscles are relaxed and the rima glottidis assumes a narrow, slit-like position. B. During a deep inhalation, the vocal ligaments are abducted by contraction of the posterior cricoarytenoid muscles, opening the rima glottidis widely into an inverted kite shape. C. During phonation, the arytenoid muscles adduct the arytenoid cartilages at the same time that the lateral crico-arytenoid muscles moderately adduct. Air forced between the adducted vocal ligaments produces tone. Stronger contraction of the same muscles seals the rima glottidis (Valsalva maneuver). D. During whispering, the vocal ligaments are strongly adducted by the lateral crico-arytenoid muscles, but the relaxed arytenoid muscles allow air to pass between the arytenoid cartilages (intercartilaginous part of rima glottidis), which is modified into toneless speech. No tone is produced 57 Extrinsic Muscles of the Larynx q Extrinsic muscles move the larynx as a unit • Suprahyoid muscles • Elevates hyoid (and larynx) • Maintain tone of the hypopharynx • • “Supra”-Originate above the hyoid bone • Stylohyoid • Geniohyoid • Mylohoid • Digastric • Stylopharyngeus Infrahyoid muscles (strap muscles) • Depresses hyoid – most depress the larynx • Active in swallowing • “Infra”- Originate below the hyoid bone • Omohyoid • Sternohyoid • Sternothyroid • Thyrohyoid – Elevates the larynx 58 Intrinsic Muscles of the Larynx q Intrinsic muscles modify the laryngeal inlet and vocal cords v Muscles of the laryngeal Inlet: • Aryepiglottic & oblique arytenoid muscles narrow the inlet • Thyroepiglottic muscle widens the inlet v Muscles of the vocal cords: • Cricothyroid • Thyroarytenoid • Posterior cricoarytenoid • Lateral cricoarytenoid • Interarytenoids= Transverse and oblique arytenoids 59 Muscles of the Larynx v Muscles of the vocal cords: • Cricothyroid –Elongates cords- main tensors • Thyroarytenoid- Shortens cords- main relaxers • Vocalis- also shortens cords to relax them • Posterior cricoarytenoid –Sole abductors of vocal folds • Lateral cricoarytenoid –Primary adductors of vocal folds 60 Intrinsic Muscles of the Larynx • Interarytenoids= Transverse and oblique muscle fibers • Adducts arytenoid cartilages- closes posterior glottis 61 Laryngeal Muscles and Their Movements 62 One of our Strongest Reflexes: • Combined action of most muscles of laryngeal inlet result in a protective sphincteric action – Inhaling noxious stimuli- eg a pungent or toxic gas- may stimulate • Adduction occurs reflexively when liquid or particles approach the laryngeal vestibule – Laryngospasm 63 Epithelium of the Larynx q Epithelium of most of the larynx is respiratory epithelium – Exception: True vocal cords are stratified squamous epithelium q Blood supply à branches of superior/inferior thyroid arteries – Venous drainageà Internal jugular 64 Innervation of the Larynx q Sensory Innervation: • Upper vocal cords and above: • Internal branch of superior laryngeal nerve (SLN) • Lower vocal cords and below is the inferior laryngeal n. • Branches off the recurrent laryngeal nerve q Motor innervation to intrinsic muscles: • Cricothyroid m. is via the external branch of the SLN • The only tensor of the vocal cords • All other muscles via the recurrent laryngeal nerve (RLN) • Mucous glands innervated by parasympathetic nerves 65 Damage to the Recurrent Laryngeal Nerve q Acute damage to the recurrent laryngeal nerve (eg with thyroid surgery) due to location • Nerve function is monitored during thyroid surgery • • Unilateral injury to RLN- paralysis of ipsilateral vocal cord abductors Bilateral injury to RLN- leaves cricothyroid unopposed- cords approximated- emergency • The cricothyroid muscle is the only intrinsic muscle of the larynx not innervated by a branch of the RLN • If the RLN is damaged- eg during thyroid surgery- the SLN maintains its function • Cricothyroid located on the anterior, outer arch of cricoid cartilage • The only tensor of the vocal cords q RLN injury can occur from any pressure or stretching • Left RLN injury due to its location under the arch of the aorta • Aortic arch aneurysm • Left atrial enlargement/mitral stenosis • may cause hoarseness 66 VIII. Trachea 67 Anatomy of the Trachea qGross anatomy of the trachea: •Fibrocartilaginous tube supported by 16-20 incomplete tracheal cartilages •Extends from C6 to T4-T5 intervertebral disc (Sternal angle) •Carina – lowermost portion of trachea at T4-T5 •In adults- ~ 2 cm in diameter; 10 cm long • Smaller in children q • • • Distances: Incisors to vocal cords=13 cm Vocal cords to carina= 13 cm Teeth to carina = 26 cm 68 Anatomy of the Trachea (continued) • Epithelium – Respiratory epithelium with mucous glands in submucosa • Rings absent posteriorly where trachea adjacent to esophagus • Posterior gaps filled by flat wall of involuntary (smooth) muscle – trachealis muscle 69 Trachea: Blood Supply and Innervation q Blood supply to the trachea is from: •Inferior thyroid arteries • Bronchial arteries • Intercostal arteries •Venous drainage via corresponding veins q Innervation: •Sensory- Vagus nerve • Carina and true vocal cords very sensitive •Motor- Mucous glands via parasympathetic fibers 70 Emergent and Surgical Airways q Tracheostomy - long-term surgical airway q Cricothyrotomy –emergency airway 71 1. The mastoid process of which bone is a landmark for Larson’s maneuver? a. Mandible b. Temporal bone c. Parietal bone d. Maxilla 2. What structure corresponds to the fauces? a. Eustachian tubes b. Palatine tonsils c. Pharyngeal tonsils d. Piriform fossa 3. Which nerve stimulates mucus production in the nose? a. CN I b. CN III c. CN V d. CN VII e. CN X 4. Which structure forms the lateral walls of the epiglottis? a. Cricoid cartilage b. Thyroid cartilage c. Aryepiglottic folds d. Glossoepiglottic fold 5. What is the large membrane that extends upward from the superior border of the thyroid cartilage? a. Cricothyroid membrane b. Thyrohyoid membrane c. Cricotracheal ligament d. Thyroarytenoid muscle 72