Larynx & Ear PDF Study Guide

Larynx & Ear DPM Program Learning Objectives: Larynx 1. Explain the structure and function of the hyoid bone (discussed in neck lecture) and larynx. 3.0 2. Describe the muscles of the larynx, in terms of attachments, actions, and innervations. 3.0 3. Describe the internal structure of the larynx. 3....

Larynx & Ear DPM Program Learning Objectives: Larynx 1. Explain the structure and function of the hyoid bone (discussed in neck lecture) and larynx. 3.0 2. Describe the muscles of the larynx, in terms of attachments, actions, and innervations. 3.0 3. Describe the internal structure of the larynx. 3.0 4. Describe the course of the right and left recurrent laryngeal nerves. 3.0 5. Explain resulting effects of nerve injuries of the larynx. 3.0 6. Palpate hyoid bone, thyroid cartilage, cricoid cartilage, and tracheal rings. 4.0 Ear 1. Explain the structure, function, and innervation of the ear. 3.0 The Larynx The complex organ of voice production, lies in the anterior part of the neck at the level of the C3-C6 vertebrae. It connects the inferior part of the pharynx (oropharynx) with the trachea. Functions: -Role in phonation for voice production -Guards the air passageway during swallowing, maintaining a patent airway Laryngeal Skeleton: -consists of nine cartilages joined by ligaments and membranes Three are single: Thyroid largest of the cartilages; 2 laminae that fuse at an angle to form the laryngeal prominence (Adam’s Apple) Cricoid forms a complete ring around the airway, the only cartilage of the respiratory tract to do so. Attached to the inferior margin of the thyroid cartilage by the median cricothyroid ligament. Epiglottic consisting of elastic cartilage, gives flexibility to the epiglottis. Prevents food from entering the larynx Three are paired: Arytenoid paired, three-sided pyramidal cartilages that articulate with the lateral parts of the superior border of the cricoid cartilage lamina. Vocal process-anterior to the vocal ligament Corniculate will not discuss Cuneiform will not discuss Don’t forget the Trachea – fibrocartilaginous tube with c-shaped cartilaginous rings that are deficient posteriorly. Extends from inferior edge of cricoid cartilage (C6) to the tracheal bifurcation at T4/T5. Epiglottis Epiglottis Hyoid bone Thyrohyoid ligament (extrinsic) Vestibular ligament Thyroid cartilage Larynx Cricoid cartilage Laryngeal prominence Vocal ligament Thyroid cartilage Arytenoid cartilage Cricothyroid ligament (intrinsic) Cricoid cartilage Trachea Tracheal Trachealcartilages cartilages a Anterior view of the intact larynx b Posterior view of the intact larynx Primary Ligaments and Membranes Thyrohyoid membrane - connects thyroid cartilage to the hyoid bone Quadrangular membrane - extends between the lateral aspects of the arytenoid and epiglottic cartilages. Free inferior edge is the vestibular ligament (false vocal cords). Free superior edge is the aryepiglottic ligament Conus elasticus (a fibro-elastic membrane composed of): Median cricothyroid ligament - connects cricoid to thyroid anteriorly (soft spot) 2 Lateral cricothyroid ligaments - from superior rim of lateral aspect of cricoid all the way around onto the vocal processes of the arytenoid cartilages. It has an anterior attachment to the thyroid angle. Vocal ligament (Cord) - free superior edge of the lateral cricothyroid ligament. Rima Glottidis – space between right and left vocal folds Aryepiglottic ligament of Quadrangular membrane Vestibular ligament Cricothyroid ligament Epiglottis Quadrangular membrane Vocal ligament Arytenoid cartilage NOTE: The conus elasticus is composed of the median and two lateral cricothyroid ligaments Thyrohyoid membrane Aryepiglottic Assists in closure of the inlet Posterior cricoarytenoid Abducts cords Oblique and Transverse Arytenoid Assist in closure of the inlet Posterior cricoarytenoid Abducts cords Thyroepiglottic Only muscles that widen inlet Thyroarytenoid (vocalis) Relaxes cords Lateral cricoarytenoid Adducts cords Cricothyroid Stretches /tenses cords **All muscles innervated by RECURRENT LARYNGEAL NERVE (CN X) with the exception of cricothyroid (external laryngeal nerve (CN X) Interior of the Larynx LARYNGEAL INLET -superior opening of the larynx formed by the epiglottis, the aryepiglottic folds, and interarytenoid notch VESTIBULE -the part of the larynx between the superior aperture and the vestibular folds VESTIBULAR FOLDS -false vocal cords; formed by the vestibular ligaments VENTRICLES -lateral expansions of the laryngeal cavity between the vestibular folds and vocal folds VOCAL FOLDS -true vocal cords; formed by the vocal ligaments RIMA GLOTTIDIS -the split or opening between the two vocal folds -alterations in the size of this opening, or changes in the tension of the vocal folds alter the sounds and/or pitch produced GLOTTIS -the vocal apparatus of the larynx; consists of the vocal folds and the opening between them (the rima glottidis) INFRAGLOTTIC CAVITY -inferior-most part of the laryngeal cavity extending from the rima glottidis superiorly to the trachea inferiorly LARYNGEAL OUTLET -located at the lower border of cricoid cartilage (C6) -the larynx is continuous with the trachea at this level Vasculature & Innervation of the Larynx VASCULATURE Superior laryngeal artery: - pierces thyrohyoid membrane with internal laryngeal nerve - branch of superior thyroid artery (off external carotid a.) Inferior laryngeal artery -branch of inferior thyroid artery (off thyrocervical trunk) LARYNGEAL NERVES **All from VAGUS Superior laryngeal nerve: Two branches: Internal laryngeal nerve (GSA & GVA) -Pierces the thyrohyoid membrane with the superior laryngeal vessels -sensation of the vocal folds and more superior aspects of larynx (also responsible for sensation to the laryngopharynx, and taste to the epiglottis and a small area on the posterior third of the tongue). -injury causes a loss of sensation and a loss of the cough reflex External laryngeal nerve (GSE) – Descends through neck with the superior thyroid artery. -motor to cricothyroid m -Paralysis of the cricothyroid muscle results in a monotone voice (inability to alter the length and tension of the vocal ligaments) -injury results in an inability to produce high frequencies and a weak voice that easily tires Recurrent laryngeal nerve (Inferior laryngeal n.) (GSE, GVA) -Ascends through neck with the inferior thyroid and inferior laryngeal arteries. The recurrent laryngeal n. enters the larynx by passing deep to the inferior pharyngeal constrictors, at this point its name changes to the inferior laryngeal n. - innervates remaining intrinsic muscles and provides sensation to the larynx for mucosa below vocal folds (also contributes to motor innervation of the cricopharyngeus part of the inferior pharyngeal constrictor). -Unilateral injury to the recurrent laryngeal nerve will result in hoarseness and possible difficulty in clearing one’s throat. Bilateral lesion will severely impair breathing (because of the loss of the abductors of the vocal cords—Posterior Cricoarytenoid) and speech will be difficult. Surface Anatomy The Ear FUNCTION: Audition or hearing (cochlear portion) Equilibrium (vestibular portion) STRUCTURE: EXTERNAL (OUTER) EAR: Collects sound waves and conducts them to the tympanic membrane. The tympanic membrane transmits waves to the ossicles of the middle ear and forms the boundary between the external and internal portions of the ear. AURICLE -it collects sounds eaves. Is elastic cartilage covered by skin. EXTERNAL AUDITORY MEATUS -conducts sounds to the tympanic membrane forcing it to vibrate -S-shaped canal that is laterally cartilaginous and medially bony MIDDLE EAR: -Transmit sound wave induced vibrations of the tympanic membrane of the inner ear OSSICLES (MALLEUS, INCUS, STAPES) -chain of bones from the tympanic membrane to the oval window of the inner ear. They transmit the sounds vibrations to the fluid the inner ear. MUSCLES: Stapedius (CN VII), Tensor tympani (CN V3) NERVES: chorda tympani (CN VII), tympanic plexus (CN VII, CN IX, sympathetics) INTERNAL (INNER) EAR: In the petrous portion of the temporal bone and contains the Vestibulocochlear Organ. COCHLEA: for auditory and sense SEMICIRCULAR CANALS & VESTIBULE: for balance and position INNERVATION: VESTIBULOCOCHLEAR NERVE (CN VIII) VESTIBULAR PORTION-concerned with equilibrium and orientation in three dimensional space COCHLEAR PART-concerned with audition