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Hanna- CN IX-XII
Question | Answer |
---|---|
Affected Nerve in Clinical deficit: Absent gag reflex | CN IX via tonsillar N (sensory limb of gag reflex). CN X (motor limb of gag reflex via pharyngeal plexus) |
Affected Nerve in Clinical deficit: Absent taste on posterior 1/3 of tongue | CN IX (via Lingual branches) |
Affected Nerve in Clinical deficit: Paresis in swallowing and Dysphagia | CN IX (Stylopharyngeus) and CN X (all other muscles of soft palate and pharynx minus TVP. Without CN X, there is no motor limb to the pharyneal plexus: soft palate would sag, uvula deviated to contralateral side) |
Affected Nerve in Clinical deficit: Dysphonia and aphonia | CN X: External branch of superior laryngeal N: cricothyroid M, Inferior Laryngeal N (From Recurent Laryngeal Ns) provide somatic motor to the rest of the laryngeal muscles. |
Affected Nerve in Clinical deficit: Hoarseness | CN X (recurrent laryngeal N) |
Affected Nerve in Clinical deficit: Protrusion of the tongue to one side | CN XII (Genioglossus on one side will be inactive, tongue will deviate towards ipsilateral side of lesion since genioglossus wags the tongue towards contralateral side when activated) |
Ligaments associated with the Larynx | 1.Cricothyroid: cricoid cartilage to thyroid cartilage (lateral). 2.Vocal: thing ligament running from vocal process of cricoid cartilage to the apex of thyroid cartilage. 3.Vestibular: runs same course as vocal ligament but lies superior. |
2 Main functions of the Larynx | 1.Guarding the Airway (most important). 2.Phonation. |
Function of the Arytenoid cartilages in the larynx | (two horns coming up from the cricoid cartilage) Alter the position of the true vocal cords during phonation. |
Cartilages associated with the Larynx | 1.Thyroid (C4). 2.Cricoid. 3.Epiglottic. 4.Artynoid. |
Location of the Hyoid bone | C3 within the superior part of Larynx |
Internal Larynx: Glottis | Vocal apparatus consisting of: 1.Vocal folds (all vocal muscles and ligaments). 2.Rima glottidis (space b/w the vocal and vestibular folds). 3.Vestibular folds (false vocal folds superior to true vocal folds. Protect the airway via Vestibular ligaments |
Muscles of the larynx: Adductors | 1.Lateral Cricoarytenoid M, 2.Arytenoids (transverse and oblique). These are innervated by inferior laryngeal N (CN X). **Both adduct vocal cords to lower volume to whisper during phonation. |
Muscles of the larynx: Abductors | 1.Posterior Cricoarytenoid: Innervated by the inferior Laryngeal N. **Actions: abducts vocal folds allowing more air to pass through and increasing the volume. |
Muscles of the larynx: Tensor | 1.Cricothyroid M: Innervated by the External branch of superior Laryngeal N. Action: tilts the thyroid anteriorly which increases tension in vocal folds (RAISES PITCH) |
Muscles of the Larynx: Relaxer | 1.Thyroatenoid M: Pulls arytenoid cartilages forward, shortening vocal cords & lowering pitch. 2.Vocalis M: Medial to thyroarytenoid, lateral to vocal fold, makes minute adjustments to volume and pitch. **Both Innervated by Inferior Laryngeal N |
Branches of CN X that innervate the Larynx | 1.Superior Laryngeal N: gives off 2 branches: Internal and External Laryngeal N (they innervate the larynx as well as the root of the tongue and epiglottis). 2.Recurrent Laryngeal N: gives off the Inferior Laryngeal N that innervates the Larynx. |
Internal Laryngeal N | Sensory: Vestibule and middle cavity (Inferior pharynx and larynx, root of the tongue). It travels with the Superior laryngeal A into the Thyrohyoid membrane. **Taste from eiglottis region |
External Laryngeal N | MOTOR: to the Cricothyroid M, inferior pharyngeal constrictor M (via pharyngeal plexus). Travels the superior thyroid A. |
Inferior Laryngeal N | SENSORY: to infraglottic cavity. MOTOR: almost all the laryngeal muscles (except cricothyroid). Travels with inferior laryngeal A inferior to inferior border of pharyngeal constrictor. |
Lesions to CN X: effects on the thoraco-abdominal region | 1.Increased HR. 2.Lack of peristalsis & sounds |
Lesions to CN X: effects on taste | Sensory taste cell bodies from the epiglottis lie in the inferior vagal ganglion. Therefore taste would be lost but would NOT be noticed unless tested. |
Lesions to CN X: effects on Ear and meninges | CN X has somatosensory fibers from the external auditory canal and the dura in the POSTERIOR cranial fossa. Both would be lost. |
Lesions to CN X: effects on the carotid body and sinus | Since CN X only give a minor fiber contribution, the carotid body and sinus would remain functional and relatively unaffected. **Damage to CN IX would cause BL pH and BP issues |
Arteries to the Larynx | 1.Superior Laryngeal A (branch off Sup thyroid A) penetrates the thyrohyoid membrane. 2.Cricothyroid A (Branch off Sup Thyroid A.) 3.Inferior Thyroid A (From Thyrocervical Trunk) supplies the inferior larynx) |
Branches of the thyrocervical Trunk | Arises from the 1st part of Subclavian near medial border of Ant Scalene. 1.Inferior thyroid A. 2.Ascending cervical branch 3.Suprascapular A. 4.Cervicodorsal Trunk (bifricates into superficial cervical A and Dorsal scapular A). |
Lymphatics of Larynx | Located above and below the vocal folds. SUPERIOR: Superior deep cervical nodes. INFERIOR: Pretracheal and Paratracheal lymph nodes drain to the inferior cervical lymph nodes. |
Lesion on which nerve would cause a lack of sensation in the vestibule? | Internal Laryngeal N |
Lesion on which nerve would cause a lack of sensation in the middle laryngeal cavity? | Internal Laryngeal N |
Lesion on which nerve would cause a lack of sensation in the Infraglottic Cavity? | Inferior Laryngeal N |
Lesion on which nerve would cause an inability to raise pitch? | External Laryngeal N (Cricothyroid M) |
Lesion on which nerve would cause an inability to lower pitch, raise volume, and lower volume? | Inferior Laryngeal N |
Laryngeal Vestibule | The opening to the larynx |
Function of the Middle part of laryngeal cavity | Phonation. **Laryngeal Ventricle is the space b/w the sup and inf folds making up the middle laryngeal cavity. |
Ifraglottic cavity | Below the folds. Includes lateral thyroid cartilage and inferior cricoid cartilage. |
Pathway of CN IX | Medulla, Jugular foramen, Sup & Inf glossopharyngeal ganglia, to either: 1.Carotid sinus/body 2.Stylopharyngeus muscle 3.tympanic N. |
Parasymp innervation of Parotid Gland pathway | Medulla, Jugular foramen, Sup & Inf glosopharyngeal ganglia, tympanic N, Tympanic plexus, lesser petrosal N, foramen ovale, otic ganglia, Auriculotemporal N, Parotid gland |
Lesions on CN IX | 1.(Carotid sinus N) Cause regulation issues of carotid sinus (BP) and carotid body (pH). 2.(lingual) Lose of SENSORY from post 1/3 of tongue. 3.(On tympanic N) Loss of GSA from middle ear and Eustacian tube, dec salivation of parotid |
Pathway of CN XI | Anterior Root C1-5, Superiorly through foramen magnum, jugular foramen, descends along internal carotid A, enters SCM, then Trapezius |
Pt presents with weakness in turning their head against resistance, where could the lesion be | Unilatreal CN XI lesion |
Pathway of CN XII | Medulla, Hypoglossal canal, travels with the cervical plexus (superior loop of Ansa Cervicalis) to middle angle of the mandible, enters the tongue **Innervates all glossus muscles except palatoglossus |
Lesion on CN XII | tongue will deviate TOWARDS the AFFECTED side. Also the tongue would protrude due to an inability to retrude. **Makes it hard to swallow** |