Pharynx and Larynx Anatomy PDF

Anatomy of the head and neck – Pharynx and larynx Anatomy of the Head & Neck The pharynx and larynx [email protected] ANATOMY 0 Lecture outcomes Ø Describe the arrangement and sub-divisions of the pharynx: naso, oro and laryngo-pharynx and the larynx Ø Describe the main contents found in eac...

Anatomy of the head and neck – Pharynx and larynx Anatomy of the Head & Neck The pharynx and larynx [email protected] ANATOMY 0 Lecture outcomes Ø Describe the arrangement and sub-divisions of the pharynx: naso, oro and laryngo-pharynx and the larynx Ø Describe the main contents found in each of these, such as muscles, arterial blood supply, innervation (motor and sensory) and lymphatics ANATOMY 1 The pharynx Ø The pharynx is the upper por>on of the alimentary canal Ø It extends from the cranial base to the lower border of the cricoid car>lage where it becomes con>nuous with the oesophagus Ø Described as a mucosa lined muscular tube, lying behind and communica>ng with the nasal, oral and laryngeal cavi>es ANATOMY 2 The nasopharynx Ø The nasopharynx is the area above the soft palate and behind the nares. The floor is formed by the soft palate while the superior constrictor muscle forms the major part of the posterior wall. On the lateral wall is the opening of the pharyngotympanic (auditory) tube and lymphoid tissue. The roof has more lymphoid tissue, the adenoid or pharyngeal tonsil ANATOMY 3 The oropharynx Ø The oropharynx is the area inferior to the soft palate and communicates anteriorly with the oral cavity. Raising of the soft palate separates it from the nasopharynx. Its anterior border is made of the palatoglossal and palatopharyngeal arches, with the palatine tonsil sitting in the space between the arches. The palatine tonsil gets a rich blood supply – the lingual, ascending pharyngeal and lesser palatine arteries – so haemorrhaging poses a threat during tonsillectomy. Palatoglossal arch Palatopharyngeal arch Posterior wall of oropharynx ANATOMY 4 The wall of the pharynx Ø Since the pharynx belongs to the digestive system (even though air passes through it), it has the same 4 layers found in the rest of the digestive system: - Mucosa - Submucosa, containing a tough fibrous coat that anchors the pharynx to the base of the skull - Muscular, consisting of 5 pairs of muscles forming an outer semicircular layer – the constrictors – and two inner – longitudinal – muscles - buccopharyngeal fascia, covering the exterior layer ANATOMY 5 The constrictor muscles Ø During swallowing, the constrictor muscles contract sequentially as peristaltic waves Ø The nerve supply is mostly through the pharyngeal branch of the vagus nerve, the inferior constrictor also supplied by the recurrent branch of vagus ANATOMY 1. 2. 3. 4. Superior constrictor Stylopharyngeus Middle constrictor Inferior constrictor 6 The constrictor muscles 2 Ø The origins and insertions of these muscles is rather complex, but in summary: Superior – from a raphe between the mandible and pterygoid plate to the pharyngeal tubercle of the occipital bone Middle – from the stylohyoid ligament and horns of the hyoid to the pharyngeal raphe Inferior – from the oblique line of thyroid and cricoid to the juncBon between the pharynx and oesophagus ANATOMY 7 The longitudinal muscles Ø The longitudinal muscles: The palatopharyngeus muscle arises from the palatal aponeurosis and inserts into the posterolateral part of the pharynx plus the posterior part of the hyoid bone and thyroid cartilage. The stylopharyngeus muscle originates from the styloid process, enters the pharynx whereby its fibres mingle with those of the palatopharyngeus muscle Ø These muscle raise the pharynx and larynx during swallowing ANATOMY 1. Superior constrictor 2. Palatopharyngeus 3. Middle constrictor 4. Stylopharyngeus 5. Inferior constrictor 8 Pharynx VAN Ø Nerve Supply - Motor: All muscles of the pharynx except stylopharyngeus are supplied by the pharyngeal branches of the vagus nerve. Stylopharyngeus is supplied by the glossopharyngeal nerve. Sensory: The glossopharyngeal nerve is the main sensory supply to the pharynx with the maxillary division of the trigeminal supplying the soft palate and the roof of the pharynx and the vagus supplying the area around the pharyngeal inlet. Ø Blood Supply: by the ascending pharyngeal, superior and inferior thyroid, facial and maxillary arteries which provide a rich anastomosis. Ø Venous Drainage: by a plexus on the pharynx that communicate with the pterygoid plexus ANATOMY 9 Lymphatic drainage of the pharynx Ø Lymph from this region drains mostly into the deep cervical nodes but some posterior ones enter the retropharyngeal nodes, which lie between the prevertebral and buccopharyngeal fasciae ANATOMY 10 The larynx Ø A complex unit responsible for voice produc>on as well as an air passageway linking the pharynx with the trachea. It also acts as a sphincter to prevent food from entering the trachea Ø The larynx lies anterior to the laryngeal part of the pharynx ANATOMY 11 The larynx 2 Ø The larynx extends from the base of the tongue (C3) to the trachea (C6). The inlet lies immediately behind the posterior third of the tongue Ø The walls of the larynx are supported by a series of cartilages - three large cartilages: thyroid, cricoid and epiglottis (unpaired). - three small paired cartilages: the arytenoid, cuneiform, and corniculate ANATOMY 12 Unpaired cartilages Ø Thyroid: The largest and consists of two plates joined anteriorly in the midline. In males the union gives an acute angle and the cartilage is usually a prominent feature of the neck (Adam’s apple). In females the union is much more obtuse Ø Cricoid: sits immediately below the thyroid car>lage at the level of C6 and is shaped like a signet ring, i.e. a thin band with a quadrilateral plate. The plate faces posteriorly. It is the only car>lage which completely encircles the larynx Thyroid ANATOMY Crycoid 13 Unpaired cartilages 2 Ø Epiglottis: a fibroelastic cartilage shaped like a leaf with the stem anchored into the angle of the thyroid laminae. The broad leaf is orientated upwards and backwards lying behind the hyoid bone and reaching to the posterior part of the tongue ANATOMY 14 Paired car>lages Ø Arytenoid (Paired): These two pyramid–shaped cartilages (highlighted in blue) lie on the posterior lamina of the cricoid cartilage and articulate via a synovial joint. They provide attachment for the vocal process as well as several muscles Thyroid Epiglottis Vocal cords Arytenoid ANATOMY © Visible15Body Paired car>lages 2 Ø Corniculate (Paired): These >ny elas>c car>lages (highlighted) sit atop the apices of the arytenoid car>lages extending their length Ø Cuneiform (Paired): These are found in the aryepigloRc folds Epiglottis Corniculate Vocal cords ANATOMY © Visible Body 16 Ligaments of the larynx Ø Thyrohyoid Membrane: A fibroelas+c sheet joining the inferior surface of the hyoid bone to the superior aspect of the thyroid car+lage. The lateral borders are free and thickened Ø Vocal Ligaments: These are thick bands of elas+c fibres running from the vocal processes of the arytenoid to the thyroid car+lage and are covered by mucous membrane, the vocal folds Ø Ventricular Ligaments: These two bands of fibres run from the lateral borders of the arytenoid car+lages to the internal lamina of the thyroid car+lage. These folds, which run above the vocal ligaments are also covered by mucous membrane and are the ventricular folds (false vocal folds) Ø Aryepiglo:c Ligaments: These pass upwards from the apices of the arytenoid car+lages to the lateral border of the epigloBs Ø Quadrangular Membrane: A thin fibroelas+c sheet filling the space between the aryepigloBc ligament and ventricular ligament Ø Cricothyroid Membrane: A fibroelas+c sheet filling the space between the vocal folds and the cricoid car+lage (conus elas+cus) ANATOMY 17 Extrinsic muscles of the larynx Ø Extrinsic muscles have a remote origin but insert into the larynx or hyoid bone. These supra and infrahyoid muscles act to move the larynx up or down ANATOMY 18 Intrinsic muscles of the larynx Ø Intrinsic Muscles So called because these originate and insert into laryngeal cartilages, e.g. cricothyroid: ANATOMY 1. Posterior cricoarytenoid 2. Lateral cricoarytenoid 3. Transverse cricoarytenoid 4. Vocalis 5. Cricothyroid 19 Intrinsic muscles of the larynx 2 ANATOMY 20 Ac>on of intrinsic muscles Ø The intrinsic muscles perform 3 separate functions: - Opens the rima glottidis to allow the passage of air in or out - Closes the vestibule and rima during swallowing to prevent aspiration of food - Controls the tension of the vocal folds for phonation 1.Posterior cricoarytenoid 2. Lateral cricoarytenoid 3. Transverse cricoarytenoid 4. Vocalis 5. Cricothyroid ANATOMY 21 Nerve supply to the larynx 1. Epiglottis 2. Lesser cornu of the hyoid bone 3. Greater cornu of the hyoid bone 4 & 5. Superior laryngeal nerve 6. Oblique arytenoids 7. Transverse arytenoids 8. Posterior crico-arytenoids 9. Thyroid gland 10. Inferior thyroid artery 11. Recurrent laryngeal nerve 12. Thyroid cartilage ANATOMY 22 Blood supply to the larynx ANATOMY 23 Larynx VAN Ø Innerva?on: via the laryngeal nerves, branching from the vagus nerve Motor: all of the intrinsic muscles of the larynx are supplied by the external laryngeal nerves, that targets the cricothyroid, and the recurrent laryngeal nerve that targets the remainder Sensory: via the internal laryngeal nerves from the mucous membrane above the vocal folds, and the recurrent laryngeal nerve from the area below the vocal folds Ø Arteries: the larger providers to the larynx are the superior and inferior thyroid arteries. These give off the superior and inferior laryngeal branches, respec>vely. The laTer accompanies the inferior laryngeal nerve, the terminal part of the recurrent ANATOMY Ø Veins: drained by the laryngeal veins that lead into the superior and inferior thyroid veins 24 Lymphatic drainage of the larynx Ø The submucosal lymphatic plexus of the larynx is drained by the deep cervical lymph nodes: - above the vocal folds lymph vessels pierce the thyrohyoid membrane to reach the upper deep cervical lymph nodes - below these join the lower deep cervical lymph nodes ANATOMY 25 Phona>on Ø Phonation normally takes place during expiration. It is possible during inspiration but it is not efficient and cannot be maintained for long Ø The breathing rate is about 15 cycles per minute with the time almost equally divided between inspiration and expiration. During speech the rhythm is altered with inspiration occurring rapidly Ø Phonation consists of converting an even flow of expired air passing through the larynx into an oscillating flow with a frequency of 16-20,000 Hz which is within the range of human hearing. To achieve this the vocal folds are adducted obstructing air flow Ø Pressure then builds up from below until it forces the folds apart allowing the air to escape. The cycle is repeat and converts the air into a series of puffs at a frequency determined by the sub-glottal pressure and the mass and tension on the vocal ligaments. The frequency of the oscillating air also determines the pitch which varies to allow intonation and expression ANATOMY 26 Questions ? Email: [email protected] ANATOMY 27