PHARYNX LARYNX 06/06/2016 BAAB

 The pharynx (plural: pharynges) is the part of the throat that is behind the mouth and nasal cavity and above the esophagus and the trachea, or the tubes going down to the stomach and the lungs.  In humans the pharynx is part of the digestive system and also of the conducting zone of the respiratory system.  The human pharynx is conventionally divided into three sections: the nasopharynx, the oropharynx and the laryngopharynx.  It is also important in vocalization.

 Structurally, in humans there are two sets of pharyngeal muscles that form the pharynx, determining the shape of its lumen. These are arranged as an inner layer of longitudinal muscles and an outer circular layer.  Nasopharynx  The upper portion of the pharynx of the nasopharynx, which extend from the base of the skull to the upper surface of the soft palate.  It includes the space between the internal nares and the soft palate.  it lies above the oral cavity.  The adenoids, also known as the pharyngeal tonsils, are lymphoid tissue structures located in the posterior wall of the nasopharynx.

 The auditory tubes, which connect the middle ear to the pharynx, open into the nasopharynx. The opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.  The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities.  The auditory tubes, open on its lateral walls forming the pharyngeal openings  Around the pharyngeal opening there are the mucosal prominences and folds.

 Folds are the (i)salpingopharyngeal fold containing the salpingopharyngeus muscle, and (ii) the salpingopalatine fold containing the levator veli palatini muscle.  The tensor veli palatini is lateral to the levator and does not contribute the fold, since the origin is deep to the cartilaginous opening.  On the posterior wall is a prominence, best marked in childhood, produced by a mass of lymphoid tissue, which is known as the pharyngeal tonsil.  pharyngeal bursa extend from the pharyngeal tonsil in the midline to the basilar process of the occipital bone of the skull.

 Oropharynx  lies behind the oral cavity extending from the uvula to the level of the hyoid bone.  It opens anteriorly into the mouth.  its anterior wall consists of the base of the tongue and the epiglottic vallecula;  the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars;  the superior wall consists of the inferior surface of the soft palate and the uvula.

 a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration.  The oropharynx is lined by non-keratinised squamous stratified epithelium. Laryngopharynx:  a.k.a. hypopharynx, is the caudal part of the pharynx; connecting the pharynx to the esophagus.  It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (larynx- anteriorly) and digestive (esophagus - posteriorly) pathways.  During swallowing, food has the "right of way", and air passage temporarily stops.  the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium. It is innervated by the pharyngeal plexus.

 the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium.  It is innervated by the pharyngeal plexus.  The vascular supply to the laryngopharynx includes the superior thyroid artery, the lingual artery and the ascending pharyngeal artery.  The primary neural supply is from both the vagus and glossopharyngeal nerves  The vagus nerve provides a branch termed "Arnolds Nerve" which also supplies the external auditory canal.  laryngopharyngeal cancer can result in referred otalgia.  This nerve is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing.

 ACTIONS OF THE PHARYNGEAL MUSCLES ◦ During swallowing, successive contraction of the superior, middle, and inferior constrictor muscles helps to propel the bolus (ball) of food down into the esophagus. ◦ In addition, contraction of the 3 longitudinal muscles of the pharynx helps to raise the pharynx, effectively aiding it in engulfing the bolus of food. ◦ In between acts of swallowing, the lowest fibers of the inferior constrictor are thought to act as a sphincter, guarding the entrance to the esophagus and preventing the entry of air into the digestive system.

 The Larynx is an apparatus made up of cartilage, ligaments, muscles, and mucous membrane, which guards the entrance to the lower respiratory passages (trachea, bronchi, and lungs) and houses the vocal cords.  The cartilages are forming the skeleton of the larynx  It is located within the anterior aspect of the neck, anterior to the inferior portion of the pharynx and superior to the trachea.

FUNCTION:  The primary function is to:- ◦ protect the lower airway by closing abruptly upon mechanical stimulation, thereby halting respiration and preventing the entry of foreign matter into the airway. ◦ Other functions of the larynx include the production of sound (phonation) ◦ coughing ◦ the Valsalva maneuver ◦ control of ventilation ◦ acting as a sensory organ.

 STUCTURE:  The larynx is composed of ◦ 3 large, unpaired cartilages (cricoid, thyroid, epiglottis); ◦ 3 pairs of smaller cartilages (arytenoids, corniculate, cuneiform); ◦ a number of intrinsic muscles (see the images below). ◦ The hyoid bone,(while technically not part of the larynx), provides muscular attachments from above that aid in laryngeal motion.

 Cartilages: ◦ All cartilages of the larynx are of hyaline in nature except the epiglottis which is the elastic cartilage. 1. Thyroid cartilage ◦ is the largest of the laryngeal cartilages. ◦ It is formed by a right and a left lamina that are separated posteriorly and joined together at an acute angle in the anterior midline, forming the laryngeal prominence (Adam’s apple). ◦ The laryngeal prominence is more apparent in men, because the angle between the 2 laminae is more acute in men (90°) than in women (120°). ◦ The posterior aspect of each lamina is elongated to form a superior horn and inferior horn.

◦ The medial surfaces of the inferior horns articulate with the outer posterolateral surface of the cricoid cartilage. ◦ The inferior border is attached to the cricoid cartilage by the cricothyroid membrane (midline) and the cricothyroid muscles(either side). ◦ The superior horn and the entire superior edge is attached to the hyoid bone by the thyrohyoid membrane.

2. Cricoid cartilage: The cricoid cartilage is a hyaline cartilage ring located at the inferior aspect of the larynx being the only complete ring of cartilage around the trachea. It has the shape of a "signet ring," with a broad portion posterior to the airway (lamina of cricoid cartilage) and a narrower portion circling anteriorly (arch of cricoid cartilage). 2 oval depressions posteriorly for the attachment of cricoarytenoid muscles which is separated by a vertical midline ridge attaching the esophagus.

3. Arytenoid cartilages: ◦ The arytenoid cartilages form part of the larynx to which the vocal ligaments and vocal folds attach. ◦ They are pyramidal in shape and have 3 surfaces, a base, and an apex. ◦ They are located superior to the cricoid cartilage in the posterior part of the larynx, with the base of the arytenoid cartilages articulating on either side with the posterior aspect of the upper border of the cricoid lamina. ◦ The anterior angle of the base of the arytenoid cartilage is elongated to form a vocal process for attachment of the vocal ligament ◦ The anterolateral surface has 2 depressions for attachment to the false vocal cord (vestibular ligament) and the vocalis muscle.

4. Corniculate cartilages: ◦ The corniculate cartilages are 2 small, conical cartilages that articulate with the apices of the arytenoid cartilages, serving to extend them posteriorly and medially. ◦ They are located in the posterior parts of the aryepiglottic folds of mucous membrane. 5. Cuneiform cartilages:  The cuneiform cartilages are 2 small, club-shaped cartilages that lie anterior to the corniculate cartilages in the aryepiglottic folds.  They form small, whitish elevations on the surface of the mucous membrane just anterior of the arytenoid cartilages.

6. Epiglottis: The epiglottis is a leaf-shaped elastic cartilage that moves down to form a lid over the glottis and protect the larynx from aspiration of foods or liquids being swallowed. It is attached via the thyroepiglottic ligament and projects posterosuperiorly to cover the superior opening of the larynx. Its midline is also attached to the body of the hyoid bone via the hyoepiglottic ligament. The depressions on either side of the median fold, between the root of the tongue and the epiglottis, are called the valleculae epiglottica.

 Ligaments of the larynx: ◦ Strong and broad ligaments are extrinsic, these are  The thyrohyoid membrane. a broad fibroelastic ligament that spans between the superior border of the thyroid cartilage and the hyoid bone above.  It contains an aperture on the lateral surfaces of each side for the superior laryngeal arteries, nerves, and lymphatics.  hyoepiglottic ligament: located anterosuperiorly, extending from the midline of the superior surface of the epiglottis to the body of the hyoid bone.  The cricotracheal ligament connects the lower border of the cricoid cartilage to the upper border of the first tracheal cartilage ring.

 Cavities of the larynx ◦ Laryngeal cavity  The laryngeal central cavity is tubular in shape and lined with mucosa. Superiorly (laryngeal inlet) opens into the pharynx and inferiorly is continuous with the lumen of the trachea. The laryngeal cavity may be divided into 3 regions: the vestibule which is the upper portion of the cavity, between the laryngeal inlet and the vestibular folds. the middle, in the middle portion of the cavity, or the voice box, is formed by the vestibular folds above and the vocal folds below. the infraglottic space, the lower portion of the cavity, in between the vocal folds and inferior opening of the larynx into the trachea.

 Laryngeal ventricles and saccules ◦ Found on either side of the middle laryngeal cavity, between the vestibular and vocal folds. ◦ the walls of these saccules contain many mucous glands that lubricate the vocal folds.  Rima vestibuli and rima glottidis ◦ The rima vestibuli is the triangular-shaped opening between the 2 adjacent vestibular folds.  The apex lies anterior and the base is formed by the posterior wall of the laryngeal cavity. ◦ The rima glottidis is a narrower, triangular-shaped opening that lies beneath the rima vestibuli,  formed by the 2 adjacent vocal folds.

 Piriform recesses ◦ The piriform recesses (piriform sinuses) are present on either side of the anterolateral wall of the laryngopharynx. ◦ They are bounded medially by the aryepiglottic folds and laterally by the thyroid cartilage and thyrohyoid membrane. ◦ They are a common place for food to become trapped.  Laryngeal muscles: ◦ Cricothyroid ◦ Posterior cricoarytenoid ◦ Lateral cricoarytenoid ◦ Transverse arytenoid – for adduction of the vocal cords ◦ Thyroarytenoid  All muscles are supplied by the reccurent laryngeal nerve except the cricothyroid muscle supplied by the superior laryngeal nerve.

 Laryngeal nerves: 1. Superior laryngeal nerve, arise from the inferior ganglia of the vagus nerve and receive a branch from the superior cervical sympathetic ganglion on each side in the upper neck. Two branches, external laryngeal nerve- injury causes hoarseness of the voice and an inability to produce high-pitched sounds. Internal laryngeal nerve- sensory to laryngeal cavity responsible for the cough reflex. 2. Recurrent laryngeal branch of the vagus nerve The left recurrent laryngeal nerve originates in the thorax, looping under the aortic arch before ascending, while the right recurrent laryngeal nerve originates in the neck. Unilateral nerve damage presents with voice changes, including hoarseness. Bilateral nerve damage may result in aphonia (inability to speak) and breathing difficulties.

 Laryngeal dissorders: ◦ Endoscopic image of an inflamed human larynx

 Acute laryngitis is the sudden inflammation and swelling of the larynx.  Chronic laryngitis is caused by smoking, dust, frequent yelling, or prolonged exposure to polluted air.  Presbylarynx is a condition in which age-related atrophy of the soft tissues of the larynx results in weak voice and restricted vocal range and stamina.  Ulcers may be caused by the inflammation or infection  Polyps and nodules are small bumps on the vocal folds caused by prolonged exposure to cigarette smoke and vocal misuse, respectively.  Two related types of cancer of the larynx, namely squamous cell carcinoma and verrucous carcinoma, are strongly associated with repeated exposure to cigarette smoke and alcohol.

 Vocal cord paresis is weakness of one or both vocal folds.  Laryngopharyngeal reflux is a condition in which acid from the stomach irritates and burns the larynx. Similar damage can occur with gastroesophageal reflux disease (GERD).  Laryngomalacia is a very common condition of infancy, the soft, immature cartilage of the upper larynx collapses inward during inhalation, causing airway obstruction.  Laryngeal perichondritis, the inflammation of the perichondrium of laryngeal cartilages.  Duchenne Muscular Dystrophy, intrinsic laryngeal muscles (ILM) are spared from the lack of dystrophin and may serve as a useful model to study the mechanisms of muscle sparing in ……………………….dystrophinopathy.