Learning Objectives

• To understand the relevant anatomy, physiology, disease processes, and investigations of the pharynx, larynx, and neck.

• The diagnosis and emergency treatment of airway obstruction.

Clinical Anatomy and Physiology

The Pharynx

• Definition: The pharynx is a fibromuscular tube forming the upper part of both the respiratory and digestive passages, extending from the base of the skull to the lower border of the cricoid cartilage at the sixth cervical vertebra, where it transitions into the esophagus. Its structure allows for the dual functions of swallowing and breathing.

• Parts: The pharynx is subdivided into three distinct parts:

  • Nasopharynx: The uppermost section located behind the nose.

  • Oropharynx: The middle segment, extending from the soft palate to the tip of the epiglottis.

  • Hypopharynx: The lowest part, transitioning into the esophagus.

Nasopharynx

• Location: Positioned anterior to the first cervical vertebra, the nasopharynx houses vital anatomical structures.

  • Adenoids: These lymphoid tissues form the superior component of Waldeyer’s ring, situated at the junction of the roof and posterior wall of the nasopharynx. They play a critical role in immune response during childhood.

  • Waldeyer’s ring: A ring of lymphoid tissue comprising adenoids, palatine tonsils, and lingual tonsils, which are instrumental in processing antigens and presenting them to T-helper cells and B cells.

• Function: The nasopharynx is key in the immune response, particularly in children, where it undergoes physiological hypertrophy, a process facilitating developing immune systems.

• Eustachian Tubes: The openings affect middle ear pressure, playing a crucial role in maintaining auditory health. Dysfunction can lead to middle ear infections.

• Fossae of Rosenmüller: This region is dorsal and superior to the Eustachian tube openings and is a common site for nasopharyngeal carcinoma, necessitating awareness during examinations.

Oropharynx

• Boundaries: The oropharynx is delineated by anatomical landmarks:

  • Superior: Soft palate

  • Inferior: Lingual surface of the epiglottis

  • Anterior: Anterior faucial pillars and circumvallate papillae of the tongue.

• Palatine Tonsils: Key components located between the anterior and posterior pillars, receiving blood supply from the facial artery, contributing to immune function and acting as a filter against pathogens.

Hypopharynx

• Borders: The hypopharynx commences at the level of the laryngeal inlet and extends to the lower border of the cricoid cartilage, continuing into the esophagus. This area serves as a conduit for food and air.

• Areas: It consists of three main regions:

  • Right and Left Piriform Fossae: Important spaces for food passage.

  • Posterior Pharyngeal Wall: Anterior boundary of the esophagus; cancer can spread here due to its close proximity to vital structures.

  • Postcricoid Region: Prone to pathology; monitoring its health is essential in clinical evaluations.

• Mucosa: The mucosal lining is continuous, and any disease processes can spread submucosally, complicating diagnoses.

• Swallowing: This involves a complex sequence of oral, pharyngeal, and esophageal phases, mediated by cranial nerves V, IX, X, and XII, making understanding each phase vital in recognizing swallowing disorders.

Anatomical Relationships around the Pharynx

Parapharyngeal Space

• Anatomy: Positioned laterally to the pharynx and structured like an inverted pyramid, the parapharyngeal space is clinically significant.

• Contents: This area includes:

  • Prestyloid Space: Contains the deep lobe of the parotid gland, important blood vessels, and lymph nodes.

  • Poststyloid Space: Contains cranial nerves IX-XII, carotid artery, internal jugular vein, and deep cervical lymph nodes, making it a critical area in surgeries or infections.

• Infection: Infections here often originate from tonsil or dental infections and pose significant surgical challenges, enhancing the need for precise anatomical knowledge.

Retropharyngeal Space

• Location: This space is posterior to the pharynx and contains retropharyngeal lymph nodes, essential for tracking infections.

• Inflammatory Processes: This space is more active in infants; excessive swelling can severely impact both swallowing and respiration, necessitating prompt medical intervention.

Larynx

• Main Function: The primary role of the larynx is to protect the tracheobronchial airway, although it also plays a vital role in phonation (voice production).

• Anatomy: The larynx is composed of several cartilages, including:

  • Hyoid Bone: Provides structure and attachment points.

  • Thyroid Cartilage: The largest cartilage; prominent in the anterior wall of the larynx.

  • Cricoid Cartilage: The only complete ring in the airway; crucial due to its role as a potential injury site during intubation.

  • Arytenoid Cartilages: Involved in vocal fold tension and movement.

• Structural Divisions: The larynx is divided into three regions: Supraglottis, Glottis, and Subglottis, each having specific functions and clinical significance.

Nerve Supply to the Larynx

1. Sensory Supply:

   • Above True Vocal Folds: Supplied by the internal branch of the superior laryngeal nerve.

   • Below True Vocal Folds: Innervated by the recurrent laryngeal nerve.

2. Motor Supply: The recurrent laryngeal nerve supplies all intrinsic muscles of the larynx, apart from the cricothyroid muscle, which is supplied by the external branch of the superior laryngeal nerve. The Posterior Cricoarytenoid Muscle is extremely important as it is the only muscle capable of abducting the vocal folds, while all other intrinsic muscles adduct them, crucial for voice modulation.

Phonation/Speech Production

• Mechanism: During phonation, the vocal folds adduct against exhaled air, leading to increased pressure and vibrations, which produce voice sounds. These sounds are articulated by the anatomical structures of the oral cavity, including the tongue, lips, and palate.

• Effects of Damage: Damage to the larynx can result in symptoms like hoarseness or dysphonia (difficulty speaking), emphasizing the importance of preserving this structure during medical procedures.

Neck Anatomy

• Divided by Sternocleidomastoid Muscle: The neck is anatomically divided into two triangles:

  • Anterior Triangle: Bounded by the inferior border of the mandible, midline, and the posterior border of the sternocleidomastoid muscle.

  • Posterior Triangle: Bounded by the anterior border of the trapezius muscle; important for accessing deep neck structures.

• Lymphatic Drainage Importance: Understanding lymphatic drainage patterns is critical for assessing potential metastases from head and neck cancers that could spread systemically through these routes.

Clinical Examination of Pharynx and Larynx

• Mouth Examination: Requires proper lighting and specialized tools, including mirrors and tongue depressors. Essential steps include inspection of the mucosa and palpation of the area for swellings or abnormalities.

• Laryngeal Examination: Utilize flexible fiberoptic endoscopy or traditional laryngoscopy to visualize laryngeal structures directly, crucial for identifying pathologies.

• Neck Examination: A systematic neck examination involves inspection for lumps, sensitivity, and a thorough palpation process to detect any abnormalities.

Investigations

Radiographic Examinations

• Plain Lateral Radiographs: These can be effective in visualizing soft tissue abnormalities and indicating the presence of foreign bodies or disease processes within the pharyngeal and laryngeal regions.

• Barium Swallow and Videofluoroscopy: Utilize these techniques to study swallowing mechanics and identify potential issues in the oral and pharyngeal phases of swallowing, allowing for dynamic assessment.

• CT Imaging: High-resolution imaging plays a vital role in assessing conditions affecting the pharynx, larynx, and neck structures. The use of contrast enhances visualization of tumors and vascular structures.

• MRI: Preferred for primary tumor staging, MRI provides exceptional soft-tissue detail, which is crucial for surgical planning and treatment evaluation.

Biopsy and Cytology

• Fine-Needle Aspiration Cytology (FNAC): This is a standard procedure for characterizing thyroid or neck masses; it aids in identifying malignancies, which is fundamental for treatment decision-making.

Diseases of the Pharynx

Nasopharynx

Conditions

1. Enlarged Adenoid: A common condition in children leading to nasal obstruction and potentially obstructive sleep apnea (OSA). Surgical removal may be indicated if symptomatically significant.

2. Obstructive Sleep Apnoea (OSA): A serious condition often resulting from enlarged tonsils and adenoids, leading to disrupted sleep patterns and long-term health risks.

3. Throat Tumours: This includes both benign tumors (e.g., angiofibroma) and malignant types (e.g., nasopharyngeal carcinoma), necessitating accurate diagnosis and management planning.

Oropharynx

Conditions

1. Acute Tonsillitis: Characterized by sore throat, fever, and difficulty swallowing, often managed with antibiotics and supportive care.

2. Quinsy (Peritonsillar Abscess): A severe painful condition where a collection of pus forms near the tonsils, potentially requiring drainage.

3. Chronic Tonsillitis: Persistent infection may lead to tonsillectomy as a definitive treatment option.

Hypopharynx

1. Tumours: Generally more aggressive than other types; characterized by significant submucosal spread, often resulting in a poor prognosis when diagnosed late. Squamous cell carcinoma is the most common type.

Emergency Conditions

Stridor and Airway Management

1. Stridor Types:

   • Inspiratory Stridor: Often indicates upper airway obstruction, commonly caused by foreign bodies.

   • Expiratory Stridor: Associated with lower airway conditions like asthma.

   • Biphasic Stridor: Indicative of complex airway compromise, necessitating immediate medical evaluation.

2. Assessment Protocol: Focused assessment and careful monitoring are critical, particularly in pediatric populations.

Emergency Procedures

1. Tracheostomy and Cricothyroidotomy: These are life-saving procedures for securing the airway in emergencies, with specific indications and procedural techniques that are critical to master.

2. Laryngeal Emergencies: Understanding treatment options and protocols for acute conditions impacting the larynx is essential for ensuring patient stability.

Concluding Summary

• The dynamics among the pharynx, larynx, and neck involve complex interactions, a range of diseases, and treatment modalities impacting speech, swallowing, and breathing functions. Recognition of clinical presentations, thorough examinations, and timely investigations are essential for effective management of these vital anatomical areas, enhancing overall patient outcomes.