ANATOMY OF PHARYNX

ANATOMY OF PHARYNX

• The pharynx is a continuous tube.

• Superior border: base of the skull.

• Inferior border: lower border of the cricoid cartilage (C6 vertebrae)

• The pharynx has three parts:
• Nasopharynx: behind the nasal cavity.
• Oropharynx: behind the oral cavity.
• Hypopharynx/laryngopharynx: behind the larynx.

Anatomy of Nasopharynx

Boundaries

• Anterior: Connects with nasal cavity through choanae

• Superior aspect/roof: Base of sphenoid sinus

• Roof and posterior wall:
• Continuous
• Related to C1 vertebrae

• Inferior imaginary line at palate:
• Separates nasopharynx from oropharynx

• Lateral wall
• Contains opening for eustachian tube
• Covered by cushion-like structure:
• Torus tubarius
• formed by Salpingopharyngeus muscle
• Pharyngeal opening of eustachian tube (ET).
• 1.25 cm behind inferior turbinate.
• Formed due to lymphatic aggregation.
• Newly discovered salivary glands present here
• Clinical Significance
• Radiotherapy over these glands
• Xerostomia
• Dysphagia
• Sparing these glands
• Improves quality of life in patients receiving radiotherapy
• Fossa of Rosenmuller:
• Recess posterior to torus tubarius
• Most Common site for carcinoma of nasopharynx.

Note

• Rathke’s pouch: Gives rise to the anterior pituitary.

Passavant's ridge

• Formed by fibres of palatopharyngeus muscle

• Separates nasopharynx from oropharynx during deglutition

• Prevents food from entering nasal cavity

Adenoid:

• Single lymphoid tissue in midline

Biopsy indicated if present

• Unilateral serous otitis media

• Older age group

• Cervical lymphadenopathy

Endoscopic Grading of Adenoid Hypertrophy:

• Grading is based on the degree of choanal space occupied.

• Each part is 25% of the airway space.

• Grade I: occupies 0-25% of the airway.

• Grade II: occupies 25-50% of the airway.

• Grade III: occupies 50-75% of the airway.

• Grade IV: occupies 75-100% of the airway.

Anatomy of Oropharynx

• Boundaries
• Superiorly: Imaginary line through the palate
• Inferiorly: Imaginary line through the tip of the epiglottis

• Relations
• Communicates with oral cavity via oropharyngeal isthmus
• Related to C2 vertebrae

• Formation
• Anterior pillars: Palatoglossus muscle
• Posterior pillars: Palatopharyngeus muscle
• Palatine tonsils: Lymphoid tissues between anterior and posterior pillars

• True oropharyngeal isthmus
• Formed by uvula with anterior pillar
• Separates oral cavity from oropharynx

• Base of tongue (posterior 1/3)
• Lies in oropharynx
• Contains:
• Median glossoepiglottic fold
• Lateral glossoepiglottic folds
• Vallecula: Depression between median and lateral folds

Tongue development and nerve supply

Anterior 2/3

• Mesoderm of arch 1 gives rise to 3 thickenings
• 2 lingual swellings
• 1 tuberculum impar

• These three thickenings fuse → form the anterior 2/3

• Sensory innervation: Lingual branch of mandibular nerve

• Taste: Chorda tympani nerve

Posterior 1/3

• Mesoderm of arch 3 and 4 gives rise to a midline swelling
• Forms Hypobranchial eminence

• The hypobranchial eminence is divided into
• Cranial (arch 3)
• Gives rise to the posterior 1/3
• Sensory and taste: Glossopharyngeal nerve
• Caudal (arch 4)
• Gives rise to the posterior-most part
• Sensory innervation: Vagus nerve
• Taste: Glossopharyngeal nerve

Sulcus terminalis

• Differentiates anterior 2/3rd from posterior 1/3rd

General Sensory Supply

• Lingual nerve

• Glossopharyngeal nerve

• Vagus nerve

Anatomy of hypopharynx

Boundaries

Subdivisions (3Ps)

• Pyriform fossa
• Two paired depressions on lateral sides of aryepiglottic folds
• Also called smuggler's pouch

• Post cricoid
• Unpaired depression in midline below arytenoids

• Posterior pharyngeal wall
• Continuous wall

Functional note

• Cricopharyngeal sphincter assists in food passage

Waldeyer's Ring

• Formed by lymphoid tissues in upper aerodigestive tract

• Function
• Protects respiratory and digestive tracts
• Mainly adenoid and palatine tonsil
• Functions until 3–5 years of age

• Adenoid → No capsule

Lymphoid Tissues of Waldeyer's Ring

Pharyngeal wall layers (in to out)

Cervical → Scale → Scalenus

1. Mucosa

2. Pharyngobasilar fascia
• Forms capsule
• Mnemonic: Pharyngo → Pharynx → more inside

3. Superior constrictor

4. Middle constrictor

5. Inferior constrictor

6. Bucco-pharyngeal fascia
• Outermost layer
• Mnemonic: Bucco → outside as compared to pharynx → outer layer

Muscles of Larynx

Constrictor muscles / Circular Muscles (3)

1. Superior constrictor
• Nerve: Vagus

2. Middle constrictor
• Nerve: Vagus

3. Inferior constrictor

• Pharyngeal pouch / Zenker's diverticulum:
• Outpouching of mucosa from Killian's dehiscence
• Pulsion diverticulum: D/T ↑pressure.
• False diverticulum: Only mucosa comes out.
• Position:
• directed posteriorly.
• Posterior midline (Starts) → Left of midline (Final).

Longitudinal Muscles (3) of pharynx

One-liners

PHARYNGEAL SPACES

1. Parapharyngeal space.

2. Retropharyngeal space.

3. Prevertebral space.

Peritonsillar space

• Between Capsule of Tonsil and Superior Constrictor Muscle

• Course
• Crypta Magna infection → Intratonsillar abscess → Capsular breach → Peritonsillitis → Peritonsillar abscess.

• Peritonsillar Abscess (Quinsy)
• Pus in peritonsillar space
• Most common in adults
• Due to deeper crypts

• Symptoms
• Pain
• Sore throat
• Difficulty swallowing
• Hot Potato Voice

• Differential diagnosis
• Unilateral enlargement of the tonsil

• Investigation
• Clinically
• Aspiration of the abscess
• Radiologically
• MRI (preferred)
• USG

• Treatment
• Incision and Drainage (I&D)
• Hot Tonsillectomy
• I&D with concurrent tonsillectomy
• Interval Tonsillectomy (Preferred)
• 4 -6 weeks later

Parapharyngeal Space

• Smallest space

• Shaped like an inverted pyramid
• Extends from base of skull to hyoid bone

Boundaries

• Laterally: mandible, medial pterygoid muscle, parotid gland

• Anteromedially: Buccopharyngeal Fascia

• Posteriorly: Carotid Sheath
• Internal carotid artery
• Internal jugular vein
• Cranial nerves: 9, 10, 11, 12

Communication

• With Retropharyngeal space

Layers of pharyngeal wall (inside → out)

1. Mucosa

2. Pharyngobasilar fascia

3. Superior Constrictor Muscle

4. Buccopharyngeal fascia

Styloid process

• Divides space into 2 compartments:
• Pre styloid Compartment
• Abscess pushes tonsil → Unilateral enlargement
• Post styloid Compartment
• Abscess presents as bulge behind tonsil

Approaches to Parapharyngeal space

• Trans-orally

• Trans-mandibular approach

Applied

• Parapharyngeal abscess
• Commonest cause
• Tonsillar infection
• Displaces tonsil medially
• Causes neck swelling → Absent in quinsy

Note

Eagle syndrome

• AKA kerato stylohyoid syndrome

• Calcified styloid process

• Recurrent throat pain

• Pain on palpation of tonsilar fossa

Retropharyngeal Space

Boundaries:

• Space of Gillette: Retropharyngeal space

• Node of Ranvier: Retropharyngeal node
• Mnemonic: Ranveer in Gillete’s ad

Alar fascia

Divides the space into:

• Anterior Compartment (True Retropharyngeal Space)
• Seen in children → Acute Retropharyngeal Abscess
• Secondary to tonsil/adenoid infections
• Ends at T4
• Contains Node of Ranvier
• Abscess from suppuration of lymph nodes
• Present as midline swelling to a side
• I & D via transoral approach→ Antibiotics

• Posterior Compartment (Danger Space)
• Extends to diaphragm/mediastinum
• Adults
• Abscess source: vertebrae
• Secondary to TB of spine
• Manifests as Chronic Retropharyngeal Abscess
• Can extend → Mediastinitis
• Present as swelling to a side of midline
• I & D → Antibiotics/ATT

Retropharyngeal abscess

Prevertebral Space

• Located between the prevertebral fascia and the vertebra body.

Boundaries:

• It is a Midline and Single Space.

• A Prevertebral Abscess originates from the Vertebra (e.g., TB of spine).
• Presents as a Midline Bulge.

Important Information (Bulge differentiation)

Table: Abscess Comparison

Questions

• Q. Identify (image: unilateral tonsil enlargement, uvula shift, neck swelling):
• Ans. Parapharyngeal abscess.
• Quinsy:
• unilateral enlargement (no neck swelling)
• Parapharyngeal abscess:
• unilateral enlargement + neck swelling.

• Q. Identify (image: swelling on the side of the abscess):
• Ans. Retropharyngeal Abscess.

• Q. Which is not true regarding acute retropharyngeal abscess?
• A. Common in children
• B. Difficulty in breathing and suckling
• C. Limited to one side of the midline
• D. Incision and drainage is done from outside through carotid sheath
• E. Forms due to suppuration in retropharyngeal lymph node
Explanation:
• I&D is via a transoral approach.

• Q. Trismus is seen in all except:
• A. Ludwigs angina
• B. Quinsy
• C. Prevertebral abscess
• D. Parapharyngeal abscess
Explanation:
• C
• Trismus is difficulty opening the mouth.
• Not seen in Prevertebral Abscess.

• Q. Identify (image: air level/gases, reversal of cervical lordosis, widening):



Ans.
• Could be Retropharyngeal abscess / Prevertebral abscess
• Indicators: air level/gases, reversal of normal cervical lordosis, widening.

• Q. Identify (image: anterior bowing of posterior wall of maxillary sinus):



Ans.
• Hollman - Miller Sign — JNA (Juvenile Nasopharyngeal Angiofibroma).
• Mass from nose goes into nasopharynx.

• Q. Identify (image: air column between mass and posterior pharyngeal wall):



Ans
• Crescent Sign/Dodd's Sign — Antrochoanal Polyp.
• Mass from nose goes into nasopharynx.

Thornwaldt Cyst (Pharyngeal Bursitis)

• Located in midline posterior nasopharyngeal wall

• Lies within adenoid mass

• Epithelial-lined median recess
• Extends from pharyngeal mucosa
• To periosteum of basiocciput

• Embryology
• Remnant of notochord attachment
• Between pharyngeal endoderm and basiocciput

• Clinical Features
• Persistent postnasal discharge / crusting
• Nasal obstruction
• Serous otitis media
• Due to Eustachian tube obstruction
• Dull occipital headache
• Recurrent sore throat
• Low-grade fever

Imaging

• MRI
• Well-defined
• Non-enhancing
• Midline nasopharyngeal mass
• T2 sagittal image shows cyst

Management

• Surgical marsupialisation

• Complete removal of cyst lining

Complication

• Thornwaldt’s disease
• Abscess formation in pharyngeal bursa

• Treatment
• Antibiotics