Clinical anatomy. physiology of the pharyns, Pharyngeal spaces. Acutediseases of the pharynx (primary and secondary angina). Peritonsillar abscess.

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Clinical Anatomy & Physiology of the Pharynx, Pharyngeal Spaces, and Acute Pharyngeal Diseases

1. Clinical Anatomy of the Pharynx

The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities in the head to the larynx and esophagus in the neck. It is a common pathway for both air and food. It attaches superiorly to the base of the skull and is continuous inferiorly with the esophagus at the level of vertebra C6. The two sides are united posteriorly in the midline by the pharyngeal raphe, which descends from the pharyngeal tubercle of the occipital bone.

Subdivisions

Region	Anterior Relationship	Key Structures
Nasopharynx	Choanae of nasal cavities	Adenoid (pharyngeal tonsil), opening of Eustachian tube (torus tubarius), fossa of Rosenmüller
Oropharynx	Oropharyngeal isthmus	Palatine tonsils, posterior 1/3 of tongue (lingual tonsil), soft palate, posterior pharyngeal wall
Laryngopharynx (hypopharynx)	Laryngeal inlet	Pyriform sinuses, post-cricoid region, posterior pharyngeal wall; continues to esophagus at C6

Muscular Wall

The pharyngeal wall consists of an outer circular layer (the constrictors) and an inner longitudinal layer:

Constrictor muscles (three overlapping constrictor muscles):
- Superior constrictor — arises from the pterygomandibular raphe and medial pterygoid plate; forms the lateral wall of the oropharynx and is directly lateral to the palatine tonsil
- Middle constrictor — arises from the hyoid bone
- Inferior constrictor — arises from the thyroid and cricoid cartilages; its lowest fibers (cricopharyngeus) form the upper esophageal sphincter
Longitudinal muscles: stylopharyngeus (CN IX), palatopharyngeus, salpingopharyngeus — these elevate the pharynx and larynx during swallowing

Nerve Supply

Motor: pharyngeal plexus (CN IX, X) — all muscles except stylopharyngeus (CN IX alone)
Sensory: nasopharynx — CN V2; oropharynx — CN IX (glossopharyngeal); hypopharynx — CN X (internal laryngeal branch)

Blood Supply

Ascending pharyngeal artery (branch of external carotid), tonsillar branch of facial artery, dorsal lingual artery, greater palatine artery

Lymphoid Ring (Waldeyer's Ring)

A ring of lymphoid tissue surrounding the pharyngeal inlet, comprising:

Pharyngeal tonsil (adenoid) — nasopharynx roof
Tubal tonsils — around Eustachian tube openings
Palatine tonsils (the "tonsils") — tonsillar fossae of oropharynx
Lingual tonsils — posterior tongue base

2. Physiology of the Pharynx

The pharynx serves three major physiological functions:

Deglutition (Swallowing)

The pharyngeal phase of swallowing is rapid (~1 second) and involuntary:

The soft palate elevates (levator veli palatini) to close the pharyngeal isthmus, sealing off the nasopharynx and preventing nasopharyngeal regurgitation
The pharyngeal constrictors contract in a sequential superoinferior wave, propelling the bolus
The larynx is elevated (longitudinal muscles), the epiglottis deflects posteriorly, and the vocal folds adduct to protect the airway
The cricopharyngeus (UES) relaxes to allow entry of the bolus into the esophagus

Respiratory Function

The pharynx is the shared aerodigestive passage; the soft palate acts as a "flutter valve" — it swings up to seal the nasopharynx from the oropharynx (during swallowing) and down to seal the oropharynx from the oral cavity.

Phonation & Resonance

The pharyngeal cavity acts as a resonating chamber for voice. Velopharyngeal closure (soft palate against posterior pharyngeal wall) is essential for non-nasal speech sounds.

Eustachian Tube Regulation

The nasopharynx contains the pharyngeal openings of the Eustachian tubes; the salpingopharyngeus and tensor veli palatini regulate middle ear pressure equalization during swallowing and yawning.

3. Pharyngeal Spaces

The pharynx is surrounded by several fascially defined potential spaces that are clinically important as routes for spread of infection.

Key Deep Neck Spaces

Space	Boundaries	Contents	Communicates With
Peritonsillar	Medial: palatine tonsil; Lateral: superior constrictor	Loose connective tissue; tonsillar branches of lingual, facial, ascending pharyngeal vessels	Parapharyngeal
Parapharyngeal	Superior: middle cranial fossa base; Inferior: hyoid; Anterior: pterygomandibular raphe; Posterior: prevertebral fascia; Medial: superior constrictor; Lateral: deep lobe of parotid + medial pterygoid	Fat, lymph nodes, internal maxillary artery, auriculotemporal/lingual/inferior alveolar nerves, deep lobe parotid, internal carotid, internal jugular, CN IX–XII, superior cervical sympathetic	Peritonsillar, submandibular, visceral, retropharyngeal, carotid, masticator, parotid spaces
Retropharyngeal	Between posterior visceral fascia (buccopharyngeal) and alar fascia; extends from skull base to T1–T2	Loose connective tissue, lymph nodes of Rouvière (present in children <5 yr)	Danger space, mediastinum (allows inferior spread)
Submandibular	Superior: floor of mouth mucosa; Inferior: digastric; divided by mylohyoid into sublingual (superior) and submaxillary (inferior) compartments	Submandibular gland, Wharton duct, lingual nerve, hypoglossal nerve, facial vessels	Parapharyngeal, sublingual

The parapharyngeal space is the central crossroads — virtually all deep neck spaces communicate with it, making it the key space for spread of infection from peritonsillar, dental, and pharyngeal sources.

4. Acute Diseases of the Pharynx

4A. Primary Angina (Acute Tonsillitis / Pharyngitis)

"Primary angina" refers to acute inflammation of the tonsils and/or pharynx as the primary (de novo) disease process, not secondary to systemic illness.

Acute Pharyngotonsillitis

Etiology:

Most common: Group A beta-hemolytic Streptococcus (GABHS) — Streptococcus pyogenes
Viral: adenovirus (most common overall cause of pharyngitis), EBV (infectious mononucleosis), HSV, parainfluenza, rhinovirus
Other bacterial: Staphylococcus aureus, Haemophilus influenzae, Fusobacterium necrophorum

Clinical features:

Sore throat, odynophagia, fever (often >38.5°C)
Tonsillar erythema and exudate (follicular or membranous)
Tender cervical lymphadenopathy (jugulodigastric nodes)
Uvular erythema and edema

Centor/McIsaac criteria for GABHS (1 point each):

Tonsillar exudate
Tender anterior cervical lymphadenopathy
Fever (history or measured)
Absence of cough (+1 for age <15; −1 for age >45)

Diagnosis: Rapid strep antigen test; throat culture (gold standard)

Treatment:

Bacterial: Penicillin V or amoxicillin × 10 days (first-line); clindamycin or azithromycin in penicillin allergy
Symptomatic: NSAIDs, corticosteroids (single-dose dexamethasone reduces duration of pain)
Viral: supportive care

Acute Follicular vs. Lacunar Tonsillitis

Follicular: white-yellow spots at tonsillar crypts (purulent follicles)
Lacunar: coalescing exudate covering tonsillar surface within crypts (lacunae)
Phlegmonous (parenchymal): diffuse tonsillar infiltration — precursor to abscess

4B. Secondary Angina

"Secondary angina" describes tonsillopharyngeal inflammation as a manifestation of a systemic disease — the tonsils/pharynx are involved secondarily.

Key causes:

Disease	Characteristic Features
Infectious mononucleosis (EBV)	Severe membranous tonsillitis, posterior cervical lymphadenopathy, hepatosplenomegaly, heterophile antibodies (Monospot), atypical lymphocytes; treat with corticosteroids — avoid ampicillin (maculopapular rash)
Agranulocytosis (drug-induced, hematological)	Necrotic/ulcerated tonsils without suppuration, high fever, no pus; neutropenia on CBC; treat underlying cause
Diphtheria (Corynebacterium diphtheriae)	Tough grey-white pseudomembrane extending beyond tonsil margins (bleeds on removal), bull-neck lymphadenopathy, toxin-mediated myocarditis and neuropathy; treat with antitoxin + penicillin/erythromycin
Vincent's angina (acute necrotizing ulcerative tonsillitis)	Mixed fusospirochetal infection (Fusobacterium + Borrelia vincenti); unilateral necrotic ulcer with grayish membrane, foul odor, no significant fever; treat with penicillin + metronidazole
Scarlet fever	GABHS pharyngitis + sandpaper rash, strawberry tongue, Pastia lines
Leukemia/lymphoma	Tonsillar enlargement with ulceration; pancytopenia; bone marrow biopsy
Syphilis	Painless ulcer (primary chancre on tonsil) or mucous patch (secondary)

5. Peritonsillar Abscess

Peritonsillar abscess (PTA) is the most common deep neck space infection in adults and represents the most frequent complication of acute tonsillitis.

Pathophysiology

PTA is a purulent infection of the Weber glands (minor salivary glands) in the potential space between the tonsil capsule and the superior constrictor muscle. It most commonly forms in the superior pole of the peritonsillar space. It usually follows an episode of acute tonsillitis but can arise de novo.

Microbiology: polymicrobial — aerobic (Streptococcus pyogenes, Staphylococcus aureus, H. influenzae) and anaerobic (Fusobacterium, Prevotella, Peptostreptococcus) organisms.

Clinical Features

Trismus — the hallmark sign (spasm of pterygoid muscles due to proximity of superior constrictor; best single clinical indicator)
Severe unilateral throat pain, often with referred otalgia (via CN IX/X)
"Hot potato" (muffled) voice — velopharyngeal dysfunction from soft palate swelling
Dysphagia and drooling
High fever, malaise
Uvular deviation to the contralateral side
Unilateral peritonsillar bulge with displacement of the tonsil medially and inferiorly
Ipsilateral jugulodigastric lymphadenopathy

Diagnosis

Clinical in most cases
Needle aspiration — both diagnostic and therapeutic; pus confirms abscess vs. cellulitis (peritonsillar cellulitis does not yield pus)
CT scan of neck with contrast — not routinely required but indicated if: clinical picture is unclear, spread to parapharyngeal/retropharyngeal space is suspected, or patient cannot open mouth for examination. CT distinguishes abscess (rim-enhancing fluid collection) from phlegmon.

Treatment

Drainage — mainstay of treatment:
- Needle aspiration (office procedure, high success rate)
- Incision and drainage (I&D) under local anesthesia
- Quinsy tonsillectomy (tonsillectomy during acute infection — used when I&D fails or severe trismus)
Intravenous antibiotics — broad-spectrum covering streptococci and anaerobes (e.g., ampicillin-sulbactam, or penicillin + metronidazole); clindamycin for penicillin allergy
Corticosteroids (IV dexamethasone) — reduce inflammation, pain, and trismus; shorten hospital stay
Hydration and analgesia

Recurrence rate: ~17%. Tonsillectomy is recommended after a second episode of PTA, or in children with recurrent tonsillitis.

Complications

Complication	Mechanism
Parapharyngeal abscess	Rupture of PTA through superior constrictor into parapharyngeal space
Retropharyngeal abscess	Further posterior spread
Mediastinitis	Inferior spread via retropharyngeal/danger space — life-threatening
Airway obstruction	Progressive swelling displacing tongue base; emergency
Jugular vein thrombophlebitis	Lemierre syndrome (Fusobacterium necrophorum septic thrombophlebitis of internal jugular vein)
Carotid artery erosion / pseudoaneurysm	Rare, catastrophic
Aspiration pneumonia	Abscess rupture
Endocarditis / septicemia	Bacteremia
Nephritis	Streptococcal antigen-mediated

Summary Table: Acute Pharyngeal Diseases

Condition	Key Organism	Hallmark Feature	Treatment
Streptococcal tonsillitis	GABHS	Exudate, tender LN, no cough	Penicillin V × 10 days
Infectious mononucleosis	EBV	Membranous tonsillitis + splenomegaly	Supportive; steroids; avoid ampicillin
Diphtheria	C. diphtheriae	Grey pseudomembrane beyond tonsil margin	Antitoxin + antibiotic
Vincent's angina	Fusobacterium + spirochetes	Unilateral necrotic ulcer, foul odor	Penicillin + metronidazole
Agranulocytosis	— (secondary)	Necrotic tonsils, no pus, severe neutropenia	Treat underlying cause
Peritonsillar abscess	Polymicrobial	Trismus + uvular deviation + muffled voice	Drain + IV antibiotics ± steroids

Sources: Gray's Anatomy for Students (Elsevier, 2023); K.J. Lee's Essential Otolaryngology, 11e; Cummings Otolaryngology Head and Neck Surgery, 7e

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