Clinical anatomy, physiologs of the pharynx. Pharyngeal spaces. Acute diseases 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

Three-dimensional diagram of the pharynx showing its three regions — nasopharynx, oropharynx, and laryngopharynx — in relation to nasal cavities, oral cavity, larynx, trachea, and esophagus.

Fig. 8.201 — Pharynx. Gray's Anatomy for Students

The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities to the larynx and esophagus. It is attached above to the base of the skull and is continuous below (at approximately vertebral level C6) with the esophagus. The pharyngeal cavity is a common pathway for both air and food. — Gray's Anatomy for Students

Subdivisions

Region	Anterior relationship	Key opening
Nasopharynx	Posterior apertures of nasal cavities (choanae)	Pharyngotympanic (Eustachian) tubes on lateral walls
Oropharynx	Posterior wall of oral cavity	Oropharyngeal isthmus (palatoglossal arches)
Laryngopharynx (Hypopharynx)	Posterior aspect of larynx	Laryngeal inlet; continuous with esophagus inferiorly

Skeletal Framework & Muscles

Superior margin attaches to the skull base (pharyngeal tubercle of occiput, petrous temporal, medial pterygoid plates, pterygomandibular raphe, mandible, and hyoid).
The posterior midline is formed by the pharyngeal raphe — a vertical fibrous cord to which the bilateral constrictor muscles attach.

Constrictor muscles (all insert into the pharyngeal raphe posteriorly):

Superior constrictor — arises from the pterygomandibular raphe and nearby bone
Middle constrictor — arises from the hyoid bone and stylohyoid ligament
Inferior constrictor — arises from the oblique line of the thyroid cartilage and cricoid cartilage; its lower fibers (cricopharyngeus) act as the upper esophageal sphincter

Longitudinal (elevator) muscles — salpingopharyngeus, stylopharyngeus, palatopharyngeus — all pass inside the constrictors and act to elevate and widen the pharynx during swallowing.

Nerve Supply

Motor: Pharyngeal plexus (CN X + CN IX + sympathetics)
Sensory: CN IX (oropharynx & nasopharynx), CN X (laryngopharynx), CN V2 (roof of nasopharynx)

Lymphoid Tissue — Waldeyer's Ring

A ring of lymphoid tissue guards the pharyngeal entrance:

Pharyngeal tonsil (adenoids) — roof of nasopharynx
Tubal tonsils — around pharyngotympanic tube openings
Palatine tonsils — in tonsillar fossae of oropharynx, between palatoglossal and palatopharyngeal arches
Lingual tonsil — posterior tongue base

Palatine tonsil vasculature (important for tonsillectomy): chief arterial supply is the tonsillar artery (branch of the facial artery); additional supply from ascending pharyngeal, lingual, greater palatine, and ascending palatine arteries. The external palatine (paratonsillar) vein passes between the tonsil and superior constrictor — injury during tonsillectomy causes hemorrhage. — Gray's Anatomy for Students

2. PHYSIOLOGY OF THE PHARYNX

The pharynx serves three major functions:

Respiration

The pharynx is part of the upper airway. The soft palate functions as a "flutter valve":

Elevates to close the pharyngeal isthmus → seals nasopharynx from oropharynx (during swallowing/speaking)
Depresses to close the oropharyngeal isthmus → seals oral cavity from oropharynx

The cricopharyngeus muscle (lower inferior constrictor) acts as the upper esophageal sphincter, normally closed at rest to prevent air entry into the esophagus.

Deglutition (Swallowing) — Pharyngeal Phase

The pharyngeal phase of swallowing involves:

Soft palate elevation closes the nasopharynx (prevents nasal regurgitation)
Sequential contraction of pharyngeal constrictors (peristaltic wave)
Larynx elevation and epiglottic deflection protects the airway
Cricopharyngeus relaxation allows the bolus to pass into the esophagus

Phonation

The pharynx acts as a resonating chamber. The nasopharynx contributes to nasal resonance; its exclusion by soft palate elevation produces oral resonance.

3. PHARYNGEAL SPACES

Detailed understanding of the fascial spaces surrounding the pharynx is essential for understanding the spread of infection, abscesses, and tumors. — Cummings Otolaryngology

Parapharyngeal Space (PPS)

The anatomic epicenter of suprahyoid neck anatomy. A fibrofatty fascial space extending from the skull base to the hyoid bone.

Contents: fat, CN V3, internal maxillary artery, ascending pharyngeal artery, venous plexus
Shape: triangular in axial plane; hourglass in coronal plane
Significance: serves as a marker — displacement of the PPS indicates the fascial space of origin of a lesion. Because few lesions arise from the PPS itself, most lesions found there have spread secondarily from an adjacent space.
The fascial spaces arranged around the PPS: Pharyngeal Mucosal Space, Carotid Space, Parotid Space, Masticator Space, Retropharyngeal Space, Prevertebral Space

Pharyngeal Mucosal Space (PMS)

Lies medial to the PPS, anterior to the prevertebral space
Encompasses mucosal surfaces of nasopharynx and oropharynx, lymphoid (adenoidal) tissue, minor salivary glands, portions of constrictor muscles, and muscles of deglutition
Extends from skull base to lower margin of cricoid cartilage
Lesions here displace the PPS laterally

Retropharyngeal Space

Located between the posterior pharyngeal wall and the prevertebral fascia
Contains loose connective tissue and lymph nodes (particularly important in children — retropharyngeal lymphadenitis and abscess)
Extends from the skull base to approximately T3 (where the alar and visceral fascia fuse)
Clinically crucial: infection here can spread inferiorly into the posterior mediastinum ("danger space" route)

Danger Space

Lies between the alar and prevertebral fascia
Potential pathway for spread of infection from the neck directly into the posterior mediastinum — a life-threatening complication

Infrahyoid Retropharyngeal Space

The infrahyoid portion of the retropharyngeal space is clinically relevant for spread of hypopharyngeal infections and post-cricoid carcinoma invasion

Prevertebral Space

Between the prevertebral fascia and the vertebral column
Infections here (e.g., Pott's disease) can bulge anteriorly to displace the pharynx

4. ACUTE DISEASES OF THE PHARYNX

4A. Primary Angina (Acute Pharyngitis / Tonsillitis)

"Angina" (from Latin angere, to strangle) in this context refers to inflammatory disease of the tonsils and pharynx. Primary angina arises directly from pharyngeal infection, as opposed to secondary angina which is a manifestation of systemic disease.

Etiology

Viruses account for most cases of acute pharyngitis.

Pathogen	Disease	Estimated %
Rhinovirus	Common cold	15–20%
Adenovirus	Pharyngoconjunctival fever	6%
Herpes simplex virus	Gingivitis/stomatitis/pharyngitis	4%
Epstein-Barr virus	Infectious mononucleosis	<1%
Streptococcus pyogenes (GABHS)	Pharyngitis, tonsillitis, scarlet fever	10–23%
Fusobacterium necrophorum	Pharyngitis, Lemierre's syndrome	5–10%
Group C Streptococcus	Pharyngitis, tonsillitis	3–6%
Corynebacterium diphtheriae	Diphtheria	<1%

— Tintinalli's Emergency Medicine

Viral Pharyngitis

Features: vesicular or petechial pattern on soft palate and tonsils, cough, rhinorrhea, conjunctivitis, hoarseness. Generally self-limited. Treatment is supportive.

Bacterial Pharyngitis / Acute Tonsillitis

The most important bacterial cause is Group A beta-hemolytic Streptococcus (GABHS, S. pyogenes) — accounting for 10–23% of cases.

Classic features of GABHS pharyngitis (Centor criteria):

Tonsillar exudate
Tender anterior cervical lymphadenopathy
Fever
Absence of cough

Treatment: Penicillin (10-day course) remains first-line. Amoxicillin is an alternative (note: causes rash in EBV mononucleosis). For penicillin-allergic patients: clindamycin or azithromycin. — K.J. Lee's Essential Otolaryngology

Bacteriology of acute bacterial tonsillitis: S. pneumoniae, Group A beta-hemolytic Streptococcus (S. pyogenes), H. influenzae.

Secondary Angina

Secondary angina refers to tonsillopharyngeal inflammation as a manifestation of systemic disease:

Infectious mononucleosis (EBV) — exudative tonsillitis + splenomegaly + lymphadenopathy; ampicillin/amoxicillin causes characteristic maculopapular rash
Agranulocytosis / leukemia — ulcerative tonsillitis with necrosis in immunocompromised states
Diphtheria (C. diphtheriae) — grayish-white pseudomembrane on tonsils that bleeds when removed; risk of myocarditis and neuropathy
Herpangina (Coxsackievirus A) — gray-white vesicles/ulcers on soft palate, uvula, tonsillar pillars
Scarlet fever — GABHS-related; strawberry tongue, "sandpaper" rash, pharyngeal exudate

4B. Peritonsillar Abscess (Quinsy)

A peritonsillar abscess (PTA) is a collection of purulent material between the tonsillar capsule, the superior constrictor muscle, and the palatopharyngeus muscle. It is the most common deep space infection of the head and neck. — Tintinalli's Emergency Medicine

Pathogenesis

Develops primarily as a complication of acute tonsillitis, with pus accumulating in the loose areolar tissue of the peritonsillar space (between the tonsil and its bed). Risk factors include:

Chronic tonsillitis
Periodontal disease
Smoking
Multiple courses of antibiotics
Previous peritonsillar abscess

Epidemiology

Primarily affects adolescents and young adults (no clear seasonal variation)
Although typically polymicrobial, in patients aged 15–24 years Fusobacterium necrophorum is the most common organism in many communities
Other organisms: GABHS, Staphylococcus, oral anaerobes

Clinical Features

Oropharyngoscopic view of right peritonsillar abscess showing the PTA displacing the right tonsil medially and the swollen uvula deviated toward the normal left tonsil.

Right peritonsillar abscess (PTA): the infected right tonsil is displaced medially; the uvula is deviated toward the normal left tonsil. — Tintinalli's Emergency Medicine

Symptom/Sign	Frequency
Sore throat	99%
Fever	54%
Inferior and medial displacement of tonsil	46%
Contralateral deflection of uvula	43%
Tender cervical lymphadenopathy	41%
Trismus	32%
"Hot potato voice" (muffled voice)	Common
Otalgia, odynophagia, dehydration	Variable

Differential Diagnosis

Peritonsillar cellulitis (no pus formed yet — edema and erythema of tonsillar pillar without fluctuance)
Retropharyngeal abscess
Infectious mononucleosis
Lymphoma
Internal carotid artery aneurysm
Neoplasm

Diagnosis

Often clinical (history + examination)
Intraoral ultrasound: sensitivity 89–95%, specificity 79–100%
CT with contrast: indicated when spread beyond peritonsillar space is suspected (lateral neck space, retropharyngeal space involvement)

Treatment

Drainage is the mainstay:

Needle aspiration — ~90% effective after a single aspiration; performed at the most fluctuant point (usually superior pole)
Incision and drainage (I&D) — definitive; some evidence of lower recurrence rate vs. needle aspiration
Quinsy tonsillectomy (immediate tonsillectomy) — reserved for patients with strong indication for tonsillectomy (sleep apnea, recurrent tonsillitis, recurrent PTA), failure to improve, or airway compromise

Antimicrobials — 10-day course covering GABHS and oral anaerobes (including F. necrophorum):

First-line: Penicillin VK + metronidazole
Penicillin-allergic: clindamycin
Toxic/unable to take PO: piperacillin-tazobactam or equivalent IV
Adjunct: single IV dose dexamethasone 10 mg — improves severity and duration of pain

Follow-up: within 24–36 hours of aspiration.

Complications (if untreated or delayed)

Airway obstruction
Spontaneous rupture with aspiration of abscess contents
Hemorrhage (erosion of carotid sheath)
Spread to retropharyngeal or parapharyngeal space
Mediastinitis (via danger space)
Lemierre's syndrome (septic thrombophlebitis of internal jugular vein)
Post-streptococcal sequelae (rheumatic fever, glomerulonephritis)

Summary Table: Key Pharyngeal Spaces

Space	Location	Contents	Clinical Relevance
Parapharyngeal	Skull base → hyoid	Fat, CN V3, vessels	Epicenter marker; secondary tumor/abscess spread
Pharyngeal mucosal	Medial to PPS	Mucosa, tonsils, constrictors	Primary site of tonsillitis, nasopharyngeal carcinoma
Retropharyngeal	Post. pharynx wall → prevertebral fascia	Loose CT, lymph nodes	Retropharyngeal abscess, mediastinal spread
Danger space	Between alar & prevertebral fascia	Loose CT	Rapid mediastinitis pathway
Prevertebral	Anterior to vertebral column	Longus colli/capitis mm.	Pott's disease, cold abscess

Sources: Gray's Anatomy for Students; Cummings Otolaryngology Head and Neck Surgery; Tintinalli's Emergency Medicine; K.J. Lee's Essential Otolaryngology.

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