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ANATOMY OF THE PHARYNX: HEAD AND NECK REGION
Mansurova Dilorom Aslonovna
Senior lecturer of the Alfraganus University
Orcid ID:0000-0003-1825-0369
Email: mansurovadilorom82@gmail.com
https://doi.org/10.5281/zenodo.14698821
Introduction
The pharynx, a central structure located in the midline of the neck, serves as a shared
pathway for the gastrointestinal tract (GIT) and the respiratory system, in addition to the oral
cavity. It is a funnel-shaped organ, wider at the upper end beneath the base of the skull and
narrower at its lower end at the level of the sixth cervical vertebra (C6), where it transitions
into the esophagus posteriorly and the larynx anteriorly. Its muscular and membranous
composition enables it to perform vital functions such as food swallowing, air conduction, and
voice production. Understanding its anatomy, embryology, neurovascular supply,
musculature, surgical implications, and clinical relevance is essential to appreciating its
significance.
Structure and Function
The pharynx is divided into three regions from top to bottom:
1.
Nasopharynx
: Located behind the posterior nasal apertures (choanae), it is exclusively
part of the respiratory system, channeling air from the nasal cavities. The lateral walls of the
nasopharynx feature the auditory (Eustachian) tubes, surrounded by mucous membrane
elevations called tubal elevations. These tubes connect to the middle ears, facilitating pressure
equalization and drainage.
2.
Oropharynx
: Positioned behind the oral cavity, this section directs the bolus toward the
laryngopharynx. During swallowing, the soft palate muscles close the choanae to prevent food
from entering the nasal cavity, while the epiglottis seals the laryngeal inlet, ensuring food
does not enter the airway.
3.
Laryngopharynx
: Located behind the laryngeal inlet, it receives the bolus from the
oropharynx and transfers it into the esophagus for digestion. Air passes through the
nasopharynx and oropharynx before entering the laryngopharynx, ultimately reaching the
larynx and trachea for respiratory conduction.
Embryology
The pharynx originates during the fourth and fifth weeks of gestation from the
pharyngeal (branchial) apparatus, which comprises arches, pouches, clefts, and membranes
essential for head and neck development. The third, fourth, and sixth pharyngeal arches
contribute to the musculature of the pharynx. The third arch forms the stylopharyngeus
muscle, while the fourth and sixth arches give rise to the constrictor and longitudinal muscle
groups. Neurovascular bundles passing through these arches provide corresponding nerve
and blood supply.
Blood Supply and Lymphatics
The pharynx receives oxygenated blood from four branches of the external carotid
artery: the ascending pharyngeal, tonsillar (a branch of the facial artery), maxillary, and
lingual arteries. Venous blood drains through pharyngeal veins into the internal jugular vein.
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Lymphatic drainage is primarily directed to the deep cervical lymph nodes (DCLNs) either
directly or indirectly via retropharyngeal or paratracheal nodes.
The Waldeyer ring, a lymphoid structure, surrounds the entrance to the GIT and
respiratory tract. It includes:
Pharyngeal tonsils
(adenoids) at the roof of the nasopharynx.
Palatine and tubal tonsils
along the lateral walls.
Lingual tonsils
at the tongue's posterior surface.
Nerves
The pharynx receives sensory (afferent) and motor (efferent) innervation:
Sensory supply
:
o
Nasopharynx
: Maxillary division of the trigeminal nerve (CN V2).
o
Oropharynx
: Glossopharyngeal nerve (CN IX).
o
Laryngopharynx
: Internal laryngeal nerve, a branch of the superior laryngeal nerve (CN
X).
Motor supply
:
o
All pharyngeal muscles, except the stylopharyngeus, are innervated by the vagus nerve
(CN X).
o
The stylopharyngeus is innervated by the glossopharyngeal nerve (CN IX).
This comprehensive anatomical, embryological, and functional overview underscores
the pharynx's critical role in integrating the GIT and respiratory systems.
Muscles of the Pharynx
The pharyngeal musculature plays a vital role in enabling the pharynx to perform
essential functions, including swallowing and airway management. The muscles are
categorized into two groups:
1.
Constrictor Muscles
:
o
Superior Constrictor
: Originates from the medial pterygoid plate, pterygoid hamulus,
pterygomandibular ligament, and mylohyoid line of the mandible. It inserts at the pharyngeal
tubercle of the occipital bone and the pharyngeal raphe. It assists in soft palate closure during
swallowing and propels the bolus downward.
o
Middle Constrictor
: Originates from the stylohyoid ligament and the lesser and greater
cornua of the hyoid bone. It inserts at the pharyngeal raphe, aiding in downward propulsion
of the bolus.
o
Inferior Constrictor
: Originates from the lamina of the thyroid cartilage and the cricoid
cartilage. It inserts into the pharyngeal raphe and facilitates bolus movement into the
esophagus.
o
Cricopharyngeus Muscle
: Derived from the inferior constrictor, it functions as a
sphincter at the lower end of the pharynx, preventing esophageal reflux into the pharynx.
2.
Longitudinal Muscles
:
o
Stylopharyngeus
: Originates from the styloid process of the temporal bone and inserts
on the posterior surface of the thyroid cartilage. It elevates the pharynx during swallowing.
o
Palatopharyngeus
: Arises from the palatine aponeurosis and inserts into the thyroid
cartilage. It aids in pharyngeal elevation and bolus propulsion, pulling the palatopharyngeal
arches medially during contraction.
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o
Salpingopharyngeus
: Originates from the auditory tube and merges with the
palatopharyngeus. It assists in elevating the pharynx during swallowing.
Physiological Variants
The pharynx is normally positioned in the midline of the neck, allowing it to efficiently
convey air and food. However, minor anatomical and physiological variations are observed,
particularly in the musculature:
Additional attachments of the longitudinal muscle group may extend to the palatine
tonsils, epiglottis, arytenoid, and thyroid cartilages.
The
salpingopharyngeus muscle
is absent in approximately 37% of individuals, with
its absence more commonly observed in thinner individuals.
Surgical Considerations
Surgical procedures involving the pharynx require precision due to its complex anatomy
and the proximity of vital neurovascular bundles. Key considerations include:
1.
Airway and Swallowing Assessment
:
o
Breathing difficulties, dysphagia, and malignancies in the pharyngeal region often
necessitate surgical intervention. Postoperative assessments are critical for ensuring effective
airway management and swallowing function.
o
Feeding tubes may be employed when oral food passage is not possible.
2.
Obstructive Sleep Apnea Treatment
:
o
Lateral pharyngoplasty often requires the preservation of the
stylopharyngeus muscle
to optimize outcomes.
3.
Airway Management
:
o
The pharynx may be bypassed via endotracheal intubation or controlled with other
airway management devices. In emergencies where these methods fail, a
cricothyroidotomy
can be life-saving.
4.
Tonsil Enlargement and Trauma
:
o
Enlarged tonsils or trauma causing airway obstruction require prompt intervention.
Severe cases, such as airway compromise due to elevated pressure or trauma, may necessitate
procedures like
thyroidectomy
or immediate airway clearance.
By understanding the structural, functional, and clinical aspects of the pharyngeal
muscles, surgical interventions can be performed more effectively, ensuring patient safety and
optimal outcomes.
Clinical Significance
Pharyngitis
Pharyngitis, commonly referred to as "sore throat," involves inflammation of the
pharynx and is most frequently caused by viral infections. Symptoms typically include
discomfort, pain, irritation, and difficulty swallowing (dysphagia). Treatment usually involves
non-steroidal anti-inflammatory drugs (NSAIDs) for both adults and children, while aspirin is
an option for adults. If caused by
Streptococcus pyogenes
, specific diagnostic testing and
targeted treatment are required.
Dysphagia
Dysphagia, or difficulty swallowing, results from muscle weakness, nerve damage, or
underlying diseases. It can lead to complications such as aspiration of food or saliva,
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malnutrition, and dehydration. Dysphagia is particularly common in approximately 50% of
elderly patients and those with neurological disorders.
Adenoiditis
Adenoiditis is the inflammation of the adenoid lymphatic tissue located in the upper
nasopharynx, often secondary to infection. Patients typically experience symptoms
resembling a cold, including rhinorrhea (runny nose), nasal obstruction, and difficulty
breathing.
Sleep Apnea
During sleep, the pharyngeal muscles may become hypotonic (weak), potentially
allowing the airways to collapse and cause breathing difficulties. Factors contributing to sleep
apnea include obesity, generalized hypotonia, and macroglossia (an enlarged tongue).
Zenker's Diverticulum
Zenker's diverticulum occurs in the laryngopharynx at the Killian dehiscence, a
triangular gap between the inferior constrictor and cricopharyngeus muscles. Weakness or
hypotonia in this area can lead to herniation of the pharyngeal mucosa and submucosa,
forming a pouch. Food accumulation in this false diverticulum (confined to mucosa and
submucosa without muscle involvement) can cause complications such as dysphagia,
regurgitation, and aspiration.
Cricopharyngeal Achalasia
Cricopharyngeal achalasia is a rare condition where the cricopharyngeus muscle fails to
relax adequately during swallowing. This prevents the upper esophageal sphincter from
opening properly, resulting in food leakage, discomfort, and dysphagia. This dysfunction can
also contribute to the development of Zenker's diverticulum.
Understanding these clinical conditions emphasizes the importance of the pharynx in
maintaining proper airway and digestive function while highlighting the need for accurate
diagnosis and management of associated disorders
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