Pharynx: Anatomy

Development

Formation of the pharyngeal (branchial) apparatus is during the 4th and 5th weeks of development.

The pharyngeal apparatus consists of:

• Arches
• Pouches
• Clefts
• Membranes that contribute to the development of the head and neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess

Pharyngeal musculature develops from the 3rd, 4th, and 6th arches:

• The 3rd pharyngeal arch gives rise to the stylopharyngeus muscle.
• The remaining muscles (constrictor and longitudinal groups) emerge from the 4th and 6th arches.
• Of note, the 5th pharyngeal arch involutes early in development and does not contribute to fetal development.

Gross Anatomy

Characteristics

• 12 cm (5 inch inches) long
• Extends from the cranial base to the inferior border of the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology anteriorly and to the inferior border of the C6 vertebra posteriorly
• The pharynx is widest (approximately 5 cm) opposite the hyoid and narrowest (approximately 1.5 cm) at its inferior end, where it is continuous with the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy.

Divisions

• Nasopharynx:
  • From the base of the skull Base of the skull The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface. Skull: Anatomy to the upper surface of the soft palate Soft palate A movable fold suspended from the posterior border of the hard palate. The uvula hangs from the middle of the lower border. Palate: Anatomy
  • Contains adenoids in the posterior wall
  • Has a respiratory function as it is the posterior extension Extension Examination of the Upper Limbs of the nasal cavities
  • The nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal) opens into the nasopharynx through 2 choanae.
• Oropharynx:
  • Has a digestive function
  • Extends from the soft palate Soft palate A movable fold suspended from the posterior border of the hard palate. The uvula hangs from the middle of the lower border. Palate: Anatomy to the superior border of the epiglottis Epiglottis A thin leaf-shaped cartilage that is covered with laryngeal mucosa and situated posterior to the root of the tongue and hyoid bone. During swallowing, the epiglottis folds back over the larynx inlet thus prevents foods from entering the airway. Larynx: Anatomy
  • Contains the palatine tonsils Tonsils Tonsillitis in the lateral walls
  • Boundaries:
    • Soft palate Soft palate A movable fold suspended from the posterior border of the hard palate. The uvula hangs from the middle of the lower border. Palate: Anatomy superiorly
    • Base of the tongue Tongue The tongue, on the other hand, is a complex muscular structure that permits tasting and facilitates the process of mastication and communication. The blood supply of the tongue originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy inferiorly
    • Palatoglossal and palatopharyngeal arches laterally
• Laryngopharynx:
  • Caudal region of the pharynx
    • Starts: superior border of the epiglottis Epiglottis A thin leaf-shaped cartilage that is covered with laryngeal mucosa and situated posterior to the root of the tongue and hyoid bone. During swallowing, the epiglottis folds back over the larynx inlet thus prevents foods from entering the airway. Larynx: Anatomy
    • Ends: inferior portion of the cricoid cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology
    • Leads to the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy
  • Lies posterior to the larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx: Anatomy → connects via the laryngeal inlet on the anterior wall
  • Piriform recesses (also called sinuses) are small cavities on either side of the laryngeal inlet.

Muscles of the pharynx

Constrictor muscles constitute the outer circular layer of muscle. During swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility, constrictor muscles constrict to propel the food bolus downward.

• Superior constrictor muscle
• Middle constrictor muscle
• Inferior constrictor muscle

Longitudinal muscles constitute the inner muscular layer and play a role in elevating the pharynx and larynx Larynx The larynx, also commonly called the voice box, is a cylindrical space located in the neck at the level of the C3-C6 vertebrae. The major structures forming the framework of the larynx are the thyroid cartilage, cricoid cartilage, and epiglottis. The larynx serves to produce sound (phonation), conducts air to the trachea, and prevents large molecules from reaching the lungs. Larynx: Anatomy during swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility and speaking.

• Palatopharyngeus
• Stylopharyngeus
• Salpingopharyngeus

Fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis

There are 2 layers to the pharyngeal fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis:

• Buccopharyngeal fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis:
  • Thin
  • Overlays the outside of the muscle wall
• Pharyngobasilar fascia Fascia Layers of connective tissue of variable thickness. The superficial fascia is found immediately below the skin; the deep fascia invests muscles, nerves, and other organs. Cellulitis:
  • Thick
  • Lines the inner side of the muscle wall
  • Provides structure → helps maintain airway Airway ABCDE Assessment patency

Neurovasculature

• Arterial blood supply:
  • Tonsillar artery (branch of the facial artery)
  • Lingual artery Lingual artery Lips and Tongue: Anatomy
  • Ascending palatine artery
  • Descending palatine artery
  • Ascending pharyngeal artery
• Pharyngeal veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology join to form a plexus that drains:
  • Superiorly → pterygoid plexus ( infratemporal fossa Infratemporal fossa The compartment that lies posterior to the maxilla and inferior to the side wall of the skull deep to the ramus of the mandible. It contains several facial nerves and the carotid arteries and the jugular veins. Skull: Anatomy)
  • Inferiorly → facial and internal jugular veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology
• Lymph Lymph The interstitial fluid that is in the lymphatic system. Secondary Lymphatic Organs drains into the deep cervical nodes, which include:
  • Retropharyngeal nodes
  • Paratracheal nodes
  • Infrahyoid nodes
• Innervation from branches off of:
  • Vagus nerve (cranial nerve (CN) X)
  • Glossopharyngeal nerve (CN IX)

Microscopic Anatomy and Function

• Stratified squamous nonkeratinizing epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology
• Lacks muscularis mucosa and submucosa
• The epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology rests on the lamina propria Lamina propria Whipple’s Disease containing a thick layer of longitudinally oriented elastic Elastic Connective Tissue: Histology fibers (a useful diagnostic feature).
• The muscularis externa is composed of irregularly arranged skeletal muscle, which represents the longitudinal and constrictor muscles of the pharynx.
• Function and role in deglutition: swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility → elevator skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology of the pharynx contract → pharynx raises and expands → receives bolus of food → elevator skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology of the pharynx relax → constrictor muscles of the pharynx contract → bolus is forced into the esophagus Esophagus The esophagus is a muscular tube-shaped organ of around 25 centimeters in length that connects the pharynx to the stomach. The organ extends from approximately the 6th cervical vertebra to the 11th thoracic vertebra and can be divided grossly into 3 parts: the cervical part, the thoracic part, and the abdominal part. Esophagus: Anatomy → initiation of peristalsis Peristalsis A movement, caused by sequential muscle contraction, that pushes the contents of the intestines or other tubular organs in one direction. Gastrointestinal Motility

Clinical Relevance

• Pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the pharynx. Affected individuals present with pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways, irritation, discomfort, and dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia of the throat. Pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis can result from bacterial or viral infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease. If a viral infection is suspected, the treatment is often supportive with hydration and with the use of NSAIDs NSAIDS Primary vs Secondary Headaches for pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways. If a bacterial infection is suspected, antibiotics are used as 1st-line therapy.
• Diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria: a bacterial infection caused by Corynebacterium diphtheriae Corynebacterium diphtheriae Diphtheria is an infectious disease caused by corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria. A sheet of thick, gray material covering the posterior pharyngeal wall is the hallmark of diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria. Erythromycin Erythromycin A bacteriostatic antibiotic macrolide produced by streptomyces erythreus. Erythromycin a is considered its major active component. In sensitive organisms, it inhibits protein synthesis by binding to 50s ribosomal subunits. This binding process inhibits peptidyl transferase activity and interferes with translocation of amino acids during translation and assembly of proteins. Macrolides and Ketolides is the 1st-line therapy for diphtheria Diphtheria Diphtheria is an infectious disease caused by Corynebacterium diphtheriae that most often results in respiratory disease with membranous inflammation of the pharynx, sore throat, fever, swollen glands, and weakness. The hallmark sign is a sheet of thick, gray material covering the back of the throat. Diphtheria; however, the infection can be prevented by vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination.
• Zenker diverticulum Diverticulum A pouch or sac opening from the colon. Diverticular Disease: The inferior pharyngeal constrictor muscle subdivides into the thyropharyngeus and cricopharyngeus muscles. Intrapharyngeal pressure can increase and form a diverticulum Diverticulum A pouch or sac opening from the colon. Diverticular Disease if there is incoordination between the contraction and relaxation of these 2 muscles. The diverticulum Diverticulum A pouch or sac opening from the colon. Diverticular Disease serves as a reservoir Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli for the accumulation of food and can lead to dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming “stuck.” Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia. Other complications include gurgling, aspiration, foul breath, and the presence of a neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast.
• Pharyngeal cancer: cancer of the tissues of the pharynx. Pharyngeal cancer includes cancer of the nasopharynx, oropharynx, and hypopharynx. Most pharyngeal cancers are squamous cell carcinomas. Common symptoms include sore throat Sore throat Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis, pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or difficulty swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility, persistent ear pain Ear Pain Acute Otitis Media, lump in the neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess or throat, hoarseness Hoarseness An unnaturally deep or rough quality of voice. Parapharyngeal Abscess or changes in voice, nosebleeds Nosebleeds Bleeding from the nose. Granulomatosis with Polyangiitis, headaches, coughing up of blood, unexplained weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, constant bad breath Bad breath An offensive, foul breath odor resulting from a variety of causes such as poor oral hygiene, dental or oral infections, or the ingestion of certain foods. Oral Cancer, and jaw Jaw The jaw is made up of the mandible, which comprises the lower jaw, and the maxilla, which comprises the upper jaw. The mandible articulates with the temporal bone via the temporomandibular joint (TMJ). The 4 muscles of mastication produce the movements of the TMJ to ensure the efficient chewing of food. Jaw and Temporomandibular Joint: Anatomy stiffness. Pharyngeal cancer is treated with surgical resection.