Oropharynx: What is it? Structure, Variations, Neurovascular Supply, Pathways of Cancer Spread and Clinical Complications

It communicates with the nasopharynx through the pharyngeal isthmus, extending posteriorly from the posterior border of the soft palate.

The oropharynx (including the tonsils and arches) is covered by a pink-red mucous membrane. Tonsils are distinguished by a pitted appearance and vary greatly in size between different people and with age.

It communicates with the oral cavity anteriorly through the oropharyngeal isthmus, demarcated by the palatoglossal arch, and includes the posterior aspect of the tongue. It communicates with the laryngopharynx, the limit of which is delimited by the superior border of the epiglottis.

The lateral walls of the oropharynx are different due to the presence of two arches. The palatoglossal arch, anteriorly, contains the palatoglossus muscle and forms the anterior border of the oropharynx.

Behind this arch is the palatopharyngeal arch, which contains palatopharyngeal. The space between these two arches is the tonsillar fossa. The volume that contains the arches and the tonsillar fossa bilaterally is known as the fauces.

Soft palate

The soft palate forms the boundary between the nasopharynx and the oropharynx. It is attached laterally to the walls of the nasopharynx / oropharynx. The anterior part is continuous with the hard palate.

The posterior border of the soft palate hangs freely and is distinguished by a conical inferior projection, the uvula. The soft palate curves downward as it passes backward.

The soft palate is covered on all surfaces by epithelium, which is of the upper respiratory pseudostratified type and inferiorly stratified squamous type. A large submucosal layer contains many glands.

In the center, various muscle attachments and the palatal aponeurosis shape the palate. The palatal aponeurosis is formed by the tendons of the tensor veli palatini, and is attached to the palatine bone anteriorly. It is thicker anteriorly and all other palatal muscles adhere to it.

palatine tonsil

The palatine tonsils are paired structures located in the tonsillar fossa, between the two arches of the oropharynx. They are ovoid in shape, generally larger in infancy, before middle age.

The tonsils rest on the tonsillar hemicapsule , a fibrous layer that is distinct from the underlying pharyngobasilar and superior constrictor fascia.

Tonsillar fossa

The tonsillar fossa is the space between the two arches of the oropharynx. It contains the palatine tonsil, the tonsillar hemicapsule, as well as the mucous membrane and underlying tissues. The floor of the tonsillar fossa is formed by the pharyngobasilar fascia and the superior constrictor.

The tonsillar fossa is important because of its close relationship with vascular and neuronal structures. From superior to inferior, these are the facial artery and the tonsillar branch, the external palatal vein, the glossopharyngeal nerve, and the pharyngeal plexus of the veins.

The descending palatal vein runs vertically in the posterior part of the fossa. The styloglossus and hyoglossus lie deeply to the pharyngobasilar fascia and superior constrictor.

Microscopic structure

The epithelium of the oropharynx (including the soft palate and tonsils) is squamous, non-keratinizing and stratified. The submucous and mucous glands are frequently seen, particularly on the underside of the soft palate (below the palatal aponeurosis).

Tonsils are characterized by an outer surface of non-keratinizing stratified squamous epithelium with 10-20 crypts penetrating their substance. The connective tissue forms partitions and is continuous with the lamina propria of the mucosa and the underlying pharyngobasilar fascia.

The crypts are lined with a mixture of non-keratinizing stratified squamous epithelium and reticulated epithelium. The last epithelium contains mesh-like cells through which the cells of the immune system can access the contents of the crypts.

Crypts are often clogged with bacteria, saliva, or other material.

The lymphoid tissue of the tonsil is divided into numerous categories. Lymphoid follicles are found along the septa of the connective tissue. Numerous IgA-producing B lymphocytes as well as T lymphocytes and antigen-presenting cells are located within the reticular epithelium.

Physiological variations

Swallowing is a major function of the oropharynx.

The first phase is voluntary, where the tongue pushes a bolus of food into the oropharynx. The bolus is held in the space between the epiglottis, the soft palate, and the base of the tongue before the second phase begins.

The second phase is rapid and involuntary. It involves elevation of the soft palate and widening of the oropharynx / laryngopharynx.

The suprahyoid and longitudinal pharyngeal muscles contract, elevating the larynx. These movements effectively occlude the nasopharynx at the pharyngeal isthmus, the oral cavity at the oropharyngeal isthmus, and the larynx at the laryngeal inlet.

The third phase is also involuntary, and consists of the sequential contraction of the constrictor muscles from superior to inferior. This pushes the food bolus into the esophagus.

Pathological variations

The tonsillectomy involves removing the palatine tonsils. The tonsillar hemicapsule divides between the underlying constrictor muscles and the pharyngobasilar fascia. The vessels are ligated as the capsule is removed.

Suministro neurovascular

Arterial supply

The arteries of the oropharynx are similar to those of the rest of the pharynx. Blood is obtained from the branches of the external carotid artery, particularly the ascending and ascending palatine arteries.

Blood in the tonsil travels in the tonsillar artery, a branch of the facial artery. A small amount of supply is derived from the dorsal lingual arteries and a branch from the ascending palatal artery.

Venous drainage

Venous blood from the oropharynx collects in a plexus outside the pharynx. The pharyngeal veins generally drain directly into the internal jugular, or alternatively into the maxillary or facial veins.

The veins of the soft palate usually pass laterally to empty into the pterygoid venous plexus.

Lymphatic

Lymphatic vessels arising from the palatine tonsils pass through the superior constrictor and terminate directly in the upper deep cervical nodes (II) or the retropharyngeal nodes (which often direct lymph to level II or III).

Lymph from the rest of the pharynx follows a similar path. Lymph from the soft palate may drain bilaterally to the upper cervical or submandibular nodes.

The posterior aspect of the tongue, frequently considered part of the oropharynx, drains bilaterally to the upper deep cervical ganglia (level II). Invasion of this structure by pharyngeal tumors requires consideration of bilateral neck irradiation.

Innervation

The oropharynx has a gill motor, visceral sensory motor, and special sensory innervation.

Branchial muscles of the soft palate and oropharynx

The muscles of the oropharynx are innervated by somatic motor fibers of the vagus nerve (X), in addition to the stylopharyngeal that is supplied by the glossopharyngeal nerve (IX).

The branchial muscles of the soft palate also receive somatic supply of branchial fluid from the vagus nerve, except for the tensor veli palatini, which is supplied by a branch of the maxillary division of the trigeminal nerve.

secretory innervation

Branches of the pterygopalatine ganglion innervate the small salivary glands of the soft palate and oropharynx. These initially arise from the greater petrosal nerve, a division of the facial nerve (VII).

Oropharyngeal sensation

Visceral sensory supply to the oropharynx (posterior and lateral walls, base of tongue) is also a function of the vagus nerve, except for the posterior third of the tongue which receives visceral supply from the glossopharyngeal nerve (IX).

The taste receptors in the soft palate are innervated by the vagus nerve. In the posterior third of the tongue, this function is performed by the glossopharyngeal nerve.

Routes of spread of cancer

Local invasion

Oropharyngeal tumors can have extensive local invasion into surrounding structures. This can include the laryngopharynx, oral cavity, or nasopharynx. Alternatively, lateral extension deep into the tissue of the tonsillar fossa can cause compression of the glossopharyngeal (IX) nerve.

The most extensive local invasion (stage T4) includes invasion of the palatine bone or mandible, larynx, and pterygoid muscles. The tumor may enclose the carotid artery (Stage T4b).

Lymphatic extension

The most common lymph nodes involved in oropharyngeal carcinoma are the retropharyngeal nodes and the upper deep cervical nodes (up to 75% of cases). Tier III and IV nodes are also involved more frequently than Tier I or V.

Hemotoxic

Distant hemotogenic spread of the malignancy is uncommon in the early stages of oropharyngeal carcinoma, but generally affects the lungs if it occurs.

Neurological extension

The oropharynx is extensively innervated by visceral motor and sensory nerves arising from the glossopharyngeal nerve and vagus nerve from the cranial nerves. Cancer can infiltrate these nerves and subsequently move to the posterior cranial fossa.

Pharyngeal functions

The main functions of the pharynx are respiratory and digestive in nature. The muscles of the pharynx assist in the swallowing mechanism and provide a path for food to move from the mouth to the esophagus.

When the tongue pushes the chewed food towards the back of the mouth, the windpipe closes and the food passes into the pharynx. Muscles work to swallow food and move it up the esophagus.

The pharynx allows inhaled air to pass from the nose into the larynx, windpipe, and then the lungs. The isthmus, which is the pathway that connects the nasal and oral pharynx, allows humans to breathe through the nose and mouth.

The pharynx works in conjunction with other speech-related muscles to produce sounds and also plays a role in sound resonance.

As it is connected to the ear cavity on both sides through the Eustachian tubes, this helps equalize the pressure created by the air on the eardrums.

Lymphoid tissues found in the pharynx play a small role in regulating the body’s immune system.

The lymphoid tissues that make up the tonsils control particles and microbes that enter the nose or throat and prevent them from mixing with air that enters the lungs or food that enters the stomach.

Clinical complications of the pharynx

Pharyngitis: refers to inflammation of the pharynx that causes swelling, redness, and pain during swallowing. Severe cases require antibiotics prescribed by the doctor.

Laryngopharyngeal reflux : This is common for those with gastric problems when stomach acids rise through the esophagus.

Tonsillitis – Palatine tonsils sometimes become inflamed with a bacterial or viral infection and then become really uncomfortable or painful. Lymph nodes are enlarged and there may be trouble speaking or swallowing. Usually a tonsillectomy is needed.

Throat paralysis : This situation can occur due to a throat infection and due to diseases such as rabies, polio, and diphtheria.

Pharyngeal cancer : this is another clinical complication of the pharynx, this form of throat cancer creates bleeding, pain in the neck and throat, caused by the sensation of lumps in the neck or throat and can lead to nasal obstruction, sore throat , earache, bleeding, swallowing problems, and sometimes deafness.

Treatment of pharyngitis

The most common disease caused in the pharynx is pharyngitis. If you have this problem, your doctor will examine your throat for gray or white patches.

The doctor will even check the nose and ear for swollen lymph nodes near the neck. If the doctor identifies a problem, then he will do a throat culture.

After the throat culture, the doctor would also perform a blood test to identify the actual cause of the pharyngitis. The blood sample is sent for tests to determine if you have mononucleosis or some other type of infection.

Most throat problems get better within a week. Antibiotics are usually prescribed to confirm that the risk of the ailment is completely rectified. In addition to pain relievers, the doctor suggests:

  • Eat cold, soft foods that are more liquid in consistency.
  • Avoid smoking.
  • Avoid hard candy, popsicles, ice cubes, and lozenges.
  • Gargle on a results base with warm, salty water.

epidemiology

The oropharynx is one of the most common causes of head and neck cancer in the United States. An estimated 11,000 to 13,000 new cases of oropharyngeal cancer are diagnosed in the United States each year.

The vast majority of these tumors are squamous cell carcinomas, a cancer that arises from squamous epithelial cells that line the upper aerodigestive tract.

Squamous cell carcinomas can also arise in many other sites, including the skin, lungs, bladder, and cervix, but tumor behavior and treatment options vary widely between different sites in the body.

Men are four times more likely than women to develop oropharyngeal squamous cell carcinoma (OPSCC), with an annual global risk of 6.2 per 100,000 men compared to 1.4 cases per 100,000 women.

The incidence in the US is highest among black and white men, and lowest among Hispanics, Native Americans, and Asian / Pacific Islanders.

Do I have a tumor of the oropharynx?

Cancers of the oropharynx commonly begin in the tonsil, soft palate, or tonsil-like tissue at the base of the tongue.

Malignant tumors usually start in the lining of the mucous membrane (called squamous cell carcinoma) but can also appear in white blood cells (lymphoma) or glandular cells (adenocarcinoma).

Early signs and symptoms of oropharyngeal tumors include the development of asymmetric tonsils, pain such as a persistent sore throat, particularly pain that shoots into one ear, difficulty or pain when swallowing, a muffled sound in the voice, or a lump in the neck. .

Your doctor may be able to see a tumor in this area without special equipment, but may need special mirrors or fiber optic telescopes. The doctor may also need to feel the back of the throat with a gloved finger.

A biopsy is necessary to confirm a diagnosis. Often times, this area must be biopsied with the patient under general anesthesia. Treatment of oropharyngeal cancer often consists of surgery or radiation therapy with or without chemotherapy.

Small tumors can be surgically removed without loss of throat function. Larger tumors can be surgically removed if necessary (for example, if chemotherapy and radiation fail) but these surgeries require reconstruction of the throat and can impair swallowing ability.

Oropharyngeal cancer usually appears in people between the ages of 45 and 70 who have abused tobacco and alcohol. The human papillomavirus has been found in more than half of these tumors and probably plays a role in the development of cancer. This virus could be transmitted through sexual contact.