Pharynx
Deep within our throats lies a remarkable structure, the pharynx, a vital crossroads where the paths of air and food diverge and converge. Far more than just a simple tube, this muscular passageway plays a critical role in some of our most fundamental life processes—from the first breath we take to the words we speak and the meals we savor. Let's journey into the pharynx to uncover its intricate design and surprising functions. The pharynx is a unique anatomical marvel, serving as a shared pathway for both the respiratory and digestive systems in humans, orchestrating a complex dance to keep food out of our lungs. Structurally, it's a dynamic, muscular tube divided into three distinct regions, each with specialized features and defenses, including crucial lymphoid tissues like tonsils. Beyond humans, the pharynx shows incredible evolutionary diversity, from supporting gills in fish embryos to forming powerful, secondary jaws in some predatory fish.
AI Summary
Deep within our throats lies a remarkable structure, the pharynx, a vital crossroads where the paths of air and food diverge and converge. Far more than just a simple tube, this muscular passageway plays a critical role in some of our most fundamental life processes—from the first breath we take to the words we speak and the meals we savor. Let's journey into the pharynx to uncover its intricate design and surprising functions.
- The pharynx is a unique anatomical marvel, serving as a shared pathway for both the respiratory and digestive systems in humans, orchestrating a complex dance to keep food out of our lungs.
- Structurally, it's a dynamic, muscular tube divided into three distinct regions, each with specialized features and defenses, including crucial lymphoid tissues like tonsils.
- Beyond humans, the pharynx shows incredible evolutionary diversity, from supporting gills in fish embryos to forming powerful, secondary jaws in some predatory fish.
The Pharynx: A Crossroads of Life
The pharynx, often simply called the throat, is a muscular funnel located just behind your mouth and nasal cavity. It's a critical junction, acting as a passageway for both the air we breathe and the food we eat, guiding them to their correct destinations—the lungs and the stomach, respectively.
In humans, this dual role requires incredible coordination. A clever flap of cartilage, the epiglottis, acts like a traffic controller, swiftly closing off the airway when you swallow to prevent food from accidentally entering your trachea, or windpipe. It's a precise mechanism we often take for granted!
Anatomy of the Human Pharynx
The human pharynx isn't just one continuous tube; it's conventionally divided into three distinct sections, each with unique characteristics and functions. These segments work together seamlessly to ensure proper breathing and digestion.
Two sets of muscles give the pharynx its shape and allow it to perform its vital squeezing and lifting actions. An inner layer of longitudinal muscles helps shorten the pharynx, while an outer layer of circular 'constrictor' muscles pushes food downwards, much like a wave, towards the esophagus.
The Nasopharynx: Air's Entrance Hall
Highest of the three sections is the nasopharynx, situated behind the nasal cavity and above the soft palate. This region is exclusively for air passage, serving as part of the respiratory system's 'conducting zone' that filters, warms, and moistens incoming air.
Here, you'll find the adenoids, also known as pharyngeal tonsils, which are crucial lymphoid tissues—part of our immune system's first line of defense against airborne pathogens. These, along with other tonsils, form Waldeyer's tonsillar ring, an immune guardian around our air and food passages.
The nasopharynx also houses the opening of the auditory tube, or Eustachian tube, which connects to your middle ear. This connection is vital for equalizing air pressure, which is why a stuffy nose or ear infection can often make your ears feel blocked or sore.
The Oropharynx: Where Paths Converge
Next is the oropharynx, located behind the oral cavity and extending down to the level of the hyoid bone. This is where the air path from the nasopharynx merges with the food path from the mouth, making it a shared route for both air and food.
The oropharynx is home to the palatine tonsils, often simply called 'the tonsils,' nestled between two muscular arches at the back of your throat. These, too, are lymphoid tissues, playing a key role in identifying and fighting off infections entering through the mouth.
This section is lined with a tough, non-keratinized stratified squamous epithelium—a durable tissue designed to withstand the friction of food passing through, unlike the more delicate respiratory lining of the nasopharynx.
The Laryngopharynx: The Final Split
The lowest section, the laryngopharynx (or hypopharynx), is where the two pathways finally diverge. Below the epiglottis, it leads directly to the esophagus for food and to the larynx for air. During swallowing, food takes precedence, and air passage is temporarily halted.
Much like the oropharynx, the laryngopharynx is also lined with stratified squamous epithelium to handle the passage of food. Its intricate nerve supply, primarily from the vagus and glossopharyngeal nerves, ensures precise control over swallowing and protection of the airway.
Interestingly, nerves like 'Arnold's nerve' (a branch of the vagus) connect the laryngopharynx to the external ear canal. This explains why sometimes stimulation of the ear can trigger a cough, or why throat cancer can cause referred pain in the ear.
Beyond Swallowing: Speech and Resonance
While its primary roles are in digestion and respiration, the pharynx also plays a crucial, though often overlooked, role in human speech. It acts as a resonating chamber, shaping the sounds produced by your vocal cords and contributing to the unique qualities of your voice.
Some languages even utilize 'pharyngeal consonants'—sounds articulated by constricting the pharynx itself. This demonstrates the incredible versatility and muscular control of this part of our anatomy.
The Pharynx Across the Animal Kingdom
The pharynx is not unique to humans; it's a fundamental structure found in nearly all vertebrates and even many invertebrates, though its form and function can vary wildly across species, reflecting diverse evolutionary paths.
Pharyngeal Arches: Evolutionary Blueprints
In vertebrates, the pharynx develops from a series of six or more 'pharyngeal arches' during embryonic development. These arches are remarkable evolutionary blueprints, giving rise to diverse structures like jaw bones, ear ossicles, and even parts of the circulatory system.
Pharyngeal Jaws: A Second Set of Teeth
Perhaps one of the most astonishing variations is found in many fish species, such as the moray eel, which possess 'pharyngeal jaws.' These are a secondary set of jaws located deep within the throat, distinct from their primary oral jaws.
When a moray eel bites prey, it first captures it with its main jaws. Then, the pharyngeal jaws rapidly extend forward, bite down on the struggling prey, and retract, effectively pulling the meal deep into the esophagus. It's an incredibly efficient, and slightly terrifying, swallowing mechanism!
Invertebrate Pharynx: Simple Yet Essential
Even some invertebrates, like tardigrades (water bears) and nematode worms, have a pharynx. In nematodes, for instance, it's a muscular, triangular-shaped food pump that grinds food and delivers it directly to the intestines—a simple but vital organ for their survival.
Article
Pharynx
The pharynx (pl.: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates, though its structure can vary across species. The pharynx carries food to the esophagus and air to the larynx. The flap of cartilage called the epiglottis stops food from entering the larynx.
In humans, the pharynx is part of the digestive system and the conducting zone of the respiratory system. (The conducting zone—which also includes the nostrils of the nose, the larynx, trachea, bronchi, and bronchioles—filters, warms, and moistens air and conducts it into the lungs). The human pharynx is conventionally divided into three sections: the nasopharynx, oropharynx, and laryngopharynx (hypopharynx).
In humans, two sets of pharyngeal muscles form the pharynx and determine the shape of its lumen. They are arranged as an inner layer of longitudinal muscles, and an outer circular layer of pharyngeal constrictor muscles.
Structure
Nasopharynx
Upper respiratory system, with the nasopharynx, oropharynx and laryngopharynx labeled at left
The upper portion of the pharynx, the nasopharynx, extends from the base of the skull to the upper surface of the soft palate. It includes the space between the internal nares and the soft palate and lies above the oral cavity. The adenoids, also known as the pharyngeal tonsils, are lymphoid tissue structures located in the posterior wall of the nasopharynx. Waldeyer's tonsillar ring is an annular arrangement of lymphoid tissue in both the nasopharynx and oropharynx. The nasopharynx is lined by respiratory epithelium that is pseudostratified, columnar, and ciliated.
Polyps or mucus can obstruct the nasopharynx, as can congestion due to an upper respiratory infection. The auditory tube, which connects the middle ear to the pharynx, opens into the nasopharynx at the pharyngeal opening of the auditory tube. The opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere.
Details of torus tubarius
The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities. On its lateral wall is the pharyngeal opening of the auditory tube, somewhat triangular in shape and bounded behind by a firm prominence, the torus tubarius or cushion, caused by the medial end of the cartilage of the tube that elevates the mucous membrane. Two folds arise from the cartilaginous opening:
• the salpingopharyngeal fold, a vertical fold of mucous membrane extending from the inferior part of the torus and containing the salpingopharyngeus muscle. • the salpingopalatine fold, a smaller fold, in front of the salpingopharyngeal fold, extending from the superior part of the torus to the palate and containing the salpingopalatine muscle. The tensor veli palatini and levator veli palatini are lateral to the fold and do not contribute.
Oropharynx
The oropharynx lies behind the oral cavity, extending from the uvula to the level of the hyoid bone. It opens anteriorly, through the isthmus faucium, into the mouth, while in its lateral wall, between the palatoglossal arch and the palatopharyngeal arch, is the palatine tonsil. The anterior wall consists of the base of the tongue and the epiglottic vallecula; the lateral wall is made up of the tonsil, tonsillar fossa, and tonsillar (faucial) pillars; the superior wall consists of the inferior surface of the soft palate and the uvula. Because both food and air pass through the pharynx, a flap of connective tissue called the epiglottis closes over the glottis when food is swallowed to prevent aspiration. The oropharynx is lined by non-keratinized squamous stratified epithelium.
The HACEK organisms (Haemophilus, Actinobacillus actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, Kingella) are part of the normal oropharyngeal flora, which grow slowly, prefer a carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children. Fusobacterium is a pathogen.
Laryngopharynx
The laryngopharynx, (Latin: pars laryngea pharyngis), also known as hypopharynx, is the caudal part of the pharynx; it is the part of the throat that connects to the esophagus. It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (laryngeal) and digestive (esophageal) pathways. At that point, the laryngopharynx is continuous with the esophagus posteriorly. The esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly. During swallowing, food has the "right of way", and air passage temporarily stops. Corresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone. The laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall. Like the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium. It is innervated by the pharyngeal plexus and by the recurrent laryngeal nerve.
The vascular supply to the laryngopharynx includes the superior thyroid artery, the lingual artery and the ascending pharyngeal artery. The primary neural supply is from both the vagus and glossopharyngeal nerves. The vagus nerve provides an auricular branch also termed "Arnold's nerve" which also supplies the external auditory canal, thus laryngopharyngeal cancer can result in referred ear pain. This nerve is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing.
Function
Pharynx
The pharynx moves food from the mouth to the esophagus. It also moves air from the nasal and oral cavities to the larynx. It is also used in human speech, as pharyngeal consonants are articulated here, and it acts as a resonating chamber during phonation.
Clinical significance
Pharynx
Pharyngitis is the painful swelling of the throat. The oropharynx shown here is very inflamed and red.
Inflammation
Inflammation of the pharynx, or pharyngitis, is the painful inflammation of the throat.
Pharyngeal cancer
Pharyngeal cancer is a cancer that originates in the neck and/or throat.
Waldeyer's tonsillar ring
Waldeyer's tonsillar ring is an anatomical term collectively describing the annular arrangement of lymphoid tissue in the pharynx. Waldeyer's ring circumscribes the naso and oropharynx, with some of its tonsillar tissue located above and some below the soft palate (and to the back of the oral cavity). It is believed that Waldeyer's ring prevents the invasion of microorganisms from going into the air and food passages and this helps in the defense mechanism of the respiratory and alimentary systems.
Etymology
Pharynx
The word pharynx () is derived from the Greek φάρυγξ phárynx, meaning "throat". Its plural form is pharynges or pharynxes , and its adjective form is pharyngeal ( or ).
Other vertebrates
Pharynx
All vertebrates have a pharynx, used in both feeding and respiration. The pharynx arises during development in all vertebrates through a series of six or more outpocketings on the lateral sides of the head. These outpocketings are pharyngeal arches, and they give rise to a number of different structures in the skeletal, muscular, and circulatory systems. The structure of the pharynx varies across the vertebrates. It differs in dogs, horses, and ruminants. In dogs, a single duct connects the nasopharynx to the nasal cavity. The tonsils are a compact mass that points away from the lumen of the pharynx. In the horse, the auditory tube opens into the guttural pouch and the tonsils are diffuse and raised slightly. Horses are unable to breathe through the mouth as the free apex of the rostral epiglottis lies dorsal to the soft palate in a normal horse. In ruminants, the tonsils are a compact mass that points towards the lumen of the pharynx.
Pharyngeal arches
Pharyngeal arches are characteristic features of vertebrates whose origin can be traced back through chordates to basal deuterostomes who also share endodermal outpocketings of the pharyngeal apparatus. Similar patterns of gene expression can be detected in the developing pharynx of amphioxi and hemichordates. However, the vertebrate pharynx is unique in that it gives rise to endoskeletal support through the contribution of neural crest cells.
Pharyngeal jaws
An illustration of the pharyngeal jaws of a moray eel
Pharyngeal jaws are a "second set" of jaws contained within the pharynx of many species of fish, distinct from the primary (oral) jaws. Pharyngeal jaws have been studied in moray eels where their specific action is noted. When the moray bites prey, it first bites normally with its oral jaws, capturing the prey. Immediately thereafter, the pharyngeal jaws are brought forward and bite down on the prey to grip it; they then retract, pulling the prey down the eel's esophagus, allowing it to be swallowed.
Invertebrates
Pharynx
Invertebrates also have a pharynx. Invertebrates with a pharynx include the tardigrades, annelids and arthropods, and the priapulids (which have an eversible pharynx).
The "pharynx" of the nematode worm is a muscular food pump in the head, triangular in cross-section, that grinds food and transports it directly to the intestines. A one-way valve connects the pharynx to the excretory canal.
• Everted pharynx of Alitta virens (also known as Nereis virens), lateral view • Pharynx of the flatworm Prorhynchus fontinalis • Pharynx of the flatworm Platydemus manokwari visible as the worm feeds on a snail • Longitudinal section through the roundworm Caenorhabditis elegans showing the position of the pharynx in the animal body • Microscopic cross section through the pharynx of a larva from an unknown lamprey species
Additional images
Pharynx
• Nose and nasal • Coronal section of right ear, showing auditory tube and levator veli palatini muscle • The entrance to the larynx, viewed from behind • Deep dissection of human larynx, pharynx and tongue seen from behind • The nasopharynx, oropharynx, and laryngopharynx or larynx can be seen clearly in this sagittal section of the head and neck.