Chapter V - Human Anatomy
In anatomy, the throat is the part of the neck anterior to the vertebral column. It consists of the pharynx and larynx.
The throat contains various blood vessels, various pharyngeal muscles, the trachea (windpipe) and the esophagus. The hyoid bone is the only bone located in the throat of mammals.
The pharynx is the part of the digestive system and respiratory system of many animals immediately behind the mouth and in front of the esophagus. In mammals, it is where the digestive tract and the respiratory tract cross, commonly called the "throat" (which term may also include the larynx) The pharynx attaches to the larynx, which is the first element of the airways. The human pharynx is bent at a sharper angle than other mammal pharynges, enabling us to produce a wider variety of sounds, but also putting us in danger of choking.
The human pharynx is conventionally divided into three sections:
Nasopharynx: Lying behind the nasal cavity. Posterosuperiorly this extends from the level of the junction of the hard and soft palates to the base of skull, laterally to include the fossa of Rosenmueller. The inferior wall consists of the superior surface of the soft palate.
Oropharynx: Which lies behind the oral cavity. The anterior wall consists of the base of tongue and 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.
Hypopharynx: Which includes the pharyngoesophageal junction (postcricoid area), the piriform sinus, and the posterior pharyngeal wall.
The larynx (plural larynges), or voice-box, is an organ in the neck of mammals involved in protection of the trachea and sound production. The larynx houses the vocal cords, and is situated at the point where the upper tract splits into the trachea and the esophagus.
The structure of the larynx is mainly composed of cartilage bound by ligaments and muscle. At the front is the thyroid cartilage, creating the prominence of the Adam's apple in humans. The inferior horns (protrusions at the bottom rear of the thyroid cartilage) of the thyroid cartilage rest on a ring-shaped cartilage called the cricoid cartilage which connects the larynx to the trachea. The cricoid cartilage resembles a signet ring (narrow in front, broader in back). Above the larynx is the hyoid bone, by which (via various muscles and ligaments) the larynx is connected to the jaw and skull. These muscles move the larynx during swallowing. The hyoid is the only floating bone in the body; it is not 'attached' to any other bones. The epiglottis is another cartilage that extents upwards behind the back of the tongue and projects down through the hyoid bone. It connects to the thyroid cartilage just beneath the thyroid notch (the Adam's apple).
The space defined by these main cartilages can be divided roughly into the supraglottis at the top and the glottis.
The glottis is defined as the space between the vocal folds (more commonly known as vocal cords), which are located at the upper rim of the cricoid cartilage. They attach to the thyroid cartilage at the front, and to the Arytenoid cartilages at the back. These are two roughly tetrahedral cartilages responsible for pulling the vocal folds together and apart (adduction and abduction — see Anatomical terms of location). The glottis is the laryngeal area of most interest to speech researchers, as it is widely believed to be where most of the control of phonation and pitch goes on. The vocal folds are muscular masses coated with a mucous membrane which protects much of the respiratory tract from foreign particles. Their inner edges contain the vocal ligament.
The supraglottis is that part of the larynx above the glottis. It contains the ventricle of the larynx (laryngeal sinus), the ventricular folds (or false vocal folds), the epiglottis, and the aryepiglottal folds — two folds of connective tissue that connect the epiglottis to the arytenoid cartilages. Muscles in the aryepiglottal folds can pull the leaf-shaped epiglottis down, sealing the larynx and protecting the trachea below from foreign objects.
During swallowing the larynx (at the epiglottis and at the glottis) closes to prevent swallowed material entering the lungs, there is also a strong cough reflex to protect the lungs. Sensation is transferred by the superior laryngeal nerve (glottis and supraglottis) and the recurrent laryngeal nerve (subglottis and muscles), both branches of the vagus nerve.
While articulation of the sound (the fine manipulation that creates the many different vowel and consonant sounds of the world's languages) is achieved by the use of the teeth, tongue, palate, and lips, sound is generated in the larynx, and that is where pitch and volume are manipulated.
The vocal folds can be held close together (by adducting the arytenoid cartilages), so that they vibrate (see phonation). The muscles attached to the arytenoid cartilages control the degree of opening.
Vocal fold length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage, and by manipulating the tension of the muscles within the vocal folds. This causes the pitch produced during phonation to rise or fall.
There are several things that can cause a larynx to not function properly. Some symptoms are hoarseness, loss of voice, pain in the throat, and breathing difficulties. Acute laryngitis is the sudden inflammation and swelling of the larynx. It is caused by the common cold or by excessive yelling. It is not serious. Chronic laryngitis is caused by smoking, dust, frequent yelling, or prolonged exposure to polluted air. It is much more serious then acute laryngitis.
Ulcers are caused by the epiglottis hitting the trachea due to the making of certain sounds. Polyps and nodules are small bumps on the vocal cords caused by excessive yelling for a long time and prolonged exposure to cigarette smoke. Finally, two types of cancer, squamous cell carcinoma and verrucous carcinoma. These are both caused almost exclusively by repeated exposure to cigarette smoke.
The trachea, or windpipe, is a tube extending from the larynx to the bronchi in mammals, and from the pharynx to the syrinx in birds, carrying air to the lungs. It is lined with ciliated cells which push particles out and cartilage rings which reinforce the trachea and prevent it from collapsing on itself during the breathing process. These numerous cartilaginous half-rings located one above the other along the trachea have open ends adjacent to the oesophagus. The rings are connected by muscular and fibrous tissue, and they are lined inside with a ciliated mucous membrane.
In ill or injured persons, the natural airway formed by the trachea may be damaged or closed off. Intubation is the medical procedure of inserting an artificial tube into the trachea to permit breathing. See also choking.
Diseases of the trachea include:
- Tracheal fracture
- Airway obstruction
The esophagus (also spelled oesophagus) or gullet is the muscular tube in vertebrates through which ingested food passes from the mouth area to the stomach. Food is passed through the esophagus by using the process of peristalsis. Specifically, in mammals, it connects the pharynx, which is the body cavity that is common to the digestive system and respiratory system behind the mouth (buccal cavity), with the stomach, where the second stage of digestion is initiated (the first stage of digestion is in the mouth, with teeth and tongue masticating food and mixing it with saliva).
The esophagus is lined with mucous membrane, and is more deeply lined with muscle that acts with peristaltic action to move swallowed food down to the stomach.
The junction between the esophagus and the stomach is not actually considered a valve, although it is sometimes called the cardiac valve, cardia or cardias, but is actually more of a stricture. Many people experience acid reflux, where stomach acid gets pushed up into the esophagus, causing a burning sensation, commonly termed heartburn. Extended exposure to heartburn may erode the lining of the esophagus, leading to a potentially cancerous condition called Barrett's Esophagus.
Some people also experience a sensation known as globus esophagus, where it feels as if a ball is lodged in the lower part of the esophagus.
The word "esophagus" is the result of the "o" being dropped from the typographic œ (oe) in "œsophagus".
Esophageal diseases and conditions
The following are diseases and conditions that affect the esophagus:
- Bleeding varices
- Chagas disease
- Caustic injury to the esophagus
- Esophageal cancer
- Esophageal web
- Esophageal speech
- Esophageal spasm
- Esophageal stricture
- Mallory-Weiss syndrome
- Neurogenic dysphasia
- Plummer-Vinson syndrome
- Schatzki's ring
- Zenker's diverticulum
All text of this article available under the terms of the GNU Free Documentation License (see Copyrights for details).
Trachea is a common biological term for an airway through which respiratory gas transport takes place in organisms.
Chapter V - Human Anatomy