Vertebrate trachea
Encyclopedia
In tetrapod
anatomy
the trachea, or windpipe, is a tube that connects the pharynx
or larynx
to the lung
s, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cell
s with goblet cell
s that produce mucus
. This mucus lines the cells of the trachea to trap inhaled foreign particles that the cilia then waft
upward toward the larynx and then the pharynx where it can be either swallowed into the stomach
or expelled as phlegm
.
Despite the name, not all vertebrates have a trachea; only non-fish
ones. The name is used in contrast with invertebrate trachea
, a structure in arthropod
anatomy.
s is, in general, similar to that in humans. In general, the reptilian
trachea is also similar.
In bird
s, the trachea runs from the pharynx
to the syrinx
, from which the primary bronchi
diverge. Swan
s have an unusually elongated trachea, part of which is coiled beneath the sternum
; this may act as a resonator to amplify sound. In some birds, the cartilagenous rings are complete, and may even be ossified
.
In amphibian
s, the trachea is normally extremely short, and leads directly into the lungs, without clear primary bronchi. A longer trachea is, however, found in some long-necked salamander
s, and in caecilian
s. While there are irregular cartilagenous nodules on the amphibian trachea, these do not form the rings found in amniote
s.
The only vertebrate to have lungs, but no trachea, is Polypterus
, in which the lungs arise directly from the pharynx.
, level with the fifth cervical vertebra
, and bifurcates into the primary bronchi
at the vertebral level of T4
.
There are about fifteen to twenty incomplete C-shaped cartilaginous rings
that reinforce the anterior and lateral sides of the trachea to protect and maintain the airway. The trachealis muscle
connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen
of the trachea to increase the air flow rate. The esophagus
lies posteriorly to the trachea. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus
. A flap-like epiglottis
closes the opening to the larynx during swallowing to prevent swallowed matter from entering the trachea.
Lined with respiratory epithelium
.
In 2008, a Columbian woman received a trachea transplant
using her own stem cells so her body would not reject the transplant.
In June 2011, surgeons in the Swedish Karolinska University Hospital
led by Professor Paolo Macchiarini
performed the first synthetic windpipe transplant on a 36-year-old African man, Andemariam Teklesenbet Beyene.
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
the trachea, or windpipe, is a tube that connects the pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
or larynx
Larynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
to the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s, allowing the passage of air. It is lined with pseudostratified ciliated columnar epithelium cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
s with goblet cell
Goblet cell
Goblet cells are glandular simple columnar epithelial cells whose sole function is to secrete mucin, which dissolves in water to form mucus. They use both apocrine and merocrine methods for secretion....
s that produce mucus
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
. This mucus lines the cells of the trachea to trap inhaled foreign particles that the cilia then waft
Waft
Waft is a term meaning to carry along gently as through the air. The term is commonly used to describe scents that have diffused in to other parts of a room, or to describe smoke as being seen moving through the air...
upward toward the larynx and then the pharynx where it can be either swallowed into the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
or expelled as phlegm
Phlegm
Phlegm is a liquid secreted by the mucous membranes of mammalians. Its definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing . Phlegm is in essence a water-based gel consisting of...
.
Despite the name, not all vertebrates have a trachea; only non-fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
ones. The name is used in contrast with invertebrate trachea
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
, a structure in arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
anatomy.
In non-humans
Allowing for variations in the length of the neck, the trachea in other mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s is, in general, similar to that in humans. In general, the reptilian
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
trachea is also similar.
In bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, the trachea runs from the pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
to the syrinx
Syrinx (biology)
Syrinx is the name for the vocal organ of birds. Located at the base of a bird's trachea, it produces sounds without the vocal cords of mammals. The sound is produced by vibrations of some or all of the membrana tympaniformis and the pessulus caused by air flowing through the syrinx...
, from which the primary bronchi
Main bronchus
Main bronchus can refer to the following lung structures:* Right main bronchus* Left main bronchus...
diverge. Swan
Swan
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...
s have an unusually elongated trachea, part of which is coiled beneath the sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
; this may act as a resonator to amplify sound. In some birds, the cartilagenous rings are complete, and may even be ossified
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...
.
In amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...
s, the trachea is normally extremely short, and leads directly into the lungs, without clear primary bronchi. A longer trachea is, however, found in some long-necked salamander
Salamander
Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by a superficially lizard-like appearance, with their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant...
s, and in caecilian
Caecilian
The caecilians are an order of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly...
s. While there are irregular cartilagenous nodules on the amphibian trachea, these do not form the rings found in amniote
Amniote
The amniotes are a group of tetrapods that have a terrestrially adapted egg. They include synapsids and sauropsids , as well as their fossil ancestors. Amniote embryos, whether laid as eggs or carried by the female, are protected and aided by several extensive membranes...
s.
The only vertebrate to have lungs, but no trachea, is Polypterus
Polypterus
Polypterus is a genus of freshwater fish in the bichir family of order Polypteriformes. The type species is the Nile bichir . Fishes in this genus live in various areas in Africa...
, in which the lungs arise directly from the pharynx.
In humans
The trachea has an inner diameter of about 25.4 millimetre (1 in) and a length of about 10 to 16 cm (3.9 to 6.3 in). It commences at the larynxLarynx
The larynx , commonly called the voice box, is an organ in the neck of amphibians, reptiles and mammals involved in breathing, sound production, and protecting the trachea against food aspiration. It manipulates pitch and volume...
, level with the fifth cervical vertebra
Cervical vertebra 5
The cervical vertebra 5 is a vertebra of the spinal column.The cervical spinal nerve 5 passes out above it.C5 and C6 are the areas that see the highest amount of cervical spine trauma....
, and bifurcates into the primary bronchi
Bronchus
A bronchus is a passage of airway in the respiratory tract that conducts air into the lungs. The bronchus branches into smaller tubes, which in turn become bronchioles....
at the vertebral level of T4
Thoracic vertebrae
In human anatomy, twelve thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. They are intermediate in size between those of the cervical and lumbar regions; they increase in size as one proceeds down the spine, the upper...
.
There are about fifteen to twenty incomplete C-shaped cartilaginous rings
Tracheal rings
The cartilages of the trachea vary from sixteen to twenty in number. Each forms a semicircular ring of hyaline cartilage, which occupies the anterior two-thirds or so of the circumference of the trachea...
that reinforce the anterior and lateral sides of the trachea to protect and maintain the airway. The trachealis muscle
Trachealis muscle
Trachealis muscle is an example of smooth muscle. It bridges the gap between free ends of C-shaped cartilages at the posterior border of the trachea, adjacent to the esophagus....
connects the ends of the incomplete rings and contracts during coughing, reducing the size of the lumen
Lumen (anatomy)
A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...
of the trachea to increase the air flow rate. The esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
lies posteriorly to the trachea. The cartilaginous rings are incomplete to allow the trachea to collapse slightly so that food can pass down the esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
. A flap-like epiglottis
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
closes the opening to the larynx during swallowing to prevent swallowed matter from entering the trachea.
Lined with respiratory epithelium
Respiratory epithelium
Respiratory epithelium is a type of epithelium found lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.-...
.
Tracheal diseases and conditions
The following are diseases and conditions that affect the trachea:- ChokingChokingChoking is the mechanical obstruction of the flow of air from the environment into the lungs. Choking prevents breathing, and can be partial or complete, with partial choking allowing some, although inadequate, flow of air into the lungs. Prolonged or complete choking results in asphyxia which...
- TracheotomyTracheotomyAmong the oldest described surgical procedures, tracheotomy consists of making an incision on the anterior aspect of the neck and opening a direct airway through an incision in the trachea...
, a surgical procedure on the neck to open a direct airway through an incision in the trachea - TracheomalaciaTracheomalaciaTracheomalacia is a condition characterized by flaccidity of the tracheal support cartilage which leads to tracheal collapse especially when increased airflow is demanded....
(weakening of the tracheal cartilage)- Tracheal collapseTracheal collapseTracheal collapse is a condition characterized by incomplete formation or weakening of the cartilagenous rings of the trachea resulting in flattening of the trachea. It can be congenital or acquired, and extrathoracic or intrathoracic. Tracheal collapse is a dynamic condition...
(in dogs)
- Tracheal collapse
- Tracheobronchial injuryTracheobronchial injuryTracheobronchial injury is damage to the tracheobronchial tree . It can result from blunt or penetrating trauma to the neck or chest, inhalation of harmful fumes or smoke, or aspiration of liquids or objects.Though rare, TBI is a serious condition; it may cause obstruction of the airway with...
(perforation of the trachea or bronchi) - Mounier-Kuhn syndromeMounier-Kuhn syndromeMounier-Kuhn syndrome is a very rare disease of the lungs and airways where the trachea and bronchi become abnormally wide...
(causes abnormal enlargement of the trachea)
In 2008, a Columbian woman received a trachea transplant
Organ transplant
Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...
using her own stem cells so her body would not reject the transplant.
In June 2011, surgeons in the Swedish Karolinska University Hospital
Karolinska University Hospital
The Karolinska University Hospital is a university hospital in Stockholm, Sweden, with two major sites in the municipalities of Huddinge and Solna....
led by Professor Paolo Macchiarini
Paolo Macchiarini
Paolo Macchiarini, M.D., Ph.D. is head and chairman of the Hospital Clínic de Barcelona, University of Barcelona in Barcelona, Spain, as well as professor of surgery at the University of Barcelona in Spain, and at the Hannover Medical School in Hannover, Germany.Dr. Macchiarini completed his...
performed the first synthetic windpipe transplant on a 36-year-old African man, Andemariam Teklesenbet Beyene.