The epiglottis is a flap of elastic cartilage Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear, larynx, and epiglottis. It contains elastic fiber networks and collagen fibers. The principal protein is elastin tissue covered with a mucus membrane, attached to the root of the tongue The tongue is a muscle on the floor of the mouth that manipulates food for chewing and swallowing . It is the primary organ of taste, as much of the upper surface of the tongue is covered in papillae and taste buds. A secondary function of the tongue is speech. It is sensitive and kept moist by saliva, and is richly supplied with nerves and blood. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term is, like tonsils The human palatine tonsils and the nasopharyngeal tonsil are lymphoepithelial tissues located in strategic areas of the oropharynx and nasopharynx, although most commonly - the term "tonsils" refers to the palatine tonsils [that can be seen in the back of the throat]. These immunocompetent tissues represent the defense mechanism of first, often incorrectly used to refer to the uvula The uvula is the conic projection from the posterior edge of the middle of the soft palate, composed of connective tissue containing a number of racemose glands, and some muscular fibers (musculus uvulae).[2]
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Anatomy and function
The epiglottis guards the entrance of the glottis The glottis is defined as the combination of the vocal folds and the space in between the folds, the opening between the vocal folds The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. They vibrate, modulating the flow of air being expelled from the lungs during phonation. It is normally pointed upward during breathing Breathing is the process that takes oxygen in and carbon dioxide in and then out of the body. Aerobic organisms require oxygen to release energy via respiration, in the form of the metabolism of energy-rich molecules such as glucose. The medical term for normal relaxed breathing is eupnea with its underside functioning as part of the pharynx The pharynx is the part of the neck and throat situated immediately posterior to (behind) the mouth and nasal cavity, and cranial, or superior, to the esophagus, larynx, and trachea, but during swallowing The purpose of swallowing is to transfer food from the mouth to the stomach. The stages of swallowing can be divided into three phases, oral, pharyngeal and esophageal, with the oral phase under voluntary neuromuscular control and the latter two phases under involuntary neuromuscular control, elevation of the hyoid bone The hyoid bone (Latin os hyoideum) is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra behind draws the larynx The larynx , commonly called the voice box, is an organ in the neck of mammals involved in protecting the trachea and sound production. It manipulates pitch and volume. The larynx houses the vocal folds, which are an essential component of phonation. The vocal folds are situated just below where the tract of the pharynx splits into the trachea and upward; as a result, the epiglottis folds down to a more horizontal position, with its upper side functioning as part of the pharynx. In this manner it prevents food from going into the trachea The trachea, or windpipe, is a tube that connects to the pharynx or larynx, allowing the passage of air to the lungs. It is lined with pseudostratified ciliated columnar epithelium cells with mucosal goblet cells which produce mucus. This mucus lines the cells of the trachea to trap inhaled foreign particles which the cilia then waft upwards and instead directs it to the esophagus The esophagus or oesophagus , sometimes known as the gullet, is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. The word esophagus is derived from the Latin œsophagus, which derives from the Greek word oisophagos , lit. "entrance for eating." In humans the esophagus is, which is posterior.
The epiglottis is one of nine cartilaginous structures that make up the larynx (voice box). While breathing, it lies completely within the pharynx. When swallowing it serves as part of the anterior of the larynx.[citation needed]
Histology
Gross appearance
In a cross section of the epiglottis it can be seen that the body consists of elastic cartilage Elastic cartilage or yellow cartilage is a type of cartilage present in the outer ear, larynx, and epiglottis. It contains elastic fiber networks and collagen fibers. The principal protein is elastin. The epiglottis has two surfaces, a lingual and a laryngeal surface, related to the oral cavity and the larynx The larynx , commonly called the voice box, is an organ in the neck of mammals involved in protecting the trachea and sound production. It manipulates pitch and volume. The larynx houses the vocal folds, which are an essential component of phonation. The vocal folds are situated just below where the tract of the pharynx splits into the trachea and respectively.
Mucosa">Mucosa The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line various body cavities that are exposed to the external environment and internal organs. They are at several places continuous with skin: at the nostrils, the lips, the ears, the genital area, and the anus
The entire lingual surface and the apical portion of the laryngeal surface (since it is vulnerable to abrasion due to its relation to the digestive tract) are covered by a stratified squamous In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous cell. Epithelium may be composed of one layer of these cells, in which case it is referred to as simple squamous epithelium, or it may possess multiple layers, referred to then as stratified squamous non-keratinized epithelium. The rest of the laryngeal surface on the other hand, which is in relation to the respiratory system, has respiratory epithelium: pseudostratified, ciliated columnar cells and mucus In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. It is a viscous colloid containing antiseptic enzymes (such as lysozyme), proteins such as lactoferrin, glycoproteins known as mucins that are produced by goblet cells in the mucous membranes and submucosal glands, immunoglobulins, and inorganic salts. This secreting Goblet cells Goblet cells are glandular simple columnar epithelial cells whose sole function is to secrete mucus. They use both apocrine and merocrine methods for secretion.
Submucosa">Submucosa In the gastrointestinal tract, the submucosa is the layer of dense irregular connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle
The lamina propria The lamina propria is a constituent of the moist linings known as mucous membranes or mucosa, which line various tubes in the body on the laryngeal surface holds nerves A peripheral nerve, or simply nerve is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system. In the central nervous system, the analogous structures are known as tracts, blood vessels The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from and serous and mucous glands (including serous demilunes).
Clinical significance
Reflexes
The glossopharyngeal nerve The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves (24 nerves total). It exits the brainstem out from the sides of the upper medulla, just rostral (closer to the nose) to the vagus nerve (CN IX) sends fibers to the upper epiglottis that contribute to the afferent limb of the gag reflex The pharyngeal reflex or gag reflex is a reflex contraction of the back of the throat, evoked by touching the soft palate. It prevents something from entering the throat except as part of normal swallowing and helps prevent choking. Different people have different sensitivities to the gag reflex. The superior laryngeal branch of the vagus nerve The vagus nerve , also called pneumogastric nerve, cranial nerve X, the Wanderer or sometimes the Rambler, is the tenth of twelve (excluding CN0) paired cranial nerves. Upon leaving the medulla between the olivary nucleus and the inferior cerebellar peduncle, it extends through the jugular foramen, then passing into the carotid sheath between the (CN X) sends fibers to the lower epiglottis that contribute to the efferent limb of the cough reflex The cough reflex has both sensory and motor (efferent) pathways. The internal laryngeal nerve, a branch of the superior laryngeal nerve (CN X), carries the sensory information away from the area above the glottis in the larynx to the CNS via cranial nerve X (vagus). Stimulation of the cough receptors by dust or other foreign particles produces a.[3]
Infection of the epiglottis
In children, the epiglottis will occasionally become infected with Haemophilus influenzae Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, is a non-motile Gram-negative rod-shaped bacterium first described in 1892 by Richard Pfeiffer during an influenza pandemic. A member of the Pasteurellaceae family, it is generally aerobic, but can grow as a facultative anaerobe. H. influenzae was mistakenly and Streptococci Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning easily bent or twisted, like a chain . Contrast in the trachea, causing massive inflammation, called "Epiglottitis Epiglottitis is inflammation of the epiglottis - the flap that sits at the base of the tongue, which keeps food from going into the trachea . Due to its place in the airway, swelling of this structure can interfere with breathing and constitutes a medical emergency. The infection can cause the epiglottis to either obstruct or completely close off". This condition has become rare in countries where vaccination Vaccination is the administration of antigenic material to produce immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens. There is strong evidence for the efficacy of the influenza vaccine, the HPV vaccine and the chicken pox vaccine among others. Vaccination is generally considered to be the most against Haemophilus influenzae (Hib) is administered.[citation needed]
Additional images
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Larynx |
Cut through the larynx of a horse |
The cartilages of the larynx. Posterior view. |
Ligaments of the larynx. Posterior view. |
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Coronal section of larynx and upper part of trachea. |
The entrance to the larynx, viewed from behind. |
Muscles of larynx. Posterior view. |
Muscles of larynx. Side view. Right lamina of thyroid cartilage removed. |
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Sagittal section of nose mouth, pharynx, and larynx. |
Larynx. 1=vocal cords, 2=vestibular fold, 3=epiglottis, 4=plica aryepiglottica, 5=arytenoid cartilage, 6=sinus piriformis, 7=dorsum of the tongue |
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Epiglottis of a two year old male shown visible from mouth |
References
- ^ Stevenson, Roger E. (2006). Human malformations and related anomalies. Oxford [Oxfordshire]: Oxford University Press. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 0-19-516568-3.
- ^ http://www.thefirstpost.co.uk/45548,features,someones-been-careless-with-my-eplglottis
- ^ April, Ernest. Clinical Anatomy, 3rd ed. Lippincott, Williams, and Wilkins.
External links
- lesson11 at The Anatomy Lesson by Wesley Norman (Georgetown University Georgetown University is a Jesuit private university located in Georgetown, Washington, DC. Father John Carroll founded the school in 1789, though its roots extend back to 1634. While the school struggled financially in its early years, Georgetown expanded into a branched university after the American Civil War under the leadership of university) (larynxsagsect)
Categories: Digestive system | Respiratory system | Human throat
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Click here for larger view. Ultra-low power view through the dissecting microscope of a sagittal slice through the human epiglottis. The core of the epiglottis is consists of a thick elastic
