Misplaced Pages

#102897

109-474: 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 . In humans, two sets of pharyngeal muscles form

218-407: A bolus before being transported down the esophagus through peristalsis . The sublingual region underneath the front of the tongue is a location where the oral mucosa is very thin, and underlain by a plexus of veins. This is an ideal location for introducing certain medications to the body. The sublingual route takes advantage of the highly vascular quality of the oral cavity, and allows for

327-419: A better ability to handle calcium changes in comparison to other muscles, and this may provide a mechanistic insight for their unique pathophysiological properties There are several things that can cause a larynx to not function properly. Some symptoms are hoarseness, loss of voice, pain in the throat or ears, and breathing difficulties. Patients who have lost the use of their larynx are typically prescribed

436-424: A blood and nerve supply which enables proprioception. This is the ability of sensation when chewing, for example if we were to bite into something too hard for our teeth, such as a chipped plate mixed in food, our teeth send a message to our brain and we realise that it cannot be chewed, so we stop trying. The shapes, sizes and numbers of types of animals' teeth are related to their diets. For example, herbivores have

545-405: A carbon dioxide-enriched atmosphere, and share an enhanced capacity to produce endocardial infections, especially in young children. Fusobacterium is a pathogen. 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

654-410: A complex digestive system as do, for example, ruminants. Instead they extract more nutrition from grass by giving their food a second pass through the gut . Soft faecal pellets of partially digested food are excreted and generally consumed immediately. They also produce normal droppings, which are not eaten. Young elephants, pandas, koalas, and hippos eat the faeces of their mother, probably to obtain

763-428: A crop or enlarged esophagus . Herbivores have evolved cecums (or an abomasum in the case of ruminants ). Ruminants have a fore-stomach with four chambers. These are the rumen , reticulum , omasum , and abomasum. In the first two chambers, the rumen and the reticulum, the food is mixed with saliva and separates into layers of solid and liquid material. Solids clump together to form the cud (or bolus ). The cud

872-408: A general response to stress conditions, the process of loading cargo proteins seems to be selective. The gastrovascular cavity functions as a stomach in both digestion and the distribution of nutrients to all parts of the body. Extracellular digestion takes place within this central cavity, which is lined with the gastrodermis, the internal layer of epithelium . This cavity has only one opening to

981-411: A hand to grab pieces of dead grass, leaves, and weeds, with bits of soil to help chew. The lips break the food down into smaller pieces. In the pharynx, the food is lubricated by mucus secretions for easier passage. The esophagus adds calcium carbonate to neutralize the acids formed by food matter decay. Temporary storage occurs in the crop where food and calcium carbonate are mixed. The powerful muscles of

1090-438: A narrow triangular opening, the rima glottidis . The portion of the cavity of the larynx above the vocal folds is called the laryngeal vestibule ; it is wide and triangular in shape, its base or anterior wall presenting, however, about its center the backward projection of the tubercle of the epiglottis. It contains the vestibular folds , and between these and the vocal folds are the laryngeal ventricles . The portion below

1199-483: A number of molars which are used to grind plant matter, which is difficult to digest. Carnivores have canine teeth which are used to kill and tear meat. A crop , or croup, is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion. In some birds it is an expanded, muscular pouch near the gullet or throat. In adult doves and pigeons, the crop can produce crop milk to feed newly hatched birds. Certain insects may have

SECTION 10

#1732801295103

1308-401: A similar function to the lungs in creating pressure differences required for sound production; a constricted larynx can be raised or lowered affecting the volume of the oral cavity as necessary in glottalic consonants. The vocal cords can be held close together (by adducting the arytenoid cartilages) so that they vibrate (see phonation ). The muscles attached to the arytenoid cartilages control

1417-589: A site for fermentation of indigestible matter by gut bacteria and for resorption of water from digests before excretion. In mammals , preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach . Mechanical and chemical digestion begin in the mouth where food is chewed , and mixed with saliva to begin enzymatic processing of starches . The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. Absorption occurs in

1526-507: A source sound with a particular fundamental frequency, or pitch. This source sound is altered as it travels through the vocal tract , configured differently based on the position of the tongue , lips , mouth , and pharynx . The process of altering a source sound as it passes through the filter of the vocal tract creates the many different vowel and consonant sounds of the world's languages as well as tone, certain realizations of stress and other types of linguistic prosody. The larynx also has

1635-415: A style of Tuvan throat singing . Both make use of the vestibular folds to create an undertone. These false vocal cords do not contain muscle, while the true vocal cords do have skeletal muscle. The most important role of the larynx is its protective function, the prevention of foreign objects from entering the lungs by coughing and other reflexive actions. A cough is initiated by a deep inhalation through

1744-508: A well-developed capacity for prolonged work. Studies suggests that mechanisms involved in the prompt sequestering of Ca (sarcoplasmic reticulum Ca -reuptake proteins, plasma membrane pumps, and cytosolic Ca -buffering proteins) are particularly elevated in laryngeal muscles, indicating their importance for the myofiber function and protection against disease, such as Duchenne muscular dystrophy . Furthermore, different levels of Orai1 in rat intrinsic laryngeal muscles and extraocular muscles over

1853-417: Is pharyngeal ( / ˌ f æ r ɪ n ˈ dʒ iː əl / or / f ə ˈ r ɪ n dʒ i əl / ). 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

1962-426: Is a vacuole formed around a particle absorbed by phagocytosis . The vacuole is formed by the fusion of the cell membrane around the particle. A phagosome is a cellular compartment in which pathogenic microorganisms can be killed and digested. Phagosomes fuse with lysosomes in their maturation process, forming phagolysosomes . In humans, Entamoeba histolytica can phagocytose red blood cells . To aid in

2071-464: Is absorbed into the blood. 95% of nutrient absorption occurs in the small intestine. Water and minerals are reabsorbed back into the blood in the colon (large intestine) where the pH is slightly acidic (about 5.6 ~ 6.9). Some vitamins, such as biotin and vitamin K (K 2 MK7) produced by bacteria in the colon are also absorbed into the blood in the colon. Absorption of water, simple sugar and alcohol also takes place in stomach. Waste material ( feces )

2180-400: Is also responsible for the ear-cough reflex in which stimulation of the ear canal results in a person coughing. 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. Inflammation of

2289-435: Is also triggered by acetylcholine and histamine . The intestinal phase has two parts, the excitatory and the inhibitory. Partially digested food fills the duodenum . This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes. Protein digestion occurs in

SECTION 20

#1732801295103

2398-456: Is an enzyme that breaks down the disaccharide sucrose , commonly known as table sugar, cane sugar, or beet sugar. Sucrose digestion yields the sugars fructose and glucose which are readily absorbed by the small intestine. DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) from the pancreas. Larynx The larynx ( / ˈ l æ r ɪ ŋ k s / ), commonly called

2507-417: Is doubled during forced respiration. During swallowing , elevation of the posterior portion of the tongue levers (inverts) the epiglottis over the glottis' opening to prevent swallowed material from entering the larynx which leads to the lungs , and provides a path for a food or liquid bolus to "slide" into the esophagus; the hyo-laryngeal complex is also pulled upwards to assist this process. Stimulation of

2616-408: Is eliminated from the rectum during defecation . Digestive systems take many forms. There is a fundamental distinction between internal and external digestion. External digestion developed earlier in evolutionary history, and most fungi still rely on it. In this process, enzymes are secreted into the environment surrounding the organism, where they break down an organic material, and some of

2725-415: Is finally moved into the small intestine, where the digestion and absorption of nutrients occurs. Microbes produced in the reticulo-rumen are also digested in the small intestine. Regurgitation has been mentioned above under abomasum and crop, referring to crop milk, a secretion from the lining of the crop of pigeons and doves with which the parents feed their young by regurgitation. Many sharks have

2834-399: Is further forward and higher relative to its position in the adult body. The larynx descends as the child grows. The laryngeal cavity ( cavity of the larynx ) extends from the laryngeal inlet downwards to the lower border of the cricoid cartilage where it is continuous with that of the trachea . It is divided into two parts by the projection of the vocal folds , between which is

2943-452: Is not part of the larynx, though the larynx is suspended from the hyoid. The larynx extends vertically from the tip of the epiglottis to the inferior border of the cricoid cartilage . Its interior can be divided in supraglottis, glottis and subglottis . There are nine cartilages, three unpaired and three paired (3 pairs=6), that support the mammalian larynx and form its skeleton. Unpaired cartilages: Paired cartilages: The muscles of

3052-423: 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 also have a pharynx. Invertebrates with a pharynx include the tardigrades , annelids and arthropods , and

3161-422: Is skeletal muscle on the floor of the mouth of most vertebrates, that manipulates food for chewing ( mastication ) and swallowing (deglutition). It is sensitive and kept moist by saliva . The underside of the tongue is covered with a smooth mucous membrane . The tongue also has a touch sense for locating and positioning food particles that require further chewing. The tongue is used to roll food particles into

3270-445: Is the breakdown of large insoluble food compounds into small water-soluble components so that they can be absorbed into the blood plasma . In certain organisms, these smaller substances are absorbed through the small intestine into the blood stream . Digestion is a form of catabolism that is often divided into two processes based on how food is broken down: mechanical and chemical digestion. The term mechanical digestion refers to

3379-417: Is the open space below the glottis. In adult humans, the larynx is found in the anterior neck at the level of the cervical vertebrae C3–C6. It connects the inferior part of the pharynx (hypopharynx) with the trachea . The laryngeal skeleton consists of nine cartilages : three single ( epiglottic , thyroid and cricoid ) and three paired ( arytenoid , corniculate , and cuneiform ). The hyoid bone

Pharynx - Misplaced Pages Continue

3488-607: Is the prototypic system. In the nitrogen-fixing Rhizobia , conjugative elements naturally engage in inter- kingdom conjugation. Such elements as the Agrobacterium Ti or Ri plasmids contain elements that can transfer to plant cells. Transferred genes enter the plant cell nucleus and effectively transform the plant cells into factories for the production of opines , which the bacteria use as carbon and energy sources. Infected plant cells form crown gall or root tumors . The Ti and Ri plasmids are thus endosymbionts of

3597-439: Is then regurgitated, chewed slowly to completely mix it with saliva and to break down the particle size. Fibre, especially cellulose and hemi-cellulose , is primarily broken down into the volatile fatty acids , acetic acid , propionic acid and butyric acid in these chambers (the reticulo-rumen) by microbes: ( bacteria , protozoa , and fungi). In the omasum, water and many of the inorganic mineral elements are absorbed into

3706-403: The cephalic phase , gastric phase , and intestinal phase . The cephalic phase occurs at the sight, thought and smell of food, which stimulate the cerebral cortex . Taste and smell stimuli are sent to the hypothalamus and medulla oblongata . After this it is routed through the vagus nerve and release of acetylcholine. Gastric secretion at this phase rises to 40% of maximum rate. Acidity in

3815-490: 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

3924-474: 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. [REDACTED] This article incorporates text in the public domain from page 1141 of the 20th edition of Gray's Anatomy (1918) General Digestion Digestion

4033-453: The superior laryngeal nerve . The external branch of the superior laryngeal nerve innervates the cricothyroid muscle . Motor innervation to all other muscles of the larynx and sensory innervation to the subglottis is by the recurrent laryngeal nerve . While the sensory input described above is (general) visceral sensation (diffuse, poorly localized), the vocal cords also receives general somatic sensory innervation (proprioceptive and touch) by

4142-467: The vocal cords apart and serve breathing. The phonatory muscles move the vocal cords together and serve the production of voice. The main respiratory muscles are the posterior cricoarytenoid muscles . The phonatory muscles are divided into adductors ( lateral cricoarytenoid muscles , arytenoid muscles ) and tensors ( cricothyroid muscles , thyroarytenoid muscles ). The intrinsic laryngeal muscles are responsible for controlling sound production. Notably

4251-400: The voice box , is an organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal inlet is about 4–5 centimeters in diameter . The larynx houses the vocal cords , and manipulates pitch and volume , which is essential for phonation . It is situated just below where

4360-403: 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

4469-459: The Larynx (1929). Negus, however, pointed out that the descent of the larynx reflected the reshaping and descent of the human tongue into the pharynx. This process is not complete until age six to eight years. Some researchers, such as Philip Lieberman , Dennis Klatt , Bart de Boer and Kenneth Stevens using computer-modeling techniques have suggested that the species-specific human tongue allows

Pharynx - Misplaced Pages Continue

4578-420: The ability to turn their stomachs inside out and evert it out of their mouths in order to get rid of unwanted contents (perhaps developed as a way to reduce exposure to toxins). Other animals, such as rabbits and rodents , practise coprophagia behaviours – eating specialised faeces in order to re-digest food, especially in the case of roughage. Capybara, rabbits, hamsters and other related species do not have

4687-434: The absorption of nutrients by increasing the surface area of the intestine. Bile helps in emulsification of fats and also activates lipases. In the large intestine, the passage of food is slower to enable fermentation by the gut flora to take place. Here, water is absorbed and waste material stored as feces to be removed by defecation via the anal canal and anus . Different phases of digestion take place including:

4796-411: The arytenoids. An example of a frog that possesses a larynx is the túngara frog . While the larynx is the main sound producing organ in túngara frogs, it serves a higher significance due to its contribution to mating call, which consist of two components: 'whine' and 'chuck'. While 'whine' induces female phonotaxis and allows species recognition, 'chuck' increases mating attractiveness. In particular,

4905-425: 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 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

5014-412: The bacteria required to properly digest vegetation. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to get any nutritional value from many plant components. An earthworm 's digestive system consists of a mouth, pharynx , esophagus , crop, gizzard , and intestine . The mouth is surrounded by strong lips, which act like

5123-404: The bacteria, which are in turn endosymbionts (or parasites) of the infected plant. The Ti and Ri plasmids are themselves conjugative. Ti and Ri transfer between bacteria uses an independent system (the tra , or transfer, operon) from that for inter-kingdom transfer (the vir , or virulence , operon). Such transfer creates virulent strains from previously avirulent Agrobacteria . In addition to

5232-565: The bacterial cytoplasm into the cytoplasm of its host's cells rather than be secreted into the extracellular medium. The conjugation machinery of some bacteria (and archaeal flagella) is capable of transporting both DNA and proteins. It was discovered in Agrobacterium tumefaciens , which uses this system to introduce the Ti plasmid and proteins into the host, which develops the crown gall (tumor). The VirB complex of Agrobacterium tumefaciens

5341-411: The blood stream. The abomasum is the fourth and final stomach compartment in ruminants. It is a close equivalent of a monogastric stomach (e.g., those in humans or pigs), and digesta is processed here in much the same way. It serves primarily as a site for acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine. Digesta

5450-464: The body. In most vertebrates , digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps: Underlying the process is muscle movement throughout the system through swallowing and peristalsis . Each step in digestion requires energy, and thus imposes an "overhead charge" on

5559-465: The degree of opening. Vocal cord length and tension can be controlled by rocking the thyroid cartilage forward and backward on the cricoid cartilage (either directly by contracting the cricothyroids or indirectly by changing the vertical position of the larynx), by manipulating the tension of the muscles within the vocal cords, and by moving the arytenoids forward or backward. This causes the pitch produced during phonation to rise or fall. In most males

SECTION 50

#1732801295103

5668-417: 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 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

5777-408: The digestion of their food, animals evolved organs such as beaks, tongues , radulae , teeth, crops, gizzards, and others. Birds have bony beaks that are specialised according to the bird's ecological niche . For example, macaws primarily eat seeds, nuts, and fruit, using their beaks to open even the toughest seed. First they scratch a thin line with the sharp point of the beak, then they shear

5886-450: The energy made available from absorbed substances. Differences in that overhead cost are important influences on lifestyle, behavior, and even physical structures. Examples may be seen in humans, who differ considerably from other hominids (lack of hair, smaller jaws and musculature, different dentition, length of intestines, cooking, etc.). The major part of digestion takes place in the small intestine. The large intestine primarily serves as

5995-520: The environments. In a channel transport system, several proteins form a contiguous channel traversing the inner and outer membranes of the bacteria. It is a simple system, which consists of only three protein subunits: the ABC protein , membrane fusion protein (MFP), and outer membrane protein . This secretion system transports various chemical species, from ions, drugs, to proteins of various sizes (20–900 kDa). The chemical species secreted vary in size from

6104-402: The extracellular environment prior to ingestion of the consequent "soup". In others, once potential nutrients or food is inside the organism , digestion can be conducted to a vesicle or a sac-like structure, through a tube, or through several specialized organs aimed at making the absorption of nutrients more efficient. Bacteria use several systems to obtain nutrients from other organisms in

6213-459: The false vocal cords for the rather obvious reason that they play no part in vocalization. The Kargyraa style of Tuvan throat singing makes use of these folds to sing an octave lower, and they are used in Umngqokolo , a type of Xhosa throat singing. The lower pair of folds are known as the vocal cords, which produce sounds needed for speech and other vocalizations. The slit-like space between

6322-482: The food further and this is combined with the churning action of the stomach. Mainly proteins are digested in stomach. The partially digested food enters the duodenum as a thick semi-liquid chyme . In the small intestine, the larger part of digestion takes place and this is helped by the secretions of bile , pancreatic juice and intestinal juice . The intestinal walls are lined with villi , and their epithelial cells are covered with numerous microvilli to improve

6431-417: The form of trypsinogen , which is activated in the duodenum by enterokinase to form trypsin. Trypsin then cleaves proteins to smaller polypeptides. Digestion of some fats can begin in the mouth where lingual lipase breaks down some short chain lipids into diglycerides . However fats are mainly digested in the small intestine. The presence of fat in the small intestine produces hormones that stimulate

6540-412: The gizzard churn and mix the mass of food and dirt. When the churning is complete, the glands in the walls of the gizzard add enzymes to the thick paste, which helps chemically breakdown the organic matter. By peristalsis , the mixture is sent to the intestine where friendly bacteria continue chemical breakdown. This releases carbohydrates, protein, fat, and various vitamins and minerals for absorption into

6649-400: The human tongue enables us to produce, particularly [i], allow humans to unconsciously infer the length of the vocal tract of the person who is talking, a critical element in recovering the phonemes that make up a word. Most tetrapod species possess a larynx, but its structure is typically simpler than that found in mammals. The cartilages surrounding the larynx are apparently a remnant of

SECTION 60

#1732801295103

6758-432: The ideal conditions of pH for amylase to work; and other electrolytes ( Na , K , Cl ). About 30% of starch is hydrolyzed into disaccharide in the oral cavity (mouth). After undergoing mastication and starch digestion, the food will be in the form of a small, round slurry mass called a bolus . It will then travel down the esophagus and into the stomach by the action of peristalsis . Gastric juice in

6867-429: The larynx are divided into intrinsic and extrinsic muscles. The extrinsic muscles act on the region and pass between the larynx and parts around it but have their origin elsewhere; the intrinsic muscles are confined entirely within the larynx and have their origin and insertion there. The intrinsic muscles are divided into respiratory and the phonatory muscles (the muscles of phonation ). The respiratory muscles move

6976-422: The larynx by aspirated food or liquid produces a strong cough reflex to protect the lungs. In addition, intrinsic laryngeal muscles are spared from some muscle wasting disorders, such as Duchenne muscular dystrophy , may facilitate the development of novel strategies for the prevention and treatment of muscle wasting in a variety of clinical scenarios. ILM have a calcium regulation system profile suggestive of

7085-414: The left and right vocal cords, called the rima glottidis, is the narrowest part of the larynx. The vocal cords and the rima glottidis are together designated as the glottis. The laryngeal cavity above the vestibular folds is called the vestibule. The very middle portion of the cavity between the vestibular folds and the vocal cords is the ventricle of the larynx, or laryngeal ventricle. The infraglottic cavity

7194-401: The legs. This is achieved by a deep inhalation followed by the adduction of the vocal cords. Grunting while lifting heavy objects is the result of some air escaping through the adducted vocal cords ready for phonation . Abduction of the vocal cords is important during physical exertion. The vocal cords are separated by about 8 mm (0.31 in) during normal respiration, but this width

7303-411: The limb muscle suggests a role for store operated calcium entry channels in those muscles' functional properties and signaling mechanisms. The extrinsic laryngeal muscles support and position the larynx within the mid-cervical cereal region. The larynx is innervated by branches of the vagus nerve on each side. Sensory innervation to the glottis and laryngeal vestibule is by the internal branch of

7412-423: 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

7521-400: 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. The anterior aspect of the nasopharynx communicates through the choanae with the nasal cavities. On its lateral wall is the pharyngeal opening of

7630-436: The mouth and mechanical digestion of the food starts by the action of mastication (chewing), a form of mechanical digestion, and the wetting contact of saliva . Saliva, a liquid secreted by the salivary glands , contains salivary amylase , an enzyme which starts the digestion of starch in the food. The saliva also contains mucus , which lubricates the food; the electrolyte hydrogencarbonate ( HCO 3 ), which provides

7739-459: 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 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

7848-431: 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

7957-418: The number of chews per bite increases relevant gut hormones and may decrease self-reported hunger and food intake. When the pyloric sphincter valve opens, partially digested food ( chyme ) enters the duodenum where it mixes with digestive enzymes from the pancreas and bile juice from the liver and then passes through the small intestine, in which digestion continues. When the chyme is fully digested, it

8066-413: The only muscle capable of separating the vocal cords for normal breathing is the posterior cricoarytenoid. If this muscle is incapacitated on both sides, the inability to pull the vocal cords apart (abduct) will cause difficulty breathing. Bilateral injury to the recurrent laryngeal nerve would cause this condition. It is also worth noting that all muscles are innervated by the recurrent laryngeal branch of

8175-465: The original gill arches in fish, and are a common feature, but not all are always present. For example, the thyroid cartilage is found only in mammals. Similarly, only mammals possess a true epiglottis , although a flap of non-cartilagenous mucosa is found in a similar position in many other groups. In modern amphibians, the laryngeal skeleton is considerably reduced; frogs have only the cricoid and arytenoid cartilages, while salamanders possess only

8284-573: The outside that functions as both a mouth and an anus : waste and undigested matter is excreted through the mouth/anus, which can be described as an incomplete gut . In a plant such as the Venus flytrap that can make its own food through photosynthesis, it does not eat and digest its prey for the traditional objectives of harvesting energy and carbon, but mines prey primarily for essential nutrients (nitrogen and phosphorus in particular) that are in short supply in its boggy, acidic habitat. A phagosome

8393-467: 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

8502-406: The pharynx and determine the shape of its lumen . They are arranged as an inner layer of longitudinal muscles and an outer circular layer. 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

8611-437: 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 ( H aemophilus , A ctinobacillus actinomycetemcomitans , C ardiobacterium hominis , E ikenella corrodens , K ingella ) are part of the normal oropharyngeal flora, which grow slowly, prefer

8720-404: The pharynx, or pharyngitis , is the painful inflammation of the throat. Pharyngeal cancer is a cancer that originates in the neck and/or throat. 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

8829-405: The physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes . Mechanical digestion takes place in the mouth through mastication and in the small intestine through segmentation contractions . In chemical digestion , enzymes break down food into the small compounds that the body can use. In the human digestive system , food enters

8938-399: The products diffuse back to the organism. Animals have a tube ( gastrointestinal tract ) in which internal digestion occurs, which is more efficient because more of the broken down products can be captured, and the internal chemical environment can be more efficiently controlled. Some organisms, including nearly all spiders , secrete biotoxins and digestive chemicals (e.g., enzymes) into

9047-472: The range of speech sounds of humans. The ability to lower the larynx transiently in some species extends the length of their vocal tract, which as Fitch showed creates the acoustic illusion that they are larger. Research at Haskins Laboratories in the 1960s showed that speech allows humans to achieve a vocal communication rate that exceeds the fusion frequency of the auditory system by fusing sounds together into syllables and words. The additional speech sounds that

9156-669: The release of pancreatic lipase from the pancreas and bile from the liver which helps in the emulsification of fats for absorption of fatty acids . Complete digestion of one molecule of fat (a triglyceride ) results a mixture of fatty acids, mono- and di-glycerides, but no glycerol . In humans, dietary starches are composed of glucose units arranged in long chains called amylose, a polysaccharide . During digestion, bonds between glucose molecules are broken by salivary and pancreatic amylase , resulting in progressively smaller chains of glucose. This results in simple sugars glucose and maltose (2 glucose molecules) that can be absorbed by

9265-413: The release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach. Inhibition of gastrin and gastric acid secretion is lifted. This triggers G cells to release gastrin , which in turn stimulates parietal cells to secrete gastric acid. Gastric acid is about 0.5% hydrochloric acid , which lowers the pH to the desired pH of 1–3. Acid release

9374-422: The same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which is waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Pepsin breaks down proteins into peptides or proteoses , which is further broken down into dipeptides and amino acids by enzymes in the small intestine. Studies suggest that increasing

9483-431: The secretion of saliva and its digestive enzymes. Food is formed into a bolus by the mechanical mastication and swallowed into the esophagus from where it enters the stomach through the action of peristalsis . Gastric juice contains hydrochloric acid and pepsin which would damage the walls of the stomach and mucus and bicarbonates are secreted for protection. In the stomach further release of enzymes break down

9592-406: The seed open with the sides of the beak. The mouth of the squid is equipped with a sharp horny beak mainly made of cross-linked proteins . It is used to kill and tear prey into manageable pieces. The beak is very robust, but does not contain any minerals, unlike the teeth and jaws of many other organisms, including marine species. The beak is the only indigestible part of the squid. The tongue

9701-447: 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

9810-548: The small Escherichia coli peptide colicin V, (10 kDa) to the Pseudomonas fluorescens cell adhesion protein LapA of 900 kDa. A type III secretion system means that a molecular syringe is used through which a bacterium (e.g. certain types of Salmonella , Shigella , Yersinia ) can inject nutrients into protist cells. One such mechanism was first discovered in Y. pestis and showed that toxins could be injected directly from

9919-613: The small intestine. Lactase is an enzyme that breaks down the disaccharide lactose to its component parts, glucose and galactose . Glucose and galactose can be absorbed by the small intestine. Approximately 65 percent of the adult population produce only small amounts of lactase and are unable to eat unfermented milk-based foods. This is commonly known as lactose intolerance . Lactose intolerance varies widely by genetic heritage; more than 90 percent of peoples of east Asian descent are lactose intolerant, in contrast to about 5 percent of people of northern European descent. Sucrase

10028-568: 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. The word pharynx ( / ˈ f ær ɪ ŋ k s / ) is derived from the Greek φάρυγξ phárynx , meaning "throat". Its plural form is pharynges / f ə ˈ r ɪ n dʒ iː z / or pharynxes / ˈ f ær ɪ ŋ k s ə z / , and its adjective form

10137-399: The speedy application of medication into the cardiovascular system, bypassing the gastrointestinal tract. Teeth (singular tooth) are small whitish structures found in the jaws (or mouths) of many vertebrates that are used to tear, scrape, milk and chew food. Teeth are not made of bone, but rather of tissues of varying density and hardness, such as enamel, dentine and cementum. Human teeth have

10246-424: The stomach and duodenum in which 3 main enzymes, pepsin secreted by the stomach and trypsin and chymotrypsin secreted by the pancreas, break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids . The digestive enzymes however are mostly secreted as their inactive precursors, the zymogens . For example, trypsin is secreted by pancreas in

10355-403: The stomach and gastrointestinal tract , and the process finishes with defecation. The human gastrointestinal tract is around 9 metres (30 feet) long. Food digestion physiology varies between individuals and upon other factors such as the characteristics of the food and size of the meal, and the process of digestion normally takes between 24 and 72 hours. Digestion begins in the mouth with

10464-435: The stomach is not buffered by food at this point and thus acts to inhibit parietal (secretes acid) and G cell (secretes gastrin) activity via D cell secretion of somatostatin . The gastric phase takes 3 to 4 hours. It is stimulated by distension of the stomach, presence of food in stomach and decrease in pH . Distention activates long and myenteric reflexes. This activates the release of acetylcholine , which stimulates

10573-513: The stomach starts protein digestion . Gastric juice mainly contains hydrochloric acid and pepsin . In infants and toddlers , gastric juice also contains rennin to digest milk proteins. As the first two chemicals may damage the stomach wall, mucus and bicarbonates are secreted by the stomach. They provide a slimy layer that acts as a shield against the damaging effects of chemicals like concentrated hydrochloric acid while also aiding lubrication. Hydrochloric acid provides acidic pH for pepsin. At

10682-462: The superior laryngeal nerve. Injury to the external branch of the superior laryngeal nerve causes weakened phonation because the vocal cords cannot be tightened. Injury to one of the recurrent laryngeal nerves produces hoarseness , if both are damaged the voice may or may not be preserved, but breathing becomes difficult. In newborn infants, the larynx is initially at the level of the C2–C3 vertebrae, and

10791-445: The tightening of the laryngeal musculature. Both coughing and throat clearing are predictable and necessary actions because they clear the respiratory passageway, but both place the vocal cords under significant strain. Another important role of the larynx is abdominal fixation, a kind of Valsalva maneuver in which the lungs are filled with air in order to stiffen the thorax so that forces applied for lifting can be translated down to

10900-492: The tract of the pharynx splits into the trachea and the esophagus . The word 'larynx' ( pl. : larynges) comes from the Ancient Greek word lárunx ʻlarynx, gullet, throatʼ. The triangle-shaped larynx consists largely of cartilages that are attached to one another, and to surrounding structures, by muscles or by fibrous and elastic tissue components. The larynx is lined by a ciliated columnar epithelium except for

11009-421: The túngara frog produces 'chuck' by vibrating the fibrous mass attached to the larynx. Vocal folds are found only in mammals, and a few lizards . As a result, many reptiles and amphibians are essentially voiceless; frogs use ridges in the trachea to modulate sound, while birds have a separate sound-producing organ, the syrinx . The ancient Greek physician Galen first described the larynx, describing it as

11118-776: The use of an electrolarynx device. Larynx transplants are a rare procedure. The world's first successful operation took place in 1998 at the Cleveland Clinic , and the second took place in October 2010 at the University of California Davis Medical Center in Sacramento. Pioneering work on the structure and evolution of the larynx was carried out in the 1920s by the British comparative anatomist Victor Negus , culminating in his monumental work The Mechanism of

11227-537: The use of the multiprotein complexes listed above, gram-negative bacteria possess another method for release of material: the formation of outer membrane vesicles . Portions of the outer membrane pinch off, forming spherical structures made of a lipid bilayer enclosing periplasmic materials. Vesicles from a number of bacterial species have been found to contain virulence factors, some have immunomodulatory effects, and some can directly adhere to and intoxicate host cells. While release of vesicles has been demonstrated as

11336-411: The vagus except the cricothyroid muscle, which is innervated by the external laryngeal branch of the superior laryngeal nerve (a branch of the vagus). Additionally, intrinsic laryngeal muscles present a constitutive Ca -buffering profile that predicts their better ability to handle calcium changes in comparison to other muscles. This profile is in agreement with their function as very fast muscles with

11445-577: The vocal cords are longer and have a greater mass than most females' vocal cords, producing a lower pitch. The vocal apparatus consists of two pairs of folds, the vestibular folds (false vocal cords) and the true vocal cords . The vestibular folds are covered by respiratory epithelium , while the vocal cords are covered by stratified squamous epithelium . The vestibular folds are not responsible for sound production, but rather for resonance. The exceptions to this are found in Tibetan chanting and Kargyraa,

11554-410: The vocal cords, followed by the elevation of the larynx and the tight adduction (closing) of the vocal cords. The forced expiration that follows, assisted by tissue recoil and the muscles of expiration, blows the vocal cords apart, and the high pressure expels the irritating object out of the throat. Throat clearing is less violent than coughing, but is a similar increased respiratory effort countered by

11663-406: The vocal folds is called the infraglottic cavity. It is at first of an elliptical form, but lower down it widens out, assumes a circular form, and is continuous with the tube of the trachea. Sound is generated in the larynx, and that is where pitch and volume are manipulated. The strength of expiration from the lungs also contributes to loudness. Manipulation of the larynx is used to generate

11772-425: The vocal folds. The cavity of the larynx extends from its triangle-shaped inlet , to the epiglottis , and to the circular outlet at the lower border of the cricoid cartilage , where it is continuous with the lumen of the trachea. The mucous membrane lining the larynx forms two pairs of lateral folds that project inward into its cavity. The upper folds are called the vestibular folds . They are also sometimes called

11881-588: The vocal tract (the airway above the larynx) to assume the shapes necessary to produce speech sounds that enhance the robustness of human speech. Sounds such as the vowels of the words ⟨see⟩ and ⟨do⟩ , [i] and [u] (in phonetic notation), have been shown to be less subject to confusion in classic studies such as the 1950 Peterson and Barney investigation of the possibilities for computerized speech recognition . In contrast, though other species have low larynges, their tongues remain anchored in their mouths and their vocal tracts cannot produce

#102897