Misplaced Pages

#474525

95-557: Cyclophoroidea is a superfamily of land snails with an operculum , terrestrial gastropods within the order Architaenioglossa , that belongs to the subclass Caenogastropoda . These terrestrial gastropods have lost the ctenidium (comb-like respiratory apparatus) and osphradium , and the pallial cavity has been modified as a lung . According to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) , this superfamily consists of

190-495: A gill and an operculum . The largest clade of land snails is the Cyclophoroidea , with more than 7,000 species. Many of these operculate land snails live in habitats or microhabitats that are sometimes (or often) damp or wet, such as in moss . Land snails have a strong muscular foot; they use mucus to enable them to crawl over rough surfaces and to keep their soft bodies from drying out. Like other mollusks, land snails have

285-436: A mantle , a specialized layer of tissue which covers all of the internal organs as they are grouped together in the visceral mass. The mantle also extends outward in flaps which reach to the edge of the shell and in some cases can cover the shell, and which are partially retractable. The mantle is attached to the shell, and creates the shell and makes shell growth possible by secretion. Most molluscs, including land snails, have

380-402: A mantle , and they have one or two pairs of tentacles on their head. Their internal anatomy includes a radula and a primitive brain. In terms of reproduction, many caenogastropod land snails (e.g., diplommatinids ) are dioecious , but pulmonate land snails are hermaphrodites (they have a full set of organs of both sexes) and most lay clutches of eggs in the soil. Tiny snails hatch out of

475-428: A shell which is part of their anatomy since the larval stage. When they are active, the organs such as the lung , heart , kidney , and intestines remain inside the shell; only the head and foot emerge. The shell grows with them in size by the process of secreting calcium carbonate along the open edge and on the inner side for extra strength. Although some land snails create shells that are almost entirely formed from

570-631: A butter sauce, but other dishes also exist such as feijoada de caracóis . Overall, Portugal consumes about 4,000 tonnes of snails each year. Traditional Spanish cuisine also uses snails ("caracoles" in Spanish; "caragols" or "cargols" in Catalan), consuming several species such as Cornu aspersum , Otala lactea , Otala punctata and Theba pisana . Snails are very popular in Andalusia , Valencia and Catalonia . There are even snail celebrations, such as

665-524: A delicacy in French cuisine , where they are called escargots . 191 farms produced escargots in France as of 2014. In an English-language menu, escargot is generally reserved for snails prepared with traditional French recipes (served in the shell with a garlic and parsley butter). Before preparing snails to eat, the snails should be fasting for three days with only water available. After three days of fasting,

760-634: A delicacy. Achatina achatina , Ghana tiger snails, are also known as some of the largest snails in the world. Snail, called "igbin" in Yoruba language is a delicacy, widely eaten in Nigeria, especially among the Yorubas and Igbos. In Cameroon , snails, usually called 'nyamangoro' and 'slow boys' are a delicacy especially to natives of the South West region of Cameroon. The snails are either eaten cooked and spiced or with

855-566: A door-like anatomical structure called an operculum . Land snails range greatly in size. The largest living species is the Giant African Snail or Ghana Tiger Snail ( Achatina achatina ; Family Achatinidae ), which can measure up to 30 cm. The largest land snails of non-tropical Eurasia are endemic Caucasian snails Helix buchi and Helix goderdziana from the south-eastern Black Sea area in Georgia and Turkey ; diameter of

950-744: A dry layer of mucus called an epiphragm . The great majority of land snails are hermaphrodites with a full set of reproductive organs of both sexes, able to produce both spermatozoa and ova . A few groups of land snails such as the Pomatiidae , which are distantly related to periwinkles , have separate sexes: male and female. The age of sexual maturity varies depending on species of snail, ranging from as little as 6 weeks to 5 years. Adverse environmental conditions may delay sexual maturity in some snail species. Most pulmonate air-breathing land snails perform courtship behaviors before mating. The courtship may last anywhere between two and twelve hours. In

1045-486: A favourite dish called 'eru'. In North Morocco , small snails are eaten as snacks in spicy soup. The recipe is identical to this prepared in Andalusia (South Spain), showing the close cultural relationship between both kinds of cuisine. Snails are eaten in several European countries, as they were in the past in the Roman Empire . Mainly three species, all from the family Helicidae , are ordinarily eaten: Snails are

SECTION 10

#1732855780475

1140-405: A large land snail can be heard 'crunching' its food: the radula is tearing away at the surface of the food that the snail is eating. The cerebral ganglia of the snail form a primitive brain which is divided into four sections. This structure is very much simpler than the brains of mammals , reptiles and birds , but nonetheless, snails are capable of associative learning . Since snails in

1235-417: A lower lobe, by the oblique fissure, which extends from the costal to the mediastinal surface of the lung both above and below the hilum . The left lung, unlike the right, does not have a middle lobe, though it does have a homologous feature, a projection of the upper lobe termed the lingula . Its name means "little tongue". The lingula on the left lung serves as an anatomic parallel to the middle lobe on

1330-443: A number of different families of land snails and slugs, prior to mating one or more love darts are fired into the body of the partner. Pulmonate land snails are prolific breeders and inseminate each other in pairs to internally fertilize their ova via a reproductive opening on one side of the body, near the front, through which the outer reproductive organs are extruded so that sperm can be exchanged. Fertilization then occurs and

1425-641: A popular dish. They are usually boiled with salt first, then served with tomato sauce or bare with oil, garlic and parsley. Snails are similarly appreciated in other Italian regions, such as Piedmont where in Cherasco there is the Italian National Institute of Heliculture. Snails (or bebbux as they are called in Maltese ) are a dish on the Mediterranean island of Malta , generally prepared and served in

1520-485: A right lung with only two lobes, or a left lung with three lobes. A variation in the airway branching structure has been found specifically in the central airway branching. This variation is associated with the development of COPD in adulthood. The development of the human lungs arise from the laryngotracheal groove and develop to maturity over several weeks in the foetus and for several years following birth. The larynx , trachea , bronchi and lungs that make up

1615-414: Is also responsible for the elastic recoil needed. Elastin is more concentrated in areas of high stress such as the openings of the alveoli, and alveolar junctions. The connective tissue links all the alveoli to form the lung parenchyma which has a sponge-like appearance. The alveoli have interconnecting air passages in their walls known as the pores of Kohn . All of the lower respiratory tract including

1710-460: Is bigger than the left, the left lung shares space in the chest with the heart. The lungs together weigh approximately 1.3 kilograms (2.9 lb), and the right is heavier. The lungs are part of the lower respiratory tract that begins at the trachea and branches into the bronchi and bronchioles , and which receive air breathed in via the conducting zone . These divide until air reaches microscopic alveoli , where gas exchange takes place. Together,

1805-422: Is divided into three lobes by a horizontal fissure , and an oblique fissure . The left lung is divided into two lobes by an oblique fissure which is closely aligned with the oblique fissure in the right lung. In the right lung the upper horizontal fissure, separates the upper (superior) lobe from the middle lobe. The lower, oblique fissure separates the lower lobe from the middle and upper lobes. Variations in

1900-401: Is held in the fluid-filled amniotic sac and so they do not function to breathe. Blood is also diverted from the lungs through the ductus arteriosus . At birth however, air begins to pass through the lungs, and the diversionary duct closes, so that the lungs can begin to respire. The lungs only fully develop in early childhood. In humans the lungs are located in the chest on either side of

1995-427: Is likely to be made up of between 30 and 50 primary lobules. The lobule is supplied by a terminal bronchiole that branches into respiratory bronchioles. The respiratory bronchioles supply the alveoli in each acinus and is accompanied by a pulmonary artery branch. Each lobule is enclosed by an interlobular septum. Each acinus is incompletely separated by an intralobular septum. The respiratory bronchiole gives rise to

SECTION 20

#1732855780475

2090-489: Is lubricated with mucus and covered with epithelial cilia . This motion is powered by succeeding waves of muscular contractions that move down the ventral of the foot. This muscular action is clearly visible when a snail is crawling on the glass of a window or aquarium. Snails move at a proverbially low speed (1 mm/s is a typical speed for adult Helix lucorum ). Snails secrete mucus externally to keep their soft bodies from drying out. They also secrete mucus from

2185-572: Is not usually considered to be a tradition of snail eating in Great Britain , common garden snails Cornu aspersum were eaten in the Southwick area of Sunderland in North East England . They were collected from quarries and along the stone walls of railway embankments during the winter when the snails were hibernating and had voided the contents of their guts. Gibson writes that this tradition

2280-451: Is strong evidence for selfing ( self-fertilization ) in the easternmost snail populations as indicated by microsatellite data. Compared to western populations, in the eastern population mucous gland structures employed in sexual reproduction are highly variable and deformed suggesting that in selfing organisms these structures have reduced function. Most species of land snail are annual, others are known to live 2 or 3 years, but some of

2375-435: Is the part of the lung distal to the respiratory bronchiole. Thus, it includes the alveolar ducts, sacs, and alveoli but not the respiratory bronchioles. The unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule . This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid. The secondary pulmonary lobule

2470-863: The Pleistocene . Archaeological evidence of snail consumption is especially abundant in Capsian sites in North Africa , but is also found throughout the Mediterranean region in archaeological sites dating between 12,000 and 6,000 years ago. Snail eggs, sold as snail caviar , are a specialty food that is growing in popularity in European cuisine. Snails contain many nutrients . They are rich in calcium and also contain vitamin B 1 and E . They contain various essential amino acids , and are low in calories and fat . However, wild-caught land snails which are prepared for

2565-462: The backbone on either side of the heart . Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange . Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their musculoskeletal systems to support and foster breathing. In early tetrapods, air

2660-425: The carina where the trachea divides into the two main bronchi. The cardiac impression is an indentation formed on the surfaces of the lungs where they rest against the heart. Both lungs have a central recession called the hilum , where the blood vessels and airways pass into the lungs making up the root of the lung . There are also bronchopulmonary lymph nodes on the hilum. The lungs are surrounded by

2755-470: The circulation , and carbon dioxide diffuses from the blood into the lungs to be breathed out . Estimates of the total surface area of lungs vary from 50 to 75 square metres (540 to 810 sq ft); although this is often quoted in textbooks and the media being "the size of a tennis court", it is actually less than half the size of a singles court . The bronchi in the conducting zone are reinforced with hyaline cartilage in order to hold open

2850-438: The esophagus behind the hilum and the pulmonary ligament , and near the lower part of the esophageal groove is a deeper groove for the inferior vena cava before it enters the heart. The weight of the right lung varies between individuals, with a standard reference range in men of 155–720 g (0.342–1.587 lb) and in women of 100–590 g (0.22–1.30 lb). The left lung is divided into two lobes, an upper and

2945-418: The heart in the rib cage . They are conical in shape with a narrow rounded apex at the top, and a broad concave base that rests on the convex surface of the diaphragm . The apex of the lung extends into the root of the neck, reaching shortly above the level of the sternal end of the first rib . The lungs stretch from close to the backbone in the rib cage to the front of the chest and downwards from

Cyclophoroidea - Misplaced Pages Continue

3040-672: The immune system . They remove substances which deposit in the alveoli including loose red blood cells that have been forced out from blood vessels. There is a large presence of microorganisms in the lungs known as the lung microbiota that interacts with the airway epithelial cells; an interaction of probable importance in maintaining homeostasis. The microbiota is complex and dynamic in healthy people, and altered in diseases such as asthma and COPD . For example significant changes can take place in COPD following infection with rhinovirus . Fungal genera that are commonly found as mycobiota in

3135-427: The pulmonary pleurae . The pleurae are two serous membranes ; the outer parietal pleura lines the inner wall of the rib cage and the inner visceral pleura directly lines the surface of the lungs. Between the pleurae is a potential space called the pleural cavity containing a thin layer of lubricating pleural fluid . Middle Lower Lingula Lower Each lung is divided into sections called lobes by

3230-457: The " L'Aplec del Caragol ", which takes place in Lleida each May and draws more than 200,000 visitors from abroad. Small to medium-sized varieties are usually cooked in one of several spicy sauces or even in soups, and eaten as an appetizer. The bigger ones may be reserved for more elaborate dishes, such as the "arroz con conejo y caracoles" (a paella -style rice with snails and rabbit meat, from

3325-474: The French style with garlic butter. Metaldehyde and iron phosphate can be used to exterminate snails. Since copper generates electric shocks that make it difficult for snails to move, it makes a great barrier material for them. Lung The lungs are the primary organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods , two lungs are located near

3420-657: The Sicilian manner. In southwestern Germany there is a regional specialty of soup with snails and herbs, called "Black Forest Snail Chowder" ( Badener Schneckensuepple ). Heliciculture is the farming of snails. Some species such as the Roman snail are protected in the wild in several European countries and must not be collected, but the Roman Snail and the Garden Snail ( Cornu aspersum ) are cultivated on snail farms. Although there

3515-473: The airways initiate a reflex known as the Hering–Breuer reflex that prevents the lungs from over-inflation, during forceful inspiration. The lungs have a dual blood supply provided by a bronchial and a pulmonary circulation . The bronchial circulation supplies oxygenated blood to the airways of the lungs, through the bronchial arteries that leave the aorta . There are usually three arteries, two to

3610-399: The airways. The bronchioles have no cartilage and are surrounded instead by smooth muscle . Air is warmed to 37 °C (99 °F), humidified and cleansed by the conducting zone. Particles from the air being removed by the cilia on the respiratory epithelium lining the passageways, in a process called mucociliary clearance . Pulmonary stretch receptors in the smooth muscle of

3705-464: The alveolar ducts that lead to the alveolar sacs, which contain two or more alveoli. The walls of the alveoli are extremely thin allowing a fast rate of diffusion . The alveoli have interconnecting small air passages in their walls known as the pores of Kohn . Alveoli consist of two types of alveolar cell and an alveolar macrophage . The two types of cell are known as type I and type II cells (also known as pneumocytes). Types I and II make up

3800-474: The alveolar septa which separate each alveolus. The septa consist of an epithelial lining and associated basement membranes . Type I cells are not able to divide, and consequently rely on differentiation from Type II cells. Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant . Type II cells are able to divide and differentiate to Type I cells. The alveolar macrophages have an important role in

3895-458: The alveoli. The four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4 . FGF10 is seen to have the most prominent role. FGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10. The development of

Cyclophoroidea - Misplaced Pages Continue

3990-410: The base of the lung. By standard reference range , the weight of the left lung is 110–675 g (0.243–1.488 lb) in men and 105–515 g (0.231–1.135 lb) in women. The lungs are part of the lower respiratory tract , and accommodate the bronchial airways when they branch from the trachea. The bronchial airways terminate in alveoli which make up the functional tissue ( parenchyma ) of

4085-416: The branch. In the development of the lungs (as in some other organs) the epithelium forms branching tubes. The lung has a left-right symmetry and each bud known as a bronchial bud grows out as a tubular epithelium that becomes a bronchus. Each bronchus branches into bronchioles. The branching is a result of the tip of each tube bifurcating. The branching process forms the bronchi, bronchioles, and ultimately

4180-468: The breakdown of the polysaccharide cellulose into simple sugars. Some species can cause damage to agricultural crops and garden plants, and are therefore often regarded as pests . Many predators, both specialist and generalist, feed on snails. Some animals, such as the song thrush , break the shell of the snail by hammering it against a hard object, such as stone, to expose its edible insides. Other predators, such as some species of frogs , circumvent

4275-402: The bronchus and bronchioles, and increases the secretions from glands. The lungs also have a sympathetic tone from norepinephrine acting on the beta 2 adrenoceptors in the respiratory tract, which causes bronchodilation . The action of breathing takes place because of nerve signals sent by the respiratory center in the brainstem , along the phrenic nerve from the cervical plexus to

4370-533: The composition of which is tightly regulated and determines how well mucociliary clearance works. Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, though they only account for around 0.5 percent of the total epithelial population. PNECs are innervated airway epithelial cells that are particularly focused at airway junction points. These cells can produce serotonin, dopamine, and norepinephrine, as well as polypeptide products. Cytoplasmic processes from

4465-454: The country and can even be found in supermarkets , sometimes placed alive near partly refrigerated vegetables . In this regard, snails are one of the few live organisms sold at supermarkets as food. They are eaten either boiled with vinegar added, or sometimes cooked alive in a casserole with tomato, potatoes and squashes . Limpets and sea snails also find their way to the Greek table around

4560-517: The country. Another snail cooking method is the Kohli Bourbouristi ( κοχλιοί μπου(ρ)μπουριστοί ), a traditional Cretan dish , which consists of fried snails in olive oil with salt, vinegar and rosemary. They often feature on Cyprus taverna menus, in the meze section, under the name karaoloi ( καράολοι ). In Sicily , snails (or babbaluci as they are commonly called in Sicilian ) are

4655-423: The diaphragm. The lobes of the lung are subject to anatomical variations . A horizontal interlobar fissure was found to be incomplete in 25% of right lungs, or even absent in 11% of all cases. An accessory fissure was also found in 14% and 22% of left and right lungs, respectively. An oblique fissure was found to be incomplete in 21% to 47% of left lungs. In some cases a fissure is absent, or extra, resulting in

4750-451: The egg with a small shell in place, and the shell grows spirally as the soft parts gradually increase in size. Most land snails have shells that are right-handed in their coiling. A wide range of different vertebrate and invertebrate animals prey on land snails. They are used as food by humans in various cultures worldwide, and are raised on farms in some areas for use as food. Land snails move by gliding along on their muscular foot , which

4845-484: The eggs develop. Each brood may consist of up to 100 eggs . Garden snails bury their eggs in shallow topsoil primarily while the weather is warm and damp, usually 5 to 10 cm down, digging with their foot. Egg sizes differ between species, from a 3 mm diameter in the grove snail to a 6 mm diameter in the Giant African Land Snail. After 2 to 4 weeks of favorable weather, these eggs hatch and

SECTION 50

#1732855780475

4940-460: The fissures are fairly common being either incompletely formed or present as an extra fissure as in the azygos fissure , or absent. Incomplete fissures are responsible for interlobar collateral ventilation , airflow between lobes which is unwanted in some lung volume reduction procedures. The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of

5035-733: The flatworms in the process and becoming the final hosts of the flatworm. Human activity poses great dangers to snails in the wild. Pollution and habitat destruction have caused the extinction of a considerable number of snail species in recent years. Snails easily suffer moisture loss. Snails are most active at night and after rainfall . During unfavourable conditions, a snail remains inside its shell, usually under rocks or other hiding places, to avoid being discovered by predators . In dry climates, snails naturally congregate near water sources, including artificial sources such as wastewater outlets of air conditioners . Land snails have been eaten for thousands of years, going back at least as far as

5130-470: The following families : Land snail Land snails are a polyphyletic group comprising at least ten independent evolutionary transitions to terrestrial life (the last common ancestor of all gastropods was marine). The majority of land snails are pulmonates that have a lung and breathe air. Most of the non-pulmonate land snails belong to lineages in the Caenogastropoda , and tend to have

5225-444: The foot to aid in locomotion by reducing friction , and to help reduce the risk of mechanical injury from sharp objects, meaning they can crawl over a sharp edge like a straight razor and not be injured. The mucus that land snails secrete with the foot leaves a slime trail behind them, which is often visible for some hours afterwards as a shiny "path" on the surface over which they have crawled. Snails (like all molluscs) also have

5320-529: The genus Polymita , and the indigenous snails of Hawaii . In an attempt to protect themselves against predators, land snails retract their soft parts into their shell when they are resting; some bury themselves. Land snails have many natural predators, including members of all the land vertebrate groups, three examples being thrushes , hedgehogs and Pareas snakes. Invertebrate predators include decollate snails , ground beetles , leeches , certain land flatworms such as Platydemus manokwari and even

5415-401: The genus Helix are terrestrial rather than freshwater or marine, they have developed a simple lung for respiration. (Most other snails and gastropods have gills , instead.) Oxygen is carried by the blood pigment hemocyanin . Both oxygen and carbon dioxide diffuse in and out of blood through the capillaries . A muscular valve regulates the process of opening and closing the entrance of

5510-406: The hilum, is a well-marked curved groove for the aortic arch , and a groove below it for the descending aorta . The left subclavian artery , a branch off the aortic arch, sits in a groove from the arch to near the apex of the lung. A shallower groove in front of the artery and near the edge of the lung, lodges the left brachiocephalic vein . The esophagus may sit in a wider shallow impression at

5605-413: The infoldings of the visceral pleura as fissures. Lobes are divided into segments, and segments have further divisions as lobules. There are three lobes in the right lung and two lobes in the left lung. The fissures are formed in early prenatal development by invaginations of the visceral pleura that divide the lobar bronchi, and section the lungs into lobes that helps in their expansion. The right lung

5700-451: The inner regions of south-eastern Spain ), "cabrillas" (snails in spicy tomato sauce, typical of western Andalusia) and the Catalan caragols a la llauna (grilled inside their own shells and then eaten after dipping them in garlic mayonnaise ) and a la gormanda (boiled in tomato and onion sauce). In Greece , snails are popular in the island of Crete , but are also eaten in many parts of

5795-448: The larger species may live over 10 years in the wild. For instance, 10-year old individuals of the Roman snail Helix pomatia are probably not uncommon in natural populations. Populations of some threatened species may be dependent on a pool of such long-lived adults. In captivity, the lifespan of snails can be much longer than in the wild, for instance up to 25 years in H. pomatia . In

SECTION 60

#1732855780475

5890-628: The left has two. The lobes are further divided into bronchopulmonary segments and lobules. The lungs have a unique blood supply, receiving deoxygenated blood sent from the heart for the purposes of receiving oxygen (the pulmonary circulation ) and a separate supply of oxygenated blood (the bronchial circulation ). The tissue of the lungs can be affected by a number of respiratory diseases , including pneumonia and lung cancer . Chronic diseases such as chronic obstructive pulmonary disease and emphysema can be related to smoking or exposure to harmful substances. Diseases such as bronchitis can also affect

5985-458: The left lung and one to the right, and they branch alongside the bronchi and bronchioles. The pulmonary circulation carries deoxygenated blood from the heart to the lungs and returns the oxygenated blood to the heart to supply the rest of the body. The blood volume of the lungs is about 450 millilitres on average, about 9% of the total blood volume of the entire circulatory system. This quantity can easily fluctuate from between one-half and twice

6080-420: The lower part of the trachea to the diaphragm. The left lung shares space with the heart, and has an indentation in its border called the cardiac notch of the left lung to accommodate this. The front and outer sides of the lungs face the ribs, which make light indentations on their surfaces. The medial surfaces of the lungs face towards the centre of the chest, and lie against the heart, great vessels , and

6175-495: The lung, and veins, arteries, nerves, and lymphatic vessels . The trachea and bronchi have plexuses of lymph capillaries in their mucosa and submucosa. The smaller bronchi have a single layer of lymph capillaries, and they are absent in the alveoli. The lungs are supplied with the largest lymphatic drainage system of any other organ in the body. Each lung is surrounded by a serous membrane of visceral pleura , which has an underlying layer of loose connective tissue attached to

6270-415: The lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments . Each bronchopulmonary segment has its own (segmental) bronchus and arterial supply . Segments for the left and right lung are shown in the table. The segmental anatomy is useful clinically for localising disease processes in

6365-425: The lung. When the valve opens, the air can either enter or leave the lung. The valve plays an important role in reducing water loss and preventing drowning. As the snail grows, so does its calcium carbonate shell. The shell grows additively, by the addition of new calcium carbonate, which is secreted by glands located in the snail's mantle . The new material is added to the edge of the shell aperture (the opening of

6460-404: The lungs contain approximately 2,400 kilometres (1,500 mi) of airways and 300 to 500 million alveoli. Each lung is enclosed within a pleural sac of two pleurae which allows the inner and outer walls to slide over each other whilst breathing takes place, without much friction. The inner visceral pleura divides each lung as fissures into sections called lobes. The right lung has three lobes and

6555-419: The lungs. A segment is a discrete unit that can be surgically removed without seriously affecting surrounding tissue. The right lung has both more lobes and segments than the left. It is divided into three lobes, an upper, middle, and a lower lobe by two fissures, one oblique and one horizontal. The upper, horizontal fissure, separates the upper from the middle lobe. It begins in the lower oblique fissure near

6650-409: The microbiota include Candida , Malassezia , Saccharomyces , and Aspergillus . The lower respiratory tract is part of the respiratory system , and consists of the trachea and the structures below this including the lungs. The trachea receives air from the pharynx and travels down to a place where it splits (the carina ) into a right and left primary bronchus . These supply air to

6745-457: The need to break snail shells by simply swallowing the snail whole, shell and all. Some carnivorous species of snails, such as the decollate snail and the rosy wolf snail , also prey on other land snails. Such carnivorous snails are commercially grown and sold to combat pest snail species. Many of these also escape into the wild, where they prey on indigenous snails, such as the Cuban land snails of

6840-416: The normal volume. Also, in the event of blood loss through hemorrhage, blood from the lungs can partially compensate by automatically transferring to the systemic circulation. The lungs are supplied by nerves of the autonomic nervous system . Input from the parasympathetic nervous system occurs via the vagus nerve . When stimulated by acetylcholine , this causes constriction of the smooth muscle lining

6935-406: The posterior border of the lung, and, running horizontally forward, cuts the anterior border on a level with the sternal end of the fourth costal cartilage ; on the mediastinal surface it may be traced back to the hilum . The lower, oblique fissure, separates the lower from the middle and upper lobes and is closely aligned with the oblique fissure in the left lung. The mediastinal surface of

7030-401: The predatory caterpillar Hyposmocoma molluscivora . In the case of the marsh snail Succinea putris , the snails can be parasitized by a microscopic flatworm of the species Leucochloridium paradoxum , which then reproduces within the snail's body. The flatworms invade the snail's eye stalks, causing them to become enlarged. Birds are attracted to and consume these eye stalks, consuming

7125-490: The protein conchiolin , most land snails need a good supply of calcium in their diet and environment to produce a strong shell. A lack of calcium, or low pH in their surroundings, can result in thin, cracked, or perforated shells. Usually, a snail can repair damage to its shell over time if its living conditions improve, but severe damage can be fatal. When retracted into their shells, many snails with gills (including some terrestrial species) are able to protect themselves with

7220-467: The pulmonary neuroendocrine cells extend into the airway lumen where they may sense the composition of inspired gas. In the bronchi there are incomplete tracheal rings of cartilage and smaller plates of cartilage that keep them open. Bronchioles are too narrow to support cartilage and their walls are of smooth muscle , and this is largely absent in the narrower respiratory bronchioles which are mainly just of epithelium. The absence of cartilage in

7315-404: The respiratory tract, begin to form during the fourth week of embryogenesis from the lung bud which appears ventrally to the caudal portion of the foregut . The respiratory tract has a branching structure, and is also known as the respiratory tree. In the embryo this structure is developed in the process of branching morphogenesis , and is generated by the repeated splitting of the tip of

7410-452: The respiratory tract. Medical terms related to the lung often begin with pulmo-, from the Latin pulmonarius (of the lungs) as in pulmonology, or with pneumo- (from Greek πνεύμων "lung") as in pneumonia. In embryonic development , the lungs begin to develop as an outpouching of the foregut , a tube which goes on to form the upper part of the digestive system . When the lungs are formed the fetus

7505-429: The right and left lungs, splitting progressively into the secondary and tertiary bronchi for the lobes of the lungs, and into smaller and smaller bronchioles until they become the respiratory bronchioles . These in turn supply air through alveolar ducts into the alveoli , where the exchange of gases take place. Oxygen breathed in , diffuses through the walls of the alveoli into the enveloping capillaries and into

7600-403: The right lung is indented by a number of nearby structures. The heart sits in an impression called the cardiac impression. Above the hilum of the lung is an arched groove for the azygos vein , and above this is a wide groove for the superior vena cava and right brachiocephalic vein ; behind this, and close to the top of the lung is a groove for the brachiocephalic artery . There is a groove for

7695-425: The right lung, with both areas being predisposed to similar infections and anatomic complications. There are two bronchopulmonary segments of the lingula: superior and inferior. The mediastinal surface of the left lung has a large cardiac impression where the heart sits. This is deeper and larger than that on the right lung, at which level the heart projects to the left. On the same surface, immediately above

7790-476: The shell is held with the apex (the tip, or the juvenile whorls) pointing towards the observer, the spiral proceeds in a clockwise direction from the apex to the opening. Some snails hibernate during the winter (typically October through April in the Northern Hemisphere). They may also estivate in the summer in drought conditions. To stay moist during hibernation, a snail seals its shell opening with

7885-408: The shell of the latter may exceed 6 cm. At the other end of the size spectrum is Angustopila psammion , a species with shell diameter of 0.60-0.68 mm. Most land snails bear one or two pairs of tentacles on their heads. In most land snails the eyes are carried on the first (upper) set of tentacles (called ommatophores or more informally 'eye stalks') which are usually roughly 75% of

7980-420: The shell). Therefore, the centre of the shell's spiral was made when the snail was younger, and the outer part when the snail was older. When the snail reaches full adult size, it may build a thickened lip around the shell aperture. At this point the snail stops growing, and begins reproducing. A snail's shell forms a logarithmic spiral . Most snail shells are right-handed or dextral in coiling, meaning that if

8075-567: The snails should be fed flour and offered water for at least a week. This process is thought to cleanse the snails. Snails are also popular in Portuguese cuisine where they are called in Portuguese caracóis , and served in cheap snack houses and taverns, usually stewed (with different mixtures of white wine , garlic, piri piri , oregano , coriander or parsley, and sometimes chouriço ). Bigger varieties, called caracoletas (especially, Cornu aspersum ), are generally grilled and served with

8170-441: The substance of the lung. The connective tissue of the lungs is made up of elastic and collagen fibres that are interspersed between the capillaries and the alveolar walls. Elastin is the key protein of the extracellular matrix and is the main component of the elastic fibres . Elastin gives the necessary elasticity and resilience required for the persistent stretching involved in breathing, known as lung compliance . It

8265-472: The table but are not thoroughly cooked, can harbor a parasite ( Angiostrongylus cantonensis ) that can cause a rare kind of meningitis . The process of snail farming is called heliciculture . The establishment of snail farms outside of Europe has introduced several species to North America, South America, and Africa, where some escapees have established themselves as invasive species . In parts of West Africa , specifically Ghana , snails are served as

8360-467: The terminal bronchioles gives them an alternative name of membranous bronchioles . The conducting zone of the respiratory tract ends at the terminal bronchioles when they branch into the respiratory bronchioles. This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs , and alveoli. An acinus measures up to 10 mm in diameter. A primary pulmonary lobule

8455-451: The trachea, bronchi, and bronchioles is lined with respiratory epithelium . This is a ciliated epithelium interspersed with goblet cells which produce mucin the main component of mucus , ciliated cells, basal cells , and in the terminal bronchioles – club cells with actions similar to basal cells, and macrophages . The epithelial cells, and the submucosal glands throughout the respiratory tract secrete airway surface liquid (ASL),

8550-464: The walls and alveolar septa . Type I cells provide 95% of the surface area of each alveoli and are flat (" squamous "), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape. Despite this, cells occur in a roughly equal ratio of 1:1 or 6:4. Type I are squamous epithelial cells that make up the alveolar wall structure. They have extremely thin walls that enable an easy gas exchange. These type I cells also make up

8645-410: The width of the eyes. The second (lower) set of tentacles act as olfactory organs. Both sets of tentacles are retractable in land snails . A snail breaks up its food using the radula inside its mouth. The radula is a chitinous ribbon-like structure containing rows of microscopic teeth. With this the snail scrapes at food, which is then transferred to the digestive tract . In a very quiet setting,

8740-480: The wild, snails eat a variety of different foods. Terrestrial snails are usually herbivorous, however some species are predatory carnivores or omnivores, including the genus Powelliphanta , which includes the largest carnivorous snails in the world, native to New Zealand. The diet of most land snails can include leaves, stems, soft bark, fruit, vegetables, fungi and algae . They may have a specialized crop of symbiotic bacteria that aid in digestion, especially with

8835-457: The young emerge. Snails may lay eggs as often as once a month. There have been hybridizations of snail species; although these do not occur commonly in the wild, in captivity they can be coaxed into doing so. Parthenogenesis has been reported only in one species of slug, but many species can self-fertilise. C. obtusus is a prominent endemic snail species of the Eastern Alps . There

8930-400: Was driven into the lungs by the pharyngeal muscles via buccal pumping , a mechanism still seen in amphibians. In humans, the primary muscle that drives breathing is the diaphragm . The lungs also provide airflow that makes vocalisation including speech possible. Humans have two lungs, a right lung and a left lung. They are situated within the thoracic cavity of the chest . The right lung

9025-437: Was introduced in the 19th century by French immigrant glass workers. "Snail suppers" were a feature of local pubs and Southwick working men were collecting and eating snails as late as the 1970s, though the tradition may now have died out. In New Caledonia , Placostylus fibratus (French: bulime ) is considered a highly prized delicacy and is locally farmed to ensure supplies. It is often served by restaurants prepared in

#474525