In anatomy and physiology , a duct is a circumscribed channel leading from an exocrine gland or organ .
34-527: The San Diego Aqueduct is a system of four aqueducts in the U.S. state of California , supplying about 70 percent of the water supply for the city of San Diego . The system comprises the First and Second San Diego Aqueducts, carrying water from the Colorado River west to reservoirs on the outskirts of San Diego. The 70-mile (110 km) First Aqueduct consists of pipelines 1 and 2, which run from
68-484: A capacity of 380 cu ft/s (11 m/s). Aqueduct (water supply) An aqueduct is a watercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the term aqueduct is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. The term aqueduct also often refers specifically to a bridge carrying an artificial watercourse . Aqueducts were used in ancient Greece ,
102-625: A construction material widely used by the Nazca culture. The time period in which they were constructed is still debated, but some evidence supports circa A.D. 540–552, in response to drought periods in the region. The Guayabo National Monument of Costa Rica, a park covering the largest archaeological site in the country, contains a system of aqueducts. The complex network of uncovered and covered aqueducts still functions well. The aqueducts are constructed from rounded river stones, which are mostly made of volcanic rock . The civilization that constructed
136-545: A fragment remains in Mexico City today. Extensive usage of elaborate aqueducts have been found to have been used in ancient Sri Lanka . The best example is the Yoda Ela or Jaya Ganga, an 87 kilometres (54 mi) long water canal carrying excess water between two artificial reservoirs with a gradient of 10 to 20 cm per kilometer during the fifth century AD. However, the ancient engineering methods in calculating
170-465: A new aqueduct is built alongside the old one because it cannot be shut down during construction. ductus Examples include: As ducts travel from the acinus which generates the fluid to the target, the ducts become larger and the epithelium becomes thicker. The parts of the system are classified as follows: Some sources consider "lobar" ducts to be the same as "interlobar ducts", while others consider lobar ducts to be larger and more distal from
204-437: A series of well-like vertical shafts, connected by gently sloping horizontal tunnels. There are three types of falaj: These enabled large scale agriculture to flourish in a dry land environment. In Persia , starting around 3000 years ago a system of underground aqueducts called qanāts were constructed, a series of well-like vertical shafts, connected by gently sloping tunnels. This technique: Throughout Petra , Jordan,
238-515: A source such as a river, spring, reservoir, qanat , or aqueduct for domestic consumption or agricultural irrigation of crop land uses. Rills were traditionally used in Middle Eastern and Mediterranean climate cultures of ancient and historical eras; and other climates and continents worldwide. They are distinguished from a 'water ditch ' by being lined to reduce absorption losses and to increase durability. The Falaj irrigation system at
272-642: A third is from the Colorado River. In modern civil engineering projects, detailed study and analysis of open-channel flow is commonly required to support flood control, irrigation systems, and large water supply systems when an aqueduct rather than a pipeline is the preferred solution. In the past, aqueducts often had channels made of earth or other porous materials but significant amounts of water are lost through such unlined aqueducts. As water gets increasingly scarce, these canals are being lined with concrete, polymers , or impermeable soil. In some cases,
306-595: Is 94 mi (151 km) long, beginning at the Colorado River Aqueduct, flowing into Lake Skinner and then into Lower Otay Reservoir near San Diego. In the first 16 mi (26 km) from the Colorado River Aqueduct to Lake Skinner, Pipeline 3 consists of an open canal handling approximately 500 cu ft/s (14 m/s). The remaining 78 mi (126 km) consist of pre-stressed 72-inch (180 cm) diameter concrete pipe and steel pipe. Pipeline 4 consists of pre-stressed concrete pipe with
340-532: Is believed to have some of the earliest aqueducts. Evidence can be found at the sites of present-day Hampi, Karnataka . The massive aqueducts near Tungabhadra River supplying irrigation water were once 15 miles (24 km) long. The waterways supplied water to royal bath tubs. In Oman from the Iron Age , in Salut, Bat, and other sites, a system of underground aqueducts called falaj or qanāts were constructed,
374-656: Is called a qanat. One historic example found in Syria, the Qanat Firaun, extends over 100 kilometers. Modern aqueducts may also make extensive use of pipelines. Pipelines are useful for transporting water over long distances when it needs to move over hills, or where open channels are poor choices due to considerations of evaporation , freezing, pollution, or environmental impact. They can also be used to carry treated water . Historically, agricultural societies have constructed aqueducts to irrigate crops. Archimedes invented
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#1732786860959408-723: Is derived from the Latin words aqua ( water ) and ductus ( led or guided ). Although particularly associated with the Romans, aqueducts were devised much earlier in Greece, the Near East , Nile Valley , and Indian subcontinent , where peoples such as the Egyptians and Harappans built sophisticated irrigation systems. The Aztecs and Incans also built such systems independently later. Roman-style aqueducts were used as early as
442-590: Is dwarfed by aqueducts in the far west of the country, most notably the 242-mile (389-km) Colorado River Aqueduct , which supplies the Los Angeles area with water from the Colorado River nearly 250 miles to the east and the 701.5-mile (1,129.0 km) California Aqueduct , which runs from the Sacramento-San Joaquin River Delta to Lake Perris . The Central Arizona Project is the largest and most expensive aqueduct constructed in
476-675: The Al Ain Oasis , in present-day Abu Dhabi Emirate , uses rills as part of its qanat water system. Sometimes in the Spanish language they are called Acequias . Rills are also used for aesthetic purposes in landscape design. Rills are used as narrow channels of water inset into the pavement of a garden , as linear water features , and often tiled and part of a fountain design. The historical origins are from paradise garden religious images that first translated into ancient Persian Gardens . Rills were later exceptionally developed in
510-616: The Colorado River Aqueduct near San Jacinto , California, to San Vicente Reservoir , approximately 15 miles (24 km) northeast of the city. Pipelines 3 and 4 make up the 94-mile (151 km) Second Aqueduct . Together, these four pipelines have a capacity of 826 cubic feet per second (23.4 m/s). The smaller, 12.5-mile (20.1 km) Fallbrook-Ocean Branch branches from the First Aqueduct into Murray Reservoir . The La Mesa-Sweetwater Branch originates from
544-954: The Moorish (Spanish) Gardens of Al-andalus , such as at the Alhambra in Granada ; and also in other Islamic gardens, cultures, and countries. Early 20th century examples are in the María Luisa Park gardens in Seville, Spain; and at the Casa del Herrero gardens in Montecito, California . Aqueducts sometimes run for some or all of their path through tunnels constructed underground. A version of this common in North Africa and Central Asia that has vertical wells at regular intervals
578-590: The Nabataean engineers took advantage of every natural spring and every winter downpour to channel water where it was needed. They constructed aqueducts and piping systems that allowed water to flow across mountains, through gorges and into the temples, homes, and gardens of Petra's citizens. Walking through the Siq , one can easily spot the remains of channels that directed water to the city center, as well as durable retention dams that kept powerful flood waters at bay. On
612-681: The South–North Water Transfer Project aims to connect the Yangtze River basin to Beijing through three separate systems. The project will reuse part of the Grand Canal of China . The simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts, for instance the Central Arizona Project uses 7.3 m (24 ft) wide channels. A major factor in
646-476: The ancient Near East , ancient Rome , ancient Aztec , and ancient Inca . The simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts. Aqueducts sometimes run for some or all of their path through tunnels constructed underground. Modern aqueducts may also use pipelines. Historically, agricultural societies have constructed aqueducts to irrigate crops and supply large cities with drinking water. The word aqueduct
680-467: The intralobular duct . This duct has the thinnest epithelium of any part of the duct system, and the epithelium is usually classified as "low" simple cuboidal . They are found in both the pancreas and in salivary glands . A striated duct ( Pflüger's ducts ) is a gland duct which connects an intercalated duct to an interlobular duct. It is characterized by the basal infoldings of its plasma membrane, characteristic of ion-pumping activity by
714-399: The parotid gland , but are more developed in the parotid gland. They are not present in pancreas . An intralobular duct is the portion of an exocrine gland inside a lobule , leading directly from acinus to an interlobular duct (between lobules). It is composed of two subdivisions, the intercalated duct and the striated duct . In the human mammary gland, the intralobular duct
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#1732786860959748-528: The water screw to raise water for use in irrigation of croplands. Another use for aqueducts is to supply large cities with drinking water. They also help drought-prone areas with water supply . Some of the Roman aqueducts still supply water to Rome today. In California , United States, three large aqueducts supply water over hundreds of miles to the Los Angeles area. Two are from the Owens River area, and
782-622: The 7th century BC, when the Assyrians built an 80 km long limestone aqueduct, which included a 10 m high section to cross a 300 m wide valley, to carry water to their capital city, Nineveh . Although particularly associated with the Romans , aqueducts were likely first used by the Minoans around 2000 BCE. The Minoans had developed what was then an extremely advanced irrigation system , including several aqueducts. The Indian subcontinent
816-530: The Colorado River Aqueduct in San Jacinto, California , just north of the San Jacinto River , continuing 70 mi (110 km) south to its terminus at San Vicente Reservoir . There are seven tunnels on the First Aqueduct, which range in length from 500 to 5,700 ft (150 to 1,740 m). The total capacity of the First Aqueduct is 196 cu ft/s (5.6 m/s). The Second Aqueduct
850-823: The First Aqueduct, flowing into Sweetwater Reservoir . The First Aqueduct was designed by the Bureau of Reclamation and constructed from 1945 to 1947 by the Navy Department . Pipeline 2, of the First Aqueduct, was built by the Bureau of Reclamation from 1952 and 1957, roughly paralleling Pipeline 1. In 1957, the construction of Pipeline 3 of the Second Aqueduct was begun by the Metropolitan Water District (MWD), completing it in May 1960. In 1968,
884-850: The United States. It stretches 336 miles from its source near Parker, Arizona to the metropolitan areas of Phoenix and Tucson . An aqueduct in New Zealand, "the Oamaru Borough Race", was constructed in the late 19th century to deliver water (and water-power) about 50 km from the Waitaki River at Kurow to the coastal town of Oamaru . In Spain, the Tagus-Segura Water Transfer system of aqueducts opened in 1979 and transports water 286 kilometres (178 mi) from north to south. In China,
918-430: The acinus. For sources that make the distinction, the interlobar ducts are more likely to classified with simple columnar epithelium (or pseudostratified epithelium ), reserving the stratified columnar for the lobar ducts. The intercalated duct , also called intercalary duct (ducts of Boll), is the portion of an exocrine gland leading directly from the acinus to a striated duct . The intercalated duct forms part of
952-604: The aqueduct system remains a mystery to archaeologists; it is suspected that Guayabo's aqueducts sat at a point of ancient cultural confluence between Aztecs, Mayans, and Incas. When Europeans saw the Aztec capital Tenochtitlan , early in the 16th century, the city was watered by two aqueducts. One of these, Chapultepec aqueduct , built c. 1420 , was rebuilt by the Spanish almost three hundred years later. Originally tracing part of its path over now-gone Lake Texcoco , only
986-588: The construction of Pipeline 4, of the Second Aqueduct, began. Pipeline 4 was completed in 1971. In 2005, the San Diego County Water Authority began construction on the 11-mile-long (18 km), 8.5-foot-wide (2.6 m) San Vicente Pipeline, connecting San Vicente Reservoir to the Second Aqueduct. Construction on the project was completed in 2010. The First Aqueduct, built of two parallel precast concrete pipes, ranging in diameter from 96 to 48 in (240 to 120 cm), branches from
1020-493: The design of all open channels is its gradient. A higher gradient allows a smaller channel to carry the same amount of water as a larger channel with a lower gradient, but increases the potential of the water to damage the aqueduct's structure. A typical Roman aqueduct had a gradient of about 1:4800. A constructed functional rill is a small canal or aqueduct of stone, brick, concrete, or other lining material, usually rectilinear in cross section , for water transportation from
1054-524: The empire, and set a standard of engineering that was not surpassed for more than a thousand years. Bridges, built in stone with multiple arches, were a distinctive feature of Roman aqueducts and hence the term aqueduct is often applied specifically to a bridge for carrying water . Near the Peruvian town of Nazca, an ancient pre-Columbian system of aqueducts called puquios were built and are still in use today. They were made of intricately placed stones,
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1088-430: The exact elevation between the two reservoirs and the exact gradient of the canal to such fine precision had been lost with the fall of the civilization in 13th Century. Modern aqueducts are a central part of many countries' water distribution infrastructure. The United States' aqueducts are some of the world's largest. The Catskill Aqueduct carries water to New York City over a distance of 120 miles (190 km), but
1122-610: The island of Samos , the Tunnel of Eupalinos was built during the reign of Polycrates (538–522 BC). It is considered an underground aqueduct and brought fresh water to Pythagoreion for roughly a thousand years. Roman aqueducts were built in all parts of the Roman Empire , from Germany to Africa, and especially in the city of Rome, where they totalled over 415 kilometres (258 mi). The aqueducts supplied fresh water to public baths and for drinking water, in large cities across
1156-535: The numerous mitochondria. Along with the intercalated ducts, they function to modify salivary fluid by secreting HCO 3 and K and reabsorbing Na and Cl using the Na-K pump and the Cl-HCO 3 pump, making the saliva hypotonic. Their epithelium can be simple cuboidal or simple columnar . Striated ducts are part of the intralobular ducts . They are found in the submandibular gland , sublingual duct , and
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