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An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels,
leaf vein A leaf ( : leaves) is any of the principal appendages of a vascular plant stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, ste ...
s, or streams. Such a connection may be normal (such as the foramen ovale in a fetus's heart) or abnormal (such as the
patent foramen ovale Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria (upper chambers) of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this d ...
in an adult's heart); it may be acquired (such as an
arteriovenous fistula An arteriovenous fistula is an abnormal connection or passageway between an artery and a vein. It may be congenital, surgically created for hemodialysis treatments, or acquired due to pathologic process, such as trauma or erosion of an arterial ...
) or innate (such as the arteriovenous shunt of a
metarteriole A metarteriole is a short microvessel in the microcirculation that links arterioles and capillaries. Instead of a continuous tunica media, they have individual smooth muscle cells placed a short distance apart, each forming a precapillary sphinct ...
); and it may be natural (such as the aforementioned examples) or artificial (such as a
surgical anastomosis A surgical anastomosis is a surgical technique used to make a new connection between two body structures that carry fluid, such as blood vessels or bowel. For example, an arterial anastomosis is used in vascular bypass and a colonic anastomosis ...
). The reestablishment of an anastomosis that had become blocked is called a reanastomosis. Anastomoses that are abnormal, whether
congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
or acquired, are often called fistulas. The term is used in medicine,
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
, mycology, geology, and geography.


Etymology

Anastomosis: medical or Modern Latin, from Greek ἀναστόμωσις, anastomosis, "outlet, opening", Gr ana- "up, on, upon", stoma "mouth", "to furnish with a mouth". Thus the ''-stom-'' syllable is cognate with that of ''stoma'' in botany or ''stoma'' in medicine.


Medical anatomy

An anastomosis is the connection of two normally divergent structures. It refers to connections between blood vessels or between other tubular structures such as loops of intestine.


Circulatory

In
circulatory anastomoses A circulatory anastomosis is a connection (an anastomosis) between two blood vessels, such as between arteries (arterio-arterial anastomosis), between veins (veno-venous anastomosis) or between an artery and a vein (arterio-venous anastomosis). ...
, many arteries naturally anastomose with each other; for example, the
inferior epigastric artery In human anatomy, inferior epigastric artery refers to the artery that arises from the external iliac artery. It anastomoses with the superior epigastric artery. Along its course, it is accompanied by a similarly named vein, the inferior epigas ...
and
superior epigastric artery In human anatomy, the superior epigastric artery is a blood vessel that carries oxygenated blood to the abdominal wall, and upper rectus abdominis muscle. It is a branch of the internal thoracic artery. It enters the rectus sheath to descend upo ...
, or the anterior and/or posterior communicating arteries in the
Circle of Willis The circle of Willis (also called Willis' circle, loop of Willis, cerebral arterial circle, and Willis polygon) is a circulatory anastomosis that supplies blood to the brain and surrounding structures in reptiles, birds and mammals, including hu ...
in the brain. The circulatory anastomosis is further divided into arterial and venous anastomosis. Arterial anastomosis includes actual arterial anastomosis (e.g., palmar arch,
plantar arch The plantar arch is a circulatory anastomosis formed from: * deep plantar artery, from the dorsalis pedis - a.k.a. dorsal artery of the foot * lateral plantar artery The plantar arch supplies the underside, or sole, of the foot. The plantar a ...
) and potential arterial anastomosis (e.g.
coronary arteries The coronary arteries are the arterial blood vessels of coronary circulation, which transport oxygenated blood to the heart muscle. The heart requires a continuous supply of oxygen to function and survive, much like any other tissue or organ of ...
and cortical branch of
cerebral arteries The cerebral arteries describe three main pairs of arteries and their branches, which perfuse the cerebrum of the brain. The three main arteries are the: * ''Anterior cerebral artery'' (ACA) * ''Middle cerebral artery'' (MCA) * ''Posterior cereb ...
). Anastomoses also form alternative routes around
capillary A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...
beds in areas that don't need a large blood supply, thus helping regulate systemic blood flow.


Surgical

Surgical anastomosis A surgical anastomosis is a surgical technique used to make a new connection between two body structures that carry fluid, such as blood vessels or bowel. For example, an arterial anastomosis is used in vascular bypass and a colonic anastomosis ...
occurs when segments of intestine, blood vessel, or any other structure are connected together surgically (anastomosed). Examples include arterial anastomosis in
bypass surgery Bypass surgery refers to a class of surgery involving rerouting a tubular body part. Types include: * Vascular bypass surgery such as coronary artery bypass surgery, a heart operation * Cardiopulmonary bypass, a technique used in coronary arter ...
, intestinal anastomosis after a piece of intestine has been resected,
Roux-en-Y anastomosis In general surgery, a Roux-en-Y anastomosis, or Roux-en-Y, is an end-to-side surgical anastomosis of bowel used to reconstruct the gastrointestinal tract. Typically, it is between stomach and small bowel that is distal (or further down the gastr ...
and
ureteroureterostomy Ureteroureterostomy ( "urétero-uréte-róstomy") is end-to-end connection (anastomosis) of the two portions of a transected ureter; also called ureteroureteral anastomosis and van Hook operation (after Weller van Hook, surgeon). __TOC__ Reasons ...
. Surgical anastomosis techniques include Linear Stapled Anastomosis, Hand Sewn Anastomosis, End-to-End Anastomosis (EEA). Anastomosis can be performed by hand or with an anastomosis assist device. Studies have been performed comparing various anastomosis approaches taking into account surgical "time and cost, postoperative anastomotic bleeding, leakage, and stricture".


Pathological

Pathological Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in th ...
anastomosis results from
trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...
or disease and may involve
vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
s,
arteries An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the p ...
, or intestines. These are usually referred to as fistulas. In the cases of veins or arteries, traumatic fistulas usually occur between artery and vein. Traumatic intestinal fistulas usually occur between two loops of intestine (entero-enteric fistula) or intestine and skin (enterocutaneous fistula).
Portacaval anastomosis A portocaval anastomosis or porto-systemic anastomosis is a specific type of anastomosis that occurs between the veins of the portal circulation and those of the systemic circulation. When there is a blockage of the portal system, portocaval anas ...
, by contrast, is an anastomosis between a vein of the
portal circulation In the circulatory system of animals, a portal venous system occurs when a capillary bed pools into another capillary bed through veins, without first going through the heart. Both capillary beds and the blood vessels that connect them are con ...
and a vein of the
systemic circulation The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
, which allows blood to bypass the liver in patients with portal hypertension, often resulting in
hemorrhoids Hemorrhoids (or haemorrhoids), also known as piles, are vascular structures in the anal canal. In their normal state, they are cushions that help with stool control. They become a disease when swollen or inflamed; the unqualified term ''he ...
,
esophageal varices Esophageal varices are extremely dilated sub-mucosal veins in the lower third of the esophagus. They are most often a consequence of portal hypertension, commonly due to cirrhosis. People with esophageal varices have a strong tendency to develop s ...
, or
caput medusae Caput medusae is the appearance of distended and engorged superficial epigastric veins, which are seen radiating from the umbilicus across the abdomen. The name ''caput medusae'' ( Latin for "head of Medusa") originates from the apparent simil ...
.


Biology


Evolution

In evolution, anastomosis is a recombination of evolutionary lineage. Conventional accounts of evolutionary lineage present themselves as the branching out of species into novel forms. Under anastomosis, species might recombine after initial branching out, such as in the case of recent research that shows that ancestral populations along human and chimpanzee lineages may have interbred after an initial branching event. The concept of anastomosis also applies to the theory of symbiogenesis, in which new
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
emerge from the formation of novel symbiotic relationships.


Mycology

In mycology, anastomosis is the fusion between branches of the same or different hyphae. Hence the bifurcating fungal hyphae can form true reticulating networks. By sharing materials in the form of dissolved ions,
hormones A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required fo ...
, and
nucleotides Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules with ...
, the fungus maintains bidirectional communication with itself. The fungal network might begin from several origins; several spores (''i.e.'' by means of
conidial anastomosis tubes Conidial anastomosis tubes (CATs) are cells formed from the conidia (a type of fungal asexual spores) of many filamentous fungi. These cells have a tubular shape and form an anastomosis (bridge) that allows fusion between conidia. CATs and germ tu ...
), several points of penetration, each a spreading circumference of absorption and assimilation. Once encountering the tip of another expanding, exploring self, the tips press against each other in pheromonal recognition or by an unknown recognition system, fusing to form a genetic singular clonal colony that can cover hectares called a
genet Genet or Genêt may refer to: Aircraft *Armstrong Siddeley Genet, aircraft engine * Armstrong Siddeley Genet Major, aircraft engine Animals and plants * Genet (biology), a colony of plants, fungi or bacteria that come from a single genetic sourc ...
or just microscopical areas. For fungi, anastomosis is also a component of reproduction. In some fungi, two different haploid mating types – if compatible – merge. Somatically, they form a morphologically similar mycelial wave front that continues to grow and explore. The significant difference is that each septated unit is binucleate, containing two unfused nuclei, i.e. one from each parent that eventually undergoes karyogamy and meiosis to complete the sexual cycle. Also the term "anastomosing" is used for mushroom gills which interlink and separate to form a network.


Botany

The growth of a strangler fig around a host tree, with tendrils fusing together to form a mesh, is called anastomosing.


Geology

In geology, anastomosis refers to quartz (or other)
veins Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated ...
displaying this property, which is often related to shearing in metamorphic regions.


Geography

Anastomosing streams consist of multiple channels that divide and reconnect and are separated by semi-permanent banks formed of cohesive material, such that they are unlikely to migrate from one channel position to another. They can be confused with
braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, '' aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment ...
s based on their planforms alone, but braided rivers are much shallower and more dynamic than anastomosing rivers. Some definitions require that an anastomosing river be made up of interconnected channels that enclose floodbasins, again in contrast with braided rivers. Rivers with anastomosed reaches include the Magdalena River in Colombia, the upper
Columbia River The Columbia River ( Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, ...
in British Columbia, Canada, the Drumheller Channels of the
Channeled Scablands The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods ...
of the state of Washington, USA, and the upper
Narew River The Narew (; be, Нараў, translit=Naraŭ; or ; Sudovian: ''Naura''; Old German: ''Nare''; uk, Нарва, translit=Narva) is a 499-kilometre (310 mi) river primarily in north-eastern Poland, which is also a tributary of the river Vis ...
in Poland. The term
anabranch An anabranch is a section of a river or stream that diverts from the main channel or stem of the watercourse and rejoins the main stem downstream. Local anabranches can be the result of small islands in the watercourse. In larger anabranches, t ...
has been used for segments of anastamosing rivers. In cave systems anastomosis is the splitting of cave passages that later reconnect.


References

{{reflist Angiology Digestive system Evolutionary biology Petrology concepts Surgery