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69-420: Most animals have a "through-gut" or complete digestive tract. Exceptions are more primitive ones: sponges have small pores ( ostia ) throughout their body for digestion and a larger dorsal pore ( osculum ) for excretion, comb jellies have both a ventral mouth and dorsal anal pores, while cnidarians and acoels have a single pore for both digestion and excretion. The human gastrointestinal tract consists of

138-404: A barium -labeled meal, breath hydrogen analysis, scintigraphic analysis following a radiolabeled meal, and simple ingestion and spotting of corn kernels . It takes 2.5 to 3 hours for 50% of the contents to leave the stomach. The rate of digestion is also dependent of the material being digested, as food composition from the same meal may leave the stomach at different rates. Total emptying of

207-416: A multicellular organism . In organisms that reproduce sexually , embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell . The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres . The blastomeres (4-cell stage) are arranged as

276-413: A symbiotic relationship. These bacteria are responsible for gas production at host–pathogen interface , which is released as flatulence . Intestinal bacteria can also participate in biosynthesis reactions. For example, certain strains in the large intestine produce vitamin B 12 ; an essential compound in humans for things like DNA synthesis and red blood cell production. However, the primary function of

345-621: A halfway-tense state but can relax in spots to allow for local distention and peristalsis . The gastrointestinal tract contains the gut microbiota , with some 1,000 different strains of bacteria having diverse roles in the maintenance of immune health and metabolism , and many other microorganisms . Cells of the GI tract release hormones to help regulate the digestive process. These digestive hormones , including gastrin , secretin , cholecystokinin , and ghrelin , are mediated through either intracrine or autocrine mechanisms, indicating that

414-441: A hollow sphere of cells surrounding a middle cavity . The embryo's cells continue to divide and increase in number, while molecules within the cells such as RNAs and proteins actively promote key developmental processes such as gene expression, cell fate specification, and polarity. Before implanting into the uterine wall the embryo is sometimes known as the pre-implantation embryo or pre-implantation conceptus . Sometimes this

483-488: A parent's body), the offspring is typically referred to as an embryo while inside of the parent, and is no longer considered an embryo after birth or exit from the parent. However, the extent of development and growth accomplished while inside of an egg or parent varies significantly from species to species, so much so that the processes that take place after hatching or birth in one species may take place well before those events in another. Therefore, according to one textbook, it

552-634: A potential avenue for preventing disease; however, this has been met with widespread condemnation from the scientific community. ART techniques are also used to improve the profitability of agricultural animal species such as cows and pigs by enabling selective breeding for desired traits and/or to increase numbers of offspring. For example, when allowed to breed naturally, cows typically produce one calf per year, whereas IVF increases offspring yield to 9–12 calves per year. IVF and other ART techniques, including cloning via interspecies somatic cell nuclear transfer (iSCNT), are also used in attempts to increase

621-468: A solid ball that when reaching a certain size, called a morula , (16-cell stage) takes in fluid to create a cavity called a blastocoel . The structure is then termed a blastula , or a blastocyst in mammals . The mammalian blastocyst hatches before implantating into the endometrial lining of the womb . Once implanted the embryo will continue its development through the next stages of gastrulation , neurulation , and organogenesis . Gastrulation

690-482: Is a clear boundary between the gut and the surrounding tissue. These parts of the tract have a mesentery . Retroperitoneal parts are covered with adventitia . They blend into the surrounding tissue and are fixed in position. For example, the retroperitoneal section of the duodenum usually passes through the transpyloric plane . These include the esophagus , pylorus of the stomach, distal duodenum , ascending colon , descending colon and anal canal . In addition,

759-409: Is a proposed phylogenetic tree of Nephrozoa: Xenacoelomorpha [REDACTED] Chordata [REDACTED] Echinodermata [REDACTED] Hemichordata [REDACTED] Ecdysozoa [REDACTED] Spiralia [REDACTED] This zoology –related article is a stub . You can help Misplaced Pages by expanding it . Embryo An embryo is the initial stage of development for

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828-588: Is a proposed major clade of bilaterian animals . It includes all bilaterians other than Xenacoelomorpha . It contrasts with the Xenambulacraria hypothesis, which instead posits that Xenacoelomorpha is most closely related to Ambulacraria . Which hypothesis is correct is controversial. Authors supporting the Xenambulacraria hypothesis have suggested that the genetic evidence used to support Nephrozoa may be due to systematic error. Below

897-410: Is a thin muscle which is derived from the embryonic mesoderm . The lower gastrointestinal tract includes most of the small intestine and all of the large intestine . In human anatomy , the intestine ( bowel or gut ; Greek: éntera ) is the segment of the gastrointestinal tract extending from the pyloric sphincter of the stomach to the anus and as in other mammals, consists of two segments:

966-475: Is about 30 m (320 sq ft). The combination of the circular folds , the villi, and the microvilli increases the absorptive area of the mucosa about 600-fold, making a total area of about 250 m (2,700 sq ft) for the entire small intestine. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions: The large intestine , also called

1035-489: Is called the pre-embryo a term employed to differentiate from an embryo proper in relation to embryonic stem cell discourses. Gastrulation is the next phase of embryonic development, and involves the development of two or more layers of cells (germinal layers). Animals that form two layers (such as Cnidaria ) are called diploblastic, and those that form three (most other animals, from flatworms to humans) are called triploblastic. During gastrulation of triploblastic animals,

1104-435: Is common for scientists to interpret the scope of embryology broadly as the study of the development of animals. Flowering plants ( angiosperms ) create embryos after the fertilization of a haploid ovule by pollen . The DNA from the ovule and pollen combine to form a diploid, single-cell zygote that will develop into an embryo. The zygote, which will divide multiple times as it progresses throughout embryonic development,

1173-423: Is one part of a seed . Other seed components include the endosperm , which is tissue rich in nutrients that will help support the growing plant embryo, and the seed coat, which is a protective outer covering. The first cell division of a zygote is asymmetric , resulting in an embryo with one small cell (the apical cell) and one large cell (the basal cell). The small, apical cell will eventually give rise to most of

1242-407: Is referred to as faeces . The outermost layer of the gastrointestinal tract consists of several layers of connective tissue . Intraperitoneal parts of the GI tract are covered with serosa . These include most of the stomach , first part of the duodenum , all of the small intestine , caecum and appendix , transverse colon , sigmoid colon and rectum . In these sections of the gut, there

1311-408: Is the formation of the three germ layers that will form all of the different parts of the body. Neurulation forms the nervous system , and organogenesis is the development of all the various tissues and organs of the body. A newly developing human is typically referred to as an embryo until the ninth week after conception, when it is then referred to as a fetus . In other multicellular organisms,

1380-400: Is the period of rapid mitotic cell divisions that occur after fertilization. During cleavage, the overall size of the embryo does not change, but the size of individual cells decrease rapidly as they divide to increase the total number of cells. Cleavage results in a blastula. Depending on the species, a blastula or blastocyst stage embryo can appear as a ball of cells on top of yolk, or as

1449-416: Is thought to have evolved within the nephrozoan clade of Bilateria , after their ancestral ventral orifice (single, as in cnidarians and acoels ; re-evolved in nephrozoans like flatworms ) stretched antero-posteriorly, before the middle part of the stretch would get narrower and closed fully, leaving an anterior orifice (mouth) and a posterior orifice (anus plus genital opening ). A stretched gut without

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1518-737: Is used for addressing fertility concerns in humans and other animals, and for selective breeding in agricultural species. Between the years 1987 and 2015, ART techniques including in vitro fertilization (IVF) were responsible for an estimated one million human births in the United States alone. Other clinical technologies include preimplantation genetic diagnosis (PGD), which can identify certain serious genetic abnormalities, such as aneuploidy , prior to selecting embryos for use in IVF. Some have proposed (or even attempted - see He Jiankui affair ) genetic editing of human embryos via CRISPR-Cas9 as

1587-523: The antiporter activities, are also instrumental in the intestine's role of drug metabolism in the detoxification of antigens and xenobiotics . In most vertebrates , including amphibians , birds , reptiles , egg-laying mammals , and some fish , the gastrointestinal tract ends in a cloaca and not an anus . In the cloaca, the urinary system is fused with the genito-anal pore. Therians (all mammals that do not lay eggs, including humans) possess separate anal and uro-genital openings. The females of

1656-462: The epidermis or outer covering of a plant, ground tissue will give rise to inner plant material that functions in photosynthesis , resource storage, and physical support, and vascular tissue will give rise to connective tissue like the xylem and phloem that transport fluid, nutrients, and minerals throughout the plant. In heart stage, one or two cotyledons (embryonic leaves) will form. Meristems (centers of stem cell activity) develop during

1725-405: The esophagus , stomach, and intestines, and is divided into the upper and lower gastrointestinal tracts. The GI tract includes all structures between the mouth and the anus , forming a continuous passageway that includes the main organs of digestion, namely, the stomach , small intestine , and large intestine . The complete human digestive system is made up of the gastrointestinal tract plus

1794-531: The lipase LIPF , expressed in chief cells , and gastric ATPase ATP4A and gastric intrinsic factor GIF , expressed in parietal cells of the stomach mucosa. Specific proteins expressed in the stomach and duodenum involved in defence include mucin proteins, such as mucin 6 and intelectin-1 . The time taken for food to transit through the gastrointestinal tract varies on multiple factors, including age, ethnicity, and gender. Several techniques have been used to measure transit time, including radiography following

1863-481: The oral cavity has adventitia. Approximately 20,000 protein coding genes are expressed in human cells and 75% of these genes are expressed in at least one of the different parts of the digestive organ system. Over 600 of these genes are more specifically expressed in one or more parts of the GI tract and the corresponding proteins have functions related to digestion of food and uptake of nutrients. Examples of specific proteins with such functions are pepsinogen PGC and

1932-433: The small intestine and the large intestine . In humans, the small intestine is further subdivided into the duodenum , jejunum , and ileum while the large intestine is subdivided into the cecum , ascending, transverse, descending, and sigmoid colon , rectum , and anal canal . The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long. Its mucosal area in an adult human

2001-456: The accessory organs of digestion (the tongue , salivary glands , pancreas , liver and gallbladder ). The tract may also be divided into foregut , midgut , and hindgut , reflecting the embryological origin of each segment. The whole human GI tract is about nine meters (30 feet) long at autopsy . It is considerably shorter in the living body because the intestines, which are tubes of smooth muscle tissue , maintain constant muscle tone in

2070-483: The blood and lymph circulatory systems. Fundamental components of this protection are provided by the intestinal mucosal barrier , which is composed of physical, biochemical, and immune elements elaborated by the intestinal mucosa. Microorganisms also are kept at bay by an extensive immune system comprising the gut-associated lymphoid tissue (GALT) There are additional factors contributing to protection from pathogen invasion. For example, low pH (ranging from 1 to 4) of

2139-552: The brain, spinal cord, or peripheral nerves. The embryonic period varies from species to species. In human development, the term fetus is used instead of embryo after the ninth week after conception, whereas in zebrafish , embryonic development is considered finished when a bone called the cleithrum becomes visible. In animals that hatch from an egg, such as birds, a young animal is typically no longer referred to as an embryo once it has hatched. In viviparous animals (animals whose offspring spend at least some time developing within

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2208-468: The butyrate induces the differentiation of Treg cells by enhancing histone H3 acetylation in the promoter and conserved non-coding sequence regions of the FOXP3 locus, thus regulating the T cells , resulting in the reduction of the inflammatory response and allergies. The large intestine contains multiple types of bacteria that can break down molecules the human body cannot process alone, demonstrating

2277-442: The cells releasing these hormones are conserved structures throughout evolution . The structure and function can be described both as gross anatomy and as microscopic anatomy or histology . The tract itself is divided into upper and lower tracts, and the intestines small and large parts. The upper gastrointestinal tract consists of the mouth , pharynx , esophagus , stomach , and duodenum . The exact demarcation between

2346-418: The colon, forms an arch starting at the cecum and ending at the rectum and anal canal . It also includes the appendix , which is attached to the cecum . Its length is about 1.5 m, and the area of the mucosa in an adult human is about 2 m (22 sq ft). Its main function is to absorb water and salts. The colon is further divided into: The gut is an endoderm -derived structure. At approximately

2415-422: The definitive gut as well. Each segment of the gut is further specified and gives rise to specific gut and gut-related structures in later development. Components derived from the gut proper, including the stomach and colon , develop as swellings or dilatations in the cells of the primitive gut. In contrast, gut-related derivatives — that is, those structures that derive from the primitive gut but are not part of

2484-452: The digestive system and epithelium of the digestive system and respiratory system. Many visible changes in embryonic structure happen throughout gastrulation as the cells that make up the different germ layers migrate and cause the previously round embryo to fold or invaginate into a cup-like appearance. Past gastrulation, an embryo continues to develop into a mature multicellular organism by forming structures necessary for life outside of

2553-487: The digestive tract called a gizzard used for grinding up food. Another feature found in a range of animals is the crop . In birds this is found as a pouch alongside the esophagus. In 2020, the oldest known fossil digestive tract, of an extinct wormlike organism in the Cloudinidae was discovered; it lived during the late Ediacaran period about 550 million years ago. A through-gut (one with both mouth and anus)

2622-426: The duodenum are as follows (starting at the stomach, and moving toward the jejunum): bulb , descending, horizontal, and ascending. The suspensory muscle attaches the superior border of the ascending duodenum to the jejunum . The suspensory muscle is an important anatomical landmark that shows the formal division between the duodenum and the jejunum, the first and second parts of the small intestine, respectively. This

2691-406: The embryo begins its existence attached to the inside of the archegonium on a parental gametophyte from which the egg cell was generated. The inner wall of the archegonium lies in close contact with the "foot" of the developing embryo; this "foot" consists of a bulbous mass of cells at the base of the embryo which may receive nutrition from its parent gametophyte. The structure and development of

2760-580: The gastrointestinal tract include the upper and lower gastrointestinal series : Intestines from animals other than humans are used in a number of ways. From each species of livestock that is a source of milk , a corresponding rennet is obtained from the intestines of milk-fed calves . Pig and calf intestines are eaten, and pig intestines are used as sausage casings. Calf intestines supply calf-intestinal alkaline phosphatase (CIP), and are used to make goldbeater's skin . Other uses are: Nephrozoa Eubilateria Ax , 1987 Nephrozoa

2829-486: The gastrointestinal tract. The mucosa surrounds the lumen , or open space within the tube. This layer comes in direct contact with digested food ( chyme ). The mucosa is made up of: The mucosae are highly specialized in each organ of the gastrointestinal tract to deal with the different conditions. The most variation is seen in the epithelium. The submucosa consists of a dense irregular layer of connective tissue with large blood vessels, lymphatics, and nerves branching into

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2898-416: The gut proper, in general, develop as out-pouchings of the primitive gut. The blood vessels supplying these structures remain constant throughout development. The gastrointestinal tract has a form of general histology with some differences that reflect the specialization in functional anatomy. The GI tract can be divided into four concentric layers in the following order: The mucosa is the innermost layer of

2967-517: The intestine that have physiological causes but do not have identifiable structural, chemical, or infectious pathologies. Several symptoms can indicate problems with the gastrointestinal tract, including: Gastrointestinal surgery can often be performed in the outpatient setting. In the United States in 2012, operations on the digestive system accounted for 3 of the 25 most common ambulatory surgery procedures and constituted 9.1 percent of all outpatient ambulatory surgeries. Various methods of imaging

3036-488: The large intestine is water absorption from digested material (regulated by the hypothalamus ) and the reabsorption of sodium and nutrients. Beneficial intestinal bacteria compete with potentially harmful bacteria for space and "food", as the intestinal tract has limited resources. A ratio of 80–85% beneficial to 15–20% potentially harmful bacteria is proposed for maintaining homeostasis . An imbalanced ratio results in dysbiosis . Enzymes such as CYP3A4 , along with

3105-413: The large intestine. Crohn's disease is widely regarded as an autoimmune disease . Although ulcerative colitis is often treated as though it were an autoimmune disease, there is no consensus that it actually is such. Functional gastrointestinal disorders the most common of which is irritable bowel syndrome . Functional constipation and chronic functional abdominal pain are other functional disorders of

3174-407: The layers of muscle are helical with different pitches. The inner circular is helical with a steep pitch and the outer longitudinal is helical with a much shallower pitch. Whilst the muscularis externa is similar throughout the entire gastrointestinal tract, an exception is the stomach which has an additional inner oblique muscular layer to aid with grinding and mixing of food. The muscularis externa of

3243-578: The middle part closed is present in another branch of bilaterians, the extinct proarticulates . This and the amphistomic development (when both mouth and anus develop from the gut stretch in the embryo) present in some nephrozoans (e.g. roundworms ) are considered to support this hypothesis. There are many diseases and conditions that can affect the gastrointestinal system, including infections , inflammation and cancer . Various pathogens , such as bacteria that cause foodborne illnesses , can induce gastroenteritis which results from inflammation of

3312-427: The most predominant bacterial groups in the GI tract, play an important role in influencing the dynamics of the gut's immune system. It has been demonstrated that the intake of a high fiber diet could be responsible for the induction of T-regulatory cells (Tregs). This is due to the production of short-chain fatty acids during the fermentation of plant-derived nutrients such as butyrate and propionate . Basically,

3381-416: The mucosa and muscularis externa . It contains the submucosal plexus , an enteric nervous plexus , situated on the inner surface of the muscularis externa . The muscular layer consists of an inner circular layer and a longitudinal outer layer. The circular layer prevents food from traveling backward and the longitudinal layer shortens the tract. The layers are not truly longitudinal or circular, rather

3450-449: The numbers of endangered or vulnerable species, such as Northern white rhinos , cheetahs , and sturgeons . Cryoconservation of genetic resources involves collecting and storing the reproductive materials, such as embryos, seeds, or gametes, from animal or plant species at low temperatures in order to preserve them for future use. Some large-scale animal species cryoconservation efforts include " frozen zoos " in various places around

3519-469: The primitive gut. The yolk sac remains connected to the gut tube via the vitelline duct . Usually, this structure regresses during development; in cases where it does not, it is known as Meckel's diverticulum . During fetal life, the primitive gut is gradually patterned into three segments: foregut , midgut , and hindgut . Although these terms are often used in reference to segments of the primitive gut, they are also used regularly to describe regions of

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3588-484: The proper Latinized form of the Greek term would be embryum . In animals, fertilization begins the process of embryonic development with the creation of a zygote, a single cell resulting from the fusion of gametes (e.g. egg and sperm). The development of a zygote into a multicellular embryo proceeds through a series of recognizable stages, often divided into cleavage, blastula, gastrulation, and organogenesis. Cleavage

3657-401: The rest of the autonomic nervous system . The coordinated contractions of these layers is called peristalsis and propels the food through the tract. Food in the GI tract is called a bolus (ball of food) from the mouth down to the stomach. After the stomach, the food is partially digested and semi-liquid, and is referred to as chyme . In the large intestine, the remaining semi-solid substance

3726-432: The rest of the embryo varies by group of plants. Since all land plants create embryos, they are collectively referred to as embryophytes (or by their scientific name, Embryophyta). This, along with other characteristics, distinguishes land plants from other types of plants, such as algae , which do not produce embryos. Embryos from numerous plant and animal species are studied in biological research laboratories across

3795-409: The sixteenth day of human development, the embryo begins to fold ventrally (with the embryo's ventral surface becoming concave ) in two directions: the sides of the embryo fold in on each other and the head and tail fold toward one another. The result is that a piece of the yolk sac , an endoderm -lined structure in contact with the ventral aspect of the embryo, begins to be pinched off to become

3864-412: The small intestine as well. Diverticulosis occurs when pouches form on the intestinal wall. Once the pouches become inflamed it is known as diverticulitis . Inflammatory bowel disease is an inflammatory condition affecting the bowel walls, and includes the subtypes Crohn's disease and ulcerative colitis . While Crohn's can affect the entire gastrointestinal tract, ulcerative colitis is limited to

3933-429: The stomach and small intestine. Antibiotics to treat such bacterial infections can decrease the microbiome diversity of the gastrointestinal tract, and further enable inflammatory mediators. Gastroenteritis is the most common disease of the GI tract. Diverticular disease is a condition that is very common in older people in industrialized countries. It usually affects the large intestine but has been known to affect

4002-455: The stomach is composed of the inner oblique layer, middle circular layer, and the outer longitudinal layer. Between the circular and longitudinal muscle layers is the myenteric plexus . This controls peristalsis. Activity is initiated by the pacemaker cells, (myenteric interstitial cells of Cajal ). The gut has intrinsic peristaltic activity ( basal electrical rhythm ) due to its self-contained enteric nervous system. The rate can be modulated by

4071-407: The stomach is fatal for many microorganisms that enter it. Similarly, mucus (containing IgA antibodies ) neutralizes many pathogenic microorganisms. Other factors in the GI tract contribution to immune function include enzymes secreted in the saliva and bile . Beneficial bacteria also can contribute to the homeostasis of the gastrointestinal immune system. For example, Clostridia , one of

4140-448: The stomach takes around 4–5 hours, and transit through the colon takes 30 to 50 hours. The gastrointestinal tract forms an important part of the immune system . The surface area of the digestive tract is estimated to be about 32 square meters, or about half a badminton court. With such a large exposure (more than three times larger than the exposed surface of the skin ), these immune components function to prevent pathogens from entering

4209-498: The structures of the mature plant, such as the stem, leaves, and roots. The larger basal cell will give rise to the suspensor, which connects the embryo to the endosperm so that nutrients can pass between them. The plant embryo cells continue to divide and progress through developmental stages named for their general appearance: globular, heart, and torpedo. In the globular stage, three basic tissue types (dermal, ground, and vascular) can be recognized. The dermal tissue will give rise to

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4278-409: The subgroup Placentalia have even separate urinary and genital openings. During early development , the asymmetric position of the bowels and inner organs is initiated (see also axial twist theory ). Ruminants show many specializations for digesting and fermenting tough plant material, consisting of additional stomach compartments . Many birds and other animals have a specialised stomach in

4347-411: The three germinal layers that form are called the ectoderm , mesoderm , and endoderm . All tissues and organs of a mature animal can trace their origin back to one of these layers. For example, the ectoderm will give rise to the skin epidermis and the nervous system, the mesoderm will give rise to the vascular system, muscles, bone, and connective tissues, and the endoderm will give rise to organs of

4416-452: The torpedo stage, and will eventually produce many of the mature tissues of the adult plant throughout its life. At the end of embryonic growth, the seed will usually go dormant until germination. Once the embryo begins to germinate (grow out from the seed) and forms its first true leaf, it is called a seedling or plantlet. Plants that produce spores instead of seeds, like bryophytes and ferns , also produce embryos. In these plants,

4485-458: The upper and lower tracts is the suspensory muscle of the duodenum . This differentiates the embryonic borders between the foregut and midgut, and is also the division commonly used by clinicians to describe gastrointestinal bleeding as being of either "upper" or "lower" origin. Upon dissection , the duodenum may appear to be a unified organ, but it is divided into four segments based on function, location, and internal anatomy. The four segments of

4554-416: The womb or egg. As the name suggests, organogenesis is the stage of embryonic development when organs form. During organogenesis, molecular and cellular interactions prompt certain populations of cells from the different germ layers to differentiate into organ-specific cell types. For example, in neurogenesis, a subpopulation of cells from the ectoderm segregate from other cells and further specialize to become

4623-469: The word "embryo" can be used more broadly to any early developmental or life cycle stage prior to birth or hatching . First attested in English in the mid-14c., the word embryon derives from Medieval Latin embryo , itself from Greek ἔμβρυον ( embruon ), lit. "young one", which is the neuter of ἔμβρυος ( embruos ), lit. "growing in", from ἐν ( en ), "in" and βρύω ( bruō ), "swell, be full";

4692-851: The world to learn about topics such as stem cells , evolution and development , cell division , and gene expression . Examples of scientific discoveries made while studying embryos that were awarded the Nobel Prize in Physiology or Medicine include the Spemann-Mangold organizer , a group of cells originally discovered in amphibian embryos that give rise to neural tissues, and genes that give rise to body segments discovered in Drosophila fly embryos by Christiane Nüsslein-Volhard and Eric Wieschaus . Creating and/or manipulating embryos via assisted reproductive technology (ART)

4761-753: The world, including in the UK's Frozen Ark , the Breeding Centre for Endangered Arabian Wildlife (BCEAW) in the United Arab Emirates, and the San Diego Zoo Institute for Conservation in the United States. As of 2018, there were approximately 1,700 seed banks used to store and protect plant biodiversity, particularly in the event of mass extinction or other global emergencies. The Svalbard Global Seed Vault in Norway maintains

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