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Bile

Bile

Bile (or gall) is a bitter, greenish-yellow alkaline fluid secreted by the liver of most vertebrates. In many species, it is stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.

Physiology

Bile salts are steroid compounds (deoxycholic and cholic acid), often conjugated with glycine and taurine, and act to some extent as a detergent, helping to emulsify fats (increasing surface area to help enzyme action), and thus aid in their absorption in the small intestine. The most important compounds are the salts of taurocholic acid and deoxycholic acid. Bile salts combine with phospholipids to break down fat globules in the process of emulsification. Emulsified droplets then are organized into many micelles which increases absorption. Besides its digestive function, bile serves as the route of excretion for the hemoglobin breakdown product (bilirubin) which gives bile its colour. Bile also contains cholesterol, which occasionally accretes into lumps in the gall bladder, forming gallstones. In species with a gall bladder (humans and most domestic animals except horses and rats), further modification of bile occurs in that organ. The gall bladder stores and concentrates bile during the fasting state. Typically, bile is concentrated five-fold in the gall bladder by absorption of water and small electrolytes - virtually all of the organic molecules are retained. The human liver produces about a quart (or litre) of bile per day. 95% of secreted bile salts are reabsorbed in the terminal ileum and re-used. Since bile increases the absorption of fats, it is an important part of the absorption of the fat-soluble vitamins: A, D, E, and K. Bile from slaughtered animals can be mixed with soap. This mixture, applied to textiles a few hours before washing, is a traditional and rather effective method for removing various kinds of tough stains.

Four humours

Yellow bile and black bile were two of the four vital fluids or humours of ancient and medieval medicine; for example, melancholia was believed to be caused by a bodily surplus of black bile. Yellow bile is sometimes called ichor.

Alkali

For the battery, see alkaline battery ---- The word alkali can mean:-
- In chemistry, an alkali is a specific type of base, formed as a carbonate, hydroxide or other ionic salt of an alkali metal or alkali earth metal element. The word alkali or the adjective alkaline are frequently used to refer to all bases, since most common bases are alkalis, although such use is really a synecdoche.
- In the western parts of the USA, natural soda or potash deposits (soda and potash themselves are both alkali salts).
- [http://www.tomlaidlaw.com/clickable/alkali.html Alkali Springs] is a place in Oregon in the USA.
- Alkali is also the NATO reporting name of the Kaliningrad K-5 air-to-air missile.

Common properties of alkalis

Alkalis are all Arrhenius bases and share many properties with other chemicals in this group (Arrhenius bases form hydroxide ions when dissolved in water). Common properties of alkaline solutions include:
- Alkalis all form aqueous solutions.
- Alkalis are bitter to taste (compared with acid solutions which are described as sour).
- Caustic (causing chemical burns).
- Slippery or soapy to the touch (due to the caustic reaction dissolving the surface of the skin and fingerprint).
- Alkalis have a pH greater than 7 and hence can be detected with litmus paper (litmus will turn blue on contact with an alkali).
- Another common test for alkalis is the use of phenolphthalein since it turns from colourless to pink when the pH moves from 8 to 10 (making it suitable for detecting all but the most dilute solutions of alkalis).

Confusion between base and alkali

The terms base and alkali are often used interchangeably, since most common bases are alkalis. It is common to speak of "measuring the alkalinity of soil" when you actually mean measuring the pH (base property). Similarly, bases which are not alkalis, like ammonia, are sometimes erroneously referred to as alkaline.

Alkali salts

Most basic salts are alkali salts. Common alkali salts include:
- sodium hydroxide (often called "caustic soda")
- potassium hydroxide (commonly called "potash")
- lye (generic term, for either of the previous two, or even for a mixture)
- calcium carbonate (sometimes called "free lime")

Alkali soil

Soil with a pH above 7.4 is normally referred to as alkaline. This soil property can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including cabbage family vegetables and buffalograss), most plant prefer a mildly acidic soil (pH between 6.0 and 6.8), and high pH levels can cause a problem. In alkali lakes (a type of salt lake), evaporation concentrates the naturally occurring alkali salts, often forming a crust of mildly basic salt across a large area. Examples of Alkali Lakes: Redberry Lake, Saskatchewan, Canada. Tramping Lake, Saskatchewan, Canada.

Etymology

The word "alkali" is derived from Arabic al qalīy = "the calcined ashes", referring to the original source of alkaline substance. Ashes were used in conjunction with animal fat to produce soap, a process known as saponification. Category:Inorganic chemistry Category:Arabic words simple:Alkali

Vertebrate

Conodonta
Hyperoartia
:Petromyzontidae (lampreys)
Pteraspidomorphi (early jawless fish)
Thelodonti
Anaspida
Cephalaspidomorphi (early jawless fish)
:Galeaspida
:Pituriaspida
:Osteostraci
Gnathostomata (jawed vertebrates)
:Placodermi
:Chondrichthyes (cartilaginous fish)
:Acanthodii
:Osteichthyes (bony fish)
::Actinopterygii (ray-finned fish)
::Sarcopterygii (lobe-finned fish)
:::Actinistia (coelacanths)
:::Dipnoi (lungfish)
:::Tetrapoda ::::Amphibia
::::Amniota
:::::Sauropsida/(Reptiles)
::::::Aves (Birds)
:::::Synapsida
::::::Mammalia Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. Vertebrates started to evolve about 530 million years ago during the Cambrian explosion, which is part of the Cambrian period (first known vertebrate is Myllokunmingia). The bones of the spinal column (or vertebral column) are called vertebrae. Vertebrata is the largest subphylum of chordates, and contains most animals with which people are generally familiar (except insects). Fish (including lampreys, but traditionally not hagfish, though this is now disputed), amphibians, reptiles, birds, and mammals (including humans) are vertebrates. Additional characteristics of the subphylum are a muscular system that mostly consists of paired masses, as well as a central nervous system which is partly located inside the backbone. The internal skeleton which defines vertebrates consists of cartilage or bone, or in some cases both. The skeleton provides support to the organism during the period of growth. For this reason vertebrates can achieve larger sizes than invertebrates, and on average vertebrates are in fact larger. The skeleton of most vertebrates, that is excluding the most primitive ones, consists of a skull, the vertebral column and two pairs of limbs. In some forms of vertebrates, one or both of these pairs of limbs may be absent, such as in snakes or whales. These limbs have been lost in the course of evolution. The skull is thought to have facilitated the development of intelligence as it protects vital organs such as the brain, the eyes and the ears. The protection of these organs is also thought to have positively influenced the development of high responsiveness to the environment often found in vertebrates. Both the vertebral column and the limbs support the body of the vertebrate overall. This support facilitates movement. Movement is normally achieved with muscles that are attached directly to the bones or cartilages. The contour of the body of a vertebrate is formed by the muscles. A skin covers the inner parts of a vertebrate's body. The skin sometimes acts as a structure for protective features, such as horny scales or fur. Feathers are also attached to the skin. The trunk of a vertebrate is hollow and houses the internal organs. The heart and the respiratory organs are protected in the trunk. The heart is located behind the gills, or where there are lungs, in between the lungs. The central nervous system of a vertebrate consists of the brain and the spinal cord. Both of these are characterized by being hollow. In lower vertebrates the brain mostly controls the functioning of the sense organs. In higher vertebrates the size of the brain relative to the size of the body is larger. This larger brain enables more intensive exchange of information between the different parts of the brain. The nerves from the spinal cord, which lies behind the brain, extend to the skin, the inner organs and the muscles. Some nerves are directly connected to the brain, linking the brain with the ears and lungs. Vertebrates have been traced back to the ostracoderms of the Silurian Period (444 million to 409 million years ago) and the conodonts, a group of eel-like vertebrates characterized by multiple pairs of bony toothplates. All vertebrates have: the ability to form bones; paired, specialised sensory organs and a brain.

External links

- [http://tolweb.org/tree?group=Amniota&contgroup=Terrestrial_vertebrates Tree of Life]
- [http://reference.allrefer.com/encyclopedia/categories/vertz.html Vertebrate Zoology] Category:Chordates ko:척추동물 ms:Vertebrata ja:脊椎動物 simple:Vertebrate th:สัตว์มีกระดูกสันหลัง

Gallbladder

The gallbladder (or cholecyst) is a pear-shaped organ that stores bile (or "gall") until the body needs it for digestion. It is connected to the liver and the duodenum by the biliary tract.

Anatomy

Not all mammals have gallbladders. The rat and horse, for example, do not have a specialized organ for the storage of bile. The gallbladder is connected to the main bile duct through the gallbladder duct (cystic duct or, in Latin, ductus cysticus). The main biliary tract runs from the liver to the duodenum, and the cystic duct is effectively a "cul de sac", serving as entrance and exit to the gallbladder. The surface marking of the gallbladder is the intersection of the mid-clavicular line (MCL) and the transpyloric plane, at the tip of the ninth rib. The blood supply is by the cystic artery and vein, which run parallel to the cystic duct. The cystic artery is highly variable, and this is of clinical relevance since it must be clipped and cut during a cholecystectomy.

Microscopic anatomy

The gallbladder has an epithelial lining characterised by recesses (called Aschoff's recesses), which are pouches inside the lining. Under the epithelium there is a layer of connective tissue, followed by a muscular wall that contracts in response to cholecystokinin.

Function

The gallbladder stores bile, which is released when food containing fat enters the digestive tract, stimulating the secretion of cholecystokinin (CCK).

Role in disease

Cholestasis

Cholestasis is the blockage in the supply of bile into the digestive tract. It can be "intrahepatic" (the obstruction is in the liver) or "extrahepatic" (outside the liver). It can lead to jaundice, and is identified by the presence of elevated bilirubin level that is mainly conjugated.

Cholelithiasis

conjugated Up to 25% of all people have gallstones (cholelithiasis), composed of cholesterol, lecithin and bile acids. These can cause colicky shooting abdominal pain, usually in relation with the meal, as the gallbladder contracts and gallstones pass through the bile duct. Surgery (cholecystectomy, removal of the gallbladder) is the most common treatment for gallstones. It can be performed laparoscopically, and it is in fact one of the most common procedures done through the laparoscope. People traditionally considered at an increased risk of cholelithiasis are people who are 5 F's:
- Female
- Fat (obesity)
- Fair (Caucasian, but this is disputed by recent studies)
- Forty (middle-aged)
- Fertile (the risk is increased in pregnancy)

Cholecystitis

:Please refer to main article: Cholecystitis Acute or chronic inflammation of the gall bladder causes abdominal pain. 90% of cases of acute cholecystitis are caused by the presence of gallstones.

Choledocholithiasis

Please refer to main article: Choledocholithiasis When gallstones obstruct the common bile duct, the patient develops jaundice and liver cell damage. It is a medical emergency, requiring endoscopic or surgical treatment.

Gallstone ileus

A rare clinical entity is ileus (bowel obstruction) by a large gallstone, or gallstone ileus. This condition develops in patients with longstanding gallstone disease, in which the gallbladder forms a fistula with the digestive tract. Large stones pass into the bowel, and generally block the gut at the level of Treitz' ligament or the ileocecal valve, two narrow points in the digestive tract. Therapy is surgical.

External links

- [http://www.nlm.nih.gov/medlineplus/ency/imagepages/19261.htm Illustration]
- [http://health.allrefer.com/health/gallbladder-disease-info.html Gallbladder Disease]
- [http://www.nlm.nih.gov/medlineplus/ency/article/000264.htm Acute cholecystitis] Category:Abdomen Category:Digestive system ja:胆嚢

Duodenum

In anatomy of the digestive system, the duodenum is a hollow jointed tube connecting the stomach to the jejunum. It is the first part of the small intestine. It starts with the duodenal bulb and ends at the ligament of Treitz. Two very important ducts open into the duodenum, namely the bile duct and the pancreatic duct. The duodenum is largely responsible for the breakdown of food in the small intestine. Brunner’s glands are only found in the duodenum and they secrete mucus. These mucus filled glands are composed of simple cuboid-shaped epithelial cells. The duodenum wall is composed of a very thin layer of smooth muscle cells that forms the muscularis mucosa. The duodenum is divided into four sections for the purposes of description. The first three sections form a "C" shape. The first comes from the pylorus, goes right and makes a sharp right angle turn downwards to become the second part of the duodenum. The second part of the duodenum is where the hepatopancreatic duct (or less often, separately, the pancreatic duct and common bile duct) empty into the gastrointestinal tract. The duodenum makes another sharp turn to the left into the third part of the duodenum before joining with the jejunum. The duodenum is almost all retroperitoneal. The pH in the duodenum is approximately 9 (slightly basic). The name duodenum is from the Latin duodenum digitorum, twelve fingers' breadths or inches. Category:Digestive system

Digestion

Digestion is the process whereby a biological entity processes a substance, in order to chemically convert the substance into nutrients. Digestion occurs at the multicellular, cellular, and sub-cellular levels. Digestion usually involves mechanical manipulation and chemical action. In most vertebrates, digestion is a multi-stage process in the digestive system, following ingestion of the raw materials, most often other organisms. The process of ingestion usually involves some type of mechanical manipulation.

Human digestion

See: Gastrointestinal tract In humans, digestion begins in the mouth where food is chewed with the teeth. The process stimulates exocrine glands in the mouth to release digestive enzymes such as salivary amylase, which aid in the breakdown of food, particularly carbohydrates. Chewing also causes the release of saliva, which helps condense food into a bolus that can be easily passed through the esophagus to the stomach. In the stomach, food is churned and thoroughly mixed with acid and other digestive enzymes with digestive fluid to further decompose it chemically. As the acidic level changes in the stomach and later parts of the digestive tract, more enzymes are activated or deactivated to extract and process various nutrients. After being processed in the stomach, food is passed to the small intestine, it is pushed through the small intestine via a process called peristalsis, this is a squeezing action, it then passes through the pyloric sphincter where it is further mixed with secretions such as bile, which helps aid in fat digestion, and the enzymes maltase, lactase and sucrase, to process sugars. (Bile also contains pigments that are by-products of red blood cell destruction in the liver; these bile pigments are eliminated from the body with the feces). Most nutrient absorption takes place in the small intestine, after which food is passed to the large intestine. Blood which has absorbed nutrients passes through the liver for filtering, removal of toxins and help processing of nutrients. In the large intestine, water is reabsorbed, and leftover waste is excreted by defecation.

Digestive organs

Organisms develop specialized organs to aid in the digestion of their food, for example different types of tongues or teeth. Insects may have a crop (or the enlargement of esophagus) while birds and cockroachs may develop a gizzard (or a stomach that acts as teeth and mechanically digests food). A herbivore may have a caecum that contains bacteria which can produce cellulase that helps break down the cellulose in plants. Ruminants, for example cows and sheep, have a specialised fore-stomach called a rumen where microbes help to break down cellulose before the food passes onto the "true" stomach or abomasum.

Digestive hormones

There are at least four hormones that aid and regulate the digestive system:
- Gastrin - is in the stomach and stimulates the gastric glands to secrete pepsinogen and hydrochloric acid. Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low pH .
- Secretin - is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver. This hormone responds to the acidity of the chyme.
- Cholecystokinin (CCK) - is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder. This hormone is secreted in resonse to fat in chyme.
- Gastric inhibitory peptide (GIP) - is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach.

Digestion in plants and fungi

Not only animals digest food. Some carnivorous plants capture other organisms, usually invertebrate animals, and chemically digest them. Fungi also are very effective at digesting organic material in a saprobiontic manner, releasing digestive enzymes externally and then absorbing the digested products.

External links

- [http://www2.ufp.pt/~pedros/qfisio/digestion.htm Human Physiology - Digestion] Category:Digestive system Category:Metabolism ja:消化

Deoxycholic acid

General
Name	Deoxycholic acid
Chemical Formula	Chemical Formula C₂₄ H₄₀ O₄
Physical
Formula weight	392.58 amu
Appearance	white to off-white crystalline powder
Melting point	174 - 176C

Deoxycholic acid, also known as deoxycholate, cholanoic acid, and 3α,12α-dihydroxy-5β-cholanate, is a bile acid. When pure, it comes in a white to off-white crystalline powder form. Deoxycholic acid is one of the 4 main acids produced by the liver. It is soluble in alcohol and acetic acid.

Applications

In the human body deoxycholic acid is used in the emulsification of fats for the absorption in the intestine. Outside the body it is used in experimental basis of cholagogues and is also use to prevent and dissolve gallstones. It is also frequently used in mesotherapy injections, mixed with phosphatidylcholine. In research it is used as a mild detergent for the isolation of membrane associated proteins. Category:Bile acids

Glycine

Glycine (Gly, G) is a nonpolar amino acid. It is the simplest of the 20 standard (proteinogenic) amino acids: its side chain is a hydrogen atom. Because there is a second hydrogen atom at the α carbon, glycine is not optically active. Since glycine has such a small side chain, it can fit into many places where no other amino acid can. For example, only glycine can be the internal amino acid of a collagen helix. Glycine is very evolutionarily stable at certain positions of some proteins (for example, in cytochrome c, myoglobin, and hemoglobin), because mutations that change it to an amino acid with a larger side chain could break the protein's structure. Most proteins contain only small quantities of glycine. A notable exception is collagen, which is about one-third glycine.

Physiological function

Glycine is an inhibitory neurotransmitter in the CNS, especially in the spinal cord. When glycine receptors are activated, Cl^- enters the neuron via ionotropic receptors, causing an inhibitory post-synaptic potential (IPSP). Strychnine is an antagonist at these ionotropic receptors. Its LD50 is 0.96 mg/kg in rats, and it usually causes death by hyperexcitability. Glycine is a required co-agonist along with Glu in CNS. In contrast to the inhibitory role of glycine in the spinal cord, this behaviour is facilitated at the (NMDA) glutaminergic receptors which are excitatory. Glycine is a non-essential amino acid, meaning that cells of the body can synthesize sufficient amounts to meet physiological requirements.

Presence in the Interstellar Medium

In 1994 a team of astronomers from the University of Illinois, led by Lewis Snyder, claimed that they had found the glycine molecule in space. It turned out that, with further analysis, this claim could not be confirmed. Nine years later, in 2003, Yi-Jehng Kuan from National Taiwan Normal University and Steve Charnley made the extraordinary claim that they detected interstellar glycine toward three sources in the interstellar medium (Kuan et al., 2003). They claimed to have identified 27 spectral lines of glycine utilizing a radio telescope. According to computer simulations and lab-based experiments, glycine was probably formed when ices containing simple organic molecules were exposed to ultraviolet light [http://www.newscientist.com/news/news.jsp?id=ns99992558]. In October of 2004, Lewis Snyder and his collaborators reinvestigated the glycine claim in Kuan et al. (2003). In a rigorous attempt to confirm the detection, Snyder et al. (2005) show that glycine was not detected in any of the three claimed sources. Should any glycine claim be substantiated, it does not prove that life exists outside the Earth, but certainly makes that possibility more likely by showing that amino acids can be formed in the interstellar medium. The finding would also indirectly support the idea of panspermia, the theory that life was brought to Earth from space.

References

- Kuan YJ, Charnley SB, Huang HC, et al. (2003) Interstellar glycine. ASTROPHYS J 593 (2): 848-867
- Snyder LE, Lovas FJ, Hollis JM, et al. (2005) A rigorous attempt to verify interstellar glycine. ASTROPHYS J 619 (2): 914-930
- Dawson, R.M.C., Elliott, D.C., Elliott, W.H., and Jones, K.M., Data for Biochemical Research (3rd edition), pp. 1-31 (1986)

External Links

-
- [http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrugs/gly_0127.shtml PDRHealth - Glycine]
- [http://www.compchemwiki.org/index.php?title=Glycine Computational Chemistry Wiki]
- [http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/GlyCleave.html Glycine cleavage system] Category:Neurotransmitters Category:Photographic chemicals ja:グリシン

Taurine

Taurine (from taurus = ox, as it was discovered in ox bile) or 2-aminoethanesulfonic acid is an acidic chemical substance found in bile which acts as an emulsifier for ingested lipids and assists in their absorption. Taurine may also come from synthetic materials.

Chemistry

Chemically it is a colorless crystalline substance with the empirical formula C₂H₇NO₃S, formed by the hydrolysis of taurocholic acid or decarboxylation of cysteine. found in the urine, as well as juices and fluids of muscle, lungs and nerve tissue of many animals, and plays several important roles in the body and is essential to newborns of many species. While it is often referred to as an amino acid, this is an inaccurate categorization since it does not contain any carboxylic acid functional groups.

Physiology and Pharmacology

Taurine has four major roles in human metabolism:
- It plays a role in digestion. It is conjugated with the bile acids chenodeoxycholic acid and cholic acid to form (at the usually above 7 pH of bile) the bile salts, sodium taurochenodeoxycholate and sodium taurocholate (see bile).
- It may assist in the formation of reactive oxygen species for the respiratory burst in neutrophil granulocytes
- There is evidence that it is an inhibitory neurotransmitter in the central nervous system.
- It has been linked to a number of other metabolic functions but its role is not clear.

Uses

It has been tested medically in the treatment of congestive heart failure, cystic fibrosis, diabetes, epilepsy and several other conditions with positive results. It is used by some as an neutralizer for monosodium glutamate[http://msgtruth.org/remedies.htm]. However, neither the harmfulness of monosodium glutamate nor the benefit of taurine has been proven. Sources of dietary taurine include shellfish and organ meats such as liver. Taurine is one of the active ingredients commonly found in energy drinks such as Red Bull, and in pills which often feature caffeine and/or other stimulant ingredients. The manufacturers claim that taurine enhances the effects of caffeine, but to date there have been no studies performed to confirm this. Taurine is essential for cats; cat food is supplemented with taurine, which is why other pet foods are not recommended for cats. In cats, taurine "helps maintain good eye health, regulate the heart beat, maintain cell membrane stability, and prevent brain cell over-activity" [http://vegweb.com/articles/anai-1039230429.shtml]. Taurine supplements may be important to counteract the effects of human aging on the natural taurine production process. As humans age, hepatic taurine production can fall or fail completely, producing low to no energy, cardiac, digestive, and mental problems, and premature death. In biomedical research, taurine is also used in buffers for gel electrophoresis of nucleic acids. Some multi-purpose solutions for contact lenses contain the ingredient taurine. For example, one provider claims that [http://amoeyecare.com/Articles/Articles.asp?Article=7] taurine protects corneal cells from osmotic stress and functions as an antioxidant. Taurine does occur naturally in tears and ocular tissues. Category:Amino acids Category:Antioxidants Category:Food additives Category:Cats ja:タウリン

Emulsification

An emulsion is a mixture of two immiscible (unblendable) substances. One substance (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include butter and margarine, mayonnaise, the photo-sensitive side of film stock, and cutting fluid for metalworking. In butter and margarine, a continuous lipid phase surrounds droplets of water (water-in-oil emulsion). Emulsification is the process by which emulsions are prepared. Emulsions tend to have a cloudy appearance, because the many phase interfaces (the boundary between oil and water is called the interface) scatter light that passes through the emulsion. Emulsions can be stable or unstable. Homemade oil and vinegar salad dressing is an unstable emulsion that will quickly separate unless shaken continuously. This phenomenon is called coalescence, and happens when small droplets recombine to form bigger ones. Fluid emulsions can also suffer from creaming, the migration of one of the substances to the top of the emulsion under the influence of buoyancy or centripetal force when a centrifuge is used. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion tends to imply that both the dispersed and the continuous phase are liquid.

Emulsifier

An emulsifier (also known as a surfactant from surface active material or emulgent) is a substance which stabilizes an emulsion. Examples of food emulsifiers are egg yolk (where the main emulsifying chemical is the phospholipid lecithin), and mustard, where a variety of chemicals in the mucilage surrounding the seed hull act as emulsifiers; proteins and low-molecular weight emulsifiers are common as well. In some cases, particles can stabilise emulsions as well through a mechanism called Pickering stabilization. Both mayonnaise and Hollandaise sauce are oil-in-water emulsions stabilized with egg yolk lecithin. Detergents are another class of surfactant, and will chemically interact with both oil and water, thus stabilising the interface between oil or water droplets in suspension. This principle is exploited in soap to remove grease for the purpose of cleaning. A wide variety of emulsifiers are used in pharmacy to prepare emulsions such as creams and lotions. lotion injection. The manufacturers emulsify the lipid soluble propofol in a mixture water, soy oil and egg lecithin.]] Whether an emulsion turns into a water-in-oil emulsion or an oil-in-water emulsion depends of the volume fraction of both phases and on the type of emulsifier. Generally, the Bancroft rule applies: emulsifiers and emulsifying particles tend to promote dispersion of the phase in which they do not dissolve very well; for example, proteins dissolve better in water than in oil and so tend to form oil-in-water emulsions (that is they promote the dispersion of oil droplets throughout a continuous phase of water). Category:Colloidal chemistry Category:Food science ja:エマルション

Taurocholic acid

Taurocholic acid, also called cholaic acid or cholyltaurine, is a deliquescent yellowish crystalline bile acid involved in the emulsification of fats. It occurs as a sodium salt in the bile of mammals. Its summary formula is C₂₆H₄₅NO₇S and its melting point is 125 °C. It is a conjugate of cholic acid with taurine. Medically it is used as a cholagogue and cholerectic. Hydrolysis of taurocholic acid yields Taurine, a nonessential amino acid. Taurocholic is also known as acidum cholatauricum. Commercially is taurocholic acid manufactured from cattle bile, a byproduct of the meat-processing industry. See also deoxycholic acid. [http://smid.blueprint.org/SMInfo.php?het=582 Formula, model] Category:Bile acids

Phospholipids

Phospholipids are formed from four components: fatty acids, a negatively-charged phosphate group, an alcohol and a backbone. Phospholipids with a glycerol backbone are known as glycerophospholipids or phosphoglycerides. There is only one type of phospholipid with a sphingosine backbone; sphingomyelin. Phospholipids are a major component of all biological membranes, along with glycolipids and cholesterol.

Phosphoglycerides

In phosphoglycerides, the carboxyl group of each fatty acid is esterified to the hydroxyl groups on carbon-1 and carbon-2. The phosphate group is attached to carbon-3 by an ester link. This molecule, known as a phosphatidate, is present in small quantities in membranes, but is also a precursor for the other phosphoglycerides.

Phosphatidyl choline

Image:Phosphatidyl-Choline.png
Phosphatidyl choline is the major component of lecithin.

Phosphatidyl ethanolamine

Image:Phosphatidyl-Ethanolamine.png
Phosphatidyl ethanolamine is the major component of cephalin.

Synthesis

In phosphoglyceride synthesis, phosphatidates must be activated first. Phospholipids can be formed from an activated diacylglycerol or an activated alcohol. Phosphatidyl serine and phosphatidyl inositol are formed from a phosphoester linkage between the hydroxyl of an alcohol (serine or inositol) and cytidine diphosphodiacylglycerol (CDP-diacylglycerol). In the synthesis of phospatidyl ethanolamine, the alcohol is phosphorylated by ATP first, and subsequently reacts with cytidine diphosphate (CDP) to form the activated alcohol. The alcohol then reacts with a diacylglycerol to form the final product. In mammals, phosphatidyl choline can be synthesized via two separate pathways; a series of reactions similar to phosphatidyl ethanolamine synthesis, and the methylation of phosphatidyl ethanolamine, which is catalyzed by phosphatidyl ethanolamine methyltransferase, an enzyme produced in the liver.

Sphingomyelin

ATP
The backbone of sphingomyelin is sphingosine, an amino alcohol formed from palmitate and serine. The amino terminal is acylated with a by a long-chain acyl CoA to yield ceramide. Subsequent substitution of the terminal hydroxyl group by phosphatidyl choline forms sphingomyelin. Sphingomyelin is present in all eukaryotic cell membranes, but is mainly present in cells of the nervous system. Sphingomyelin is wrapped around nerve cells by Schwann cells to form the myelin sheath. Multiple Sclerosis is a disease characterised by deterioration of the myelin sheath and so nerve impulses cannot be conducted along the nerve.

Amphipathic character

Due to its polar nature, the head of a phospholipid is hydrophilic (attracted to water); the nonpolar tails are hydrophobic (not attracted to water). When placed in water, phospholipids form a bilayer, where the hydrophobic tails line up against each other, forming a membrane with hydrophilic heads on both sides extending out into the water. This allows it to form liposomes spontaneously, or small lipid vesicles, which can then be used to transport materials into living organisms and study diffusion rates into or out of a cell membrane. This membrane is partially permeable, very flexible, and has fluid properties, in which embedded proteins and phospholipid molecules are constantly moving laterally across the membrane because of the forces generated by their vibrations. Such movement can be described by the Fluid Mosaic Model, which describes the membrane as a "mosaic" of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane... oh - and your mom goes to college!

References

# Berg, J.M., J.L. Tymoczko, and L. Stryer, Biochemistry. 5th ed. 2002, New York: W.H. Freeman. xxxviii, 974, [976] (various pagings)
- th:ฟอสโฟไลปิด

Micelle

In chemistry, a micelle (also micella, plural micellae) is an aggregate of surfactant molecules, usually of globular shape, but other geomtrical shapes are possible (ellipsoid, cyllinder, vesicules, lamellae etc.). Micelles only form when the concentration of surfactant is greater than the critical micellar concentration (CMC), and the temperature of the system is greater than the critical micellar temperature (a.k.a. Krafft temperature). The spontaneous formation of micelles is driven by the increase of entropy (degree of disorder) of the solvent (usually water). The surrounding water molecules make "extra" hydrogen bonds (in comparison with the water structure in a bulk of water) to make a "cage" in which the hydrophobic part of surfactant molecule is enclosed, and when these hydrophobic parts are expelled from the surrounding water (by forming agreggates), breaking of these "extra" hydrogen bonds increases the enthropy of the system. The resulting state then has the maximum possible enthropy. Surfactants are chemicals that are amphipathic, which means that they contain both hydrophobic (usually long hydrocarbon chain(s)) and hydrophilic (ionic or polar) groups. The most common ionic surfactants are soaps (like Sodium oleate), hexadecyl- (or cetyl-)trimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS), and poly(ethylene oxide) glycol ethers are common nonionic surfactants. Micelles can exist in different shapes, including spherical, cylindrical, discoidal, or even vesicular, controlled largely by the molecular geometry of the surfactant, but also strongly influenced by the solution conditions (temperature, salt type and concentration, etc.). In an aqueous or other polar solvent, the core of a micelle consists of the hydrophobic part of the molecules, while the hydrophilic groups remain on the surface of the molecule so that they can maintain favorable contact with water. In the case of ionic surfactants, the electric charge of the ionic "heads" is partially neutralized (~50-90%) by the oppositely charged ions (counterions) located in the diffuse Gouy-Chapman layer around the micelle. Ionic micelles bear a significant surface charge that influences the system's properties (e.g. electrical conductivity). In a nonpolar solvent, the hydrophilic groups form the core of the micelle, and the hydrophobic groups remain on the surface of the micelle (so-called reverse micelle). Full theoretical descriptions of ionic micellar systems are, unfortunately, constrained by some (still) unsolvable problems (circular-reference-like theoretical problems). When surfactants are present above the CMC, they can act as emulsifiers. For instance, micelles formed by detergents in water assist in process of cleaning by incorporating hydrophobic material (such as oil, grease, or dirt) into their core. This is what happens when you wash your hands with soap. It is also the basis for emulsion polymerization.

Bilirubin

Bilirubin is a yellow breakdown product of haem (heme in American English). Haem is a special ring-shaped molecule that is found in haemoglobin and is essential to the oxygen-carrying capacity of blood.

Physiology

Bilirubin is essentially a waste product, formed when red blood cells die and hemoglobin is broken down. Haemoglobin is broken down within the macrophages to haem and globins; the haem is further degraded to Fe²⁺, carbon monoxide and bilirubin via the intermediate compound biliverdin. Since bilirubin is poorly soluble in water, it is carried to the liver bound to albumin. Bilirubin is made water-soluble in the liver by conjugation with uridine diphosphoglucuronic acid or UDPGA. As part of bile, the soluble or "conjugated" bilirubin then passes through the common bile duct and is either temporarily stored in the gallbladder or passes right away into the gut. Some of the excreted bilirubin may be reabsorbed from the gut (entero-hepatic circulation). Bacteria in the intestines modify bilirubin to form stercobilinogen, causing the brown color of feces. The yellow colour of urine is a result of urobilin, another breakdown product of bilirubin. In diseases where too much haemoglobin is broken down or the removal of bilirubin does not function properly, the accumulating bilirubin in the body causes jaundice.

Bilirubin blood tests

Bilirubin is broken down by light, and blood collection tubes (especially serum tubes) should therefore be protected from such exposure. Bilirubin is found in blood either in the soluble, conjugated form ("direct"), or bound to albumin ("indirect"). The terms "direct" and "indirect" refer to the fact that soluble bilirubin can be measured directly, whereas insoluble, or indirect, bilirubin must be solubilised before measurement. Although both direct and indirect bilirubin can be measured separately, it is more common to measure just total bilirubin. To further elucidate the causes of jaundice or increased bilirubin, it is usually simpler to look at other liver function tests (especially the enzymes ALT, AST, GGT, Alk Phos), blood film examination (haemolysis, etc.) or evidence of infective hepatitis (e.g., Hepatitis A, B, C, delta E, etc). Bilirubin is an excretion product, and the body does not control levels. Bilirubin levels reflect the balance between production and excretion. Thus, there is no "normal" level of bilirubin.

Interpretation

The reference range for total bilirubin is 2 - 14 μmol/L or 0.3 - 1.9 mg/dL. For direct bilirubin, it is 0 - 4 μmol/L or 0 - 0.3 mg/dL. Mild rises in bilirubin may be caused by
- Haemolysis or increased breakdown of blood.
- Gilbert's syndrome - slightly increased bilirubin due to an inherited enzyme deficiency. This has no clinical significance. Moderate rise in bilirubin may be caused by
- Drugs (especially anti-psychotic, some sex hormones, and a wide range of other drugs).
- Hepatitis (levels may be moderate or high). Very high levels of bilirubin may be caused by
- Neonatal hyperbilirubinaemia, where the newborn's liver is not able to properly conjugate the bilirubin (see jaundice).
- Unusually large bile duct obstruction, eg stone in common bile duct, tumour obstructing common bile duct etc.
- Severe liver failure with cirrhosis.
- Severe hepatitis.
- Criggler-Najjar syndrome Cirrhosis may cause normal, moderately high or high levels of bilirubin, depending on exact features of the cirrhosis.

Jaundice

Jaundice may be noticeable in the sclera (white) of the eyes at levels above about 30-50 μmol/l, and in the skin at higher levels. Jaundice is classified depending upon whether the bilirubin is free or conjugated to glucuronic acid into:
- Conjugated jaundice
- Unconjugated jaundice

Bilirubin toxicity

Unconjugated hyperbilirubinaemia in the neonate can lead to kernicterus in which there is damage to certain brain regions. The newborn has abnormal reflexes and unusual eye movements.

Bilirubin benefits

Reasonable levels of bilirubin can be beneficial to the organism. Evidence is accumulating that suggests bilirubin can protect tissues against oxidative damage caused by free radicals and other reactive oxygen species.

Chemistry

Bilirubin consists of an open chain of four pyrroles (tetrapyrrole); by constrast, the haem molecule is a ring of four pyrroles, called porphyrin. Bilirubin is very similar to the pigment phycobilin used by certain algae to capture light energy, and to the pigment phytochrome used by plants to sense light. All of these contain an open chain of four pyrroles. Like these other pigments, bilirubin changes its conformation when exposed to light. This is used in the phototherapy of jaundiced newborns: the illuminated version of bilirubin is more soluble than the unilluminated version. Several textbooks and research articles show incorrect chemical structures for the two isoforms of bilirubin. [http://www.nsta.org/main/news/stories/college_science.php?news_story_ID=48991]

Cholelithiasis

In medicine, gallstones (Choleliths) are crystalline bodies formed within the body by accretion or concretion of normal or abnormal bile components. Cholesterol stones are usually green, but are sometimes white or yellow in color and account for about 80 percent of gallstones. They are made primarily of cholesterol. Pigment stones are small, dark stones made of bilirubin and calcium salts that are found in bile. They account for the other 20 percent of gallstones. Risk factors for pigment stones include cirrhosis, biliary tract infections, and hereditary blood cell disorders, such as sickle cell anemia. Stones of mixed origin also occur. Gallstones can occur anywhere within the biliary tree, including the gallbladder and the common bile duct. Obstruction of the common bile duct is choledocholithiasis; obstruction of the biliary tree can cause jaundice; obstruction of the outlet of the pancreatic exocrine system can cause pancreatitis. Cholelithiasis is the presence of stones in the gallbladder - chole- means "gall bladder", lithia meaning "stone", and -sis means "process". Gallstones vary in size and may be as small as a grain of sand or as large as a golf ball. The gallbladder may develop a single, often large, stone or many smaller ones, even several thousand.

Causes

Progress has been made in understanding the process of gallstone formation. Researchers believe that gallstones may be caused by a combination of factors, including inherited body chemistry, body weight, gallbladder motility (movement), and perhaps diet. Cholesterol gallstones develop when bile contains too much cholesterol and not enough bile salts. Besides a high concentration of cholesterol, two other factors seem to be important in causing gallstones. The first is how often and how well the gallbladder contracts; incomplete and infrequent emptying of the gallbladder may cause the bile to become overconcentrated and contribute to gallstone formation. The second factor is the presence of proteins in the liver and bile that either promote or inhibit cholesterol crystallization into gallstones. Other factors also seem to play a role in causing gallstones but how is not clear. Obesity has been shown to be a major risk factor for gallstones. A large clinical study showed that being even moderately overweight increases one's risk for developing gallstones. This is probably true because obesity tends to cause excess cholesterol in bile, low bile salts, and decreased gallbladder emptying. Very low calorie, rapid weight-loss diets, and prolonged fasting, seem to also cause gallstone formation. In addition, increased levels of the hormone estrogen as a result of pregnancy, hormone therapy, or the use of birth control pills, may increase cholesterol levels in bile and also decrease gallbladder movement, resulting in gallstone formation. No clear relationship has been proven between diet and gallstone formation. However, low-fiber, high-cholesterol diets, and diets high in starchy foods have been suggested as contributing to gallstone formation.

Non-Medical options

A non-medical option embraced by a growing number of medical doctors as well as individuals is a gall bladder flush. There are variations but the common denominators are drinking epsom salts in water to dialite the bile ducts, and then drinking a 1/2 cup of fresh squeezed lemon juice and 1/2 cup of cold pressed olive oil shaken together. The mono-saturated fats in the olive oil stimulate bile production in the liver causing the gall bladder to flush. The acid in the lemon juice serves to break up stones, and make the preparation easier to consume. Immediately after consuming the preparation it is reccomended to lie on one's right side for 30 minutes or go to bed for the evening. The next morning another glass of water with epsoms salts to dialate the bile ducts and the gallstones are passed in the stool that day. Repeated flushes are often necessary to fully relieve intense gall bladder pain. A program of yearly maintenance is often reccomended for those consuming a western diet.

Medical options

Cholesterol gallstones can sometimes be dissolved by oral ursodeoxycholic acid. This drug is very expensive, however, and the gallstones recur once the drug is stopped. Obstruction of the common bile duct with gallstones can sometimes be relieved by endoscopic retrograde sphinceterotomy (ERS) following endoscopic retrograde cholangiopancreatography (ERCP).

Surgical options

Cholecystectomy (gallbladder removal) has a 99% chance of eliminating the recurrence of cholelithiasis. The lack of a gall bladder does not seem to have any negative consequences in some, however many people experience disturbances in digestion. There are two surgery options: open procedure and laparoscopic: see the cholecystectomy article for more details.
- Open procedure: This involves a large incision into the abdomen (laparotomy) below the right lower ribs. A week of hospitalization, normal diet a week after release and normal activity a month after release.
- Laparoscopic: 3-4 small puncture holes for camera and instruments (available since the 1980s). Typically same-day release or one night hospital stay, followed by a week of home rest and pain medication. Can resume normal diet and light activity a week after release. (Decreased energy level and minor residual pain for a month or two.) Studies have shown that this procedure is as effective as the more invasive open cholecystectomy, provided the stones are accurately located by cholangiogram prior to the procedure so that they can all be removed.

External links

- [http://www.pueblo.gsa.gov/cic_text/health/gallstones/gallstns.txt Public domain NIH/NIDDK e-pub on gallstones]
- [http://www.nlm.nih.gov/medlineplus/ency/presentations/100021_1.htm Gallbladder removal - series] from Medical Encyclopedia Category:Gastroenterology Category:Surgery ja:胆石

Horse

The Horse (Equus caballus) is a sizeable ungulate mammal, one of the seven modern species of the genus Equus. It has long played an important role in transport, whether ridden or used for pulling vehicles. They are also used for food. Though horses may have been domesticated in one isolated locale in 4500 BC, the unequivocal date of (1) domestication and (2) use as a means of transport dates to no earlier than circa 2000 BC, evidenced by the Sintashta chariot burials (see Domestication of the horse). Nevertheless, a close cousin of the horse, the donkey, was likely domesticated and used for transport circa 3000 BC (see discussions at Donkey and [http://nefertiti.iwebland.com/timelines/topics/means_of_transportation.htm]). Until the mid 20th century, armies used horses extensively in warfare: soldiers still call the groups of machines that now take the place of the horse on the battlefield "cavalry" units, sometimes keeping traditional names (Lord Strathcona's Horse, et cetera).

Domestication of the horse and surviving wild species

The earliest evidence for the domestication of the horse comes from Central Asia and dates to about 4,000 BCE. Competing theories exist about the time and place of domestication. However, wild species continued into historic times, including the Forest Horse, Equus caballus silvaticus (also called the Diluvial Horse); it is thought to have evolved into Equus caballus germanicus, and may have contributed to the development of the heavy horses of northern Europe, such as the Ardennais. The Tarpan, Equus caballus gmelini, became extinct in 1880. Its genetic line is lost, but a substitute has been recreated by "breeding back", crossing living domesticated horses that had features selected as primitive, thanks to the efforts of the brothers Lutz Heck (director of the Berlin zoo) and Heinz Heck (director of Tierpark Munich Hellabrunn). The resulting animal is more properly called the Wild Polish Horse or Konik. Konik] Only one true wild-horse species survives: Przewalski's Horse, Equus caballus przewalskii, a rare Asian species. Mongolians know it as the taki, while the Kirghiz people call it a kirtag. Wild populations exist in Mongolia; see: http://www.treemail.nl/takh/.

Wild vs. feral horses

One can distinguish between wild animals, whose ancestors have never undergone domestication, and feral animals, who had domesticated ancestors but who now live in the wild. Several populations of feral horses exist, including those in the West of the United States and Canada (often called "mustangs") and in parts of Australia (called brumbies) and in New Zealand (called "Kaimanawa horses"). These feral horses may provide useful insights into the behavior of their ancestral wild horses. The Icelandic horse (pony-sized but called a horse) provides an opportunity to compare contemporary and historical breed appearances and behaviour. Introduced by the Vikings into Iceland, Icelandic horses did not subsequently undergo the intensive selective breeding that took place in the rest of Europe from the middle ages onwards, and so they consequently bear a closer resemblance to pre-medieval breeds. The Icelandic horse has a four-beat gait called the "tölt", which equates to the rack exhibited by several American gaited breeds.

Other equids

Other members of the horse family include zebras, donkeys, and hemionids. The Donkey, Burro or Domestic Ass, Equus asinus, like the horse, has many breeds. A mule is a hybrid of a male ass and a mare and is infertile. A hinny is the less common hybrid of a female ass and a stallion. Recently breeders have begun crossing various species of zebra with mares or female asses to produce "zebra mules"—zorses and zonkeys (also called zedonks). This will probably remain a novelty hybrid as these individuals tend to inherit some of the nervous, difficult nature of their zebra parent. Full species list:
- Domesticated Horse (Equus caballus)
- Tarpan (Equus caballus gmelini)
- Przewalski's Horse (Equus caballus przewalskii)
- Donkey (Equus asinus)
- Onager (Equus hemionus)
- Kiang (Equus kiang)
- Mountain Zebra (Equus zebra)
- Plains Zebra (Equus quagga)
- Grevy's Zebra (Equus grevyi)

Evolution

All equids are part of the family Equidae, which dates back more than 50 million years. One of the first species was the tiny Hyracotherium. In the course of the million years, the horses evolved from leaf-eating forest-dwellers into grass-eating fast-running inhabitants of the open plains. The Evolution of the Horse lead to a reduction of the number of toes: from 5 per foot, to 3 per foot, to only 1 toe per foot. The genus Equus, to which all living equids belong, evolved a few million years ago. Examples of extinct horse genera include: Propalaeotherium, Mesohippus, Miohippus, Orohippus, Pliohippus, Anchitherium, Merychippus, Parahippus, Hipparion and Hippidion.

Natural History of the horse

Hippidion] In nature, horses function as prey animals. They have a natural tendency to flee from danger, though they will fight if cornered. Their eyes lie to the side of the head, giving them a wide view while grazing (slightly less than 180 degrees to each side, overlapped in front and leaving a blind spot in the rear). Even domesticated horses startle easily and must, for the safety of riders, undergo careful introductions to strange objects and situations. Horses live in family groups in primarily grassland habitats. These normally consist of a mature stallion, his harem of about one to ten mares, and the mares' offspring. Once young males reach breeding age and begin to attempt to breed with mares or to challenge the herd stallion, the latter drives them out of the herd to form "bachelor bands" with other young stallions. Usually not until a stallion reaches 7 or 8 years old does he stand a real chance of acquiring mares, eventually becoming, if successful in the attempt, a "band stallion", i.e. having a harem of his own, having separated female equids from another stallion's band. harem An alpha mare dictates the direction in which a family herd travels, while the stallion brings up the rear, "herding" his family. Recently, researchers have observed that a form of democracy appears to exist among horses. For instance, if the majority of the herd wants to stop and eat, the whole herd follows suit and stops.

Specialized vocabulary

The English-speaking world measures the height of horses in hands. One hand is defined in British law as 101.6 mm and is derived from a previous definition of 4 inches. Adult horses can range in size from 5 hands (0.5 m) (a very small miniature horse or falabella) to over 19 hands (1.8 m). By convention, 15.2 hh means 15 hands, 2 inches (1.57 m) in height, measured at the highest point of the withers. Usually, size alone marks the difference between horses and ponies. The threshold is 14.2 hh (1.47 m) for an adult. Below the threshold it is a pony, above the threshold it is a horse. Thus normal variations can mean that a horse stallion and horse mare can become the parents of an adult pony. However, a distinct set of characteristic pony traits, developed in northwest Europe and further evolved in the British Isles, muddies the issue of whether we use the word "pony" to describe a size or a type. Many people consider the Shetland pony as the archetypical pony, with its proportions very different from horses. Several small breeds appear as "horses" or "ponies" interchangeably, including the Icelandic, Fjord, and Caspian. Breeders of miniature horses favor that name because they strive to reproduce horse-like conformation in a very small size, even though their animals undeniably descend from ponies.

Words for gaits

All horses move naturally in four basic gaits, the walk, trot, canter/lope ("canter" in English riding, "lope" in Western), and the gallop.
- the walk - a "four beat" lateral gait in which a horse must have three feet on the ground and only one foot in the air at any time. The walking horse will lift first a hind leg, then the foreleg on the same side, then the remaining hind leg, then the foreleg on the same side. To get a horse into walk from halt, one must gently squeeze the sides of the horse and release the pressure on the reins. To get a horse to walk from trot, one must take sitting trot and gently apply pressure on the reins.
- the trot/jog - a "two beat" diagonal gait in which a foreleg and opposite hindleg (often called "diagonals") touch the ground at the same time. In this gait, each leg bears weight separately, making it ideal to check for lameness or for stiffness in the joints. To get a horse to trot fom walk you must soften your reins and apply more pressure with the leg. There are two types of trot a rider can do. Rising trot, where the rider stands up slightly in the saddle each time the horses outside front leg goes forward, and sitting trot, where the rider sits in the saddle and goes with the horse's movement.
- the canter/lope - A "three beat" gait in which a foreleg and opposite hindleg strike the ground together, and the other two legs strike separately. A cantering horse will first stride off with the outside hind leg, then then inside hind and outside fore together, then the inside front leg, and finally a period of suspension in which all four legs are off the ground. the rhythm should be 1-2-3, 1-2-3, etc. When cantering in a straight line, it does not usually matter which foreleg (or leading leg) goes first, but both leads should receive equal practice time, as otherwise the horse may become "one-sided" or develop a reluctance to canter on a specific lead. In the arena, the horse should canter on the inside lead. In making a fairly tight turn, the inside leg (the one nearest to the center of the turn) should lead, as this prevents the horse from "falling in". to get a horse to canter on the correct leg from trot, one must go into sitting trot, place their outside leg slightly behind the girth and squeeze with the inside leg. To get a horse to canter from gallop, one must alter the position of the body slightly back in the saddle, then you must place the outside leg behind the girth to allow the horse to canter on the correct leg, and apply pressure on the reins. Also called "lope" when riding in a Western show class. The canter is not a natural gait, but a restrained form of a gallop. Shetland pony
- the gallop - Another "four beat" gait which follows a similar progression to the canter, except the two paired legs land separately, the hind leg landing slightly before the foreleg. The gallop also involves having a leading leg. In turning at a very rapid rate, it is even more important that the horse use the appropriate lead, leading with the left leg if making a left turn, and the right leg if making a right turn, since the faster the turn the more the horse needs to lean into the turn. Horses that usually are galloped in a straight line need to be caused to alternate leads so that they do not suffer a muscular imbalance and subsequent difficulty making turns in one direction or the other. To get a horse into gallop, the rider must alter their position so they are slightly more forward in the saddle, then they should allow the horse to head and gently kick the horse's sides. The gallop is usually used in races or fox hunting. However, one would not gallop a horse during training in a ring or enclosed area, due to the fact that the horse may slip in attempting to gallop in such an area. Although a race track is an enclosed area, it is designed for a horse to gallop around, without being too enclosed which may cause the horse to slip while turning. Some horses have other gaits other than the most common three above. These horses are called Gaited Horses.
- tölt or tolt is a four beat running walk and can be ridden at any speed, from slow dancing steps to the speed of a galloping horse. This beat is natural to the Icelandic breed.
- pace is a lateral two-beat gait more commonly used in racing. In the pace, the legs move in lateral pairs, in a two beat gait, similar to the trot (however, in a trot, the legs move in diagonal pairs). In most countries pacers are raced in front of a sulky, an open mouthed two-wheeled vehicle drawn by one horse. These horses are commonly called "pacers" because of their unique gait.
- corto, largo, fino are the smooth four-beat gaits performed by Paso Finos. Similar natural four-beat gaits are found in breeds such as the Peruvian Paso. The corto occurs naturally, and is similar to the trot in speed. The largo is extended and high-speed, and the fino is very collected. This is the gait emphasized in high-level competition. Trainers have developed various artificial gaits for reasons such as appearance, and to improve the riding or driving quality. For details, see Horse gaits. Cited: Sly, Debbie. "The Practical Rider's Handbook". London: Lorenz Books, 1997.

Words relating to horses

You can view an entire equine dictionary at: [http://ultimatehorsesite.com/dictionary/dictionary.html The Horse Dictionary]
- Bronco - a wild, untamed horse, typically used in reference to the American mustang.
- Brumby - a wild or untrained Australian horse
- Charger - a medieval war horse
- cob - any horse of a short-legged, stout variety, with short legs, and a compact body, neck and back
- colt - an unaltered male horse from birth till the age of 4.
- destrier - a heavy, strong medieval war horse
- draught horse - heavy, muscular beast of burden
- filly - female horse from birth till the age of 4.
- foal - infant horse of either sex
- garron - small and disdained horse
- gelding - a castrated male horse of any age
- God dog - how the Apaches referred to horses
- green - a term used to describe an inexperienced horse
- hack - (noun) a horse for hire, or adapted to general work, used for driving or riding. Although the word sometimes means an old, worn out horse, it is also used to signify an extremely elegant horse used for riding on social occasions ("park hack", "hunter hack" etc.) (verb)- to ride a horse for pleasure, not as training
- hackney - a specific breed of flashy, elegant driving pony
- Hand - a unit of measuring used frequently to measure a horses height. One hand is equal to 4 inches (appox. 10 cm)
- horse - adult equine of either sex over 14.2 hh (58 inches, 1.47 m)
- jennet - a small horse, particularly a Spanish one
- mare - adult female horse
- mustang - a feral horse found in the western plains of North America
- nag - small horse or pony used for riding (uncomplimentary term)
- palfrey - a smooth gaited type, a riding horse, a woman's horse
- pony - equine 14.2 hh or less (58 inches, 1.47 metres)
- School Horse/Pony- A horse owned by a riding academy
- shelt or shelty - a Shetland pony
- stallion - adult, male horse that is able to produce offspring
- weanling - a young horse that has just been weaned from their mother (usually 6 months or a little older)
- yearling - male or female horse two years old In horse racing the definitions of colt, filly, mare, and horse differ from those given above. Thoroughbred racing defines a colt as a male horse less than five years old and a filly as a female horse less than five years old; harness racing defines colts and fillies as less than four years old. Horses older than colts and fillies become known as horses and mares respectively.

Words relating to horse anatomy

harness racing ; withers: the highest point of the shoulder seen best with horse standing square and head slightly lowered. The tops of the two shoulder blades and the space between them define the withers. ; mane and forelock: long and relatively coarse hair growing from the dorsal ridge of the neck, lying on either the left or right side of the neck, and the continuation of that hair on the top of the head, where it generally hangs forward. (See illustration.) ; Dock: the point where the tail connects to the rear of the horse. ; Flank: Where the hind legs and the stomach of the horse meet. ; Pastern: The connection between the coronet and the fetlock. ; Fetlock: Resembles the ankle of the horse. ; Coronet: The part of the hoof that connects the hoof to the pastern. ; Cannon: Resembles the shin of the horse. ; Muzzle: the chin, mouth, and nostrils make up the muzzle on the horse's face. ; Crest: the point on the neck where the mane grows out of. ; Poll: the portion of the horse's neck right behind the ears. ; Hock: Hindlimb equivalent to the Heel, the main joint on the hind leg. ; Stifle: corresponds to the elbow of a horse, except on the hind limb. ; Gaskin: also known as the "second thigh," the large muscle on the hind leg, just above the hock, below the stifle. ; Jowl: the cheek bone under the horses ear on both sides Chestnut: on the inside of every leg

Horse coat colors and markings

withers Horses exhibit a diverse array of coat colors and distinctive markings, and a specialized vocabulary has evolved to describe them. In fact, one will often refer to a horse in the field by his or her coat color rather than by breed or by gender. Coat colors include:
- Appaloosa - a breed of horse with spots, any color mixed with white. There are different patterns: blanket- white blanket that typically starts around or behind withers with dark spots mostly over the hips, snowflake - solid with white spots over hips, and leopard - which is white with dark spots over all the coat. A true Appaloosa is actually a breed, not a color.
- Bay- From light brown to very dark brown with black mane and tail with black points. Three types - Dark bay, blood bay, light bay and just bay.
- Black- There are two types of black, fading black and jet black. Ordinary black horses will fade to a rusty brownish color if the horse is exposed to sunlight on a regular basis. Jet black is a blue-black shade that is fadeproof. Black foals are usually born a mousy grey color. As their foal coat begins to shed out, their black color will show through,but jet black foals are born jet black. Usually for a horse to be considered black it must be completely black with no brown at all, only white markings.
- Brown - A bay without any black points.
- Buckskin- A bay horse with a gene that 'dilutes' the coat colour to a yellow, cream, or gold while keeping the black points (mane, tail, ears, legs).
- Chestnut- A reddish body color with no black.
- Cremello - A chestnut horse with two dilute genes that washes out almost all colour. Often called pseudo albinos, they have blue eyes. There are no true albino horses.
- Dun - Yellowish brown with a dorsal stripe along the back and occasionally zebra stripings on the legs.
- Fleabitten - refers to usually red hairs flecked in the coat of a gray horse.
- Gray - A horse with black skin and clear hairs. Gray horses can be born any color, and eventually most will turn gray or white with age. If you would define the horse as white it is still grey unless it is albino. Some gray horses that are very light must wear sunscreen.
- Grulla- A black horse with a dun gene. It is often a grayish/silver colored horse with dark dun factors.
- Pinto - a multi-colored horse with large patches of brown, white, and/or black and white. Piebald is black and white, while Skewbald is white and brown. Specific patterns such as tobiano, overo, and tovero refer to the orientation of white on the body.
- Paint - In 1962, the American Paint Horse Association began to recognize pinto horses with known Quarter Horse and/or Thoroughbred bloodlines as a separate breed. Today, Paint horses are the world's fifth most popular breed. Also palomino paint - palomino with white.
- Palomino-chesnut horse that has one cream dilute gene that turns the horse to a golden, yellow, or tan shade with a flaxen (white) mane and tail. Often cited as being a color "within three shades of a newly minted coin", palominos actually come in all shades from extremely light, to deep chocolate.
- Perlino - Exactly like a cremello but a bay horse with two dilute genes.
- Roan - a color pattern that causes white hairs to be sprinkled over the horse's body color. Red roans are chesnut and white hairs, blue roans are black/bay with white hairs. Roan can happen on any body color; for example, there are palomino roans and dun roans. Roans are distinguishable from greys because roans typically do not change colour in their lifetimes, unlike gray that gradually gets lighter as a horse ages. Roans also have solid colored heads that do not lighten.
- Splash - a genetically controlled horse coat variation.
- Tobiano - a genetic trait among horses which produces a characteristic white pattern in the coat.
- White - Any non-albino white horse is called a gray, even though they appear white. All white, may be the result of overlapping pinto, appaloosa, or sabino markings. Rarely there are true white horses born and are documented to have a dominant white gene (see Gray (horse) for a discussion of these). These horses have normal eye colour, and they stay white for life. Markings include: On the face:
- Star
- Snip
- Stripe
- Blaze
- White Face (sometimes called Bald Face) On the legs:
- Coronet
- Pastern
- Sock
- Stocking Elsewhere:
- Cowlicks (hair whorls)--can occur on any part of the animal, but are mainly seen on the forehead and neck. For horse color and marking genetics see Equine coat color genetics. Another good resource for horse color is: [http://ultimatehorsesite.com/colors/index.html Horse color, markings, and genetics]. Another that has numerous photographs of various colors and markings is [http://equinecolor.com/ Equine color].

The origin of modern horse breeds

Equine coat color genetics]] Horses come in various sizes and shapes. The draft breeds can top 20 hands (80 inches, 2 metres) while the smallest miniature horses can stand as low as 5.2 hands (22 inches, 0.56 metres). The Patagonian Fallabella, usually considered the smallest horse in the world, compares in size to a German Shepherd Dog. Several schools of thought exist to explain how this range of size and shape came about. These schools grew up reasoning from the type of dentition and from the horses' outward appearance. One school, which we can call the "Four Foundations", suggests that the modern horse evolved from two types of early domesticated pony and two types of early domesticated horse; the differences between these types account for the differences in type of the modern breeds. A second school -- the "Single Foundation" -- holds only one breed of horse underwent domestication, and it diverged in form after domestication through human selective breeding (or in the case of feral horses, through ecological pressures). Finally, certain geneticists have started evaluating the DNA and mitochondrial DNA to construct family trees. See: Domestication of the horse

Breeds, studbooks, purebreds and landraces

Domestication of the horse The idea of a "purebred" animal gained importance in Europe during the 19th century but selective breeding has occurred almost everywhere man has kept horses. The Arabs had a reputation for breeding their prize mares to only the most worthy stallions, and kept extensive pedigrees of their "asil" (purebred) horses. During the late middle ages the Carthusian monks of southern Spain, themselves forbidden to ride, bred horses which nobles throughout Europe prized; the lineage survives to this day in the Andalusian horse or caballo de pura raza español. The modern landscape of breed designation presents a complicated picture. Some breeds have closed studbooks; a registered Thoroughbred, Arabian, or Quarter Horse must have two registered parents of the same breed, and no other criteria for registration apply. Other breeds tolerate limited infusions from other breeds—the modern Appaloosa for instance must have at least one Appaloosa parent but may also have a Quarter Horse, Thoroughbred, or Arabian parent and must also exhibit spotted coloration to gain full registration. Still other breeds, such as most of the warmblood sporthorses, require individual judging of an individual animal's quality before registration or breeding approval. Breed registries also differ as to their acceptance or rejection of breeding technology. For example, all Thoroughbred registries require that a registered Thoroughbred be a product of a natural mating. A foal born of two Thoroughbred parents, but by means of artificial insemination, is barred from the Thoroughbred studbook. Some other breed registries allow artificial insemination, embryo transfer, or both.

Hotbloods, warmbloods, and coldbloods

The Arabian horses, whether originating on the Arabian peninsula or from the European studs (breeding establishments) of the 18th and 19th centuries, gained the title of "hotbloods", for their fiery temperaments. The Thoroughbred is also included in the "hotblood" category. The slow, heavy draft horses class as "coldbloods", as they usually possess a quite calm temperament. The term "warmbloods" covers everything else, but the term also specifically refers to the European breeds, such as the Hanoverian, that have dominated dressage and show jumping since the 1950s. True hotbloods usually offer greater riding challenges than other horses, especially the coldblood. They show more excitability, and often more dominance; and the longer you ride them, the more excited they become, instead of merely getting tired (although any breed of horse can succumb to fatigue). The list of horse breeds provides a partial alphabetical list of breeds of horse extant today, plus a discussion of rare breeds' conservation.

Horses in sport today

Racing in all its forms

Humans have always had a desire to know which horse (or horses) could move the fastest, horse-racing has ancient roots. Today, several categories of racing exist:

Races subject to formal gambling

Under saddle: # Thoroughbred flat racing; (under the aegis of the Jockey Club in the United Kingdom and the Jockey Club of North America) # Thoroughbred National Hunt racing or steeplechasing in the UK # Quarter Horse Racing--mostly in the United States, and sanctioned there by the American Quarter Horse Association. # Appaloosa Horse Racing # Arabian Horse Racing In harness: # The United States Trotting Association organizes harness Racing in the United States (although the horses may also pace) # Harness Racing in Europe, New Zealand and Australia

Amateur races without gambling

# Endurance riding, a sport in which the Arabian dominates at the top level, has become very popular in the United States and in Europe. The American Endurance Ride Conference organizes the sport in North America. Endurance races take place over a given, measured distance and the horses have an even start. Races begin at 20 miles and peak at 100 miles. Note especially the Tevis Cup. # Ride and Tie (in North America, organized by Ride and Tie Association). Ride and Tie involves three equal partners: two humans and one horse. The humans alternately run and ride. Thoroughbreds have a pre-eminent reputation as a racing breed, but Arabians, Quarter Horses, and Appaloosas also race on the flat in the United States. Quarter Horses traditionally raced for a quarter mile, hence the name. Steeplechasing involves racing on a track where the horses also jump over obstacles. It occurs most commonly in the United Kingdom. Standardbred trotters and pacers race in harness with a sulky or racing bike. In France they also race under saddle.

Show Sports

The traditional competitions of Europe

The three following count as Olympic disciplines:
- Dressage ("training" in French) involves the progressive training of the horse to a high level of impulsion, collection, and obedience. Competitive dressage has the goal of showing the horse carrying out, on request, the natural movements that it performs without thinking while running loose. One dressage master has defined it as "returning the freedom of the horse while carrying the rider."
- Show jumping comprises a timed event judged on the ability of the horse and rider to jump over a series of obstacles, in a given order and with the fewest refusals or knockdowns of portions of the obstacles. At the Grand Prix level fences may reach a height of as much as 6 feet.
- Eventing, combined training, horse trials, "the Military," or "the complete test" as its French name translates, puts together the obedience of dressage with the athletic ability of show jumping, the fitness demands of a long endurance phase (a.k.a. "roads and tracks") and the "cross-country" jumping phase. In the last-named, the horses jump over fixed obstacles, unlike show jumping, where the majority of the obstacles will fall down or apart if hit by the horse.

Found in the United States

- Huntseat riding as a show discipline derived from English foxhunting and from the natural desire for people to prove that the superiority of their mount. In the modern show ring hunters show "on the flat" at the walk, trot, and canter, and "over fences". For equitation, see below. Hunter classes in various divisions and fence heights demonstrate the horse's ability to jump smoothly and safely. A winning show hunter has very good conformation, a smooth jumping style (with tightly-folded front legs), a good length of stride, and an appealing manner.
- Saddleseat (also known as Park or English Pleasure riding), a uniquely American discipline, developed to show to best advantage the extravagantly animated movement of high-stepping gaited breeds such as the American Saddle Horse and the Tennessee Walker. Riders also commonly show Arabians and Morgans saddleseat in the United States.
- Equitation refers to those classes where judges assess the rider, not the performance of the horse. Equitation classes occur in the Huntseat, Saddleseat, and Western disciplines.

Western riding

Dressage, jumping and cross-country offer forms of what Americans refer to as 'English riding'. Western riding evolved stylistically from traditions brought to the Americas by the Spanish, and its skills stem from the working needs of the cowboy in the American West. A main differentiating factor comes from the need of the cowboy to rope cattle with a lariat (or lasso). The cowboy must control the horse with one hand and use the lariat with the other hand. That means that horses must learn to neck rein, that is, to respond to light pressure of the slack rein against the horse's neck. Once the cowboy has twirled the lariat and thrown its loop over a cow's head, he must snub the rope to the horn of his saddle. For roping calves, the horse learns to pull back against the calf, which falls to the ground, while the cowboy dismounts and ties the calf's feet together so that he can be brand it, treat it for disease, and so on. Working with half-wild cattle, frequently in terrain where one cannot see what lurks behind the next bush, means the ever-present very great danger of becoming unseated in an accident miles from home and friends. These multiple work needs mean that cowboys require different tack, most notably a curb bit (usually with longer bars than an English equitation curb or pelham bit would have) which works by leverage, long split reins (the ends of which can serve as an impromptu quirt) and a special kind of saddle. The Western saddle has a very much more substantial frame (traditionally made of wood) to absorb the shock of roping, a prominent pommel surmounted by a horn (a big knob for snubbing the lasso after roping an animal), and, frequently, tapaderos ("taps") covering the front of the stirrups to prevent the cowboy's foot from slipping through the stirrup in an accident and resulting in a frightened horse dragging him behind it. The cowboy's boots, which have high heels of an uncommon shape, also feature a specific design to prevent the cowboy's foot from slipping through the stirrup. Technically, fewer differences between 'English' and Western riding exist than most people think. The outfit of the competition Western rider differs from that of the dressage or 'English' rider. In dressage all riders wear the same to prevent distraction from the riding itself. But show -- in the form of outfit (and silver ornaments on saddle and tack) -- forms part of Western riding. The riders must wear cowboy boots, jeans, a shirt with long sleeves, and a cowboy hat. Riders can choose any color, and optionally accoutrements such as bolo ties, belt buckles, and (shiny) spurs. Competitions exist in the following forms:
- Western pleasure - the rider must show the horse in walk, jog (a slow, controlled trot), trot and lope (a slow, controlled canter). The horse must remain under control, with the rider directing minimal force through the reins and otherwise using minimal interference.
- Reining - considered by some the "dressage" of the western riding world, reining requires horse and rider to perform a precise pattern consisting of canter circles, rapid "spins" (a particularly athletic turn on the haunches), and the sliding stop (executed from a full gallop).
- Cutting: more than any other, this event highlights the "cow sense" prized in stock breeds such as the Quarter horse. The horse and rider select and separate a calf out of a small group. The calf then tries to return to its herdmates; the rider loosens the reins and leaves it entirely to the horse to keep the calf separated, a job the best horses do with relish, savvy, and style. A jury awards points to the cutter. <

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