Heredity is the passing on of traits from parents to their offspring, either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic information of their parents. Through heredity, variations between individuals can accumulate and cause species to evolve by natural selection; the study of heredity in biology is genetics. In humans, eye color is an example of an inherited characteristic: an individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype; the complete set of observable traits of the structure and behavior of an organism is called its phenotype. These traits arise from the interaction of its genotype with the environment; as a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's sunlight. However, some people tan more than others, due to differences in their genotype: a striking example is people with the inherited trait of albinism, who do not tan at all and are sensitive to sunburn.
Heritable traits are known to be passed from one generation to the next via DNA, a molecule that encodes genetic information. DNA is a long polymer; the sequence of bases along a particular DNA molecule specifies the genetic information: this is comparable to a sequence of letters spelling out a passage of text. Before a cell divides through mitosis, the DNA is copied, so that each of the resulting two cells will inherit the DNA sequence. A portion of a DNA molecule that specifies a single functional unit is called a gene. Within cells, the long strands of DNA form condensed structures called chromosomes. Organisms inherit genetic material from their parents in the form of homologous chromosomes, containing a unique combination of DNA sequences that code for genes; the specific location of a DNA sequence within a chromosome is known as a locus. If the DNA sequence at a particular locus varies between individuals, the different forms of this sequence are called alleles. DNA sequences can change through mutations.
If a mutation occurs within a gene, the new allele may affect the trait that the gene controls, altering the phenotype of the organism. However, while this simple correspondence between an allele and a trait works in some cases, most traits are more complex and are controlled by multiple interacting genes within and among organisms. Developmental biologists suggest that complex interactions in genetic networks and communication among cells can lead to heritable variations that may underlie some of the mechanics in developmental plasticity and canalization. Recent findings have confirmed important examples of heritable changes that cannot be explained by direct agency of the DNA molecule; these phenomena are classed as epigenetic inheritance systems that are causally or independently evolving over genes. Research into modes and mechanisms of epigenetic inheritance is still in its scientific infancy, this area of research has attracted much recent activity as it broadens the scope of heritability and evolutionary biology in general.
DNA methylation marking chromatin, self-sustaining metabolic loops, gene silencing by RNA interference, the three dimensional conformation of proteins are areas where epigenetic inheritance systems have been discovered at the organismic level. Heritability may occur at larger scales. For example, ecological inheritance through the process of niche construction is defined by the regular and repeated activities of organisms in their environment; this generates a legacy of effect that modifies and feeds back into the selection regime of subsequent generations. Descendants inherit genes plus environmental characteristics generated by the ecological actions of ancestors. Other examples of heritability in evolution that are not under the direct control of genes include the inheritance of cultural traits, group heritability, symbiogenesis; these examples of heritability that operate above the gene are covered broadly under the title of multilevel or hierarchical selection, a subject of intense debate in the history of evolutionary science.
When Charles Darwin proposed his theory of evolution in 1859, one of its major problems was the lack of an underlying mechanism for heredity. Darwin believed in the inheritance of acquired traits. Blending inheritance would lead to uniformity across populations in only a few generations and would remove variation from a population on which natural selection could act; this led to Darwin adopting some Lamarckian ideas in editions of On the Origin of Species and his biological works. Darwin's primary approach to heredity was to outline how it appeared to work rather than suggesting mechanisms. Darwin's initial model of heredity was adopted by, heavily modified by, his cousin Francis Galton, who laid the framework for the biometric school of heredity. Galton found no evidence to support the aspects of Darwin's pangenesis model, which relied on acquired traits; the inheritance of acquired traits was shown to have little basis in the 1880s when August Weismann cut the tails off many generations of mice and found that their offspring continued to develop tails.
Scientists in Antiquity had a variety of ideas about heredity: Theophrastus proposed that male flowers caused f
In chemistry, an alcohol is any organic compound in which the hydroxyl functional group is bound to a carbon. The term alcohol referred to the primary alcohol ethanol, used as a drug and is the main alcohol present in alcoholic beverages. An important class of alcohols, of which methanol and ethanol are the simplest members, includes all compounds for which the general formula is CnH2n+1OH, it is these simple monoalcohols. The suffix -ol appears in the IUPAC chemical name of all substances where the hydroxyl group is the functional group with the highest priority; when a higher priority group is present in the compound, the prefix hydroxy- is used in its IUPAC name. The suffix -ol in non-IUPAC names typically indicates that the substance is an alcohol. However, many substances that contain hydroxyl functional groups have names which include neither the suffix -ol, nor the prefix hydroxy-. Alcohol distillation originated in India. During 2000 BCE, people of India used. Alcohol distillation was known to Islamic chemists as early as the eighth century.
The Arab chemist, al-Kindi, unambiguously described the distillation of wine in a treatise titled as "The Book of the chemistry of Perfume and Distillations". The Persian physician, alchemist and philosopher Rhazes is credited with the discovery of ethanol; the word "alcohol" is from a powder used as an eyeliner. Al- is the Arabic definite article, equivalent to the in English. Alcohol was used for the fine powder produced by the sublimation of the natural mineral stibnite to form antimony trisulfide Sb2S3, it was considered to be the essence or "spirit" of this mineral. It was used as an antiseptic and cosmetic; the meaning of alcohol was extended to distilled substances in general, narrowed to ethanol, when "spirits" was a synonym for hard liquor. Bartholomew Traheron, in his 1543 translation of John of Vigo, introduces the word as a term used by "barbarous" authors for "fine powder." Vigo wrote: "the barbarous auctours use alcohol, or alcofoll, for moost fine poudre."The 1657 Lexicon Chymicum, by William Johnson glosses the word as "antimonium sive stibium."
By extension, the word came to refer to any fluid obtained by distillation, including "alcohol of wine," the distilled essence of wine. Libavius in Alchymia refers to "vini alcohol vel vinum alcalisatum". Johnson glosses alcohol vini as "quando omnis superfluitas vini a vino separatur, ita ut accensum ardeat donec totum consumatur, nihilque fæcum aut phlegmatis in fundo remaneat." The word's meaning became restricted to "spirit of wine" in the 18th century and was extended to the class of substances so-called as "alcohols" in modern chemistry after 1850. The term ethanol was invented 1892, combining the word ethane with the "-ol" ending of "alcohol". IUPAC nomenclature is used in scientific publications and where precise identification of the substance is important in cases where the relative complexity of the molecule does not make such a systematic name unwieldy. In naming simple alcohols, the name of the alkane chain loses the terminal e and adds the suffix -ol, e.g. as in "ethanol" from the alkane chain name "ethane".
When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the -ol: propan-1-ol for CH3CH2CH2OH, propan-2-ol for CH3CHCH3. If a higher priority group is present the prefix hydroxy-is used, e.g. as in 1-hydroxy-2-propanone. In cases where the OH functional group is bonded to an sp2 carbon on an aromatic ring the molecule is known as a phenol, is named using the IUPAC rules for naming phenols. In other less formal contexts, an alcohol is called with the name of the corresponding alkyl group followed by the word "alcohol", e.g. methyl alcohol, ethyl alcohol. Propyl alcohol may be n-propyl alcohol or isopropyl alcohol, depending on whether the hydroxyl group is bonded to the end or middle carbon on the straight propane chain; as described under systematic naming, if another group on the molecule takes priority, the alcohol moiety is indicated using the "hydroxy-" prefix. Alcohols are classified into primary and tertiary, based upon the number of carbon atoms connected to the carbon atom that bears the hydroxyl functional group.
The primary alcohols have general formulas RCH2OH. The simplest primary alcohol is methanol, for which R=H, the next is ethanol, for which R=CH3, the methyl group. Secondary alcohols are those of the form RR'CHOH, the simplest of, 2-propanol. For the tertiary alcohols the general form is RR'R"COH; the simplest example is tert-butanol, for which each of R, R', R" is CH3. In these shorthands, R, R', R" represent substituents, alkyl or other attached organic groups. In archaic nomenclature, alcohols can be named as derivatives of methanol using "-carbinol" as the ending. For instance, 3COH can be named trimethylcarbinol. Alcohols have a long history of myriad uses. For simple mono-alcohols, the focus on this article, the following are most important industrial alcohols: methanol for the production of formaldehyde and as a fuel additive ethanol for alcoholic beverages, fuel additive, solvent 1-propanol, 1-butanol, isobutyl alcohol for use as a solvent a
Cocaine known as coke, is a strong stimulant used as a recreational drug. It is snorted, inhaled as smoke, or dissolved and injected into a vein. Mental effects may include loss of contact with reality, an intense feeling of happiness, or agitation. Physical symptoms may include a fast heart rate and large pupils. High doses can result in high blood pressure or body temperature. Effects begin within seconds to last between five and ninety minutes. Cocaine has a small number of accepted medical uses such as numbing and decreasing bleeding during nasal surgery. Cocaine is addictive due to its effect on the reward pathway in the brain. After a short period of use, there is a high risk, its use increases the risk of stroke, myocardial infarction, lung problems in those who smoke it, blood infections, sudden cardiac death. Cocaine sold on the street is mixed with local anesthetics, quinine, or sugar, which can result in additional toxicity. Following repeated doses a person may have decreased ability to feel pleasure and be physically tired.
Cocaine acts by inhibiting the reuptake of serotonin and dopamine. This results in greater concentrations of these three neurotransmitters in the brain, it can cross the blood–brain barrier and may lead to the breakdown of the barrier. Cocaine is a occurring substance found in the coca plant, grown in South America. In 2013, 419 kilograms were produced legally, it is estimated. With further processing crack cocaine can be produced from cocaine. Cocaine is the second most used illegal drug globally, after cannabis. Between 14 and 21 million people use the drug each year. Use is highest in North America followed by South America. Between one and three percent of people in the developed world have used cocaine at some point in their life. In 2013, cocaine use directly resulted in 4,300 deaths, up from 2,400 in 1990; the leaves of the coca plant have been used by Peruvians since ancient times. Cocaine was first isolated from the leaves in 1860. Since 1961, the international Single Convention on Narcotic Drugs has required countries to make recreational use of cocaine a crime.
Topical cocaine can be used as a local numbing agent to help with painful procedures in the mouth or nose. Cocaine is now predominantly used for lacrimal duct surgery; the major disadvantages of this use are cocaine's potential for cardiovascular toxicity and pupil dilation. Medicinal use of cocaine has decreased as other synthetic local anesthetics such as benzocaine, proparacaine and tetracaine are now used more often. If vasoconstriction is desired for a procedure, the anesthetic is combined with a vasoconstrictor such as phenylephrine or epinephrine; some ENT specialists use cocaine within the practice when performing procedures such as nasal cauterization. In this scenario dissolved cocaine is soaked into a ball of cotton wool, placed in the nostril for the 10–15 minutes before the procedure, thus performing the dual role of both numbing the area to be cauterized, vasoconstriction; when used this way, some of the used cocaine may be absorbed through oral or nasal mucosa and give systemic effects.
An alternative method of administration for ENT surgery is mixed with adrenaline and sodium bicarbonate, as Moffett's solution. Cocaine is a powerful nervous system stimulant, its effects can last from 30 minutes to an hour. The duration of cocaine's effects depends on the route of administration. Cocaine can be in the form of fine white powder, bitter to the taste; when inhaled or injected, it causes a numbing effect. Crack cocaine is a smokeable form of cocaine made into small "rocks" by processing cocaine with sodium bicarbonate and water. Crack cocaine is referred to. Cocaine use leads to increases in alertness, feelings of well-being and euphoria, increased energy and motor activity, increased feelings of competence and sexuality. Coca leaves are mixed with an alkaline substance and chewed into a wad, retained in the mouth between gum and cheek and sucked of its juices; the juices are absorbed by the mucous membrane of the inner cheek and by the gastrointestinal tract when swallowed. Alternatively, coca leaves can be consumed like tea.
Ingesting coca leaves is an inefficient means of administering cocaine. Because cocaine is hydrolyzed and rendered inactive in the acidic stomach, it is not absorbed when ingested alone. Only when mixed with a alkaline substance can it be absorbed into the bloodstream through the stomach; the efficiency of absorption of orally administered cocaine is limited by two additional factors. First, the drug is catabolized by the liver. Second, capillaries in the mouth and esophagus constrict after contact with the drug, reducing the surface area over which the drug can be absorbed. Cocaine metabolites can be detected in the urine of subjects that have sipped one cup of coca leaf infusion. Orally administered cocaine takes 30 minutes to enter the bloodstream. Only a third of an oral dose is absorbed, although absorption has been shown to reach 60% in controlled settings. Given the slow rate of absorption, maximum physiological and psychotropic effects are attained 60 minutes after cocaine is administered by ingestion.
While the onset of these effects is slow, the effects are sustained for approxima
American Heart Association
The American Heart Association is a non-profit organization in the United States that funds cardiovascular medical research, educates consumers on healthy living and fosters appropriate cardiac care in an effort to reduce disability and deaths caused by cardiovascular disease and stroke. Formed in New York City in 1924 as the Association for the Prevention and Relief of Heart Disease, it is headquartered in Dallas, Texas; the American Heart Association is a national voluntary health agency. They are known for publishing guidelines on cardiovascular disease and prevention, standards on basic life support and advanced cardiac life support, in 2014 issued its first guidelines for preventing strokes in women, they are known for operating a number of visible public service campaigns starting in the 1970s, operate a number of fundraising events. In 1994, the Chronicle of Philanthropy, an industry publication, released a study that showed the American Heart Association was ranked as the 5th "most popular charity/non-profit in America."
The Association was listed as the 22nd largest charity by Forbes in 2018. The mission of the organization, updated in 2018, is "To be a relentless force for a world of longer, healthier lives." The American Heart Association grew out of a set of smaller precursor groups. The primary precursor was the Association for the Prevention and Relief of Heart Disease, formed in New York City in 1915, to study whether patients with heart disease could safely return to work. Several similar organizations formed or evolved in Boston and Chicago in the 1920s. Recognizing the need for a national organization to share research and promote findings, the American Heart Association was formed in 1924 by six cardiologists representing several of these precursor groups; the AHA remained small until the 1940s when it was selected for support by Procter & Gamble, via their PR firm, from a list of applicant charities. Procter & Gamble gave $1.5 million from its radio show, Truth or Consequences, allowing the organization to go national.
Proctor & Gamble turned cottonseeds from a waste product of cotton production into something that could be sold as a "heart-healthy" alternative to its competition - animal fats, which were saturated. Proctor & Gamble were the inventors of the fake trans-fat margarine called Crisco, touted by the AHA as healthier than butter. We now know that the artificial trans-fat from hydrogenated vegetable oils are unhealthy for us. However, the trans fat CLA from grass-fed cows is considered healthy and is widely sold as a supplement. Recommendations regarding limiting saturated fats and cholesterol emerged from a series of scientific studies in the 1950s, related American Heart Association dietary guidelines emerged between 1957 and 1961; the 1957 AHA report included: Diet may play an important role in the pathogenesis of atherosclerosis, The fat content and total calories in the diet are important factors, The ratio between saturated and unsaturated fat may be the basic determinant, A wide variety of other factors beside fat, both dietary and non-dietary, may be important.
By 1961, these finding had been strengthened, leading to the new 1961 AHA recommendations: Maintain a correct body weight, Engage in moderate exercise, e.g. walking to aid in weight reduction, Reduce intake of total fat, saturated fat, cholesterol. Increase intake of polyunsaturated fat, Men with a strong family history of atherosclerosis should pay particular attention to diet modification, Dietary changes should be carried out under medical supervision; these recommendations continued to become more precise from 1957 to 1980, but maintained "a general coherence among them". In 1994, the Chronicle of Philanthropy, an industry publication, released the results of the largest study of charitable and non-profit organization popularity and credibility; the study showed that the American Heart Association was ranked as the 5th "most popular charity/non-profit in America" of over 100 charities researched with 95% of Americans over the age of 12 choosing Love and Like A lot description category.
In 2003 published the “Seventh Report of the Joint National Committee on Prevention, Detection and Treatment of High Blood Pressure”. On October 28, 2009 The American Heart Association and the Ad Council launched a hands-only CPR public service announcement and website. On November 30, 2009, The American Heart Association announced a new cardiac arrest awareness campaign called Be the Beat; the campaign's aim is to teach 12- to 15-year-olds fun ways to learn the basics of cardiopulmonary resuscitation and how to use an automated external defibrillator. In 2004 the AHA launched the "Go Red for Women" campaign targeting women, with information about risks and action they can take to protect their health. All revenues from the local and national campaigns go to support awareness, research and community programs to benefit women, it carried out a campaign in 2012 to educate more people on how to carry out hands-only CPR. The 2012 campaign, which began in New York City, had Jennifer Coolidge as the spokesperson.
In 2014, the American Heart Association issued its first guidelines for preventing strokes in women. In 2015, the American Heart Association endorsed the Tobacco 21 campaign, urging local and national governments to raise the tobacco and nicotine sales age from 18 to 21. In 2018, the American Heart Association and American College of Cardiology issued new guidelines for clinicians on the management of cholesterol as a way to reduce risk for heart attack and stroke. Newly included in the guidelines is a
The endocardium is the innermost layer of tissue that lines the chambers of the heart. Its cells are embryologically and biologically similar to the endothelial cells that line blood vessels; the endocardium provides protection to the valves and heart chambers. The endocardium underlies the much more voluminous myocardium, the muscular tissue responsible for the contraction of the heart; the outer layer of the heart is termed epicardium and the heart is surrounded by a small amount of fluid enclosed by a fibrous sac called the pericardium. The endocardium, made up of endothelial cells, controls myocardial function; this modulating role is separate from the homeometric and heterometric regulatory mechanisms that control myocardial contractility. Moreover, the endothelium of the myocardial capillaries, closely appositioned to the cardiomyocytes, is involved in this modulatory role. Thus, the cardiac endothelium controls the development of the heart in the embryo as well as in the adult, for example during hypertrophy.
Additionally, the contractility and electrophysiological environment of the cardiomyocyte are regulated by the cardiac endothelium. The endocardial endothelium may act as a kind of blood–heart barrier, thus controlling the ionic composition of the extracellular fluid in which the cardiomyocytes bathe. In myocardial infarction, ischemia of the myocardium can extend to the endocardium, disrupting the inner lining of the heart. Less extensive infarctions are "subendocardial" and do not affect the epicardium. In the acute setting, subendocardial infarctions are more dangerous than transmural infarctions because they create an area of dead tissue surrounded by a boundary region of damaged myocytes; this damaged region will conduct impulses more resulting in irregular rhythms. The damaged region may become more life-threatening. In the chronic setting, transmural infarctions are more dangerous due to the greater amount of muscular damage and the development of scar tissue leading to impaired systolic contractility, impaired diastolic relaxation, increased risk for rupture and thrombus formation.
During depolarization the impulse is carried from endocardium to epicardium, during repolarization the impulse moves from epicardium to endocardium. In infective endocarditis, the endocardium is affected by bacteria. Heart Myocardium Histology image: 64_06 at the University of Oklahoma Health Sciences Center - "Heart and AV valve" Histology image: 64_07 at the University of Oklahoma Health Sciences Center - "Heart and AV valve"
Heavy metals are defined as metals with high densities, atomic weights, or atomic numbers. The criteria used, whether metalloids are included, vary depending on the author and context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would be more concerned with chemical behaviour. More specific definitions have been published, but none of these have been accepted; the definitions surveyed in this article encompass up to 96 out of the 118 known chemical elements. Despite this lack of agreement, the term is used in science. A density of more than 5 g/cm3 is sometimes quoted as a used criterion and is used in the body of this article; the earliest known metals—common metals such as iron and tin, precious metals such as silver and platinum—are heavy metals. From 1809 onwards, light metals, such as magnesium and titanium, were discovered, as well as less well-known heavy metals including gallium and hafnium.
Some heavy metals are either essential nutrients, or harmless, but can be toxic in larger amounts or certain forms. Other heavy metals, such as cadmium and lead, are poisonous. Potential sources of heavy metal poisoning include mining, industrial wastes, agricultural runoff, occupational exposure and treated timber. Physical and chemical characterisations of heavy metals need to be treated with caution, as the metals involved are not always defined; as well as being dense, heavy metals tend to be less reactive than lighter metals and have much less soluble sulfides and hydroxides. While it is easy to distinguish a heavy metal such as tungsten from a lighter metal such as sodium, a few heavy metals, such as zinc and lead, have some of the characteristics of lighter metals, lighter metals such as beryllium and titanium, have some of the characteristics of heavier metals. Heavy metals are scarce in the Earth's crust but are present in many aspects of modern life, they are used in, for example, golf clubs, antiseptics, self-cleaning ovens, solar panels, mobile phones, particle accelerators.
There is no agreed criterion-based definition of a heavy metal. Different meanings may be attached depending on the context. In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, a chemist would be more concerned with chemical behaviour. Density criteria range from above 3.5 g/cm3 to above 7 g/cm3. Atomic weight definitions can range from greater than sodium. Atomic numbers of heavy metals are given as greater than 20. Definitions based on atomic number have been criticised for including metals with low densities. For example, rubidium in group 1 of the periodic table has an atomic number of 37 but a density of only 1.532 g/cm3, below the threshold figure used by other authors. The same problem may occur with atomic weight based definitions; the United States Pharmacopeia includes a test for heavy metals that involves precipitating metallic impurities as their coloured sulfides." In 1997, Stephen Hawkes, a chemistry professor writing in the context of fifty years' experience with the term, said it applied to "metals with insoluble sulfides and hydroxides, whose salts produce colored solutions in water and whose complexes are colored".
On the basis of the metals he had seen referred to as heavy metals, he suggested it would useful to define them as all the metals in periodic table columns 3 to 16 that are in row 4 or greater, in other words, the transition metals and post-transition metals. The lanthanides satisfy Hawkes' three-part description. In biochemistry, heavy metals are sometimes defined—on the basis of the Lewis acid behaviour of their ions in aqueous solution—as class B and borderline metals. In this scheme, class A metal ions prefer oxygen donors. Class A metals, which tend to have low electronegativity and form bonds with large ionic character, are the alkali and alkaline earths, the group 3 metals, the lanthanides and actinides. Class B metals, which tend to have higher electronegativity and form bonds with considerable covalent character, are the heavier transition and post-transition metals. Borderline metals comprise the lighter transition and post-transition metals; the distinction between the class A metals and the other two categories is sharp.
A cited proposal to use these classification categories instead of the more evocative name heavy metal has not been adopted. A density of more than 5 g/cm3 is sometimes mentioned as a common heavy metal defining factor and, in the absence of a unanimous definition, is used to populate this list and guide the remainder of the article. Metalloids meeting the applicable criteria–arsenic and antimony for example—are sometimes counted as heavy metals in environmental chemistry, as is the case here. Selenium is include
A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The atrium primes the pump. Interventricular means between the ventricles. In a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, the left ventricle pumps blood into the systemic circulation through the aorta. Ventricles generate higher blood pressures; the physiological load on the ventricles requiring pumping of blood throughout the body and lungs is much greater than the pressure generated by the atria to fill the ventricles. Further, the left ventricle has thicker walls than the right because it needs to pump blood to most of the body while the right ventricle fills only the lungs. On the inner walls of the ventricles are irregular muscular columns called trabeculae carneae which cover all of the inner ventricular surfaces except that of the conus arteriosus, in the right ventricle.
There are three types of these muscles. The third type, the papillary muscles give origin at their apices to the chordae tendinae which attach to the cusps of the tricuspid valve and to the mitral valve; the mass of the left ventricle, as estimated by magnetic resonance imaging, averages 143 g ± 38.4 g, with a range of 87–224 g. The right ventricle is equal in size to that of the left ventricle and contains 85 millilitres in the adult, its upper front surface is circled and convex, forms much of the sternocostal surface of the heart. Its under surface is flattened, forming part of the diaphragmatic surface of the heart that rests upon the diaphragm, its posterior wall is formed by the ventricular septum, which bulges into the right ventricle, so that a transverse section of the cavity presents a semilunar outline. Its upper and left angle forms a conical pouch, the conus arteriosus, from which the pulmonary artery arises. A tendinous band, called the tendon of the conus arteriosus, extends upward from the right atrioventricular fibrous ring and connects the posterior surface of the conus arteriosus to the aorta.
The left ventricle is longer and more conical in shape than the right, on transverse section its concavity presents an oval or nearly circular outline. It forms a small part of the sternocostal surface and a considerable part of the diaphragmatic surface of the heart; the left ventricle is thicker and more muscular than the right ventricle because it pumps blood at a higher pressure. The right ventricle is triangular in shape and extends from the tricuspid valve in the right atrium to near the apex of the heart, its wall is thickest at the apex and thins towards its base at the atrium. By early maturity, the walls of the left ventricle have thickened from three to six times greater than that of the right ventricle; this reflects the typical five times greater pressure workload this chamber performs while accepting blood returning from the pulmonary veins at ~80mmHg pressure and pushing it forward to the typical ~120mmHg pressure in the aorta during each heartbeat. During systole, the ventricles contract.
During diastole, the ventricles fill with blood again. The left ventricle receives oxygenated blood from the left atrium via the mitral valve and pumps it through the aorta via the aortic valve, into the systemic circulation; the left ventricular muscle must relax and contract and be able to increase or lower its pumping capacity under the control of the nervous system. In the diastolic phase, it has to relax quickly after each contraction so as to fill with the oxygenated blood flowing from the pulmonary veins. In the systolic phase, the left ventricle must contract and forcibly to pump this blood into the aorta, overcoming the much higher aortic pressure; the extra pressure exerted is needed to stretch the aorta and other arteries to accommodate the increase in blood volume. The right ventricle receives deoxygenated blood from the right atrium via the tricuspid valve and pumps it into the pulmonary artery via the pulmonary valve, into the pulmonary circulation; the typical healthy adult heart pumping volume is ~5 liters/min, resting.
Maximum capacity pumping volume extends from ~25 liters/min for non-athletes to as high as ~45 liters/min for Olympic level athletes. In cardiology, the performance of the ventricles are measured with several volumetric parameters, including end-diastolic volume, end-systolic volume, stroke volume and ejection fraction. Ventricular pressure is a measure of blood pressure within the ventricles of the heart. During most of the cardiac cycle, ventricular pressure is less than the pressure in the aorta, but during systole, the ventricular pressure increases, the two pressures become equal to each other, the aortic valve opens, blood is pumped to the body. Elevated left ventricular end-diastolic pressure has been described as a risk factor in cardiac surgery. Noninvasive approximations have been described. An elevated pressure difference between the aortic pressure and the left ventricular pressure may be indicative of aortic stenosis. Right