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{{#invoke:Hatnote|hatnote}} {{ safesubst:#invoke:Unsubst||$N=Use dmy dates |date=__DATE__ |$B= }} {{#invoke:Infobox|infobox}}{{safesubst:#invoke:Check for unknown parameters|check|unknown= | Type | type | Name | neuron_name | name | MapPosIGNORE_PARAMETER | MapIGNORE_PARAMETER | TA98IGNORE_PARAMETER | ImageMap | Imagemap | image_map | MapWidth | map_caption | MapCaption | Image | image | image_neuron | Width | image_size | Alt | alt | Caption | caption | caption_neuron | Image2 | image2 | Width2 | image2_size | Alt2 | alt2 | Caption2 | caption2 | caption2_neuron | Latin | Greek | part_of | PartOf | is_part_of | IsPartOf | CarnegieStage | days | Days | system | System | components | Components | location | function | neurotransmitter | morphology | afferents | efferents | Origin | Origins | origin | origins | Insertion | Insertions | insertion | insertions | Articulation | Articulations | articulations | Supplies | DrainsFrom | Drainsfrom | BranchFrom | Branchfrom | Source | source | DrainsTo | Drainsto | BranchTo | Branchto | Blood | blood | artery | Artery | vein | Vein | nerve | Nerve | NerveRoot | lymph | Lymph | Action | action | PhysicalExam | Antagonist | precursor | Precursor | gives_rise_to | GivesRiseTo | From | To | Innervates | FiberType | acronym | Acronym | code | Code | BrainInfoType | BrainInfoNumber | NeuroLex | NeuroLexID | Dorlands | DorlandsID | DorlandsPre | DorlandsSuf | TH | TE | FMA | MeshName | Meshname | MeSHname | MeshYear | MeshNumber | BamsSlug | GraySubject | GrayPage}} {{#invoke:Listen|main}} The heart is a muscular organ in humans and other animals, which pumps blood through the blood vessels of the circulatory system.<ref name="tabers">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Blood provides the body with oxygen and nutrients, and also assists in the removal of metabolic wastes.<ref name="Guyton">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> The heart is located in the middle compartment of the mediastinum in the chest.<ref name="Moore's 6">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria; and lower left and right ventricles.<ref name="StarrEvers2009">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref><ref name=K2008>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart.<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Fish in contrast have two chambers, an atrium and a ventricle, while reptiles have three chambers.<ref name=K2008/> In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow.<ref name="Moore's 6"/> The heart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium, myocardium, and endocardium.<ref name="CNX2014">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

The heart pumps blood through both circulatory systems. Blood low in oxygen from the systemic circulation enters the right atrium from the superior and inferior vena cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation, through the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle and is pumped out through the aorta to the systemic circulation−where the oxygen is used and metabolized to carbon dioxide.<ref name="Guyton">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> In addition the blood carries nutrients from the liver and gastrointestinal tract to various organs of the body, while transporting waste to the liver and kidneys.{{ safesubst:#invoke:Unsubst||date=__DATE__ |$B= {{#invoke:Category handler|main}}{{#invoke:Category handler|main}}[citation needed] }} Normally with each heartbeat the right ventricle pumps the same amount of blood into the lungs as the left ventricle pumps to the body. Veins transport blood to the heart and carry deoxygenated blood - except for the pulmonary and portal veins. Arteries transport blood away from the heart, and apart from the pulmonary artery hold oxygenated blood. Their increased distance from the heart cause veins to have lower pressures than arteries.<ref name="Guyton">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref><ref name="Moore's 6"/> The heart contracts at a resting rate close to 72 beats per minute.<ref name="Guyton">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Exercise temporarily increases the rate, but lowers resting heart rate in the long term, and is good for heart health.<ref name="Guyton Sports Physiology">{{#invoke:citation/CS1|citation |CitationClass=book }}</ref>

Cardiovascular diseases (CVD) are the most common cause of death globally as of 2008, accounting for 30% of deaths.<ref name="WHO CVD 2013"/><ref name=Harrisons>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> Of these more than three quarters follow coronary artery disease and stroke.<ref name="WHO CVD 2013">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Risk factors include: smoking, being overweight, little exercise, high cholesterol, high blood pressure, and poorly controlled diabetes, among others.<ref>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> Diagnosis of CVD is often done by listening to the heart-sounds with a stethoscope, ECG or by ultrasound.<ref name="Moore's 6"/> Specialists who focus on diseases of the heart are called cardiologists, although many specialties of medicine may be involved in treatment.<ref name="Harrisons"/>

Heart sections
Intro  Structure  Development  Physiology  Clinical significance   History   Society and culture  Other animals   Additional images   References  External links  

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