Heart Definition and 159 Threads

The heart is a muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs. In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest.In humans, other mammals, and birds, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. Fish, in contrast, have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. 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.The heart pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node. These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along the conduction system of the heart. The heart receives blood low in oxygen from the systemic circulation, which enters the right atrium from the superior and inferior venae 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. The heart beats at a resting rate close to 72 beats per minute. Exercise temporarily increases the rate, but lowers resting heart rate in the long term, and is good for heart health.Cardiovascular diseases (CVD) are the most common cause of death globally as of 2008, accounting for 30% of deaths. Of these more than three-quarters are a result of coronary artery disease and stroke. Risk factors include: smoking, being overweight, little exercise, high cholesterol, high blood pressure, and poorly controlled diabetes, among others. Cardiovascular diseases frequently do not have symptoms or may cause chest pain or shortness of breath. Diagnosis of heart disease is often done by the taking of a medical history, listening to the heart-sounds with a stethoscope, ECG, and ultrasound. Specialists who focus on diseases of the heart are called cardiologists, although many specialties of medicine may be involved in treatment.

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  1. Loren Booda

    Understanding Heart Cancer: Incidence and Impact on the Human Body

    While assessing the various tissues in the human body, I was unable to recall ever having heard of the cardiovascular system being affected by cancer. Does cancer of the heart exist, and what is its incidence relative to other cancers?
  2. Monique

    Acute Heart Failure: Recent Deaths and Revivals

    omg, is there an epidemic or something? All of a sudden a lot of seemingly healthy people seem to be dropping down dead and it is giving me the creeps. My friends' soccer coach recently died on the field, that Hungarian soccer player Miklo, last weekend Marco Pantani and today a 20 yr old girl...
  3. iansmith

    New Medication Against Heart Attack

    http://www.canada.com/national/nationalpost/news/story.html?id=93235391-40d9-47f1-a09e-ec318750ab9f
  4. B

    How Does Heart Rate Affect Weight Loss During Exercise?

    Exercise and heart rate After reading a thread about overweight Americans I got to wondering about something; how does your heart rate factor into increasing your metabolism during exercise? Does the metabolic rate of your body cause you to actually lose weight or only cause you to lose...
  5. Ivan Seeking

    Second black hole may lurk at Milky Way's heart

    http://www.newscientist.com/news/news.jsp?id=ns99993847
  6. Iacchus32

    The Heart of Reality: The Mysteries of Life

    What is life, if not that which is held internally? What is essence, if not that which is contained within form? Doesn't this suggest that life is an "interior process," by which the external "material world" exists to serve? And, that perhaps we should spend some time focusing on our "interior...
  7. Raavin

    Can Body Heat Power an Artificial Heart?

    Powering and artificial heart?? Is there any way that one can construct a heat exchanger that concentrates the energy from heat into a smaller space? Eg a big plate at a certain temperature which concentrates heat into a higher temperature in a smaller area. I'm thinking not. If you can't, is...
  8. Andre

    Exploring the Nuclear Heart of the Earth

    The Nuclear Heart of the Earth or the scientific version: Nuclear georector origine of oceanic basalt 3He/4He, evidence and implications There are a few far fetched hypotheses and perhaps some flaws, I would say, but other than that, some good explanations for existing evidence. What...
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