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Visit the American Heart Association website to help locate a course near your home in the United States. There are also many other national and regional heart associations that offer the same service, depending upon the location.

Shape and size of the heart

The shape of the heart is similar to a pinecone, rather broad at the superior surface and tapering to the apex (see [link] ). A typical heart is approximately the size of your fist: 12 cm (5 in) in length, 8 cm (3.5 in) wide, and 6 cm (2.5 in) in thickness. Given the size difference between most members of the sexes, the weight of a female heart is approximately 250–300 grams (9 to 11 ounces), and the weight of a male heart is approximately 300–350 grams (11 to 12 ounces). The heart of a well-trained athlete, especially one specializing in aerobic sports, can be considerably larger than this. Cardiac muscle responds to exercise in a manner similar to that of skeletal muscle. That is, exercise results in the addition of protein myofilaments that increase the size of the individual cells without increasing their numbers, a concept called hypertrophy. Hearts of athletes can pump blood more effectively at lower rates than those of nonathletes. Enlarged hearts are not always a result of exercise; they can result from pathologies, such as hypertrophic cardiomyopathy    . The cause of an abnormally enlarged heart muscle is unknown, but the condition is often undiagnosed and can cause sudden death in apparently otherwise healthy young people.

Chambers and circulation through the heart

The human heart consists of four chambers: The left side and the right side each have one atrium    and one ventricle    . Each of the upper chambers, the right atrium (plural = atria) and the left atrium, acts as a receiving chamber and contracts to push blood into the lower chambers, the right ventricle and the left ventricle. The ventricles serve as the primary pumping chambers of the heart, propelling blood to the lungs or to the rest of the body.

There are two distinct but linked circuits in the human circulation called the pulmonary and systemic circuits. Although both circuits transport blood and everything it carries, we can initially view the circuits from the point of view of gases. The pulmonary circuit    transports blood to and from the lungs, where it picks up oxygen and delivers carbon dioxide for exhalation. The systemic circuit    transports oxygenated blood to virtually all of the tissues of the body and returns relatively deoxygenated blood and carbon dioxide to the heart to be sent back to the pulmonary circulation.

The right ventricle pumps deoxygenated blood into the pulmonary trunk    , which leads toward the lungs and bifurcates into the left and right pulmonary arteries    . These vessels in turn branch many times before reaching the pulmonary capillaries    , where gas exchange occurs: Carbon dioxide exits the blood and oxygen enters. The pulmonary trunk arteries and their branches are the only arteries in the post-natal body that carry relatively deoxygenated blood. Highly oxygenated blood returning from the pulmonary capillaries in the lungs passes through a series of vessels that join together to form the pulmonary veins    —the only post-natal veins in the body that carry highly oxygenated blood. The pulmonary veins conduct blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and on to the many branches of the systemic circuit. Eventually, these vessels will lead to the systemic capillaries, where exchange with the tissue fluid and cells of the body occurs. In this case, oxygen and nutrients exit the systemic capillaries to be used by the cells in their metabolic processes, and carbon dioxide and waste products will enter the blood.

Questions & Answers

why when sex of an individual is determined by y chromosome found in male therefore why there is many women than male
pamfili Reply
I'm not sure if I fully understand your question.
are you sure it is more
samir
i don't remember what I said.
I'm not sure if I fully understand your question.
roughly taking a lead.
samir
Muscle of mastication
JIMOH Reply
difference between seminiferous tubules and ejaculatory duct
Muhammad Reply
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Musibi
wats dis group
Kity
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Agemo Reply
what is azygous vein
Karan Reply
Sir muscle contraction ka topic kis part m milega
sonugora Reply
Sir muscle contraction ka topic kis part m milega
sonugora Reply
what is manipulated
Ambika Reply
life circle of RBC and the life circle of WBC.
Yemi Reply
RBC 120days
Zeph
RBC 120days and WBC 10-12days
sai
what is cardiac vascular system
Hari
what is anatomy?
Md Reply
what is manipulated
Ambika
anatomy is the branch of medical science which deal with the gross structure of body or organ
Ambika
note shoulder joint
jagadeesh
what is cardiovascular system
Hari
what is manipulated
Ambika
anatomical position
Ambika
?
Ambika
Scapula
sonugora
Study of internal structures
sonugora
the system of heart and vessels
Manar
what is collar Bone?
jagadeesh
positive feedback mechanism
Sirimala Reply
what is immunology
Riya Reply
immunology is a branch of medicine that study's the body immune system
SAMUEL
Immunology This is the study of specific and non-specific resistance of the body against infection i.e. the study of the immune response of a host to a foreign substance, which includes study of various reactions which are induced in the body by introduction of a substance.
Kaluki
what is role of elimination need like fluid and also stools
Munmun Reply
bone
Vijay
what is joint pain
Vijay
is the physical suffering caused by illness or injury of the joint
malulu
pls can someone describe shock,types ,pathophysiology and treatment
Isaac
this is what I'm thinking "After taking out everything the body needs, the bowel then expels the leftover waste."
isaiah
I think elimination also helps in the continuation of the digestive system because if the unwanted fluids and stools does not come out of the system it can create a problem in the digestive. system resulting in diseases.
Martha
shock is a condition whereby the circulating system is unable to get enough blood and oxygen to vital organs like the brain,heart,eye,kidney and others.
Martha
causing depression of those organs.
Martha
there are 2 classification of shock. primary shock: this occurs immediately after injury due emotional stimulus or pain.example hearing a bad news,sudden obstruction of airway.sudden heart attack. secondary shock :it occurs when primary shock is delayed
Martha
types of shock syncope (faint) oligaemic or hyppvovaemic shock. Anaphylactic shock. neurogenic/ physical shock septic sock catdiogenic shock.
Martha
What is the difference between dna duplication and chromosomes duplication?
to help you identify the human body parts to help you live a healthy life the study of Anatomy helps one to work in any health sector
sophia Reply
okay.

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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