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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

how many classes of drugs do we have?
Jesse Reply
I'm not sure lol
Leti
we have 7classes,e.g stimulant, Cannabis etc
Orpha
scheduled 5...classes stimulants, depressants, hallucinogens, dissociatives, opioids, inhalants and cannabis.
jessica
site of fracture in the kneel
holuwahseun Reply
what is pelvis
Aisha Reply
Complex of bones that connect the trunk and the legs,supports and balance the trunk.
Orpha
What is d most heaviest organ in d body
Abraham Reply
Liver
Akasi
The skin
Akasi
skin
Divya
why skin?
Sam
liver
Anne
water
Mehdi
Heart
Biplob
the brain
lehumo
skin
Emma
skin
jessica
largest internal organ is the liver
jessica
liver is the heaviest organ
Eyyammeh
the liver is the heaviest organs
Khh
What is the meaning? What does it entails to? What are the works of Arthropologists?
Orpha Reply
bones of appendicular skeleton
hemalatha Reply
Fore limbs, hind limbs, pectoral and pelvic girdle
Abraham
Functions of the thoracic cage
Fereh Reply
protect all the organs and tissues from any impact or injury
Javier
It protects the heart other tissues in the chest region
Abraham
why sickle cell carrier people don't get malaria
Boakye Reply
Bcos mosquitoes are not attracted by their blood due to poor oxygen
Abraham
What is the amniotic fluid
bollywood Reply
amniotic fluid is the fluid that is inside the uterus with the baby.
Fati
shielded
Varun
This fluid serves as a cushion for the growing fetus but also serves to facilitate the exchange of nutrients, water, and biochemical products between mother and fetus.
Anne
it also reduces friction during birth as it wets the birth canal during delivery
steve
Amniotic fluid can be taken out by inserting needle to detect birth abnormalities as the foetus cells are present in amniotic fluid. This process is known as amniocentesis.
Biplav
structure of heart and it's function (10 mark )
Priyanka Reply
not possible
Abraham
What is the best book on physiology?
cesar Reply
describe varicocele
malulu
what do you mean by peritoneum
Siba Reply
It is thick covering surrounding the abdomen
Awais
r8
how to become good in Anatomy and physiology
malulu
hi
Milkah
hlo
Wani
What are is the last solution to abdomen pain in pregnant women
Umoru
no it is in kidney
Tantray
Kk
Umoru
structure of heart and it's function
Priyanka
Serous membrane lining the cavity of the abdomen
bollywood
it is four lobs structure and it is triangular in shaped. it 's function pumping the blood
ABDULLAH
explain root of lungs
ABDULLAH
Glomerular pressure -capsule pressure -colloid osmosis pressure
malulu Reply
how to describe mechanism of micturition
malulu
spleen is important?
AKASH Reply
helpful in destruction of rbc
It is imp in storing blood and destruction of microbes and harmful particles
Awais
ty sir
AKASH
K
Umoru
what are the sources of glucose in the body
malulu
describe mechanism of micturition
malulu
Pancreatic hormones with function
mami Reply
Insulin, which helps to regulate our blood sugar levels.
Bb
glucagon which is antagonistic to insulin increase the blood glucose level,. Somatostatin help to regulate the levels of both insulin and glucagon
Ashish
thnks for helping
nimco
thanks
Narendra
what is a lymph node.?
AKASH
lymph nodes are small kidney shaped organs of the lymphatic system.
Trishauna
there are several hundred lymph nodes found mostly throughout the thorax and abdomen of the body with the highest concentrations in the auxiliary (armpit) and inguinal groin regions.
Trishauna

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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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