Download JH WEEKLIES ISSUE #24 2011

JH WEEKLIES ISSUE #24
2011-2012
The Human Heart
TERMS TO KNOW
right atrium
cardiology
Erasistratus of Chios
right ventricle
coronary heart disease
Galen of Pergamon
left atrium
congenital heart disease
Andreas Vesalius
left ventricle
angina
William Harvey
inferior vena cava
arrhythmia
Raymond de Vieussens
pulmonary arteries
atherosclerosis
Stephen Hales
pulmonary veins
cardiomyopathy
Rene T. H. Laennec
aorta
myocardial infarction
Willem Einthoven
septum
hypertension
James B. Herrick
pericardium
stroke
Robert E. Gross
tricuspid valve
On the fabric of the
F. John Lewis
mitral valve
human body
Christiaan Barnard
aortic valve
pulmonary valve
Willem DeVries
Introduction
The heart is one of the most vital organs in the human body. It is a muscular organ that contracts
and expands, providing continuous blood circulation throughout the body. The pumping of the
heart is called the Cardiac Cycle, which occurs about 72 times per minute.
Without blood, the human body would stop working. Blood functions by transporting oxygen
from the lungs to body tissue and carbon dioxide from body tissue to the lungs, transporting
nourishment from digestion and hormones from glands throughout the body, and
transporting disease fighting substances to the tissue and waste to the kidneys.
This WEEKLIES edition will provide some additional information about the structure and
function of the human heart, heart disease, history of the study of the heart, and interesting facts
about the heart.
Structure and Function
The human heart is divided into four main chambers: the two upper chambers are called the left
atrium and right atrium and the two lower chambers are called the right ventricle and left
ventricle (see detailed explanations of the four chambers below). There is a thick wall of muscle
separating the right side and the left side of the heart called the septum. The heart is enclosed in
a double-walled protective sac called the pericardium. There are four valves that determine the
pathway of blood flow through the heart: tricuspid valve, mitral valve, aortic valve, and
pulmonary valve.
right atrium - Receives deoxygenated blood from the superior and inferior vena cava and the
coronary sinus and pumps it into the right ventricle via the tricuspid valve. The inferior vena
cava is the largest vein in the body and it carries deoxygenated blood from the lower half of the
body into the right atrium of the heart.
right ventricle - Receives deoxygenated blood from the right atrium via the tricuspid valve and
pumps it into the pulmonary artery via the pulmonary valve. The pulmonary arteries carry
deoxygenated blood from the heart to the lungs. They are the only arteries that carry
deoxygenated blood.
left atrium - Receives oxygenated blood from the pulmonary veins and pumps it into the left
ventricle via the mitral valve. The pulmonary veins are large blood vessels that carry
oxygenated blood from the lungs to the left atrium of the heart. In humans there are four
pulmonary veins, two from each lung. They carry oxygenated blood, which is unusual since
almost all other veins carry deoxygenated blood
left ventricle - Receives oxygenated blood from the left atrium via the mitral valve and pumps it
into the aorta via the aortic valve. The aorta is the largest artery in the body, originating from
the left ventricle of the heart and extending down to the abdomen, where it branches off into two
smaller arteries. The aorta distributes oxygenated blood to all parts of the body.
Heart Disease
The human heart and its disorders are studied in the field of cardiology. According to the
Centers for Disease Control and Prevention, more than 600,000 Americans die of heart disease
each year. Heart disease is the leading cause of death for both men and women, causing almost
25 percent of all deaths. Every year about 785,000 Americans have their first heart attack, and
another 470,000 who have already had one or more heart attacks have another attack. Major risk
factors for heart disease include obesity, inactivity, poor diet, high blood pressure, high
cholesterol, smoking, drinking, and diabetes. The main preventative recommendations for heart
disease include exercise, diet, stress reduction, and boosting the immune system.
There are a variety of heart diseases. The most common is coronary heart disease, which refers
to the failure of your blood vessels to circulate blood to your heart and organs due to build up on
the walls of your circulatory system. Congenital heart disease is caused by birth defects that
one way or other weaken the heart muscle and is one the primary causes of early childhood death
in America. Below is a list of some other common heart conditions.
Angina - Pain felt in the chest due to insufficient blood supply to the heart, generally as the
result of arteriosclerosis of the coronary arteries, usually experienced during exercise or stress.
Arrhythmia - A disruption of the regular rhythmic beating of the heart.
Atherosclerosis - A process in which the blood vessels narrow and harden through build-up of
plaque in the walls of arteries.
Cardiomyopathy - A disease in which the heart muscle becomes inflamed and doesn’t work as
well as it should.
High blood pressure/hypertension - Forces your heart and arteries to work harder, and your
major organs are affected. It directly increases the risk of coronary heart disease, stroke, heart
failure, and kidney failure, especially when combined with other risk factors.
Myocardial infarction – The heart muscle stops functioning due to loss of blood flow, nutrients,
or electric signal.
Stroke - Affects the arteries leading to and within the brain. Strokes occur when blood vessels
that carry oxygen and nutrients to the brain are either blocked by a clot (thrombosis or embolism)
or burst. When that happens, part of the brain can’t get the blood (and oxygen) it needs, so it
begins to die.
History of the Study of the Heart:
280 – 250 B.C. Erasistratus of Chios: Founded a school of anatomy in Alexandria; was the
first to discover that the heart functioned as a natural pump and was among the first to
distinguish between veins and arteries.
A.D. 162 – 217 Galen of Pergamon: Arguably the most accomplished of all medical
researchers of antiquity. He contributed greatly to the understanding of numerous scientific
disciplines, including anatomy, physiology, and pathology. His theories dominated and
influenced Western medical science for nearly two millennia.
1543 Andreas Vesalius: Known as the “father of modern anatomy,” he wrote On the fabric of
the human body which presented a careful examination of the organs and structure of the human
body.
1628 William Harvey: English Physician who was the first to describe blood circulation.
1706 Raymond de Vieussens: French anatomy professor who was the first to describe the
structure of the heart’s chambers and vessels.
1733 Stephen Hales: English clergyman and scientist who was the first to measure blood
pressure.
1816 Rene T. H. Laennec: French physician who invented the stethoscope.
1903 Willem Einthoven: Dutch physiologist who developed the electrocardiograph.
1912 James B. Herrick: American physician who first discovered sickle cell disease as well as
the mechanism of a heart attack.
1938 Robert E. Gross: American surgeon who performed the first heart surgery.
1952 F. John Lewis: American surgeon who performed first successful open heart surgery.
1967 Christiaan Barnard: South African surgeon who performed the first whole heart
transplant from one person to another.
1982 Willem DeVries: American surgeon who implanted a permanent artificial heart, designed
by American physician Robert Jarvik, into a patient.
Heart Facts
The human embryonic heart begins beating at around 21 days after conception.
The adult human heart has a mass of between 250 and 350 grams and is about the size of
a fist.
The average adult has 5.6 liters (or 6 quarts) of blood that circulates through the body
three times every minute.
Your heart beats more than 100,000 times each day pumping 2,000 gallons of blood
through the 60,000 miles of blood vessels that feed your organs and tissues.
The heart pumps about 1 million barrels of blood during an average lifetime. That’s
enough to fill more than 3 super tankers.
Based on an average of 72 beats per minute, a human heart will beat more than three
billion times in the lifetime of an 80 year old.
If you took all of the blood vessels out of an average adult, and laid them out in one line,
the line would be close to 100,000 miles long