Cardiovascular Diseases
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| Anatomy and Physiology of the Cardiovascular System |
Anatomy of the Heart
From the moment it begins beating until the moment it stops, the human heart works
tirelessly. In an average lifetime, the heart beats more than two and a half billion times,
without ever pausing to rest. Like a pumping machine, the heart provides the power needed
for life.
The heart is a muscle that pump blood to whole body and receive blood from whole body. It is
a hollow, cone shaped, located within the thorax and resting upon the diaphragm. Heart size
varies with body size, it is generally about 14 centimeters long and 9 centimeters wide in an
average adult.
Heart consists of four chambers, two smaller ones on top, (the atria ) and two larger ones on
the bottom, ( the ventricles).
Between the chambers are four one-way valves:
*the tricuspid valve, the opening between the right atrium and the right ventricle, it permit
the movement of blood in one direction.
*the pulmonic valve, between the right ventricle and the pulmonary artery
*the mitral ( bicuspid ) valve, between the left atrium and left ventricle
*the aortic valve. Between the left ventricle and the aorta
The mitral valve has two flaps; the others have three. Under normal conditions, the valves
permit blood to flow in only one direction. Blood flow occurs only when there's a difference in
pressure across the valves that causes them to open.
These valves ensure that the blood flows in the right direction and are part of the sounds we
here through our stethoscopes.
We can simplify the functions of these chambers into two types, those that receive blood
from outside the heart, the atria, and those which send the blood outside of the heart, the
ventricles. It is the smooth function of both sets of chambers that provide the circulation of
blood to the rest of the body.
The heart is actually 3 layers of tissue; the "endocardium" a thin lining in the chambers; the
"myocardium" a thick layer of contractile muscle cells with specialized fibers forming a
conduction system through the muscle; and the visceral pericardium or "epicardium" that
covers the other layers. Surrounding all of this is the parietal "pericardium" a sac like
membrane that encases the heart in the chest. The two Pericardium layers secrete fluid to
lubricate the heart during its contraction, making it easier to move in the "sac."
The Coronary Arteries
All parts of the heart (the muscle fibers, the electrical system, etc.) require food and oxygen
to live and do their jobs, just like any other muscle. The way they get these essential
elements is through the blood via the coronary arteries.
The coronary arteries stem from the aorta and then branch into three main arteries. These
arteries, in turn, branch off into smaller vessels, so the oxygen can reach the heart tissues.
The three main coronary arteries are the right coronary artery, the left anterior descending
artery., and the circumflex artery. Each of the coronary arteries delivers blood to a specific
part of the heart. The right coronary artery delivers blood to the back and bottom part of the
heart. The left anterior descending artery gives blood to the front part of the heart and the
left circumflex furnishes the left side portion of the heart.
The coronary arteries have no direct communication with one another, if the end artery is
blocked, the tissue beyond it is likely to die because it receives no other blood supply from
the alternative vessels, this leads to what we call myocardial ischemia.
Blood Vessels:
In a general sense, a vessel is defined as a hollow utensil ( أداة ) for carrying something: a cup,
a bucket, a tube.
Blood vessels, then, are hollow utensils for carrying blood. Located throughout the body,
blood vessels are hollow tubes that circulate blood.
There are three varieties of blood vessels: arteries, veins, and capillaries. During blood
circulation, the arteries carry blood away from the heart. The capillaries connect the arteries to
veins. Finally, the veins carry the blood back to the heart.
If we took all of the blood vessels out of an average child, and laid them out in one line, the
line would be over 60,000 miles long. An adult's vessels would be closer to 100,000 miles
long.
Besides circulating blood, the blood vessels provide two important means of measuring vital
health statistics: pulse and blood pressure. We measure heart rate, or pulse, by touching an
artery. The rhythmic contraction of the artery keeps pace with the beat of the heart. Since an
artery is near the surface of the skin, while the heart is deeply protected, we can easily touch
the artery and get an accurate measure of the heart's pulse.
When we measure blood pressure, we use the blood flowing through the arteries because it
has a higher pressure than the blood in the veins. Our blood pressure is measured using two
numbers. The first number, which is higher, is taken when the heart beats during the systole
phase. The second number is taken when the heart relaxes during the diastole phase.
Those two numbers stand for millimeters. A column of mercury rises and falls with the beat of
the heart. The height of the column is measured in millimeters.
Normal blood pressure ranges from 110 to 150 millimeters (as the heart beats) over 60 to 80
millimeters (as the heart relaxes). It is normal for your blood pressure to increase when we
are exercising and to decrease when we are sleeping.
Arteries
The heart pumps blood out through one main artery called the dorsal aorta. The main artery
then divides and branches out into many smaller arteries so that each region of the body has
its own system of arteries supplying it with fresh, oxygen-rich blood.
Arteries are tough on the outside and smooth on the inside. An artery actually has three
layers: an outer layer of tissue, a muscular middle, and an inner layer of epithelial cells. The
muscle in the middle is elastic and very strong. The inner layer is very smooth so that the
blood can flow easily with no obstacles in its path.
The muscular wall of the artery helps the heart pump the blood. When the heart beats, the
artery expands as it fills with blood. When the heart relaxes, the artery contracts, exerting a
force that it strong enough to push the blood along. This rhythm between the heart and the
artery results in an efficient circulation system.
The arteries deliver the oxygen-rich blood to the capillaries where the actual exchange of
oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the
veins for transport back to the lungs and heart.
Unlike the arteries and veins, capillaries are very thin and fragile. The capillaries are actually
only one epithelial cell thick. They are so thin that blood cells can only pass through them in
single file. The exchange of oxygen and carbon dioxide takes place through the thin capillary
wall. The red blood cells inside the capillary release their oxygen which passes through the wall
and into the surrounding tissue. The tissue releases its waste products, like carbon dioxide,
which passes through the wall and into the red blood cells.
Arteries and veins run parallel throughout the body with a web-like network(شبكة نسيج) of
capillaries, embedded in tissue, connecting them. The arteries pass their oxygen-rich blood to
the capillaries, which allow the exchange of gases within the tissue. The capillaries then pass
their waste-rich blood to the veins for transport back to the heart.
Arteries are connected with capillaries by arterioles (the subdivision of arteries into thinner
tubes and fine branches, the microscopic continuations of the arteries ),, and veins connected
with capillaries by venules (are microscopic vessels that continue from the capillaries and
merge to form veins ) producing a net work in the body.
Capillaries are also involved in the body's release of excess heat. During exercise, for
example, body and blood temperature rises. To help release this excess heat, the blood
delivers the heat to the capillaries which then rapidly release it to the tissue. The result is that
the skin takes on a flushed, red appearance.
Veins
Veins are similar to arteries but, because they transport blood at a lower pressure, they are
not as strong as arteries. Like arteries, veins have three layers: an outer layer of tissue,
muscle in the middle, and a smooth inner layer of epithelial cells. However, the layers are
thinner, containing less tissue.
Veins receive blood from the capillaries after the exchange of oxygen and carbon dioxide has
taken place. Therefore, the veins transport waste-rich blood back to the lungs and heart. It is
important that the waste-rich blood keeps moving in the proper direction and not be allowed
to flow backward. This is accomplished by valves that are located inside the veins. The valves
are like gates that only allow traffic to move in one direction.
The vein valves are necessary to keep blood flowing toward the heart, but they are also
necessary to allow blood to flow against the force of gravity. For example, blood that is
returning to the heart from the foot has to be able to flow up the leg. Generally, the force of
gravity would discourage that from happening. The vein valves, however, provide footholds
for the blood as it climbs its way up.
Blood that flows up to the brain faces the same problem. If the blood is having a hard time
climbing up, you will feel light-headed and possibly even faint. Fainting is your brain's natural
request for more oxygen-rich blood. When you faint, your head comes down to the same
level as your heart, making it easy for the blood to quickly reach the brain.
Because it lacks oxygen, the waste-rich blood that flows through the veins has a deep
purplish color. Because the walls of the veins are rather thin, the waste-rich blood is
sometimes visible through the skin as a bluish color. Look at your wrist, or hands, or ankles.
You can probably see your veins carrying your blood back to your heart.
From the moment it begins beating until the moment it stops, the human heart works
tirelessly. In an average lifetime, the heart beats more than two and a half billion times,
without ever pausing to rest. Like a pumping machine, the heart provides the power needed
for life.
The heart is a muscle that pump blood to whole body and receive blood from whole body. It is
a hollow, cone shaped, located within the thorax and resting upon the diaphragm. Heart size
varies with body size, it is generally about 14 centimeters long and 9 centimeters wide in an
average adult.
Heart consists of four chambers, two smaller ones on top, (the atria ) and two larger ones on
the bottom, ( the ventricles).
Between the chambers are four one-way valves:
*the tricuspid valve, the opening between the right atrium and the right ventricle, it permit
the movement of blood in one direction.
*the pulmonic valve, between the right ventricle and the pulmonary artery
*the mitral ( bicuspid ) valve, between the left atrium and left ventricle
*the aortic valve. Between the left ventricle and the aorta
The mitral valve has two flaps; the others have three. Under normal conditions, the valves
permit blood to flow in only one direction. Blood flow occurs only when there's a difference in
pressure across the valves that causes them to open.
These valves ensure that the blood flows in the right direction and are part of the sounds we
here through our stethoscopes.
We can simplify the functions of these chambers into two types, those that receive blood
from outside the heart, the atria, and those which send the blood outside of the heart, the
ventricles. It is the smooth function of both sets of chambers that provide the circulation of
blood to the rest of the body.
The heart is actually 3 layers of tissue; the "endocardium" a thin lining in the chambers; the
"myocardium" a thick layer of contractile muscle cells with specialized fibers forming a
conduction system through the muscle; and the visceral pericardium or "epicardium" that
covers the other layers. Surrounding all of this is the parietal "pericardium" a sac like
membrane that encases the heart in the chest. The two Pericardium layers secrete fluid to
lubricate the heart during its contraction, making it easier to move in the "sac."
The Coronary Arteries
All parts of the heart (the muscle fibers, the electrical system, etc.) require food and oxygen
to live and do their jobs, just like any other muscle. The way they get these essential
elements is through the blood via the coronary arteries.
The coronary arteries stem from the aorta and then branch into three main arteries. These
arteries, in turn, branch off into smaller vessels, so the oxygen can reach the heart tissues.
The three main coronary arteries are the right coronary artery, the left anterior descending
artery., and the circumflex artery. Each of the coronary arteries delivers blood to a specific
part of the heart. The right coronary artery delivers blood to the back and bottom part of the
heart. The left anterior descending artery gives blood to the front part of the heart and the
left circumflex furnishes the left side portion of the heart.
The coronary arteries have no direct communication with one another, if the end artery is
blocked, the tissue beyond it is likely to die because it receives no other blood supply from
the alternative vessels, this leads to what we call myocardial ischemia.
Blood Vessels:
In a general sense, a vessel is defined as a hollow utensil ( أداة ) for carrying something: a cup,
a bucket, a tube.
Blood vessels, then, are hollow utensils for carrying blood. Located throughout the body,
blood vessels are hollow tubes that circulate blood.
There are three varieties of blood vessels: arteries, veins, and capillaries. During blood
circulation, the arteries carry blood away from the heart. The capillaries connect the arteries to
veins. Finally, the veins carry the blood back to the heart.
If we took all of the blood vessels out of an average child, and laid them out in one line, the
line would be over 60,000 miles long. An adult's vessels would be closer to 100,000 miles
long.
Besides circulating blood, the blood vessels provide two important means of measuring vital
health statistics: pulse and blood pressure. We measure heart rate, or pulse, by touching an
artery. The rhythmic contraction of the artery keeps pace with the beat of the heart. Since an
artery is near the surface of the skin, while the heart is deeply protected, we can easily touch
the artery and get an accurate measure of the heart's pulse.
When we measure blood pressure, we use the blood flowing through the arteries because it
has a higher pressure than the blood in the veins. Our blood pressure is measured using two
numbers. The first number, which is higher, is taken when the heart beats during the systole
phase. The second number is taken when the heart relaxes during the diastole phase.
Those two numbers stand for millimeters. A column of mercury rises and falls with the beat of
the heart. The height of the column is measured in millimeters.
Normal blood pressure ranges from 110 to 150 millimeters (as the heart beats) over 60 to 80
millimeters (as the heart relaxes). It is normal for your blood pressure to increase when we
are exercising and to decrease when we are sleeping.
Arteries
The heart pumps blood out through one main artery called the dorsal aorta. The main artery
then divides and branches out into many smaller arteries so that each region of the body has
its own system of arteries supplying it with fresh, oxygen-rich blood.
Arteries are tough on the outside and smooth on the inside. An artery actually has three
layers: an outer layer of tissue, a muscular middle, and an inner layer of epithelial cells. The
muscle in the middle is elastic and very strong. The inner layer is very smooth so that the
blood can flow easily with no obstacles in its path.
The muscular wall of the artery helps the heart pump the blood. When the heart beats, the
artery expands as it fills with blood. When the heart relaxes, the artery contracts, exerting a
force that it strong enough to push the blood along. This rhythm between the heart and the
artery results in an efficient circulation system.
The arteries deliver the oxygen-rich blood to the capillaries where the actual exchange of
oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the
veins for transport back to the lungs and heart.
Unlike the arteries and veins, capillaries are very thin and fragile. The capillaries are actually
only one epithelial cell thick. They are so thin that blood cells can only pass through them in
single file. The exchange of oxygen and carbon dioxide takes place through the thin capillary
wall. The red blood cells inside the capillary release their oxygen which passes through the wall
and into the surrounding tissue. The tissue releases its waste products, like carbon dioxide,
which passes through the wall and into the red blood cells.
Arteries and veins run parallel throughout the body with a web-like network(شبكة نسيج) of
capillaries, embedded in tissue, connecting them. The arteries pass their oxygen-rich blood to
the capillaries, which allow the exchange of gases within the tissue. The capillaries then pass
their waste-rich blood to the veins for transport back to the heart.
Arteries are connected with capillaries by arterioles (the subdivision of arteries into thinner
tubes and fine branches, the microscopic continuations of the arteries ),, and veins connected
with capillaries by venules (are microscopic vessels that continue from the capillaries and
merge to form veins ) producing a net work in the body.
Capillaries are also involved in the body's release of excess heat. During exercise, for
example, body and blood temperature rises. To help release this excess heat, the blood
delivers the heat to the capillaries which then rapidly release it to the tissue. The result is that
the skin takes on a flushed, red appearance.
Veins
Veins are similar to arteries but, because they transport blood at a lower pressure, they are
not as strong as arteries. Like arteries, veins have three layers: an outer layer of tissue,
muscle in the middle, and a smooth inner layer of epithelial cells. However, the layers are
thinner, containing less tissue.
Veins receive blood from the capillaries after the exchange of oxygen and carbon dioxide has
taken place. Therefore, the veins transport waste-rich blood back to the lungs and heart. It is
important that the waste-rich blood keeps moving in the proper direction and not be allowed
to flow backward. This is accomplished by valves that are located inside the veins. The valves
are like gates that only allow traffic to move in one direction.
The vein valves are necessary to keep blood flowing toward the heart, but they are also
necessary to allow blood to flow against the force of gravity. For example, blood that is
returning to the heart from the foot has to be able to flow up the leg. Generally, the force of
gravity would discourage that from happening. The vein valves, however, provide footholds
for the blood as it climbs its way up.
Blood that flows up to the brain faces the same problem. If the blood is having a hard time
climbing up, you will feel light-headed and possibly even faint. Fainting is your brain's natural
request for more oxygen-rich blood. When you faint, your head comes down to the same
level as your heart, making it easy for the blood to quickly reach the brain.
Because it lacks oxygen, the waste-rich blood that flows through the veins has a deep
purplish color. Because the walls of the veins are rather thin, the waste-rich blood is
sometimes visible through the skin as a bluish color. Look at your wrist, or hands, or ankles.
You can probably see your veins carrying your blood back to your heart.
