System: The Circle of Blood
On average, your body has about 5 liters of blood
continually traveling through it by way of the circulatory
system. The heart, the lungs, and the blood vessels work
together to form the circle part of the circulatory system.
The pumping of the heart forces the blood on its journey.
The body's circulatory system really has three
distinct parts: pulmonary circulation, coronary circulation,
and systemic circulation. Or, the lungs (pulmonary), the
heart (coronary), and the rest of the system (systemic). Each
part must be working independently in order for them to all
work together.
Systemic Circulation: It's All Throughout the Body
Systemic circulation supplies nourishment to all of
the tissue located throughout your body, with the exception
of the heart and lungs because they have their own systems.
Systemic circulation is a major part of the overall circulatory
system.
The blood vessels (arteries, veins, and capillaries) are
responsible for the delivery of oxygen and nutrients to the
tissue. Oxygen-rich blood enters the blood vessels through
the heart's main artery called the aorta. The forceful
contraction of the heart's left ventricle forces the blood into
the aorta which then branches into many smaller arteries
which run throughout the body. The inside layer of an artery
is very smooth, allowing the blood to flow quickly. The
outside layer of an artery is very strong, allowing the blood
to flow forcefully. The oxygen-rich blood enters the
capillaries where the oxygen and nutrients are released. The
waste products are collected and the waste-rich blood flows
into the veins in order to circulate back to the heart where
pulmonary circulation will allow the exchange of gases in the
lungs.
During systemic circulation, blood passes through
the kidneys. This phase of systemic circulation is known as
renal circulation. During this phase, the kidneys filter much
of the waste from the blood. Blood also passes through the
small intestine during systemic circulation. This phase is
known as portal circulation. During this phase, the blood
from the small intestine collects in the portal vein which
passes through the liver. The liver filters sugars from the
blood, storing them for later.
Pulmonary Circulation: It's All in the Lungs
Pulmonary
circulation is the
movement of blood from
the heart, to the lungs, and
back to the heart again.
This is just one phase of
the overall circulatory
system.
The veins bring
waste-rich blood back to
the heart, entering the
right atrium throughout two large veins called vena cavae.
The right atrium fills with the waste-rich blood and then
contracts, pushing the blood through a one-way valve into
the right ventricle. The right ventricle fills and then
contracts, pushing the blood into the pulmonary artery
which leads to the lungs. In the lung capillaries, the exchange
of carbon dioxide and oxygen takes place. The fresh, oxygenrich blood enters the pulmonary veins and then returns to
the heart, re-entering through the left atrium. The oxygenrich blood then passes through a one-way valve into the left
ventricle where it will exit the heart through the main artery,
called the aorta. The left ventricle's contraction forces the
blood into the aorta and the blood begins its journey
throughout the body.
The one-way valves are important for preventing any
backward flow of blood. The circulatory system is a network
of one-way streets. If blood started flowing the wrong way,
the blood gases (oxygen and carbon dioxide) might mix,
causing a serious threat to your body.
You can use a stethoscope to hear pulmonary
circulation. The two sounds you hear, "lub" and "dub," are
the ventricles contracting and the valves closing.
Coronary Circulation: It's All in the Heart
While the circulatory system is busy providing
oxygen and nourishment to every cell of the body, let's not
forget that the heart, which works hardest of all, needs
nourishment, too. Coronary circulation refers to the
movement of blood through the tissues of the heart. The
circulation of blood through the heart is just one part of the
overall circulatory system.
Serious heart damage may occur if the heart tissue
does not receive a normal supply of food and oxygen. The
heart tissue receives nourishment through the capillaries
located in the heart.
The circulatory system is an organ system that passes
nutrients (such as amino acids, electrolytes and lymph),
gases, hormones, blood cells, etc. to and from cells in the
body to help fight diseases and help stabilize body
temperature and pH to maintain homeostasis.
This system may be seen strictly as a blood
distribution network, but some consider the circulatory
system as composed of the cardiovascular system, which
distributes blood,[1] and the lymphatic system,[2] which
distributes lymph. While humans, as well as other
vertebrates, have a closed cardiovascular system (meaning
that the blood never leaves the network of arteries, veins
and capillaries), some invertebrate groups have an open
cardiovascular system. The most primitive animal phyla lack
circulatory systems. The lymphatic system, on the other
hand, is an open system.
heart, it is by definition a part of the systemic circulatory
system.
The heart pumps oxygenated blood to the body and
deoxygenated blood to the lungs. In the human heart there
is one atrium and one ventricle for each circulation, and with
both a systemic and a pulmonary circulation there are four
chambers in total: left atrium, left ventricle, right atrium and
right ventricle. The right atrium is the upper chamber of the
right side of the heart. The blood that is returned to the right
atrium is deoxygenated (poor in oxygen) and passed into the
right ventricle to be pumped through the pulmonary artery
to the lungs for re-oxygenation and removal of carbon
dioxide. The left atrium receives newly oxygenated blood
from the lungs as well as the pulmonary vein which is passed
into the strong left ventricle to be pumped through the aorta
to the different organs of the body.
Two types of fluids move through the circulatory
system: blood and lymph. The blood, heart, and blood
vessels form the cardiovascular system. The lymph, lymph
nodes, and lymph vessels form the lymphatic system. The
cardiovascular system and the lymphatic system collectively
make up the circulatory system.
The main components of the human cardiovascular
system are the heart, the veins, and the blood vessels.[3] It
includes: the pulmonary circulation, a "loop" through the
lungs where blood is oxygenated; and the systemic
circulation, a "loop" through the rest of the body to provide
oxygenated blood. An average adult contains five to six
quarts (roughly 4.7 to 5.7 liters) of blood, which consists of
plasma, red blood cells, white blood cells, and platelets. Also,
the digestive system works with the circulatory system to
provide the nutrients the system needs to keep the heart
pumping.
The Pulmonary circulation is the portion of the
cardiovascular system which transports oxygen-depleted
blood away from the heart, to the lungs, and returns
oxygenated blood back to the heart.
Oxygen deprived blood from the vena cava enters
the right atrium of the heart and flows through the tricuspid
valve into the right ventricle, from which it is pumped
through the pulmonary semilunar valve into the pulmonary
arteries which go to the lungs. Pulmonary veins return the
now oxygen-rich blood to the heart, where it enters the left
atrium before flowing through the mitral valve into the left
ventricle. Then, oxygen-rich blood from the left ventricle is
pumped out via the aorta, and on to the rest of the body.
The coronary circulatory system provides a blood
supply to the heart. As it provides oxygenated blood to the
The cardiovascular systems of humans are closed,
meaning that the blood never leaves the network of blood
vessels. In contrast, oxygen and nutrients diffuse across the
blood vessel layers and enters interstitial fluid, which carries
oxygen and nutrients to the target cells, and carbon dioxide
and wastes in the opposite direction. The other component
of the circulatory system, the lymphatic system, is not
closed.
About 98.5% of the oxygen in a sample of arterial
blood in a healthy human breathing air at sea-level pressure
is chemically combined with hemoglobin molecules. About
1.5% is physically dissolved in the other blood liquids and not
connected to hemoglobin. The hemoglobin molecule is the
primary transporter of oxygen in mammals and many other
species