Vascular System
The muscular organ which pumps the blood via its inherent contractile
activity. The heart can be viewed as two separate pumps--the
right-sided pump serving the pulmonary circulation and
the left-sided pump serving the systemic circulation
Simply stated, each side of the heart has a receiving
portion ad a pumping portionThe vascular system is made
up of arteries, veis, and capillaries. Arteries are
blood vessels that carry blood away from the heart.
Veins are blood vessels that return blood o the heart.
Capillaries are the smallest blood vessels, and are
the locus of nutrient and gas exchange between the blood
plasma and the peripheral tissues of the The cardiac
cycle and cardiovascular circuitry
The cardiac cycle is classically divided into seven
discrete phases, but will be radically simplified here.
For a more detailed description, please refer to the
cardiac cycle.
The cardiac cycle consists of alternating periods of relaxed filling
and active ejection of blood. These actions are attributable to
the inherent contractile activity of the heart which is, after all,
made of specialized muscle fibers. Cardiac contractio is coordinated
by a specialized pacemaker-and-conduction system see te heart for
more details. During the diastolic phase of the cardiac cycle, the
ventriles are filling with blood. During the systolic phase, the
rightand left ventricles are contacting, forcing their collecte
blood into the pulmonary and systemic circuits, respectively. Although
it is a gross oversimplification, the atria can be hought of acontinually
filling.The pulmonary and systemic circuits are routes-in-sequence.
Blood is pumped from the right heart to the lungs, returns to the
left heart, then is pumped to the periphery, then returns to the
right heart to eginthe sequence anew. This enables a perpetual cycle
of oxgenation, systemic delivery, metabolic deoxygenation, nd return.he
primary purpose of the pulmonary circulation is to oxygenate the
blood. Deoxygenated blood returning from the periphral tissues of
the body collects in the right atrium of the heart, fills the right
ventricle during diastole, and iejected into the pulmonary arteries
duing systole. These arteries carry the blood to the lungs, where
it passes through a capillary network close to air-filled alveoli.
This enables the release of carbon dioxide and the uptake of oxygen
from the air.
The now oxygenated blood returns to the left atrium
via the pulmonary vein, fills the left ventricle during diastole,
and is ejected into the aorta, the major artery which suplies blood
to the body via its numerous brnches. This is the starting point
for the systemic circulation, which consists of the intricate network
of arteries, arterioles, capillary beds, venules, and veins that
service the peripheral tissues of the body whih include the brain
and other organs, the skeletal muscles, etc.The major functions
of the renal system are to filter metabolic wastes from the blood
passing through the peripheral circulation and to mediate systemic
blood pressure via the renin-angiotensin-II-aldosterone sysem. Compromise
of renal function, as occurs in widely-varying conditions, inherently
disposes the patient to toxic states and/or cardiovascular pathologies.
The circulatory system is often subdivided into various
functional circuitsSplanchnic circulation
Also called visceral circulation, the splanchnic circulation
is the part of the systemic circulation that supplies
the digestive organs. The major arteries of the splanchnic
circulation branch directly off the aorta and include
the celiac artery superior mesenteric artery,
Portal circulationThere are two exceptions to the system
of double circulation.The deoxygenated blood from the
capillaries of the gastrointestinal tract drains into
the portal vein which, instead o going directly back
to the heart, leads to th liver. This allows the liver
to take up the nutrients that were extracted by the
intestines from food. The liver also neutralizes some
toxins taken up by the intestines. Blood from the liver
drains via the hepatic veins into the inferior vena
cava and then the right side of the heart.There is also
a small portal flow from the hypothalamus to the anterior
pituitary gla
Fetal circulationThe circulatory system of the fetus is different,
as the fetus does not use its anatomical changes, including closure
of the ductus arteriosus and foramen ovale. See also: coronary circulation.
mechanism used to transfer some component of a fluid
from one flowing current of fluid to another across a permeable
barrier between them. It is used extensively in biological systems
for a wide variety of purposes (it is also a key concept in chemical
engineering thermodynamics). For example, fish use countercurrent
exchange in their gills to transfer oxygen from the surrounding
water into their blood, and birds use a countercurrent heat exchanger
between blood vessels in their legs to keep heat concentrated within
their bodies.
Countercurrent exchangeThe diagram to the right presents
a generic representation of a countercurrent exchange system, with
two parallel tubes containing fluid separated by a pThe earliest
theory of beauty can be found in the works of early Greek philosophers
from the pre-Socratic period, such as Pythagoras. The extant writings
attributed to Pythagoras reveal that the Pythagorean school, if
not Pythagoras himself, saw a strong connection between mathematics
and beauty. In particular, they noted that objects proportioned
according to the golden ratio seemed more attractive. Some modern
research seems to confirm this, in that people whose facial features
are symmetric and proportioned according the golden ratio are consistently
ranked as more attractive than those whose faces are not.According
to an ancient Indian definition, the beautiful is that which from
moment to moment is always new. That is to say, it removes the mind
from the world in which things grow old.
Even mathematical formulae can be considered beautiful.
eip + 1 = 0 is commonly considered one of the most beautiful
theorems in mathematics (see Euler's identity). The
poet Edna St. Vincent Millay wrote that "Euclid
alone has looked on beauty bare" in an allusion
to the austere beauty many people have found in the
reasoning in the geometer Euclid's Elements.Another
connection between mathematics and beauty which played
a prominent role in Pythagoras' philosophy was the way
in which musical tones can be arranged in mathematical
sequences, which repeat at regular intervals called
octaves.Different cultures have deified beauty, typically
in female forms. Here is a list of the goddesses of
beauty in three different mythologies
ermeable barrier. The substance to be exchanged, whose
concentration is represented by the darkness of the
orange shading, transfers across the barrier in the
direction from greater concentration to lesser concentration.
With the two flos moving in opposite directions, the
countercurrent exchage system is able to maintain a
constant cocentration gradient between the two flows
over their entire
e fibers. Cardiac contractio is coordinated by a specialized pacemaker-and-conduction
system see te heart for more details. During the diastolic phase
of the cardiac cycle, the ventriles are filling with blood. During
the systolic phase, the rightand left ventricles are contacting,
forcing their collecte blood into the pulmonary and systemic circuits,
respectively. Although it is a gross oversimplification, the atria
can be hought of acontinually filling.The pulmonary and systemic
circuits are routes-in-sequence. Blood is pumped from the right
heart to the lungs, returns to the left heart, then is pumped to
the periphery, then returns to the right heart to eginthe sequence
anew. This enables a perpetual cycle of oxgenation, systemic delivery,
metabolic deoxygenation, nd return.he primary purpose of the pulmonary
circulation is to oxygenate the blood. Deoxygenated blood returning
from the periphral tissues of the body collects in the right atrium
of the heart, fills the right ventricle during diastole, and iejected
into the pulmonary arteries duing systole. These arteries carry
the blood to the lungs, where it passes through a capillary network
close to air-filled alveoli. This enables the release of carbon
dioxide and the uptake of oxygen from the air.
The now oxygenated blood returns to the left atrium
via the pulmonary vein, fills the left ventricle during diastole,
and is ejected into the aorta, the major artery which suplies blood
to the body via its numerous brnches. This is the starting point
for the systemic circulation, which consists of the intricate network
of arteries, arterioles, capillary beds, venules, and veins that
service the peripheral tissues of the body whih include the brain
and other organs, the skelet
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