Chapter 26.3 The Circulatory System

This textbook is designed specifically for Kansas State's Biology 198 Class. The course is taught using the studio approach and based on active learning. The studio manual contains all of the learning objectives for each class period and is the record of all student activities. Hence, this textbook is more of a reference tool while the studio manual is the learning tool.
Authors: Robert Bear, David Rintoul, Bruce Snyder, Martha Smith-Caldas, Christopher Herren, and Eva Horne
Kansas State University Libraries
New Prairie Press
Bear, Robert; Rintoul, David; Snyder, Bruce; Smith-Caldas, Martha; Herren, Christopher; and Horne, Eva, "Principles of Biology" (2016). Open Access Textbooks. 1. https://newprairiepress.org/textbooks/1
The textbook was originally published and is also available to download at http://cnx.org/contents/[e-mail] is licensed under a Creative Commons Attribution License 4.0 license.

Episode Transcript

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Welcome to Principles of Biology. Thisbook was written by the Open Alternative Textbook
Initiative at Kansas State University and isbeing released as a podcast and distributed under
the terms of the Creative Commons AttributionLicense. Today's episode is chapter twenty six
point three the circulatory System. Allhyperlinks, images and sources can be found

(00:22):
at the link to the book.In the description, observation by means of
the microscope will reveal more wonderful thingsthan those viewed in regard to mere structure
and connection. For while the heartis still beating the contrary i e.
In opposite directions and the different vessels, movement of the blood is observed in
the vessels, though with difficulty,so that the circulation of the blood is
clearly exposed. Marcello Malpighe d Pollinibis, sixteen sixty one. Malpegi's work,

(00:49):
mostly on frogs, outline the finermicroscopic details of circulation, following the work
of Harvey, who described the circulatorysystem at a macroscopic level. In all
animals except a few simple types.The circulatory system is used to transport nutrients
and gases through the body. Simplediffusion allows some water, nutrient waste,

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and gas exchange into primitive animals thatare only a few cell layers thick.
However, bulk flow is the onlymethod by which the entire body of large
or more complex organisms is accessed circulatorysystem architecture. The circulatory system is effectively
a network of cylindrical vessels, thearteries, veins, and capillaries that emanate

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from a pump the heart. Inall vertebrate organisms, as well as some
invertebrates, this is a closed systemin which the blood is not free in
a cavity. In a closed circulatorysystem, blood is contained inside blood vessels
and circulates unidirectionally from the heart aroundthe systemic circulatory route, then returns to
the heart again, as illustrated inFigure A. As opposed to a closed

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system, arthropods, including insects,crustaceans, and most molluscs, have an
open circulatory system, as illustrated inFigure B. In an open circulatory system,
the fluid is not enclosed in theblood vessels, but is pumped into
a cavity called a hemocial Rather thanblood. This fluid is called hemolymph because

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the blood mixes with the interstitial fluidas the heart beats and the animal moves.
The hemolymp circulates around the organs withinthe body cavity, and then re
enters the hearts through openings called ostia. This movement allows for gas and nutrient
exchange. An open circulatory system doesnot use as much energy as a closed
system to operate or to maintain.However, there is a trade off with

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the amount of blood that can bemoved to highly metabolically active organs and tissues.
Illustration A shows the closed circulatory systemof an earthworm. Dorsal and ventral
blood vessels run along the top andbottom of the intestine, respectively. The
dorsal and ventral blood vessels are connectedby ring like hearts. Hearts are also

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associated with the dorsal blood vessel.These hearts pump blood forward, and the
ring like hearts pump blood down tothe ventral vessel, which returns blood to
the back of the body. Illustrationbee shows the open circulatory system of a
bee. The dorsal blood vessel,which contains multiple hearts, runs along the
top of the bee. Blood exitsthe dorsal blood vessel through an opening in

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the head into the body cavity.Blood re enters the blood vessels through openings
in the hearts called ostia. Ina closed circulatory systems, the heart pumps
blood through vessels that are separate fromthe interstitial fluid of the body. Most
vertebrates and some invertebrates like this annelidearthworm, have a closed circulatory system.

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In bee open circulatory systems, afluid called hemolymph is pumped through a blood
vessel that empties into the body cavity. Hemolymph returns to the blood vessel through
openings called ostea. Arthropods like thisbee and most molluscs have open circulate tory
systems. Circulatory system variation in animals. The circulatory system varies from simple systems

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and invertebrates to more complex systems.In vertebrates. The simplest animals, such
as the sponges periphera and rhodifers rotiphera, do not need a circulatory system because
diffusion allows adequate exchange of water,nutrients, and waste, as well as
dissolved gases, as shown in figurey. Organisms that are more complex but still

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only have two layers of cells intheir body plan, such as jellies nideria
and comb jellies tinaphra, also useddiffusion through their epidermis and internally through the
gastrovascular compartment. Both their internal andexternal tissues are bathed in an aqueous environment
and exchange fluids by diffusion on bothsides. As illustrated in Figure B.
Exchange of fluids is assisted by thepulsing of the jellyfish body. Illustration A

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shows a cross section of a spongewhich has a thin vase like body bathed
both inside and out by fluid.Illustration beach shows a bell shaped jellyfish.
Simple animals consisting of a single celllayer such as a sponge, or only
a few cell layers such as thebee jellyfish, do not have a circulatory
system. Instead, gases, nutrients, and wastes are exchanged by diffusion.

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For more complex organisms, diffusion isnot efficient for moving gases, nutrients,
and waste effectively through the body.Natural selection led to the development of more
efficient systems. Most arthropods and manymolluscs have open circulatory systems. In an
open system, an elongated beating heartpushes the humleim through the body, and

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muscle contractions help to move fluids.The larger, more complex crustaceans, including
lobsters, have developed arterial like vesselsto push blood through their bodies, and
the most active molluscs, such assquids, have evolved a closed circulatory system
and are able to move rapidly tocatch prey. Closed circulatory systems are found
in all vertebrates. However, thereare significant differences in the structure of the

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heart and the circulation of blood betweenthe different vertebrate groups due to adaptation during
evolution and associated differences in anatomy.Figure illustrates the basic circulatory systems of some
vertebrates, fish, amphibians, reptiles, and mammals. Illustration A shows the
circulatory system of fish, which havea two chambered heart with one atrium and

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one ventricle. Blood in systemic circulationflows from the body into the atrium,
then into the ventricle. Blood exitingthe heart enters gill circulation, where gases
are exchanged by gill capillaries from thegill's blood reenters systemic circulation, where gases
in the body are exchanged by bodycapillaries. Illustration beach shows the circulatory system

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of amphibians, which have a threechambered heart with two atriums and one ventricle.
Blood in systemic circulation enters the heart, flows into the right atrium,
then into the ventricle. Blood leavingthe ventricle enters pulmonary and skin circulation.
Capillaries in the lung and skin exchangegases, oxygenating the blood from the lungs

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and skin. Blood re enters theheart through the left atrium. Blood flows
into the ventricle, where it mixeswith blood from systemic circulation. Blood leaves
the ventricle and enters systemic circulation.Illustration seat shows the circulatory system of reptiles,
which have a four chambered heart.The right and left ventricle are separated

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by a septum, but there isno septum separating the right and left atrium,
so there is some mixing of bloodbetween these two chambers. Blood from
systemic circulation enters the right atrium,then flows from the right ventricle and enters
pulmonary circulation, where blood is oxygenatedin the lungs. From the lungs,
blood travels back into the heart throughthe left atrium. Because the left and

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right atrium are not separated, somemixing of oxygenated and deoxygenated blood occurs.
Blood is pumped into the left ventriclethen into the body. Illustration D shows
the circulatory system of mammals, whichhave a four chambered heart. Circulation is
similar to that of reptiles, butthe four chambers are completely separate from one

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another, which improves efficiency. Afish have the simplest circulatory systems of the
vertebrates. Blood flows unidirectionally from thetwo chambered heart through the gills and then
the rest of the body. BAmphibians have two circulatory roots, one for
oxygenation of the blood through the lungsand skin, and the other to take
oxygen to the rest of the body. The blood is pumped from a three

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chambered heart with two atria and asingle ventricle. C Reptiles also have two
circulatory roots. However, blood isonly oxygenated through the lungs. The heart
is three chambered, but the ventriclesare partially separated, so some mixing of
oxygenated and deoxygenated blood occurs, exceptin crocodilians and birds. D. Mammals

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and birds have the most efficient heart, with four chambers that completely separate the
oxygenated and deoxygenated blood. It pumpsonly oxygenated blood through the body and deoxygenated
blood to the lungs. As illustratedin figure of fish have a single circuit
for blood flow and a two chamberedheart that has only a single atrium and
a single ventricle. The atrium collectsblood that has returned from the body,

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and the ventricle pumps the blood tothe gills, where gas exchange occurs and
the blood is reoxygenated. This iscalled the gill circulation. The blood then
continues through the rest of the bodybefore arriving back at the atrium. This
is called the systemic circulation. Thisunidirectional flow of blood produces a gradient of
oxygenated to deoxygenated blood around the fish'ssystemic circuit. The result is a limit

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in the amount of oxygen that canreach some of the organs and tissues of
the body, reducing the overall metaboliccapacity of fish. In amphibians, reptiles,
birds, and mammals, blood flowis directed in two circuits, one
through the lungs and back to theheart, which is called the pulmonary circulation,
and the other throughout the rest ofthe body in its organs, including
the brain, systemic circulation. Inamphibians, gas exchange also occurs through the

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skin during pulmonary circulation and is referredto as polo cutaneous circulation, as shown
in Figure B. Amphibians have athree chambered heart that has two atria and
one ventricle, rather than the twochambered heart of fish. The two atria
superior heart chambers perceive blood from thetwo different circuits the lungs and the systems,
and then there is some mixing ofthe blood in the hearts ventricle inferior

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heart chamber, which reduces the oxygenconcentration in the blood pumped from the ventricle.
The advantage to this arrangement is thathigh pressure in the vessels pushes blood
to the lungs and body. Themixing is mitigated by a ridge within the
ventricle that diverts oxygen rich blood throughthe systemic circulatory system and deoxygenated blood to
the polo cutaneous circuit. For thisreason, amphibians are often described as having

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double circulation. Most reptiles also havea three chambered heart similar to the amphibian
heart, that directs blood to thepulmonary and systemic circuits. As shown in
Figure C, the ventricle is dividedmore effectively by a partial septum, which
results an even less mixing of oxygenatedand deoxygenated blood. Some reptiles, alligators,

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and crocodiles are the most primitive animalsto exhibit a four chambered heart.
Crocodilians have a unique circulatory mechanism wherethe heart shuns blood from the lungs towards
the stomach and other organs during longperiods of submergence, for instance, while
the animal waits for prey or staysunderwater waiting for prey to rot. One
adaptation includes two main arteries that leavethe same part of the heart. One

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takes blood to the lungs and theother provides an alternate root to the stomach
and other parts of the body.Two other adaptations include a hole in the
heart between the two ventricles called theforamen of panizza, which allows blood to
move from one side of the heartto the other, and specialized connective tissue
that slows the blood flow to thelungs. Together, these adaptations have made

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crocodiles and alligators one of the mostsuccessful and ancient animal groups on Earth.
In mammals and birds. The heartis also divided into four chambers, two
atria and two ventricles, as illustratedand figured. The oxygenated blood is completely
separated from the deoxygenated blood, whichimproves the efficiency of double circulation and is

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probably required for the warm blooded lifestyleof mammals and birds. The four chambered
heart of birds and mammals evolved independentlyfrom ancestors with a three chambered heart.
The independent evolution of the same ora similar biological trait is referred to as
convergent evolution. Components of blood oxygenbinding proteins hemoglobin, hemocyanin, et cetera,

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are one of the main components ofblood in all animals. The blood
is more than those proteins, though, Blood is actually a term used to
describe the liquid that moves through thevessels and includes plasma, the liquid portion
which contains water, proteins, salts, lipids, and glucose, and the
cells red and white cells and sellfragments called platelets. Plasma is actually the

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major component of blood and contains thewater proteins, electrolytes, lipids, and
glucose. The cells are responsible forcarrying the gases, red cells and immune
the response white the platelets are responsiblefor blood clotting. In humans, cellular
components make up approximately forty five percentof the blood and the liquid plasma fifty

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five percent. Blood is twenty percentof a human's extracellular fluid and eight percent
of the weight of an average human. The roll of blood in the body,
blood, like the human blood illustratedin figure, is important for regulation
of the bodies systems and homeostasis.Blood helps maintain homeostasis by stabilizing pH temperature,

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osmotic pressure and by eliminating excess heat. Blood supports growth by distributing nutrients
and hormones and by removing waste.Blood plays a protective role by transporting clotting
factors and platelets to prevent blood lossand transporting the disease fighting agents or white
blood cells to sites of infection.Illustration shows different types of blood cells and

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cellular components. Red blood cells aredisc shaped and pockered in the middle.
Platelets are long and thin and abouthalf the length red blood cells. Neutrophils,
monocytes, lymphocytes, eosinophils, andbasophils are about twice the diameter of
red blood cells and spherical Monocytes andeosinophils have us shaped nuclei. Eosinophiles contain

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granules, but monocytes do not.Basophils and neutrophiles both have irregularly shaped,
multilobed nucleion granules. The cells andcellular components of human blood are shown.
Red blood cells to liver oxygen tothe cells and remove carbon dioxide. White
blood cells, including neutrophils, monocytes, lymphocytes, eosinophils, and basophils,

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are involved in the immune response.Platelets form clots that prevent blood loss after
injury. Red blood cells, redblood cells, or erythrocytes erythroequals red psychequals
cell are specialized cells that circulate throughthe body, delivering oxygen to cells.
They are generated by division of stemcells and the bone marrow. In mammals,

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red blood cells are small, biconcavecells that at maturity do not contain
a nucleus or mitochondria and are onlyseven to eight m in size. In
birds and reptiles, erythrocytes have nucleiand mitochondria. The red coloring of human
blood comes from the iron containing proteinhemoglobin, illustrated in Figure A. The
principal job of these proteins is tocarry oxygen, but they also transports carbon

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dioxide as well. Hemoglobin is packedinto human red blood cells at a rate
of about two hundred and fifty millionmolecules of hemoglobin per cell. Each hemoglobin
molecule binds for oxygen molecules, sothat each red blood cell carries one billion
molecules of oxygen. There are approximatelytwenty five trillion red blood cells and the
five liters of blood in the humanbody, which could carry up to twenty

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five sextillion, twenty five by tentwenty one molecules of oxygen in the body
at any time. In mammals,the lack of organells and erythrocytes leaves more
room for the hemoglobin molecules, andthe lack of mitochondria also prevents use of
the oxygen for metabolic respiration. Notall organisms use hemoglobin as the method of

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oxygen transport. Invertebrates that utilize hemolymphrather than blood use different pigments to bind
to the oxygen. These pigments usecopper or iron to the oxygen. Invertebrates
have a variety of other respiratory pigments. Hemocyanin a blue green copper containing protein
illustrated in Figure BA, is foundin molluscs, crustaceans, and some of

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the arthropods. Chlorocurin, a greencolored iron containing pigment, is found in
four families of polykete tube worms.Hemmerhythrin, a red iron containing protein,
is found in some polykeete worms andannelids, and is illustrated in Figure C.
Despite the name hemorhythrin does not containa hem group, and its oxygen
carrying capacity is poor compared to hemoglobin. Molecular Model A shows the structure of

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hemoglobin, which is made up offour protein subunits, each of which is
coiled into helices left right, bottomand top. Parts of the molecule are
symmetrical. For small hem groups areassociated with hemoglobin. Oxygen is bound to
the hem Molecular model BEAT shows thestructure of hemocyanin, a protein made up
of coiled helices and ribbon like sheets. Two copper ions are associated with the

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protein. Molecular model C shows thestructure of hem rythrin, a protein made
of coiled hollicies with four iron ironsassociated with it. In most vertebrates,
a hemoglobin delivers oxygen to the bodyand removes some carbon dioxide. Hemoglobin is
composed of four protein subunits, twoalpha chains and two beta chains, and

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ahin group that has iron associated withit. The iron reversibly associates with oxygen
and in so doing is oxidized fromphase two plus to phase three plus.
In most molluscs and some arthropods,b hemocyanin delivers oxygen. Unlike hemoglobin.
Hemolymph is not carried in blood cells, but floats free in the hemolymph.

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Copper instead of iron, binds theoxygen, giving the hemolymph of blue green
color. In hanelids such as theearthworm and some other invertebrates see hemerhythrin carries
oxygen like hemoglobin. Hemerhythrin is carriedin blood cells and has iron associated with
it, but despite its name,hemerythrin does not contain hem The small size

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and large surface area of red bloodcells allows for rapid diffusion of oxygen and
carbon dioxide across the plasma membrane.In the lungs, carbon dioxide is released
in oxygen is taken in by theblood. In the tissues, oxygen is
released from the blood and carbon dioxideis bound for transport back to the lungs.
White blood cells white blood cells,also called leucocytes lucoequals white, make

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up approximately one percent by volume ofthe cells and blood. The roll of
white blood cells is very different thanthat of red blood cells. As you
have learned previously, they are primarilyinvolved in the immune response to identify and
target pathogens such as invading bacteria,viruses, and other foreign organisms. White

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blood cells are formed continually. Someonly live for hours or days, but
some live for years. The morphologyof white blood cells differs significantly from red
blood cells. They have nuclei anddo not contain hemoglobin. The different types
of white blood cells are identified bytheir microscopic appearance after histologic staining, and
each has a different specialized function.The two main groups, both illustrated in

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figure, are the granulocytes, whichinclude the neutrophils, eosinophils, and basophills,
and the agranulocytes, which include themonocytes and lymphocytes. Granulocytes contain granules
in their cytoplasm. Biogranulocytes are sonamed because of the lack of granules in
their cytoplasm. Some leukocytes become macrophagesthat either stay at the same site or

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move through the bloodstream and gather atsites of infection or inflammation, where they
are attracted by chemical signals from foreignparticles and damaged cells. Lymphocytes are the
primary cells of the immune system andinclude B cells, T cells, and
natural killer cells. B cells destroybacteria and inactivate their toxins. They also

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produce antibodies. T cells attack viruses, fungi, some bacteria, transplanted cells,
and cancer cells. T cells attackviruses by releasing toxins that kill the
viruses. Natural killer cells attack avariety of infectious microbes and certain tumor cells.
Platelets and coagulation factors. Blood mustclot to heal wounds and prevent excess

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blood loss. Small cell fragments calledplatelets brombsites are attracted to the wound site,
where they adhere by extending many projectionsand releasing their contents. These contents
activate other platelets and also interact withother coagulation factors, which convert fibrinogen,
a water soluble protein present in bloodserum, into fibrine, a non water

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soluble protein, causing the blood toclot. Many of the clotting factors require
vitamin K to work, and vitaminK deficiency can lead to problems with blood
clotting. Many platelets converge and sticktogether at the wound site, forming a
platelet plug, also called the fibrineclot, as illustrated in Figure B.
The plug or clot lasts for anumber of days and stops the loss of

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blood. Platelets are formed from thedisintegration of larger cells called megacaryosytes, like
that shown in Figure A. Foreach megacaryosite, two thousand to thirty hundred
platelets are formed, with one hundredand fifty thousand to four hundred thousand platelets
present in each cubic millimeter of blood. Each platelet is disc shaped and two

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to four micrometers in diameter. Theycontain many small vesicles but do not contain
a nucleus. PARTI shows a large, somewhat irregularly shaped cell called a megacaryosite,
shedding small, oblong platelets. PartBEE shows a fibrine clot plugging a
cut in a blood vessel. Theclot is made up of platelets and a

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fibrous material called fibrine. A.Platelets are formed from large cells called megacaryosytes.
The megacaryosite breaks up into thousands offragments that become platelets. B Platelets
are required for clotting of the blood. The platelets collect at a wound site
in conjunction with other clotting factors,such as fibrinogen, to form a fibrine

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clot that prevents blood loss and allowsthe wound to heal. Plasma and serum.
The liquid component of blood is calledplasma, and it can separated from
the blood cells by spinning or centrifugingthe blood at high rotations three thousand rpm
or higher. The blood cells andplatelets are separated by centrifugal forces to the
bottom of a specimen tube the upperliquid layer. The plasma consists of ninety

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percent water, along with various substancesrequired for maintaining the bodies pH osmotic load
and for protecting the body. Theplasma also contains the coagulation factors and antibodies.
The plasma component of blood without thecoagulation factors is called the serum.
Serum is similar to interstitial fluid,in which the correct composition of key ions

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acting as electrolytes is essential for normalfunctioning of muscles and nerves. Other components
in the serum include proteins that assistwith maintaining pH and osmotic balance while giving
viscosity to the blood. The serumalso contains antibodies, specialized proteins that are
important for defense against viruses and bacteria. Lipids, including cholesterol, are also

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transported in the serum, along withvarious other substances including nutrients, hormones,
metabolic waste, plus external substances suchas drugs, viruses, and bacteria.
Evolution connection blood types related to proteinson the surface of the red blood cells.
Red blood cells are coated in antigensmade of glycolipids and glycoproteins. The

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composition of these molecules is determined bygenetics, which have evolved over time.
In humans, the different surface antigensare grouped into twenty four different blood groups,
with more than one hundred different antigenson each red blood cell. The
two most well known blood groups arethe abio shown in figure and RH systems.
The surface antigens in the A bioblood group are glycolipids called antigen A

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and antigen B. People with bloodtype A have antigen A, those with
blood type BEE have antigen B,those with blood type A BEE have both
antigens, and people with blood typeO have neither antigen. Antibodies are found
in the blood plasma can react withthe A or bantigens. Individuals with type
A blood have antibodies to thy BEblood cells. When type A and type

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BEE blood are combined, agglutination clumpingof the blood occurs because of antibodies in
the plasma that bind with the opposingantigen. This causes clots that coagulate in
the kidney, causing kidney failure indeath. Type O blood has neither A
or bantigens, and therefore TYPO bloodcan be given to all blood types.
Type O negative blood is the universaldonor. Type A B positive blood is

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the universal acceptor because it has bothA and bantigen. Typo Type A,
type BEE and type A B redblood cells are shown. Typo cells do
not have any antigens on their surface. Type A cells have A antigen on
their surface. Type B cells haveBE antigen on their surface. Type A

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B cells have both antigens on theirsurface. Human red blood cells may have
either type A or BE glycoproteins ontheir surface. Both glycoproteins combined AB or
neither O. The glycoproteins serve asantigens and can elicit an immune response in
a person who receives a transfusion containingunfamiliar antigens. TYPO blood, which has

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no way or be antigens, doesnot elicit an immune response when injected into
a person of any blood type.Thus O is considered the universal donor.
Persons with type A B blood canaccept blood from any blood type, and
type A B is considered the universalacceptor. Mammalian heart and blood vessels,
the heart is a complex muscle thatpumps blood through the three divisions of the

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circulatory system, the coronary vessels thatserve the heart, pulmonary heart and lungs,
and systemic systems of the body.As shown in figure. Coronary circulation
is intrinsic to the heart and takesblood directly from the main artery aorta coming
from the heart to provide oxygen forthe hard working heart muscle. For pulmonary
and systemic circulation, the heart hasto pump blood to the lungs or the

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rest of the body, respectively.Invertebrates, the lungs are relatively close to
the heart in the thoracic cavity.The shorter distance to pump means that the
heart muscle wall on the right sideof the heart is not as thick as
the left side, which must haveenough pressure to pump blood all the way
to your big toe. Illustration showsblood circulation through the mammalian systemic and pulmonary

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circuits. Blood enters the left atriumthe upper left chamber of the heart through
veins of the systemic circuit. Themajor vein that feeds the heart from the
upper body is the superior vena cava, and the major vein that feeds the
heart from the lower body is theinferior vena cava. From a left atrium,
blood travels down to the left ventricle, then up to the pulmonary artery.

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From the pulmonary artery, blood enterscapillaries of the lung. Blood is
then collected by the pulmonary vein andre enters the heart through the upper left
chamber of the heart. The leftatrium, blood travels down to the left
ventricle, then re enters the systemiccircuit through the aorta, which exits through
the top of the heart. Bloodenters tissues of the body through capillaries of

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the systemic circuit. The mammalian circulatorysystem is divided into three circuits, the
systemic circuit, the pulmonary circuit,and the coronary circuit. Blood is pumped
from veins of the systemic circuit intothe right atrium of the heart, then
into the right ventricle. Blood thenenters the pulmonary circuit and is oxygenated by

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the lungs. From the pulmonary circuit, blood re enters the heart through the
left atrium. From the left ventricle, blood re enters the systemic circuit through
the aorta and is distributed to therest of the body. The coronary circuit,
which provides blood to the heart,is not shown. Structure of the
heart. The heart muscle is asymmetricalas a result of the distance blood must

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travel in the pulmonary and systemic circuits. Since the right side of the heart
sends blood to the pulmonary circuit,it is smaller than the left side,
which must send blood out to thewhole body in the systemic circuit, as
shown in figure. In humans,the heart is about the size of a
clenched fist. It is divided intofour chambers, two atria and two ventricles.

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There is one atrium and one ventricleon the right side and one atrium
and one ventricle on the left side. The atria are the chambers that receive
blood from the circulation, and theventricles are the chambers that pump blood into
the circulation. The right atrium receivesdeoxygenated blood from the superior vena cava,
which drains blood from the jugular veinthat comes from the brain and from the

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veins that come from the arms,as well as from the inferior vena cava,
which drains blood from veins that comefrom the lower organs and the legs.
In addition, the right atrium receivesblood from the coronary sinus, which
drains deoxygenated blood from the heart itself. This deoxygenated blood then passes to the
right ventricle through the atrioventricular valve orthe tricuspid valve. After it is filled,

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the right ventricle pumps the blood throughthe pulmonary arteries bypassing the semilunar valve
or pulmonic valve to the lungs Forreoxygenation. After blood passes through the pulmonary
arteries, the right semilunar valves close, preventing the blood from flowing backwards into
the right ventricle. The left atriumthen receives the oxygen rich blood from the

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lungs via the pulmonary veins. Thisblood passes through the bicuspid valve or mitral
valve the atrioventricular valve on the leftside of the heart to the left ventricle,
where the blood is pumped out throughaorta, the major artery of the
body, taking oxygenated blood to theorgans and muscles of the body. Once
blood is pumped out of the leftventricle and into the aorta, the aortic

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semilunar valve or aortic valve closes,preventing blood from flowing backward into the left
ventricle. This pattern of pumping isreferred to as double circulation and is found
in all mammals. The heart hasits own blood vessels that supply the heart
muscle with blood. The coronary arteriesbranch from the aorta and surround the outer

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surface of the heart like a crown. They diverge into capillaries, where the
heart muscle is supplied with oxygen,before converging again into the coronary veins to
take the deoxygenated blood back to theright atrium, where the blood will be
reoxygenated through the pulmonary circuit. Theheart muscle will die without a steady supply
of blood. Atherosclerosis is the blockageof an artery by the build up of

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fatty plaques. Because of the sizenarrow of the coronary arteries in their function
in serving the heart itself, atherosclerosiscan be deadly in these arteries. The
slowdown of blood flow and subsequent oxygendeprivation that results from atherosclerosis causes severe pain
known as angina, and complete blockageof the arteries will cause myocardial infarction,

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the death of cardiac muscle tissue,commonly known as a heart attack. Arteries,
veins, and capillaries. The bloodfrom the heart is carried through the
body by a complex network of bloodvessels. Figure arteries take blood away from
the heart. The main artery isthe aorta that branches into major arteries that
take blood to different limbs and organs. These major arteries include the carotid artery

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that takes blood to the brain,the brachial arteries that take blood to the
arms, and the thoracic artery thattakes blood to the thorax and then into
the hepatic, renal, and gastricarteries for the liver, kidney, and
stomach, respectively. The iliac arterytakes blood to the lower limbs. The
major arteries diverge into minor arteries andthen smaller vessels called arterials, to reach

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more deeply into the mussels and organsof the body. Illustration shows the major
human blood vessels. From the heart, blood is pumped into the aorta and
distributed to systemic arteries. The carotidarteries bring blood to the head, The
brachial arteries bring blood to the arms. The thoracic aorta brings blood down the

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trunk of the body along the spine. The hepatic, gastric, and renal
arteries, which branch from the thoracicaorta, bring blood to the liver,
stomach, and kidneys, respectively.The iliac artery brings blood to the legs.
Blood is returned to the heart throughtwo major veins. The superior vena
cava at the top and the inferiorvena cava at the bottom. The jugular

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veins return blood from the head.The basilic veins return blood from the arms.
The hepatic, gastric, and renalveins return blood from the liver,
stomach, and kidneys, respectively.The iliac vein returns blood from the legs.
The major human arteries and veins areshown credit modification of work by Marianna

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ruis Viareal arterials diverge into capillary beds. Capillary beds contain a large number ten
to one hundred of capillaries that branchamong the cells and tissues of the body.
Capillaries are narrow diameter tubes that canfit red blood cells through in single
file and are the sites for theexchange of nutrients, waste, and oxygen

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with tissues. At the cellular level. Fluid also crosses into the interstitial space
from the capillaries. The capillaries convergeagain into venules that connect to minor veins
that finally connect to major veins thattake blood high in carbon dioxide back to
the heart. Veins are blood vesselsthat bring blood back to the heart.

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The major veins drain blood from thesame organs and limbs that the major arteries
supply. Fluid is also brought backto the heart via the lymphatic system.
This podcast will be released episodically andfollow the sections of the textbook in the
description. For a deeper and understanding, we encourage you review the text version
of this work voice by voicemaker Dotayne. This was produced by Brandon Casturo as

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a creative common Sense production.