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The circulatory system is made up of the
heart, blood vessels, and the blood.
The circulatory system functions to transport
waste products, oxygen, carbon dioxide,
hormones, urea, and nutrients.
The circulatory system also plays a role in
the body’s immune system.
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The circulatory system is made up
of the heart, blood vessels, and
blood.
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Blood vessels include arteries,
veins, and capillaries.
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The heart is a two-pump system
made of muscles that pushes blood
through out the body.
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One pump sends blood to the lungs
and the other sends blood to the
rest of the body.
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Pulmonary circulation  the blood that flows from the
heart to the lungs
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Systemic circulation  the blood that flows from the
heart to the rest of the body
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The heart is located in the center of the chest and
is surrounded by the pericardium.
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The pericardium is a fluid-filled sac.
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The heart has 3 layers.
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The thin outer layer is the epicardium, which is
home to the coronary arteries.
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Coronary arteries give the heart its blood supply
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The muscular middle layer is the myocardium.
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The thin inner layer lining the heart is called the
endocardium.
The heart pumps around 5 liters
of blood per minute and contracts an
average of 70-75 times per minute.
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The heart consists of 4 chambers.
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Right side of the heart
1.
2.
3.
4.
Deoxygenated blood from the body comes into the right atrium
via the superior vena cava (vein) and the inferior vena cava
(vein).
The deoxygenated blood passes through the tricuspid valve and
moves into the right ventricle.
Deoxygenated blood leaves the right ventricle via the
pulmonary valve and enters the pulmonary artery.
This blood enters the lungs and exchanges its CO2 for O2.
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Left side of the heart
1.
2.
3.
4.
Oxygenated blood from
the pulmonary vein enters
the left atrium.
Oxygenated blood moves
through the mitral valve
(bicuspid) and into the left
ventricle.
Oxygenated blood moves
from the left ventricle
through the aortic valve to
the aorta.
Oxygenated blood is
transported all over the
body via the aorta.
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The peripheral circulation is make up of
the pulmonary circulation and the
systemic circulation.
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Blood runs in a closed system through
blood vessels and the four chambers of
the heart.
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The three main types of blood vessels in
this closed system are arteries, veins, and
capillaries.
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Blood is transferred to and from the lungs
by the pulmonary artery, capillaries in the
lungs, and the veins that drain those
capillaries.
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Blood is transferred to the body and back
via the systemic circulation, which is
made up of the aorta and systemic
arteries and veins.
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Arteries and veins are made of three main layers.
1. Tunica adventitia  outer layer
2. Tunica media  smooth muscle layer
3. Tunica intima  the inner layer
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Arteries carry blood away from the heart.
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Arteries = Away
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Arteries carry oxygenated blood
(except for the pulmonary artery)
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Arteries are very elastic and are
thick-walled.
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Arteries do not have valves.
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A pulse is taken from an artery.
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The blood that comes out of an
artery is usually bright red
because it is oxygenated.
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The largest artery in the body is the aorta.
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Smaller arteries branch off of the massive
aorta.
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Arterioles are the smallest arteries
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Most of the time phlebotomists will not
draw from arteries because they are
under high pressure and are buried
deeper in the body.
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Arterial punctures are used to evaluate
the body’s acid/base balance, O2 &
CO2 concentration.
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Veins carry blood to the heart
 Veins carry deoxygenated blood back to
the heart (except for the pulmonary
vein)
 Veins have thin walls and are not very
elastic.
 Veins have valves to prevent backflow.
 There is no pulse in a vein.
 The blood that comes out of a vein is
dark red because of its lack of
oxygen.
 Small veins are known a venules.
Veins
 Venous blood is the most common specimen collected
by the phlebotomist.
 Veins are more accessible because they are closer to
the skin’s surface.
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Capillaries are the smallest major
blood vessels in the body.
They are one cell layer thick.
Capillaries are the site of gas
exchange between the blood and
body cells.
The cells get O2 and they give up
CO2 and waste products.
At one end of a capillary is an
arteriole and at the other is a
venule.
Capillaries are the site of
nutrients and waste product
exchange between the blood and
the tissue cells.
Small
Smallest
Large
Vein  Venules  Capillaries  Arterioles  Artery
The antecubital fossa of the upper extremities is the
preferred site of venipuncture.
 The antecubital fossa is the depressed area in front
of the elbow.
 This is the first area a phlebotomist should check
because it is home to major arm veins that lie close
to the surface.
 Veins are easier to locate and puncture with a
needle.
 These veins are usually large enough to receive the
needle and should be visible or palpable (able to
touch) after application of the tourniquet.
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The major surface veins are called
the antecubital veins.
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There are 3 major veins located in
this area.
1.
Median cubital vein
 1st choice
 Large
 Tends not to move during
venipuncture
2.Cephalic
vein 
 2nd choice
 More difficult to locate
 Sometimes moves
 Can be the only vein to
palpate in obese patients
3. Basilic vein 
 3rd choice
 Least anchored
 Located near the brachial artery
 If a needle is inserted too deep the
artery could be punctured.
Do not draw blood from an arm that has IV fluids
running.
 The fluid will alter the results of tests run on that
blood.
 Do not draw blood from an artificial fistula site (AV),
used in dialysis.
 There are some veins that should not be used for
venipuncture.
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Sclerosed veins
Tortuous veins
Thrombotic veins
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Sclerosed veins
 Veins that are hard and cordlike
 Can be caused by disease,
inflammation, chemotherapy,
or repeated venipunctures.
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Tortuous veins
 Winding or crooked veins
 Susceptible to infection
 Blood flow is impaired so specimen may
lead to erroneous (incorrect) results
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Thrombotic veins
 Veins that have clots
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Veins of the back of the hand and wrist are acceptable
for drawing blood.
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NEVER draw from veins located on the underside
of the wrist.
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Legs, ankles, and foot veins are not to be used
for routine venipuncture.
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Taking blood from these sites can cause
complications like phlebitis and thrombosis.
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Each facility and doctor has a policy for drawing
on legs, ankles, and feet.
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All arteries are not to be used for venipuncture.
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Arterial puncture is to be done by specialized personnel only.