Circulatory System
Allied Health Sciences I
Instructor: Melissa Lewis
Functions of the
Circulatory System:

1) Circulates our blood all over our bodies via
heart pump
 2)Arteries, veins, and capillaries are the
structures that take the blood from the heart
to the cells and return it back to the heart
 3) Blood carries our oxygen and nutrients to
the cells and the waste products away.
 4)Lymph system returns the excess fluid back
to our general circulation. Our lymph nodes
produce lymphocytes to filter the pathogenic
bacteria.
Organs of the
Circulatory
System:
 The
heart, arteries, and capillaries make
up the circulatory system
 The blood and the lymphatic system
are also a part of the circulatory system
The Heart:
 Main
organ of the circulatory system
 About 5 inches long, 3.5 inches wide,
and weighs less than 1lb.
 Vital organ (four chambers)
 If our brain goes without blood flow for 5
or more seconds we lose
consciousness, 15-20 muscles
convulse, 6-9 min. brain damage.
The Heart cont…
 It
is located in the thoracic cavity b/w
the lungs, behind the sternum, in front
of the thoracic vertebrae, and above the
diaphragm.
 The hearts apex or tip lies on the
diaphragm and points to the left of the
body (this is where you can hear your
heartbeat the best
The Heart cont…
 Circulates
blood through blood vessels
throughout the body.
 Hollow muscular double pump
 At rest the heart pumps about 75
gallons of blood per hour.
 Beats or contracts 72-75 beats per
minute (100,000 times per day)
The heart cont…
 Pericardium
surrounds the heart.
 Made up of two layers of fibrous tissue
 There is a space b/w the two layers that
is filled a lubricating fluid called
pericardial fluid. This helps prevent the
two layers from rubbing together and
causing friction.
The Heart cont…

The myocardium is the muscle tissue of the
heart.
 The inner lining of the heart is a smooth
tissue called endocardium.
 This lining covers the heart valves and lines
the blood vessels.
 Septum- Thick muscular wall that separates
the right and left sides of the heart
 It completely separates the right side of the
heart from the left side of the heart. This
blood does not mix.
Structures leading to and
from the heart:
 1)
Superior vena cava- large venous
blood vessel that carries deoxygenated
blood from the upper body to the right
atrium.
 2)Inferior vena cava- large venous
blood vessel that carries deoxygenated
blood from lower body to right atrium.
Structures…cont…

3)Coronary sinus- carries blood from the right
heart muscle to the right atrium.
 4)Pulmonary artery- takes blood away from
the right ventricle to the lungs for oxygen.
 5)Pulmonary veins- bring oxygenated blood
from the lungs to the left atrium.
 6)Aorta- takes blood away from the left
ventricle to the rest of the body
Chambers and valves of
the heart:
 The
septum divides the heart into two
valves and each half divided into two
parts. This creates four chambers. The
two upper chambers are called right and
left atrium(atria). These may be referred
to as auricles. The two lower chambers
are called the right and left ventricles.
Chambers and valves of
the heart cont…
 The
heart has four valves that allow
blood to flow only in one direction.
These valves open and close during the
contracting of the heart. This opening
and closing keeps the blood from
flowing backwards or backing up into a
chamber of which it has left.
Two sets of Valves:
 Atrioventricular
 1)Tricuspid
Valves
valve- located b/w the right
atrium and right ventricle. (3 points of
attachment)
 2)Bicuspid or mitral valve- located b/w the
left atrium and left ventricle.
Two sets of valves cont…
 Semi-lunar
 1)
valves:
Pulmonary semilunar valve- found at the
orifice (opening) of the pulmonary artery.
The blood travels from the right ventricle
into the pulmonary artery, and then into the
lungs.
 2)Aortic semilunar valve- found at the
orifice of the aorta. This valve makes
possible for blood to flow from the left
ventricle into the aorta. The blood is not
allowed to flow back into the left ventricle.
Electrical Network of the
Heart:


There are a group of conducting cells located at the
opening of the superior vena cava into the right
atrium. These cells are called the sinoatrial node (SA
node) or the Pacemaker of the heart.
The SA node sends out an electrical impulse that
begins the heart beat. This impulse spreads over the
atria and this makes them contract or depolarize.
This causes the blood to flow from the atria chamber
to the atrioventricular openings. The electrical
impulse goes to the AV node. This is another group of
cells that is located b/w the atria and ventricular.
Electrical network
cont…

From the AV node, the electrical impulse goes
to the conducting fibers in the septum. These
fibers are called the atrioventricular bundle
(bundle of his).
 It divides into a right and left branch. These
branches each subdivide into a fine network
of branches that spread throughout the
ventricles called the purkinje network. The
electrical impulse shoots along the Purkinje
fibers to the ventricles causing them to
contract.
The Cardiac Cycle:
 The
SA node stimulates the contraction
of both atria. Blood flows from the atria
into the ventricles through the open
tricuspid and mitral valves. At the same
time, the ventricles are relaxed, allowing
them to fill with the blood. At this point,
since the semilunar valves are closed,
the blood cannot enter the pulmonary
artery or aorta.
Cardiac Cycle cont…

The AV node stimulates the contraction of
both ventricles so that the blood in the
ventricles is pumped into the pulmonary
artery and the aorta through the semilunar
valves, which are now open. At this point the
atria are relaxed and the tricuspid and mitral
valves close.
 The ventricles relax; the semilunar valves are
closed to prevent the blood flowing back into
the ventricles. The heart rests
(repolarization). The cycle begins again with
the signal from the SA node.
Cardiac Cycle cont…

This represents one heartbeat.
 This cycle takes 0.8 seconds. Average
heartbeat is 72-75 bpm
 An electrocardiogram (ECG or EKG) is used
to record the electrical activity of the heart
that causes the contraction (systole) and the
relaxation (diastole) of the atria and ventricles
during the cardiac cycle.
 The way the heart is made allows it to
function as a double pump. It has a right and
left side.
Cardiac Cycle Cont….

Right heart- deoxygenated blood flows into
the heart from the superior and inferior vena
cava to the right atrium to the tricuspid valve
to the right ventricle through the pulmonary
semilunar valves to the pulmonary artery,
which takes blood to the lungs for oxygen.
 Left Heart- Oxygenated blood flow into the
heart from the lungs by the pulmonary veins
to the left atrium through the bicuspid (mitral)
valve to the left ventricle to the aorta to
general circulation
 These two side work at the same time-thus a
double pump.
Paths of Circulation

Cardiopulmonary Circulation- takes
deoxygenated blood from the heart to the
lungs where carbon dioxide is exchanged for
oxygen. In the lungs the arteries branch into
many small arteries called arterioles. These
connect to dense capillary beds that lie in the
alveoli lung tissue. This is where the O2 and
CO2 exchange takes place: The CO2 leaves
the RBC’s and is discharged in the air in the
alveoli to be exhaled by the lungs. The O2
from the air in the alveoli combines with the
hemoglobin In the RBC’s. From these
capillaries the blood travels into small veins
or venules.
Paths of Circulation
Cont…

The venules from the R and L lung form large
pulmonary veins. These veins carry the
oxygenated blood from the lungs back to the
heart and into the L atrium.
 Systemic/General Circulation- (systemic
circulates blood from the heart to the tissues
and cells and back to the heart). The aorta is
the largest artery in the body and it branches
first into the coronary artery and this artery
takes blood to the myocardium (heart or
cardial muscle).

Paths of Circulation
Cont…
As the ascending aorta comes up to the top
of the heart it forms and arch. There are 3
branches that come from this arch: The
brachiocephalic, the left common carotid and
the left and the right subclavian arteries.
 These arteries carry blood to the arms, neck
and head. From the aortic arch, the aorta
descends along the mid-dorsal wall of the
thorax and abdomen. Many arteries branch
off the descending aorta, and carries
oxygenated blood to the body
Paths of circulation
Cont….

The blood then travels through the branched
arteries to the arteioroles and then to
numerous capillary beds and to the tissues.
Hormones, nutrients oxygen and other
materials are transferred from the blood as
well as other hormones and nutrients from
the small intestines and liver are also
absorbed by the blood. Blood then runs from
the capillaries first into tiny veins, through
increasingly larger veins, and finally into one
or more of the veins which exit fro the organ.
Eventually the deoxygenated blood empties
into the inferior vena cava and goes to the R
atrium. The superior vena cava also carries
deoxygenated blood from the upper body to
the R atrium.
As Blood Flows:

1. Deoxygenated blood
from body tissue
 2. Superior/inferior
vena cava
 3. Coronary Sinus
 4. Right Atrium
 5. Tricuspid valve
opens
 6. Right Ventricle
 7. Pulmonic valve
 8. Pulmonary artery
 9. Both lungs
 10. CO2 & O2
exchange (alveolar via
pulmonary veins)












11. Left atrium
12. Mitral valve opens
13. Left ventricle
14. Aortic valve opens
15. Aorta-transplants
oxygenated blood to
body cells
16. Arteries
17. Arterioles
18. Capillaries
19. Venules
20. Veins
**VERYIMPORTANT**
LEARN THIS PLEASE!!
Paths of circulation
cont…
 Coronary
circulation- brings oxygenated
blood to the heart muscle. It has two
branches: L and R coronary arteries.
 There are many branches of these
arteries and the gas exchange takes
place. The deoxygenated blood returns
through the coronary veins to the
coronary sinus. The coronary sinus is a
trough in the posterior wall of the R
atrium.
Paths of circulation
cont…
 Portal
circulation- Takes blood from the
organs of digestion to the liver through
the portal vein.
 Fetal circulation- only occurs in the
pregnant female. The fetus obtains
oxygen and nutrients from the mother’s
blood.
Blood Vessels:

There three types of blood vessels. Arteries,
capillaries and veins.
 Arteries carry oxygenated blood away from
the heart to the capillaries where gas
exchange takes place. One exception is the
pulmonary artery. Arteries are elastic,
muscular and thick walled. The thickness of
the arteries makes them the strongest of the
three types of blood vessels
Blood vessels cont…
 The
artery walls are composed of three
layers:
 Tunica
adventitia or externa is the outer
layer. This layer is composed of fibrous
connective tissue with bundles of smooth
muscle cells and this make up allows the
great elasticity. The arteries have to be
elastic due to the sudden large increases
in internal pressure, created by the large
volume of blood forced into them at each
heart contraction. With arteriosclerosis the
arteries become hardened and the systolic
blood pressure increases greatly.
Blood vessels cont….
 Tunica
media is the middle arterial
layer. It is composed of muscle cells
arranged in a circular pattern and this
consists of three layers: endothelium,
areola, and elastic tissue. The
endothelium allows for the smooth flow
of the blood through the artery
Blood vessels cont…
 Tunica
intima is the inner layer and
consists of three smaller layers:
endothelium, areolar, and elastic tissue.
The endothelium allows for the smooth
flow of the blood through the artery
Blood vessels cont…

Capillaries

Capillaries are the smallest of the blood vessels
and they can only be seen through a compound
microscope. Capillaries connect the arterioles with
the venules. As the arteries branch they eventually
lose their connective tissue and muscle layers and
only an endothelial cell layer remains. This
endothelial cell layer makes up capillaries. The
walls are super thin and allow for the permeability
of many cells and substances. Also tiny openings
in the walls of the capillaries allow white blood
cells to leave the bloodstream and enter the tissue
spaces to help destroy invading bacteria.
Veins:
 Carry
deoxygenated blood away from
capillaries to the heart
 3 layers: tunica externa, tunica media,
& tunica intima
 Less elastic & muscular than arteries
 Have thinner walls than arteries
 So, veins collapse easily when not filled
with blood
Veins cont…:
 Veins
contain valves along their whole
length
 So the venous blood only flows in one
direction (towards the heart)
 Valves prevent the backflow of blood
away from the heart
Blood Pressure:

Systolic = The top number
 It is the pressure in the heart when the heart
is contracting
 Diastolic = The bottom number
 It is the pressure in the heart when the heart
is resting or in between beats
 Example: If someone’s BP is 102/76 The
102 is their systolic reading the the 76 is their
diastolic reading
 Average BP is 120/80 mm Hg for an adult
Pulse Sites:

1. Brachial artery-located in crook of elbow
 2. Common carotid artery-located in neck
 3. Femoral artery-located in groin/inguinal
area
 4. Dorsalis pedis artery-located on top of
foot
 5. Popliteal artery- located behind the knee
 6. Radial artery- located at wrist on thumb
side
 7. Temporal artery-located on side of
forehead
Heart Diseases

Arrhythmia or dysrhythmia- any change or
deviation in the normal rhythm of the heart
 Brady cardia- Slow heart rate (less than 60
bpm)
 Tachycarida- fast heart rate (more than 100
bpm)
 Murmurs- indicates some defects in the
valves of the heart. These are classified
according to the valves they affect or
according to the hearts cardiac cycle. If the
murmur occurs while the heart is contracting
it is called a systolic murmur if it is while the
Heart diseases cont…
 Mitral
valve prolapse- a condition in
which the valve b/w the L atrium and L
ventricle closes imperfectly. Symptoms
include fatigue, palpitations (heart feels
like its racing), headache, chest pain
and anxiety.
Infectious diseases of the
heart

Bacteria or viruses usually are the cause of
infectious disease of the heart and are
treated with antibiotics.
 Pericarditis- inflammation of the outer
membrane covering the heart. Symptoms are
chest pain, cough, dyspnea (SOB or difficulty
breathing) , rapid pulse, and fever
 Myocarditis- inflammation of the heart
muscle. Symptoms are the same as above.
Infectious diseases of the
heart cont…

Endocarditis- inflammation of the membrane
that lines the heart and covers the valves.
This causes the formation of rough spots in
the endocardium,which may lead to the
development of a fatal blood clot (thrombus)
 Rheumatic heart disease- may result from a
person having frequent strep throat infections
during childhood; these infections may lead to
rheumatic fever. The antibodies which form to
protect the child from the strep throat or
rheumatic fever may also attack the lining of
the heart, especially the bicuspid or mitral
valve. If you have strep throat, it is important
that you be treated with antibiotic therapy
Coronary Artery Disease

These involve the coronary artery, which
supply the heart muscle (myocardium) with its
blood supply.
 Angina Pectoris- severe chest pain when the
heart does not receive enough oxygen. This
is a symptom of an underlying problem with
the heart not receiving enough oxygen due to
impaired coronary circulation. The pain
radiates from the precordial area to the left
shoulder and down the ulnar nerve in the L
arm. It comes on suddenly by stress or
physical exhaustion. It can be treated with
nitroglycerine.
Coronary Artery Disease
cont…

Myocardial infarction- “heart attack” and is
caused by a lack of blood supply to the heart
muscle. Can be caused by a blockage of a
coronary artery as a result of arteriosclerosis
or atherosclerosis. The amount of oxygen
tissue damage depends on the amount of
heart muscle that is deprived of oxygen or
blood. Symptoms are crushing, severe pain
radiating to the L shoulder, arm neck and jaw.
Pts. C/o of nausea, increased perspiration,
fatigue, and dyspnea.
Heart Failure

This occurs when the ventricles cannot
effectively contract to remove the blood and
therefore it pools in the heart. If the L ventricle
fails, dyspnea occurs. If the R ventricle fails,
engorgement of organs with venous blood
occurs, as well as edema ( excessive fluid in
the tissues) and ascites (abdominal
accumulation of serous fluid in the abdominal
cavity). Other symptoms include lung
congestion and coughing)
Congestive Heart
Failure
 This
is similar to heart failure, but in
addition there is edema of the lower
extremities. Blood backs up into the
lung vessels, and fluid extends into the
air passages. Treatment is with
cardiotonics (drugs that strengthen and
slow the heart beat such as digoxin)
and diuretics (drugs which reduce the
amount of fluid in the body).
Rhythm/Conduction
Defects
 This
is when there is a defect in the
conduction system of the heart.
 Heart Block- Interruption of the AV node
message from the SA node.
 First
degree heart block is characterized by
a delay at the AV node before the impulse
is transmitted to the ventricles.
Rhythm/conduction defects
cont…

Second degree heart block can be in two
forms. One occurs I cycles of delayed
impulses until the SA node fails to conduct to
the AV node, then returns to near normal. A
second form is characterized by a pattern of
only every second, third or fourth impulse
being conducted to the ventricles. This
causes a decreases in heart output and
usually progresses in to the third degree.
Rhythm/conduction defects
cont…

Third degree heart block is known as
COMPLETE HEART BLOCK. There is no
impulse carried over from the pacemaker.
There is a built in safety factor. The atria
continue to beat 72 bpm while the ventricle s
contract independently at about half the atrial
rate, adequate to sustain life by resulting in a
severe decrease in cardiac output.
Rhythm/conduction defects
cont…

Premature contractions is an arrhythmia
disorder, which occurs when an area of the heart
known as an ectopic pacemaker and sparks and
stimulates a contraction of the myocardium.
There are three types:



Premature atrial contractions (PACs) cause the atria to
contract ahead of the anticipated time.
Premature junctional contractions (PJCs) have the
ectopic pacemaker focused at the junction of the AV
node and the bundle of his. Usually there is no clinical
significance. Causes: stress, nicotine, caffine, or
fatigue
Premature ventricle contractions (PVCs) originate in
the ventricles and cause contractions ahead of the
next anticipated beat. Can be benign or deadly.
Fibrillation
Occurs when the muscle contracts
randomly without any coordination. This
is a life threatening condition. An
electrical device called a defibrillator is
used to discharge a strong electrical
current through the patients heart
Disorders of the blood
vessels

Aneurysm- ballooning out of an artery by a thinning
arterial wall, caused by a weakening of the blood
vessels. Pain or pressure but no symptoms
 Atherosclerosis- occurs when deposits of fatty
substances form along the walls of arteries
 Arteriosclerosis- thickening of the walls b/c of a loss
of elasticity as aging occurs
 Gangrene- death of body tissue due to an insufficient
blood supply caused by disease or injury
 Phlebitis- Inflammation of a lining of a vein,
accompanied by clotting
 Embolism- traveling blood clot. Pulmonary embolism
is in the lungs
Disorders of the blood
vessels

Varicose veins- swollen veins which result
from a slowing down of blood flow back to the
heart
 Hemorrhoids- varicose veins in the lower
rectum and the tissues around the anus
 Peripheral vascular disease- blockage of
arteries
 Hypertension- high BP, “Silent Killer” one in
five Americans has it
 Hypotension- low BP
Disorders of the blood
vessels
 Transient
Ischemic Attacks- these are
temporary interruptions of the blood flow
to the brain. Pts may experience stroke
like symptoms which lasts 24 hours
 Cerebral vascular accident- (Stroke)
Sudden interruption of blood supply to
the brain. Results in loss of O2 to brain
cell causing impairment of the brain
tissue and/or death. (Sx = hemiplegia)