1. Transport (nutrients, wastes, oxygen, CO2, homones)
2. Immunity (leukocytes, antibodies)
3. Temperature regulation (cold, constricts; hot, dilates)
4. Penile erection
COMPONENTS OF CIRCULATORY SYSTEM
3. Blood vessels (arteries, capillaries, veins)
4. Lymph vessels
The heart is the simplest organ in the body. It does only one thing: pumps blood. It beats
42 million times a year. It’s about the size of your clenched fist. Some of you have big
fists, some have smaller fists. Its location is deep to the sternum. Take your left fist and
place it on the sternum, then angle the bottom of your wrist to the left. When you say the
Pledge of Allegiance, your hand is not over your heart. It’s not on the left, it’s in the
center. The heart is located in the MEDIASTINUM, which is the central compartment
of the thoracic cavity.
Layers of tissues around the heart:
1. PERICARDIUM: surrounds the heart (like a heart in baggie). The function is to
lubricate the heart, so as it beats, it won’t rub against anything. The pericardium
is divided into two layers with a space between them filled with fluid;
a. PARIETAL PERICARDIUM (outermost layer of thoracic cavity). Two
i. SEROUS LAYER (simple squamous epithelium). Watery fluid.
ii. FIBROUS LAYER (moderately dense fibrous connective tissue)
b. PERICARDIAL CAVITY (Between the two layers, where the serous
c. VISCERAL PERICARDIUM (aka EPICARDIUM) Outermost layer of
heart. It also has two layers:
i. SEROUS LAYER
ii. FIBROUS LAYER
2. MYOCARDIUM: The heart muscle itself (myocardium), made of what tissue?
3. ENDOCARDIUM: The lining on the inside of the heart. Has two layers:
a. ENDOTHELIUM (simple squamous epithelium that provides a smooth
surface for the blood to pass by)
b. Loose fibrous connective tissue (deep to the endothelium)
PERICARDITIS: inflamed outer layer of heart.
Fluid accumulates in pericardia cavity, putting pressure on heart improper beat
Pericarditis can be caused by damage to the blood vessels blood leak into pericardial
cavity pressure improper beat. Pericarditis can lead to pericardial friction rub,
adhesions, and excess fluid in the pericardial cavity.
CARDIAC TAPENADE: In severe cases of pericarditis, or if there is a stab wound to the
heart wall that causes fluid to exude into the pericardial cavity, the excess fluid compresses
the heart and diminishes the heart’s ability to pump. Don’t get this confused with arrhythmia
that is caused from a problem with the SA or AV node. The irregular heart beat from cardiac
tapenade is caused from fluid entering the pericardial cavity and putting pressure on the
heart. Treatment is to stick a needle in the cavity and drain the fluid.
ENDOCARDITIS (more serious):
Bacteria enter bloodstream (dental procedures, IV drug abuse, catheter) damage to
lining and valves blood clots.
Those who already have damaged heart valves need prophylactic antibiotics.
Don’t get endocarditis (bacterial infection) mixed up with pericarditis, which can
lead to cardiac tapenade.
THE HEART IS TWO PUMPS: LEFT AND RIGHT
LEFT PUMP: From lungs to body
RIGHT PUMP: From body to lungs
Each pump has two types of chambers: ATRIUM and VENTRICLE
The superior and inferior vena cavae (with deoxy blood) empty into the right atrium.
It pours through the TRICUSPID (RIGHT AV) VALVE into the R Ventricle.
R Atrium contracts, pushes blood into the ventricle ventricle expands, then contracts
with force. To prevent the blood from going back up into the atrium, need a valve.
Valves are like a swinging door that can only open one direction. But you can push
against this door, since it’s only tissue. But if you tie a rope to the doorknob, it won’t be
able to go the wrong way. Rope = CHORDAE TENDONAE, which is attached to
pieces of myocardium called PAPILLARY MUSCLES. The contraction pulls on the
chordae tendonae to close the valves, preventing a PROLAPSED VALVE (turned inside
With the ventricular contraction, blood can go only one way: into the PULMONARY
ARTERY (the only artery with deoxy blood). When the ventricles relax, the
PULMONARY SEMILUNAR VALVE closes to prevent blood from going from the
pulmonary artery back into the right ventricle. Does it have a chordae tendonae? No; the
blood is not being forced back, it just falls back, so there’s not as much pressure.
Blood then goes into lungs, gets oxygenated, and returns on the left side through the
PULMONARY VEINS (the only veins with oxy blood), into the LEFT ATRIUM, and
down through the MITRAL VALVE (BICUSPID VALVE) into the LEFT
VENTRICLE, (with chordae tendonae), which contracts, then the blood goes past the
AORTIC SEMILUNAR VALVE, into the AORTA, and back to the body.
• Therefore, the left ventricle is the chamber which is responsible for generating the
largest pressure upon contraction.
The semilunar valves are located between the ventricles and the great arteries.
SUMMARY OF BLOOD FLOW
Deoxy blood sup/inf vena cava R atrium tricuspid valve with chordae tendonae
R ventricle pulmonary semilunar valve pulmonary artery lungs pulmonary
veins Left atrium mitral (bicuspid) valve with chordae tendonae left ventricle
aortic semilunar valve aorta rest of body.
If there is stenosis (blockage) of the mitral valve, where will the blood back up into?
The pulmonary circulation.
The pressure of blood against blood vessel walls is called blood pressure.
Blood pressure is recorded systole over diastole. Normal resting blood pressure is said to
be 120/80. When blood pressure is too high, it is called HYPERTENSION.
The sound your heart makes when it is beating is the sound of the valves closing.
The heart normally beats at a rate of 60-80 beats per minute. A faster or slower heart rate
is an indication of a problem.
The left and right ventricles contract at the same time = SYSTOLE.
When the ventricles are relaxed = DIASTOLE.
At which stage do the atria contract? Diastole.
Start of Systole: Closing of valves (tricuspid and mitral) causes blood to hit the valves,
making a sound (“Lub”). Systole of the ventricle means that this chamber is
End of Systole: Closing of semilunar aortic and pulmonary valves causes blood to hit the
valves, making a sound (“Dub”)
Lub-Dub is the sound of the blood hitting the closed valves.
Start of Systole: Closing of the large valves (tricuspid and mitral) = “LUB”
sound from blood hitting them.
End of Systole: Closing of semilunar valves (aortic and pulmonary)= “DUB”
sound (“Dub”) from blood hitting them.
If the valve leaks, it doesn’t close all the way = HEART MURMUR = Lub-squirt.
Most murmurs are benign; fairly common, esp. in babies and some adults.
PROLAPSED VALVE is more serious.
Mitral valve is most likely to prolapse because it pumped the hardest. See how much
thicker the left ventricle is? Mitral Valve Prolapse is the most common heart valve
disorder. Might need artificial valve.
• The Sapien Transcatheter Heart Valve (THV) is made of cow tissue and polyester
supported with a stainless steel mesh frame. To replace the diseased valve, the
Sapien THV is compressed into the end of a long, thin, tube-like device called a
delivery catheter, which is slightly wider than a pencil, and inserted into the
femoral artery through a small cut in the leg and threaded to the site of the
What controls the heart beat?
There is a small region in the right atrium = SA NODE (Sino-atrium node) = pacemaker
of the heart. Its job is to speed up or slow down the heart rate as needed. SA node sends
an electrical signal (action potential) to the AV NODE (atrio-ventricular node) atrium
contraction pauses transmitted to both ventricles via conduction of myofibers sends
the action potential to all parts of the heart so it can contract.
• The heart does not need a nerve to stimulate it to contract; rather, specialized
heart cells can spontaneously start an action potential that spreads to depolarize
the rest of the cardiac muscle cells.
• First the Sinoatrial (SA) node starts an action potential which causes the atria to
• This depolarization will then reach the AV node at the bottom portion of the right
atrium and there is a delay here because these cells are so small in diameter.
• Another delay in the transmission of the depolarization at the bundle of His (AV
bundle) because these special heart cells travel through the atrioventricular
septum which is non-conductive fibrous connective tissue. The Bundle of His
slows down the electrical pathway to give the atria a chance to finish contacting.
• Next, the depolarizing event travels through the left and right bundle branches,
found in the interventricular septum, to finally arrive at the Purkinje fibers in the
lateral walls of the myocardium of the ventricles.
Normal heart rate is about 60-80 beats a minute
Tachycardia means the heart beats too fast (>100 BPM).
Bradycardia means the heart beats too slowly (<50 BPM).
Marathon runners may have bradycardia because their heart is in such good
shape…before doing CPR, check for heart beat for a full 10 seconds!
We can see the heart’s electrical signals on an electrocardiogram, called an EKG (also
known as ECG; both stand for Electocardiogram). It shows the contractions of the atria
and ventricles. Each bump, peak, and depression on the EKG readout is coded with a
letter (either P,Q,R,S,T, or U). Doctors evaluate an EKG by the height and width of each
of these peaks and depressions. Don’t get an EKG (for the heart) mixed up with an EEG
(for the brain)!
24 Hour Scanner
Some people only have symptoms once in a while, and the symptoms do not
occur during the doctor’s examination.
They can be sent home with a device that reads their heart beats for 24 hours.
The doctor can print out the scanned pages to see if an abnormal heart beat
ARRHYTHMIA = problem with the SA or AV node improper heart beat.
Treatment is medicines or a pacemaker.
FIBRILLATION is when the heart beat is not really present…it just vibrates. A heart in
fibrillation does not contract rhythmically; it just quivers without pumping blood. It
needs an electric shock from a defibrillator. This machine is never used when someone’s
heart is beating with a lub-dub sound, even if it is irregular, because it can cause the heart
to stop. Whatever caused the fibrillation in the first place is not treated, so it may not
work, but it’s worth a try! Most large public facilities have them. There are three on this
campus. Disneyland has one every 100 yards.
If someone with a pacemaker dies, does their heart keep beating?
No. A pacemaker can only stimulate an irregularly beating heart, not a dead one. The
pacemaker would almost certainly be triggered, since it would detect the absence of a
regular heartbeat, but it would be to no avail.
THE HEART NEEDS ITS OWN BLOOD/O2
The endocardium gets plenty of O2 from the blood cells that touch this layer as they
travel through the heart, but the oxygen does not diffuse all the way into the myocardium,
which is a deeper layer. Therefore, the myocardium needs its own blood supply by
CORONARY ARTERIES and VEINS. They are on the surface of the heart, and there
are four of them.
The Four Main Coronary Arteries
Right Coronary (the left one is too short to be counted)
Someone with a quintuple bypass also has blockage in a branch off one of
Another important vessel
The coronary sinus is a collection of veins joined together to form a large vessel that
collects blood from the myocardium of the heart and delivers it into the right atrium.
The more you exercise, the more branches of the coronary arteries are formed between
themselves, and the better the blood supply to the heart.
When blood vessels fuse together where they meet it is said that they ANASTOMOSE.
This is a safety mechanism that allows blood to get through if one of the vessels gets
If one of the four coronary arteries becomes clogged, ISCHEMIA (lack of oxygen) to
part of the heart muscle will result. This is a painful condition, and the pain of it is called
ANGINA (heart pain). If nothing is done immediately to increase the blood flow, the
myocardial tissue can die; this condition is called a HEART ATTACK.
People who have an angina attack can take nitroglycerine as a tablet under the tongue that
dissolves quickly. This medicine will dilate the blood vessels. When a person has their
first angina attack, the doctor will order an ANGIOGRAM to look for a narrowing in an
artery. If a coronary artery is found to have a severe blockage, they can do a
CORONARY BYPASS. In this procedure, the doctor takes another blood vessel graft
(from the greater saphenous vein in the thigh) and sews it in around the blockage. For
double or triple bypasses, that’s how many vessels are affected.
ANGINA: heart pain, usually caused from not enough oxygen to the
ISCHEMIA: lack of blood/oxygen
MYOCARDIAL INFARCTION: heart attack from blood clot in coronary
artery, causing ischemia, which causes angina
Not enough blood to the heart’s myocardium layer MILD ISCHEMIA
severe pain: ANGINA (also can be called angina pectoris)
Treatment is nitroglycerine to open arteries
Complete blockage not enough O2 to that area = SEVERE ISCHEMIA that
part of heart muscle dies = MYOCARDIAL INFARCTION.
Heart muscle never regenerates. If a large area dies, person will die.
What are symptoms of a heart attack? Chest pain, pain down left arm, shortness of breath,
nausea, tight pressure in chest. A common symptom is death. 50% of first heart attacks
are fatal within 2 hours. If a person receives good treatment in the first 2 hours, they are
more likely to survive. About ¾ million people die each year from heart attacks.
A drug that can stop heart attacks in progress by dissolving clots is t-PA
Angioplasty is a surgical procedure to clean out a clogged artery.
A beta blocker is a drug that slows down the heart rate
Aspirin reduces blood clot formation
Nitroglycerine dilates the coronary arteries so more blood can get in.
FUN FACTS ABOUT THE HEART
--According to German researchers, the risk of heart attack is higher on Monday than any
other day of the week; there is more stress on that day.
--A Giraffe’s heart is 2 feet across.
--Heart disease is a big killer, but what animal causes the most human deaths?
An annual human death due to sharks is 10; however, 100 more people die each year
from being stepped on by cows.
--But the whitetail deer causes the most deaths because of all the traffic accidents they cause.
CIRCULATORY DISEASE CONDITIONS
The leading cause of untimely death in the Western countries of the world is
There are several hereditary factors that influence whether a person will get
1. family history of heart attack
2. gender (males are high risk)
3. race/ethnicity (African Americans high risk)
Whether or not you have a hereditary factor, there are some things you can do to prevent
heart disease with diet and exercise. Included in this is knowing your cholesterol level,
lowering your LDL intake, use olive and canola oil rather than butter/cream.
Some studies also suggest that antioxidant vitamins (A, E, and C) may help, but
remember that too much vitamin A and E cause a lot more harm to the liver than good to
Causes of High Blood Pressure
ARTERIOSCLEROSIS (hardening of the arteries): caused by a build-up of calcium
deposits in the artery wall; artery cannot expand with blood surges. Tends to be
hereditary. The blood vessel becomes hard like a rock; it can’t expand or contract, causes
increase in blood pressure. Diet and exercise don’t help this much. Both arteriosclerosis
and atherosclerosis cause high blood pressure.
ATHEROSCLEROSIS (build-up of fat and cholesterol in the arteries): caused from
eating fatty food = build-up of fat inside artery narrowing of artery Spasm shut or
When fat builds up in a lump in one place, it is called a PLAQUE. It causes the lumen to
narrow, restricting blood flow. If this fatty plaque breaks off and travels in the
bloodstream, it is now called an EMBOLISM. An embolism can also be made of blood.
How a thrombus becomes embolism
If a platelet catches on a piece of this fat, it can start a blood clot (thrombus).
If a piece of the clot (thrombus) breaks off and enters the circulation, it is now
called an embolism, it can lodge in a smaller blood vessel and block the oxygen
to all the tissue past that point, and the tissue dies.
A thrombus is made of BLOOD. It is a blood clot that is located on the inside
wall of a blood vessel (usually a vein but not always) and it has not moved
An embolism can be made of FAT or BLOOD. It is either a build up of fat in a
vessel (usually an artery but not always) that has broken off a piece or a blood clot
(usually in a vein but not always) that has broken off a piece. It travels and gets
lodged in a smaller vessel somewhere.
If the embolism lodges in the coronary arteries it is a myocardial infarct (Heart
If the embolism lodges in an artery in the brain it is a stroke
If the embolism lodges in the lungs PULMONARY EMBOLISM.
An ANGIOGRAM is a procedure to inject dye into the arteries and x-ray to see if there
is narrowing (sclerosis) of a vessel. This can be done anywhere in the body that is of
interest, but frequently it is done to check the coronary arteries.
If an artery is too narrow, an ANGIOPLASTY can be performed to open it up. This
involves sticking a balloon into the artery and inflating it, causing the vessel to enlarge a
little to increase blood flow. This can be done anywhere in the body, but is frequently
done in coronary arteries.
For an artery that has become extremely narrow from plaques, you can do a
CORONARY BYPASS. Take another blood vessel graft (a superficial vein from the
thigh) and go around the blockage. For double or triple bypasses, that’s how many
vessels are affected. People who exercise have the same number of heart attacks as those
who don’t, but they tend to survive them.
Even a small clot can be a problem. If it happens to enter the interior of the heart and
lodge in the wall of the atrium, it can block the conduction of the signal of the AV node
VENTRICULAR FIBRILLATION.(the ventricles are unable to pump blood
efficiently due to rapid, random contraction of cardiac muscle fibers). The muscle doesn’t
contract as a unit.
Treatment is defibrillate with electric shock closes down heart maybe it will restart.
High blood pressure is due to high pressure of blood against the walls of the blood vessels;
the blood vessels compensate by developing a thicker wall. The vessels can no longer
expand during systole, so the vessel gets thicker and thicker, and the blood pressure goes up
more. If the blood pressure gets too high, an ANEURYSM can form, which is a weakening
in the wall of the blood vessel, causing it to expand like a balloon. If it ruptures, it’s very
dangerous. The aorta is the first artery that leaves the heart. It is under high pressure, so it is
susceptible to rupture; you’ll be dead in three heart beats. Can also get aneurysms in the
brain that cause stroke. Aneurysms have no symptoms.
Coronary artery disease terms
Atherosclerosis – fatty deposits
Angina pectoris – chest pain
Myocardial infarction – blocked coronary artery
Silent ischemia – no pain or warning before heart attack
Stroke – ruptured blood vessel in the brain. Also called Cerebral Vascular
Clarification of Terminology
A blocked artery can occur anywhere in the body.
A blocked CORONARY artery is what causes a heart attack. The coronary
arteries are those that supply the myocardium of the heart.
Ischemia is a lack of oxygen from lack of blood flow. It can occur anywhere in
When there is ischemia in your leg from sitting on it wrong, it is from lack of
blood flow to the muscles of your leg. it gives you a pins and needles feeling but
it will repair itself when you restore the blood flow.
When there is ischemia in the heart, it is from a lack of blood flow to the
myocardium of the heart (the actual muscle tissue of the heart).
The only arteries that supply the heart are the coronary arteries. Therefore,
ischemia in the heart can only be caused by some blockage in at least one
In this case, a heart attack will ensue because ischemia in the heart causes
permanent damage quickly.
Fortunately. there are four coronary arteries, so many people can survive a heart
attack if not all of them are blocked. That's why some heart attacks are called
"mild heart attacks"; only a small piece of the myocardium died off and the heart
is able to keep beating properly.
When blockage in a coronary artery is detected by an angiogram before the artery
closes completely, a surgical bypass procedure can be done.
If only one of the coronary arteries is affected, it is called a coronary bypass
procedure. If two arteries are a problem, it is called a double bypass. If three are
involved, it is a triple bypass. If all four are getting clogged, they will do a
quadruple bypass, the most serious type of situation.
Predictors of Heart Attack
1. High Blood Pressure
2. High Cholesterol
3. Large Waist Size
1. Normal blood pressure is below 120/80.
Pre-hypertension is 120 to 139 (systolic) and/or 80 to 89 (diastolic).
Hypertension – also known as high blood pressure -- is 140 or higher (systolic)
and 90 or higher (diastolic).
One in three adults in the U.S. has high blood pressure or pre-hypertension.
2. Cholesterol levels you DON’T want
Total cholesterol higher than of 200 mg/dL.
HDL ("good" cholesterol) lower than 50 mg/dL (females) or 40 mg/dL (males).
LDL (“bad” cholesterol) higher than 100
Unless you have other major risk factors, like diabetes, you want your
LDL closer to 70.
Triglycerides of greater than 150 mg/dL.
3. Waist sizes you DON’T want
FEMALES: waist size more than 35 inches
MALES: waist size more than 40 inches
Measure around your belly button.
If patients lose even 1 inch off their waist, there are improvements in all the other
heart health numbers
If they gain even 1 inch, there is a worsening in those numbers. It's a much better
indicator of heart health than weight.
Other Heart Conditions
Congestive heart failure is progressive weakening of the heart as it fails to keep up with
the demands of pumping blood. The congestion backs up into the lungs and the person
may cough up blood.
Hypertrophic cardiomyopathy is a congenital condition where the walls of the left
ventricle are so thick that the lumen is too small to hold much blood.
Disorders of Conduction
Rapid, random firing of electrical impulses in the ventricles
Rapid, random firing of electrical impulses of the AV node
Most Common Heart Problems
Congestive heart failure
FUN FACT: Can you die from laughing?
It's certainly possible to die while laughing -- probably by choking on something. But
laughing is actually very good for you. According to the Indiana University School of
Medicine, laughing helps relax tense muscles, lowers blood pressure, and even burns
calories. People with heart disease are 40% less likely to laugh in a given situation than
people without heart disease. The key here seems to be stress reduction; stress impairs the
production of endothelial cells, which form a protective lining in our blood vessels. A
weak endothelium can lead to hardened arteries and, quite literally, a hardened heart.
EMBRYONIC DEVELOPMENT OF THE HEART
The heart is the most common site for congenital defects (those one is born with).
During fetal life, the mother provides the oxygen and nutrients through the placenta. If
there is a problem with the baby’s heart, it is not a problem until birth, although it can be
detected by ultrasound.
At 28 days (two weeks after a woman misses her period), The human heart first starts to
beat and pump blood in the embryo at the start of the fourth week.
You have to stop smoking and drinking before you get pregnant. By the time you know
you’re pregnant, it’s too late for the baby’s heart.
Where is the fetus getting the oxygen during the nine months in the womb? The mother, not
the lungs. So there’s no sense in sending half of the body’s blood to the lungs for oxygen.
► When oxygenated blood from the placenta is carried to the fetus by the umbilical
vein, where does it go?
► About half of this blood enters the inferior vena cava of the fetus, while the other
half enters the liver of the fetus.
► The blood in the inferior vena cava empties into the right atrium of the heart, and
then moves directly into the left atrium instead of going to the lungs.
► Blood moves from the right atrium to the left atrium by going through a hole
called the foramen ovale.
► Thus, blood bypasses the pulmonary circulation (does not go to the lungs of the
► There is a foramen ovale in the skull and another one in the heart. The foramen
ovale in the heart normally closes shortly after birth, and is then called the
► A ‘blue baby” has low oxygen levels in the blood that may be due to failure of the
foramen ovale to close at birth.
► When the foramen ovale fails to close, it is called a patent foramen ovale.
► Patent (Pay-tent) means “open”
► Not all of the blood in the right atrium goes through the foramen ovale to bypass
the pulmonary circulation, because the lung tissue needs some oxygen.
► Therefore, some of the blood entering the right atrium does not pass directly to
the left atrium through the foramen ovale, but enters the right ventricle (same as
an adult) and is pumped into the pulmonary artery and goes to the lungs.
► However, the lung tissue of the fetus do not need that much blood, so there is a
special connection between the pulmonary artery and the aorta in the fetus, which
directs most of this blood away from the lungs and back to the aorta.This
connecting blood vessel is called the DUCTUS ARTERIOSIS.
► At birth, there is an immediate change. Half of the blood needs to go to the lungs.
► At the first breath, a flap closes over the foramen ovale, and a muscle around the
ductus arteriosus constricts, causing instant closing, and seals shut permanently.
► The foramen ovale is now called the fossa ovalis, and the ductus arteriosus is now
called the ligamentum arteriosum.
► When a baby has not started walking, it doesn’t need as much oxygen, so a patent
foramen ovale might not be noticed until they start to walk and run at age 2-3.
► However, every time the baby cries, it might turn blue.
► A patent foramen ovale can be surgically closed by going through the blood
vessels without cutting into the heart tissue.
► A patent foramen ovale in an adult is just a tiny opening and can be heard as a
► You can also have a patent ductus arteriosus, which also requires surgery.
More significant problems: interventricular septal defect (between right and left
ventricle). Requires open heart surgery. If heart is totally deformed, need transplant.
The Heart in Adulthood and Old Age
Hardening and thickening of valve cusps
Decline in cardiac reserve
Sympathetic control over heart is less efficient
Less severe in the physically active
Fibrosis of cardiac muscle tissue
Lowers the amount of blood the heart can pump