The Human Heart
and
Circulatory System
Angela L. Pruitt, MSN, RN, CNS
A & P: Cardiovascular
Heart Trivia
• Average human heart beats 36.5 million times/yr.
• Heart weighs about 10 ounces.
• Size of a fist.
– Blue Whale’s heart is as big as a car!
• Yawning may be due to inadequate oxygen being carried
by the cardiovascular system.
• German researchers- risk for heart attack is higher on
Monday’s.
• Women’s hearts beat faster.
• Athletes resting heart rate is 35 – 40 bpm.
• Human body blood vessels approx. 70,000 miles.
• 7% of body weight is blood.
Introduction
• CV System : heart, blood vessels
• Arteries, capillaries, veins
• Vital for supplying O2 and nutrients to tissues;
remove waste
• Pulmonary Circuit – Lungs
– Deoxygenated blood
• Systemic Circuit – remaining
– Oxygenated blood to all body cells
Structure, Size & Location
• Hollow, Cone shaped
• Muscular organ
• Two sides have separate
functions
• The size of your fist
– About 14 cm long / 9 cm
wide
• SEPTUM thick section
between the ventricles
called the
Location of Heart in Body
1. Beneath sternum in the
Mediastinum
• Lungs bilaterally; spine
posterior
2. BASE – upper right; 2nd
rib (ICS)
3. APEX – lower left; 5th rib
(ICS)
Anatomy of Heart
Pump
• Right side – lungs
• Left side - body
Systemic Circulation
– Left side sends blood at
high pressures to body
Pulmonary Circulation
Connected to blood vessels to carry
oxygen and nutrients to body cells and
remove waste products
– Right side sends blood
through lungs at lower
pressure
How Does the Heart Function?
• http://video.about.com/heartdisease/How-theHeart-Functions.htm
Circulation is a ONE WAY SYSTEM
ARTERIES
•oxygen-rich blood away from
your heart.
VEINS
•oxygen-poor blood back to
your heart.
PULMONARY CIRCULATION
Roles Are Switched
•pulmonary artery brings
oxygen-poor blood into your
lungs.
•pulmonary vein brings
oxygen-rich blood back to your
heart.
How does Pulmonary & Systemic
System look?
Covering of Heart- Pericardium
Fluid filled sac, encloses heart.
Lubricate, protect, reduce
friction
Outer layer – tough fibrous
Two inner layers
• Visceral– covers heart
Pericardial sac – formed
by parietal and fibrous
pericardium
• Parietal– middle layer
• Pericardial cavity –
serous fluid to reduce
friction
What is Friction?
• RUBBING OF ONE OBJECT OR SURFACE
AGAINST ANOTHER:
PERICARDITIS
– Inflammation of the Pericardium
– Due to infection- viral or bacterial
– Cause adhesions( the layers stick
together) - FRICTION
– VERY PAINFUL
• Heard- Pericardial RUB
• Sounds like cellophane being rubbed
Three Layers of Wall of the Heart
1. Epicardium – outer, connective tissue
– Serous membrane, reduces friction
– Blood & lymph capillaries; coronary arteries
2. Myocardium – middle, muscle fibers
– Thickest layer
– Pumps blood out of heart
3. Endocardium – inner, elastic and collagen
fibers;
– contain the Purkinje fibers
MYOCARDIAL LAYERS HELPS THE HEART CONTRACT!
Layers
Four CHAMBERS of the Heart
Two Atria
(upstairs)
Two Ventricles
(downstairs)
• Top, thin walls
• Bottom; Larger, thicker
walls
• Receive blood
• Receive blood from Atria
returning to the heart • Contract to pump blood
& pumps to ventricles
to body
• Low pressure
• High Pressure
SEPTUM – separates right & left side; never mixes blood
Four CHAMBERS of the Heart
TWO ATRIA
Right Atrium (RA)
TWO VENTRICLES
Right Ventricle (RV)
• Receives from superior • Blood goes only to
& inferior vena cava
lungs
Left Atrium (LA)
Left Ventricle (LV)
• Smaller, thicker walls
• Receives blood from
pulmonary veins
• Blood goes through
aorta to vessels in
entire body
Heart Valves – One Way Blood Flow
Prevents blood from backing up into the heart
ATRIOVENTRICULAR
VALVES
Separate Atria from Ventricles
• Have cusps, Chordae tendinae
attach
– Tricuspid Valve – Right
• Stops backflow from RV
into RA
– Mitral (bicuspid) - Left
• Stops backflow from LV
into LA
Heart Valves – How Do They Work?
Chordae Tendineae
attach the cusp of AV
valve to papillary muscle
Papillary Muscles
in the inner heart wall
contract during ventricular
contraction
prevent backflow of blood
through the A-V valves.
• http://video.about.com/heartdisease/How-the-Valves-Work.htm
Semilunar Valves
– Pulmonic Valve
• Prevents return of
blood on Right side to
ventricles
• Pulmonary Artery into
RV
– Aortic Valve
• Stops backflow from
Aorta into LV
Open & Close based on
pressure changes
http://www.youtube.com/watch?v=MduG0mbW09A&feature=fvwrel
Path of Blood Flow
• Unoxygenated blood enters the
heart (returns) to the RA via
Superior & Inferior Vena Cava
– Low oxygen, high CO2
• Enters RA ~ blood pass
through Tricuspid valve into RV
• RV contracts, forces blood
through Tricuspid into RV,
then closes.
• Blood sent through Pulmonic
Valve, into Pulmonary Arteries
to LUNGS
• Capillaries of alveoli in lungs
get rid of Co2 and pick up O2.
• Gas Exchange occurs to
oxygenate blood
– High Oxygen, low CO2
• Returns to LA via
Pulmonary Veins
• LA, contracts~blood forced
through Mitral Valve to LV
• LV contracts, closes Mitral
valve ~ forces open Aortic
Valve as blood enters
Aorta
• Aorta sends blood to body
for distribution
•
•
•
•
Average: 60 bpm = 3600 bp hr.
X 24hrs= 86,400 beats
X 365 days= 31,536,000 beats
X 17 years= 536,112,000 beats in your life
time to date without missing a beat and still
going strong.
• Name another pump that can do that?????
How does the Heart receive Blood
Supply? Coronary Arteries!!
• Openings come off the first
branch of aorta
• Delivers fresh blood to supply
the heart muscle with blood.
• Right and Left coronary
arteries branches feed heart
muscle
• Capillaries of the myocardium
have continuous blood supply,
so form collaterals as alternate
pathways for blood, should
one artery become blocked.
Low or Blocked flow of Coronary
Arteries CAUSE
•
•
•
•
•
•
Angina pectoris
Myocardial Infarction
Thrombus
Embolus
Arrhythmia
Valvular Prolapse or
Stenosis
• Arteriosclerosis
• When arteries are
obstructed, the blood flow
is stopped or decreased.
• Condition is called a
myocardial infarction or
heart attack.
– There is no blood
supply going to the
muscles of the heart.
Coronary Veins
• Cardiac veins drain blood from the heart muscle
• Carry blood to the coronary sinus,
• Empties into the right atrium.
How the Heart Pumps: Cardiac Cycle
• Hose with a one-way valve in it.
• Squeeze your hand around the hose
it will push the blood out forcing the
valve to open.
• Relax your hand, the valve will close.
Although the valve is closed the
blood still flows forward, but not as
much. The flow is still enough to
keep the blood circulating
• The act of squeezing the hand is
similar to a
– heart contraction or systole
(systolic).
– heart relaxation or diastole
(diastolic).
The Cardiac Cycle :
the start of one heart beat to
the start of the next
heartbeat.
Cardiac Cycle
Pressure rises & falls with contraction and relaxation of A & V;
opens & closes valves
• Atria beat in unison
followed by contraction of
both ventricles,
• the entire heart relaxes for
a brief moment.
• Atria fill, pressure is
greater than the ventricles,
forces the A-V valves open
force blood into ventricles
• Ventricles contract,
pressure inside increases
sharply, causing A-V
valves to close and the
Aortic and Pulmonic valves
open.
• Papillary muscles contract,
pull on Chordae tendinae
and prevent backflow of
blood through the A-V
valves.
Heart Sounds
• “lubb – dupp”
• Sounds due to
vibrations caused by
the closing of the
valves
• Ventricular contraction
– Lubb – first sound
• AV valves closing;
Tricuspid & Mitral Valves
• Ventricular relaxation
– Dupp – second sound
• Pulmonic & Aortic Valves
snap shut
• ABNORMAL SOUNDS
• Murmur
– Valves are damaged,
not closing properly
• Swishing sound
• Can be benign or
serious
• Not uncommon for
teens and women over
40 to have murmurs.
• Open heart showing heart beating
• http://www.youtube.com/watch?v=18zlNa21
6vI
• Heart sounds
• http://depts.washington.edu/physdx/audio/no
rmal.mp3
• http://www.blaufuss.org/
Conduction System
• http://video.about.com/heartdisease/ConductionSystem.htm
FUNCTIONAL SYNCYTIUM
Specialized cardiac muscle
tissue.
Mass of merging cells that
function as one unit.
When one portion is
stimulated, the resulting
impulse passes to the other
fibers of the network and the
whole section contracts as a
unit,
Self exciting and Rhythmic
Nodes of Conduction System
Sinoatrial Node – “Pacemaker”
– Just beneath epicardium
– Located near RA at opening of
Superior Vena Cava
– Reach threshold and initiate
impulse on own;
• Self excitation
– Spreads to surrounding
myocardium to stimulate
contraction of R & L Atria at
rate of 70 to 80 times/min
– Impulse passes to AV Node
• Atrioventricular Node
Atrioventricular Node
– Just beneath the endocarium
– Located inferior portion of
septum that separates atria
– Interatrial Septum
– Delay impulse transmission
– Allows atria to empty and
ventricles to fill with blood
– Move rapidly to AV Bundle
(BUNDLE OF HIS)
– Divides into R & L
branches
Nodes of Conduction System
AV Bundle (BUNDLE OF HIS) Papillary Muscles
– Divides into R & L branches
– Located just beneath
endocardium
Perkinje Fibers
– Halfway down Ventricular
Septum
– Spread into the Papillary
Muscles
•
•
– Project inward from the
ventricular walls, continue
downward to apex of heart.
– Curve around and pass
upward over lateral walls
– Many small branches.
– Irregular whorls allow
contraction with a twisting
motion to squeeze blood out
of ventricles, into aorta and
pulmonary trunk
The heart has a firing squad. If the SA node doesn’t fire, the AV node fires.
If the SA and AV node fail, the ventricles fire their own impulse.
What regulates or influences the
amount of blood pumped?
Cardiac Control Center: Medulla Oblongata
Parasympathetic – Inhibits or slows
Sympathetic – Excite and increases - Norepinephrine
1.
Strenuous exercise
– HR 
2. B/P Changes
–  ; Vagus Nerve
3. Temperature
–  ; Hypothalmus
Electrolytes (Ions)
1. Potassium (K+)
•
High: Decrease rate & force of
contraction
•
Low: irritates heart; V-Tach or
V-Fib
2. Calcium (Ca++)
•
High:  HR; prolongs heart
contraction
•
Low: Slows heart action