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Cardiovascular
System
• Consists of blood, heart and
blood vessels
• Cardiology – study of the heart
The Heart
• Located in the mediastinum –
mass of tissue that extends
from the sternum to the
vertebral column
• Rests on the diaphragm
• Approx. the size of closed
fist
• Apex – pointed end (leans
toward left)
• Base – rounded end (toward
right)
• Mass: females ~ 250g
males ~ 300g
Function of the Heart
• Pump oxygenated blood to
the tissues and
deoxygenated blood to the
lungs
Coverings of Heart
• Pericardium – double layered
sac that covers the heart
oParietal pericardium – outer layer
oVisceral pericardium – inner layer
(also called epicardium)
oPericardial cavity – fluid filled space
between the two layers; contains
fluid to decrease friction
Layers of the Heart Wall
• Epicardium – thin, protective
outer layer
• Myocardium - thick middle
layer; makes up most of heart;
function is to pump blood
• Endocardium - smooth, inner
lining; also forms valves of
heart
Chambers of the Heart
• 4 chambers
o2 atria – (upper, thin-walled) receive
blood
• Have auricles – pouches that increase
the surface area of the atria so it
can hold a greater volume of blood
• Separated by interatrial septum
o2 ventricles – (lower, thicker) pump
blood
• Separated by interventricular septum
• Right atrium -receives
deoxygenated blood from
superior vena cava, inferior
vena cava & coronary sinus
oSuperior vena cava – returns blood to
heart from head, neck & arms
oInferior vena cava – returns blood to
heart from chest, abdomen, pelvis &
legs
oCoronary sinus – returns blood to
right atrium from myocardium
• Left atrium - receives
oxygenated blood from the
lungs via the pulmonary veins
• Right ventricle - receives blood
from the right atrium & pumps
it out to the lungs via the
pulmonary arteries
• Left ventricle - forms apex
oReceives blood from left
atrium & pumps it out to
tissues of the body via the
aorta
Features of Ventricles
• Trabeculae carneae – ridges in
the ventricle
• Papillary muscle - masses of
myocardium that project into
the ventricles
Heart Valves
• Function is to keep blood flowing
in one direction (prevents
backflow)
• 2 types of valves
o1. Atrioventricular valves (AV)
o2. Semilunar valves (SL)
Atrioventricular Valves
• Tricuspid valve – between right atria
& right ventricle (3 cusps)
• Bicuspid valve – between left atria &
left ventricle (2 cusps)
o Also called the mitral valve
• Chordae tendineae - connective tissue
strands that connect papillary muscle
to cusps of atrioventricular valves
Semilunar Valves
• valves at the base of large
vessels that carry blood from
the ventricles
• Pulmonary semilunar valve –at
exit of right ventricle in base
of pulmonary trunk
• Aortic semilunar valve – at exit
of left ventricle in base of
ascending aorta
• Valves open & close in response to
pressure:
• Atria fill with blood…causes
increased pressure on AV valves.
Atria contract, AV valves open,
blood flows into ventricles.
• Ventricles fill with blood…causes
increased pressure on SL valves.
Ventricles contract, SL valves
open, blood flows into vessels.
Coronary Circulation: Blood
Supply for the Heart
• Coronary arteries - surround the
heart like a crown
oBranch off the ascending aorta
oSupplies heart cells with oxygen &
nutrients
• Coronary sinus – returns blood to
the right atrium
Fetal Circulation
• Blood doesn’t need to go to lungs in a fetus
• 2 shunts:
o Foramen ovale – an opening on the
interatrial septum of fetal heart
• Closes to form the fossa ovalis
o Ductus arteriosum – shunts blood from the
pulmonary trunk to the aortic arch
• Closes to form the ligamentum arteriosus
(connects arch of aorta and pulmonary
trunk)
o Both shunts close by birth or w/in 1st year
o If shunts don’t close, surgery is required
Conduction System
• Cardiac muscle is autorhythmic – it
generates its own action potentials
for muscle contraction
• Both atria contract simultaneously,
followed by both ventricles
• Specialized cardiac muscles act as
nerve tissue to distribute the
impulse
• 1. Excitation begins in sinoatrial node
(SA node…also known as the
pacemaker) in the right atrium.
• 2. Action potential spreads to left
atrium, allowing both atria to contract
simultaneously
• 3. Action potential spreads to
atrioventricular node (AV node)
located between right & left atria
o Action potential slows at AV node so atria can
fully empty and ventricles can fill; also AV node
has smaller fibers
• 4. Action potential spreads to
Atrioventricular bundle, then to
right & left bundle branches within
the interventricular septum
• 5. Purkinje fibers send the action
potential to the ventricles, causing
them to contract 0.2 seconds after
atria contract
Electrocardiogram
(EKG or ECG)
• Recording of electrical activity of
heart to check the conduction
system
• Uses multiple electrodes attached
to body
• Stress test – EKG during
strenuous exercise; compares
resting heart to stressed heart
• P wave – atrial contraction
(depolarization); SA node activity
• PQ interval – impulse delay at AV node
• QRS complex – ventricular contraction
(depolarization);Purkinje fiber activity
oIt’s so much larger due to greater
muscle mass of ventricles
• T wave – ventricular relaxation
(repolarization)
**why can’t we see atrial relaxation??**
EKG Abnormalities
• Large P Wave - enlarged atria
• Large Q wave – myocardial infarction
(heart attack)
• Large R wave - enlarged ventricles
• Flat T wave - coronary artery disease
• Wider PQ interval - abnormal conduction
• Arrhythmia – abnormal beating of heart
due to malfunction of conduction system
o Tachycardia - fast heart rate
o Bradycardia - slow heart rate
o Asystole - lack of heart rate
Cardiac Cycle
• All the events associate with one complete
heart beat
• Systole – contraction Diastole – relaxation
Atrial systole = ventricular diastole
atria contract, ventricles relax
AV valves open, SL valves closed
ventricles fill with blood
Atrial diastole = ventricular systole
atria relax, ventricles contract
AV valves close, SL valves open
atria fill with blood
Heart Sounds
• Caused by the turbulence of blood when
heart valves close
• Stethoscope – instrument used to listen
to heart sounds
• Lubb – first sound heard; AV valves
closing after ventricular systole begins
• Dupp – second sound heard; SL valves
close at beginning of ventricular
diastole
Heart Murmur
• Abnormal heart sound
• Gurgling noise before, between or after
lubb-dupp sound
• Most murmurs indicate a valve disorder
• Mitral stenosis – narrowing of the mitral
valve
• Mitral valve prolapse – part of mitral
valve is pushed back into the atria
o Occurs in 10-15% of population ( 65%
are female)
Heart Disorders
• 1. Ischemia – partial block of blood flow
due to constriction or obstruction of a
vessel
• 2. Hypoxia – lack of O2 to heart muscle
• 3. Angina – chest pain
• 4. Myocardial infarction – heart attack
due to myocardial cells dying
• 5. Sudden cardiac death – conduction
system stops; heart stops beating
• 6. Congenital defects – present at birth
Nervous System Control
• Autonomic nervous system – no conscious
control
o Heart controlled by two branches of ANS
• 1. Sympathetic Nervous System – increases
heart rate & force of contractions due to
release of norepinephrine
• 2. Parasympathetic Nervous System –
decreases heart rate due to the release of
acetylcholine
• Both work together to maintain homeostasis