Unit 4: CARDIOVASCULAR SYSTEM
Functions of the Heart
• Generating blood pressure
• Routing blood
– Heart separates pulmonary and systemic
circulations
• Ensuring one-way blood flow
– Heart valves ensure one-way flow
• Regulating blood supply
The double pump
The double pump
Lungs
the right side of the
the left side of the
system
system
deals with
deals with
deoxygenated blood.
oxygenated blood.
Body cells
Location and Orientation within the Thorax
• Heart – typically weighs 250–350 grams
(healthy heart)
• Largest organ of the mediastinum
– Located between the lungs
– Apex lies to the left of the midline
– Base is the broad posterior surface
Location and Orientation within the Thorax
Located in thoracic cavity in
mediastinum
The membrane around the
heart is PERICARDIUM
Pericardium
Heart Walls: 3 Distinct Layers
1. Endocardium:
the innermost layer of the heart (endothelial cells)
2. Myocardium:
the thickest main layer, consists of cardiac muscle.
3. Epicardium:
the thin, outer covering around the heart
Heart Walls : 3 Distinct Layers
Anatomy of the Heart
♥ Heart is enclosed in a membranous sac called
pericardium.
♥ Consists of 2 separate pumps that maintain
unidirectional flow of blood; the Left & Right heart.
♥ Left heart pumps oxygenated blood  Systemic
circulation.
♥ Right heart pumps deoxygenated blood  Pulmonary
circulation.
♥ Each pump contains 2 chambers: an atrium &
a ventricle.
Heart Chambers
Chambers
Atria- (2) upper chambers
Thin walled
Receive blood from
veins
Send blood to ventricles
Ventricles- (2) lower
chambers
Thick walled
Receive blood from
artery
Pump blood out through
arteries
Pulmonary valve
Left atrium
Aortic valve
Right atrium
Mitral valve
Left ventricle
Tricuspid valve
Septum
Right ventricle
Inferior View of the Heart
The coronary circulation consists of the blood vessels that
supply blood to (coronary artery), and remove blood from the
heart muscle (coronary sinus) itself.
♥ 2 Atria:
■
■
Chambers of the Heart
♥ 2 Ventricles:
Thin-walled chambers.
Receive blood returning to
heart.
Thicker, muscular walls.
■ Pump blood from heart.
■ Each has same capacity
& pumps same volume of
blood in a given period of
time.
■
Ventricles
• Both ventricles (Right & left) – thick walled
• Left ventricle – three
times thicker than right
– Left ventricle has to
push the blood to all
the body parts while RV
has to push the blood
to closely lying lungs
only
Valves of the Heart
♥ 2 Atrioventricular (AV)
♥ 2 Semilunar valves :
■ One way valves.
■ At origin of pulmonary artery
■ One way valves.
& aorta.
■ Allow blood to flow from
■ Pulmonary (Right) & Aortic
atria into ventricles.
(Left).
■ Tricuspid (Right) & Mitral (Left). ■ Open during ventricular contraction.
valves:
Pathway of Blood Through the Heart
• Oxygen-poor blood draining
from the body through
veins into the superior and
inferior vena cava flows to
the right atrium, through
the tricuspid valve, and into
the right ventricle.
• As the right ventricle
contracts, oxygen-poor
blood passes through the
pulmonary valve into the
pulmonary arteries and on
to the lungs to receive
oxygen.
Pathway of Blood Through the Heart
• Oxygen-rich blood from the
lungs enters the heart
through the pulmonary
veins, passing into the left
atrium.
• Then through the mitral
valve to the left ventricle.
Contraction of the left
ventricle forces blood
through the aortic valve into
the aorta.
• Various arteries branch off
from the aorta to supply
blood to all parts of the body.
Blood Flow Through the Heart
Pulmonary and Systemic Circulations
• Pulmonary circulation:
– Path of blood from right ventricle through the lungs and back to the
heart.
• Systemic circulation:
– Oxygen-rich blood pumped to all organ systems to supply nutrients.
• Rate of blood flow through
systemic circulation = flow
rate through pulmonary
circulation.
The Pulmonary and Systemic Circuits (‫)الدائرة‬
Systemic circuit
• Longer than
pulmonary
circuit
• Offers greater
resistance to
blood flow
Conducting System (‫)إجراء النظام‬
• Cardiac muscle tissue has intrinsic ability to
– Generate and conduct impulses (‫)نبضات‬
– Signal these cells to contract rhythmically
• Conducting system
– A series of specialized cardiac muscle cells
– Sinoatrial (SA) node sets the inherent rate of
contraction
Physiology of Cardiac Muscle

The heart is composed of 2 major types of cardiac
Cells:
1: Contractile cells.
2: Autorhythmic (or automatic) cells.
Contractile cells: Contract when stimulated, in same
way as skeletal muscle except for longer duration.
Heart : Conducting Tissues
•
•
•
•
Sinoatrial Node (SA node)
Located high on the right atrium.
Pacemaker of the heart.
Causes the wave of
contractions
in the atria.
– Sending
blood
into the
ventricles
Cardiac Cycle
• Heart is two pumps that work together, right and
left half
• Repetitive contraction (systole) and relaxation
(diastole) of heart chambers
• Blood moves through circulatory system from
areas of higher to lower pressure.
– Contraction of heart produces the pressure
Heartbeat
• 70 – 80 beats per minute at rest
– Systole – contraction of a heart chamber
– Diastole – expansion/relaxation of a heart
chamber
Electrocardiogram (ECG/EKG)
• Electrocardiogram:
– Measure of the electrical activity of the heart per unit
time.
• Potential differences generated by heart are conducted to
body surface where they can be recorded on electrodes on
the skin.
• Does NOT measure the flow of blood through the
heart.
Cardiac Output (CO)
• Is volume of blood pumped/min by each
ventricle
• Heart Rate (HR) = 70 beats/min
• Stroke volume (SV) = blood pumped/beat
by each ventricle
– Average is 70-80 ml/beat
• CO = SV x HR
• Total blood volume is about 5.5L