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1. © 2019 McGraw-Hill Education
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Anatomy and Physiology
Chapter 12
Heart
Ma. Estrella L. Goco-Marasigan, MD

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The Cardiovascular System 1
The heart is a muscular organ that is essential for
life because it pumps blood through the body.
The heart is a member organ of the
cardiovascular system, which consists of the
heart, blood vessels, and blood.
The heart of a healthy adult, at rest, pumps
approximately 5 liters (L) of blood per minute.
For most people, the heart continues to pump at
approximately that rate for more than 75 years.

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The Cardiovascular System 2
Figure 12.1

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The Cardiovascular System 3
The heart is a member organ of the cardiovascular
system, which consists of the heart, blood vessels,
and blood.
The heart is actually two pumps in one, with the
heart’s right side pumping to the lungs and back to
the left side of the heart through vessels of the
pulmonary circulation.
The left side of the heart pumps blood to all other
tissues of the body and back to the right side of the
heart through vessels of the systemic circulation.

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The Circulatory System
Figure 12.2

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Functions of the Heart
1.Generates blood pressure
2.Routes blood
3.Ensures one-way blood flow
4.Regulates blood supply

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Heart Characteristics
Size:
size of a fist and weighs
less than 1 lb.
Location:
between lungs in thoracic
cavity
Orientation:
apex (bottom) towards
left side
Figure 12.3

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Pericardia
Pericardium:
double-layered sac that
anchors and protects heart
Parietal pericardium:
membrane around heart’s
cavity
Visceral pericardium:
membrane on heart’s surface
Pericardial cavity:
space around heart
Figure 12.4

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Heart External Anatomy 1
A coronary sulcus extends around the heart,
separating the atria from the ventricles.
Two grooves, or sulci, which indicate the division
between the right and left ventricles, extend
inferiorly from the coronary sulcus.
The anterior interventricular sulcus extends
inferiorly from the coronary sulcus on the anterior
surface of the heart.

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Heart External Anatomy 2
The posterior interventricular sulcus extends
inferiorly from the coronary sulcus on the posterior
surface of the heart.
The superior vena cava and inferior vena cava carry
blood from the body to the right atrium, and four
pulmonary veins carry blood from the lungs to the
left atrium.
Two arteries, often called the great vessels or great
arteries, carry blood away from the ventricles of
the heart.

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Heart External Anatomy 3
The pulmonary trunk, arising from the right
ventricle, splits into the right and left pulmonary
arteries, which carry blood to the lungs.
The aorta arising from the left ventricle, carries
blood to the rest of the body.

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Surface Anatomy of the Heart 1
Figure 12.5a

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Surface Anatomy of the Heart 2
Figure 12.5c

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Heart Chambers
Four Chambers:
•left atrium (LA)
•right atrium (RA)
•left ventricle (LV)
•right ventricle (RV)
Coronary sulcus:
•separates atria from ventricles

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The Atria
Superior chambers
Holding chambers
Small, thin walled
Contract minimally to push blood into ventricles
Interatrial septum:
•separates right and left atria

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Ventricles
Inferior chambers
Pumping chambers
Thick, strong walled
Contract forcefully to propel blood out of heart
Interventricular septum:
•separates right and left ventricles

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Atrioventricular Heart Valves
Valves between the atria and ventricles
Tricuspid valve:
•AV valve between RA and RV
•3 cusps
Bicuspid valve (mitral):
•AV valve between LA and LV
•2 cusps

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Valvular Control
Each ventricle contains cone-shaped, muscular
pillars called papillary muscles.
These muscles are attached by strong,
connective tissue strings called chordae
tendineae to the free margins of the cusps of the
atrioventricular valves.
When the ventricles contract, the papillary
muscles contract and prevent the valves from
opening into the atria by pulling on the chordae
tendineae attached to the valve cusps.

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Semilunar Heart Valves
The semilunar valves have three half-moon
shaped cusps, and are valves between the
pulmonary trunk and aorta.
Pulmonary valve:
•between RV and pulmonary trunk
Aortic valve:
•between LV and aorta

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Internal Anatomy of the Heart
Figure 12.6

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Heart Valves 1
Figure 12.7
(a) ©VideoSurgery/Science Source; (b) ©Oktay Ortakcioglu/iStock/360/Getty Images RF

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Heart Valves 2
Figure 12.8

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Cardiac Skeleton 1
A plate of connective tissue, sometimes called
the cardiac skeleton, or fibrous skeleton,
consists mainly of fibrous rings that surround
the atrioventricular and semilunar valves and
give them solid support.
This connective tissue plate also serves as
electrical insulation between the atria and the
ventricles and provides a rigid attachment site
for cardiac muscle.

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Cardiac Skeleton 2
Figure 12.9

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Blood Flow through Heart 1
1.RA
2.Tricuspid valve
3.RV
4.Pulmonary semilunar valve
5.Pulmonary trunk
6.Pulmonary arteries
7.Lungs
8.Pulmonary veins
9.LA
10.Bicuspid valve
11.LV
12.Aortic semilunar valve
13.Aorta
14.Body

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Blood Flow through Heart 2
Figure 12.10

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Blood Supply to the Heart 1
Coronary arteries:
•supply blood to heart wall
•originate from base of aorta (above aortic semilunar
valve)
Left coronary artery:
•has 3 branches
•supply blood to anterior heart wall and left ventricle

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Blood Supply to the Heart 2
Right coronary artery:
•originates on right side of aorta
•supply blood to right ventricle
Cardiac veins:
•drain blood from the cardiac muscle
•parallel to the coronary arteries
•most drain blood into the coronary sinus
•from the coronary sinus into the right atrium

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Blood Supply to the Heart 3
Figure 12.11

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Heart Wall
Epicardium:
•surface of heart (outside)
Myocardium:
•thick, middle layer
composed of cardiac muscle
Endocardium:
•smooth, inner surface
Figure 12.12

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Cardiac Muscle
1 centrally located
nucleus
Branching cells
Rich in mitochondria
Striated (actin and
myosin)
Ca
2+
and ATP used for
contractions
Intercalated disks
connect cells
Figure 12.12
(b) ©Ed Reschke

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Cardiac Muscle Action Potentials 1
Changes in membrane channels’ permeability
are responsible for producing action potentials
and is called pacemaker potential.
1.Depolarization phase:
•Na
+
channels open
•Ca
2+
channels open
2. Plateau phase:
•Na
+
channels close
•Some K
+
channels open
•Ca
2+
channels remain open

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Cardiac Muscle Action Potentials 2
3. Repolarization phase:
•K
+
channels are open
•Ca
2+
channels close
Plateau phase prolongs action potential by
keeping Ca
2+
channels open.
In skeletal muscle action potentials take 2 msec,
in cardiac muscle they take 200-500 msec.

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Action Potentials in Skeletal and
Cardiac Muscle
Figure 12.14

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Conduction System of Heart 1
Contraction of the atria and ventricles is
coordinated by specialized cardiac muscle cells
in the heart wall that form the conduction
system of the heart.
All the cells of the conduction system can
produce spontaneous action potentials.
The conduction system of the heart includes the
sinoatrial node, atrioventricular node,
atrioventricular bundle, right and left bundle
branches, and Purkinje fibers.

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Conduction System of Heart 2
Sinoatrial node (SA node):
•in RA
•where action potential originates
•functions as pacemaker
•large number of Ca
2+
channels

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Conduction System of Heart 3
Atrioventricular node (AV node):
•located in the lower portion of the right atrium
•action potentials from SA node sent to this node
•action potentials spread slowly through it
•slow rate of action potential conduction allows the
atria to complete their contraction before action
potentials are delivered to the ventricles

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Conduction System of Heart 4
Atrioventricular bundle:
•action potentials from AV node travel to AV bundle
•AV bundle divides into a left and right bundle branches

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Conduction System of Heart 5
Purkinje Fibers
•at the tips of the left and right bundle branches, are
Purkinje fibers
•Purkinje fibers pass to the apex of the heart and then
extend to the cardiac muscle of the ventricle walls
•action potentials are rapidly delivered to all the cardiac
muscle of the ventricles

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Action Potential Path through Heart
1.SA node
2.AV node (atrioventricular)
3.AV bundle
4.Right and Left Bundle branches
5.Purkinje fibers

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Conduction System of the Heart
Figure 12.15

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Electrocardiogram (EKG)
ECG (EKG)
•record of electrical events in heart
•diagnoses cardiac abnormalities
•uses electrodes
•contains P wave, QRS complex, T wave

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Components of ECG/EKG
P wave:
•depolarization of atria
QRS complex:
•depolarization of ventricles
•contains Q, R, S waves
T wave:
•repolarization of ventricles

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Electrocardiogram
Figure 12.16

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Cardiac Cycle 1
The cardiac cycle is a summative description of
all the events that occur during one single
heartbeat.
The heart is a two sided pump, with the atria
being primers for pumps and the ventricles
being the actual pumps.

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Heart Chamber Contractions
Cardiac muscle contractions produce pressure
changes within heart chambers.
Pressure changes are responsible for blood
movement.
Blood moves from areas of high to low pressure.

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Cardiac Cycle 2
Atrial systole:
•contraction of atria
Ventricular systole:
•contraction of ventricles
Atrial diastole:
•relaxation of atria
Ventricular diastole:
•relaxation of ventricles

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Cardiac Cycle 3
Figure 12.17

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Events of the Cardiac Cycle
Figure 12.18

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Heart Sounds
Heart sounds are produced due to the closure of
heart valves.
A stethoscope is used to hear heart sounds
The first heart sound makes a ‘lubb’ sound.
The second heart sound makes a ‘dupp’ sound.
The first heart sound is due to the closure of the
atrioventricular valves.
The second heart sound is due to the closure of
the semilunar valves.

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Heart Valve Locations
Figure 12.19
©Juice Images/Alamy RF

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Regulation of Heart Function 1
Stroke Volume:
•volume of blood pumped per ventricle per contraction
•70 milliliters/beat
Heart Rate:
•number of heart beats in 1 min.
•72 beats/min.

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Regulation of Heart Function 2
Cardiac Output:
•volume of blood pumped by a ventricle in 1 min.
•5 Liters/min.
Cardiac output equals stroke volume multiplied
times heart rate
CO = SV x HR

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Intrinsic Regulation of the Heart 1
Intrinsic regulation refers to the mechanisms
contained within the heart itself that control
cardiac output.
Venous return:
•the amount of blood that returns to heart
Preload:
•the degree ventricular walls are stretched at end of
diastole
Venous return, preload, and stroke volume are
related to each other

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Intrinsic Regulation of the Heart 2
Starlings Law of the Heart:
•relationship between preload and stroke
•volume
•influences cardiac output
•Example - exercise increases venous return, preload,
stroke volume, and cardiac output
After load:
•pressure against which ventricles must pump blood

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Extrinsic Regulation of Heart
Extrinsic regulation refers to mechanisms external
to the heart, such as either nervous or chemical
regulation.
Nervous system control of the heart occurs through
the sympathetic and parasympathetic divisions of
the autonomic nervous system. influences of heart
activity are carried through the autonomic nervous
system.
Both sympathetic and parasympathetic nerve fibers
innervate the SA node.

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Baroreceptor Reflex 1
The baroreceptor reflex is a mechanism of the
nervous system that plays an important role in
regulating heart function.
Baroreceptors:
•monitor blood pressure in the aorta and carotid
arteries
•changes in blood pressure cause changes in
•frequency of action potentials
•involves the medulla oblongata

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Baroreceptor Reflex 2
Figure 12.20

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Chemoreceptor Reflex 1
The chemoreceptor reflex involves chemical
regulation of the heart.
Chemicals can affect heart rate and stroke
volume.

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Chemoreceptor Reflex 2
Chemical actions:
•epinephrine and norepinephrine from the adrenal
medulla can increase heart rate and stroke volume
•excitement, anxiety, and anger can increase cardiac
output
•depression can decrease cardiac output
•medulla oblongata has chemoreceptors for changes in
pH and CO
2
•K
+
, Ca
2+
, and Na
+
affect cardiac function

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Chemoreceptor Reflex—pH
Figure 12.21

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Summary of Extrinsic Regulation
Figure 12.22

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Heart Disease
Coronary Artery Disease
•due to decrease blood supply to the heart
•coronary arteries are narrowed for some reason
Myocardial Infarction (heart attack)
•due to closure of one or more coronary arteries
•area(s) of cardiac muscle lacking adequate blood
supply die, and scars (infarct)

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Heart Procedures
Angioplasty:
•procedure opens blocked blood vessels
Stent:
•structures inserted to keep vessels open
Bypass:
•procedure reroutes blood away from blocked arteries

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Thank you.