Chap. 19– The Heart
(Cardiology)
19-1
Chap. 19 (Heart) Study Guide
1. Critically read Chapter 19 pp. 719-739 before
19.5 “Blood Flow” section
2. Comprehend Terminology (those in bold)
3. Study-- Figure questions, Think About It
questions, and Before You Go On (sectionending) questions
4. Do Testing Your Recall— 1, 2, 4-8, 11-19
5. Do True or False– 1-4, 7, 9-10
6. Do Testing Your Comprehension-- #1
2
What are you going to do with
your heart?
♥ “The best and most beautiful things in
the world cannot be seen or even
touched—they must be felt with the
heart.”
--Hellen Keller
♥ “Happiness comes only when we push
our brains and hearts to the farthest
reaches of which we are capable.”
--Leo C. Rosten
19-3
I. Overview of
cardiovascular system
19-4
§ Introduction
• The circulatory system—
– Three component: the pump, the
passageway, and the transport
medium
– What are they respectively?
• The pump-• The passageway-• The transport medium-19-5
§ Two circuits in the
cardiovascular system (1)
1. Pulmonary circulation—
– Function?
– The route?
• R. ventricle  Pulmonary arteries 
Lungs  Pulmonary veins  L. atrium
Figure 19.1
19-6
Lungs
Pulmonary
capillaries
Pulmonary
arteries
= O2-poor blood
Pulmonary
circulation
Pulmonary
veins
= O2-rich blood
Right
side of
heart
19-7
§ Two circuits in the
cardiovascular system (2)
2. Systemic circulation—
– Functions?
– The route? (Students work on it.)
• Starts which chamber of the heart? 
Major vessels? Destinations? 
Two major veins?  Ends at which
chamber of the heart?
Fig. 19.1
19-8
Systemic
circulation
Left side
of heart
= O2-poor blood
= O2-rich blood
Systemic
veins
Systemic
arteries
Organ
systems
Systemic
capillaries
19-9
II. Gross anatomy of the heart
19-10
§ Shape and size of the heart
• Base – broad superior portion
• Apex - inferior end (a blunt point)
• 3.5 in. wide at base,
5 in. from base to apex, and 2.5 in.
anterior to posterior
• weighs 10 oz (300 gram; size of your
fist)
Fig. 19.2
19-11
Aorta
Superior
vena cava
Base of
heart
Apex of
heart
Next Topic
19-12
Diaphragm
§ Heart Position (1)
19-13
§ Heart Position (2)
19-14
§ Heart Position (3)
19-15
§ Pericardial sac (pericardium) -1
• Def. the double-walled, membranous
covering that encloses the heart
• Function– Friction free
• Peircardial fluid— Figure x
Cardiac Disorders here (Table 19.3):
• Pericarditis– inflammation here
• Pericardial effusion– fluid in pericardial
cavity
• Cardiac tamponade– accumulation of fluid
16
here
Figure x
Pericardial
cavity
Heart
19-17
§ Pericardial sac (pericardium) - 2
1. Parietal pericardium– 2 SUBLAYERS
– A-outer, tough/fibrous layer (CT) + B-deep thin
serous layer– turns inward . . . forms #2 below
2. Visceral pericardium (a.k.a. epicardium of
heart wall)
– INNER, thin, smooth, moist serous layer
– covers heart surface
3. Pericardial cavity: between 1 + 2 above
– filled with ____________________
Fig. 19.3
19-18
Functions?
3
1
2
19-19
§ Heart Wall (from outermost layer)
1. Epicardium (a.k.a. visceral pericardium)
– serous membrane covers heart
2. Myocardium
– thick muscular layer
– fibrous skeleton - network of collagenous and
elastic fibers (special section for this one)
3. Endocardium - smooth inner lining
– What type of epi.? Simple _________ epi.
– Continuous with endothelium cells . . .
Fig. 19.3
19-20
2
3
1
19-21
§ Fibrous skeleton of the heart (1)
– What is it? Four CT rings fuse with . . .
– Structure details– Four fibrous rings,
surrounds the 4 valves; in sheets of
tissue that interconnect these rings
– Location? In the walls between …
Figure 19.8
19-22
(Rear)
Right AV valve
Fibrous skeleton
including fibrous rings
Left AV valve
Aortic valve
Pulmonary semilunar
valve
Ventricular
myocardium
(Front)
19-23
§ Fibrous skeleton of the heart (2)
Functions–
– 1. Structure support-- firm base of the
heart valves and openings of great
vessels
– 2. It anchors the cardiac muscle
– 3. An electrical insulator:
• Separate the atria from the ventricles
and direct A.P. to specific pathways
19-24
Checkpoint Questions
1. Does most of the heart lie to
the right or left of the median
plane?
2. Name, in order, the three
layers of the heart wall
beginning with the outermost
layer.
19-25
§ Heart Chambers
• 4 chambers—
– A. right and left ATRIA
– auricles? Ear-like structures . . .
– B. right and left VENTRICLES
• 3 sulci (grooves)— on the surface
• Largely fat and coronary blood vessels
– A. Atrioventricular (coronary) sulcus– B+C. Anterior and posterior interventricular
sulci
Figure 19.5 a+b
19-26
Coronary
Anterior view sulcus?
19-27
Posterior view
19-28
§ Heart Chambers – Internal (Fig. 19.7)
1. Interatrial septum
– wall that separates atria
2. Pectinate muscles
– internal ridges of myocardium
in right atrium and both
auricles; (@ absorber)
3. Interventricular septum
– wall that separates ventricles
Wave/sound
absorber
4. Trabeculae carneae
– internal ridges in both
ventricles (@ absorber)
19-29
19-30
Checkpoint Questions
1. Which heart chamber has the
thickest walls? What is the
significance of this structural
difference?
2. Do the atrial pectinate muscles
more nearly resemble the
ventricular papillary muscles
or the trabeculae carneae?
19-31
§ Heart
valves (1)
1. Two atrioventricular (AV) valves—
– A. Right AV valve– also called the
tricuspid valve
– B. Left AV valve– also called . . .
• Function-blood from the atria to ventricles .
..
Figure 19.8 (a,b)
19-32
Aorta
Pulmonary artery
Superior vena cava
Pulmonary valve
Pulmonary veins
Right atrium
Right AV valve
Right ventricle
Inferior vena cava
Pulmonary veins
Left atrium
Left AV valve
Aortic valve
Chordae tendineae
Papillary muscle
Left ventricle
Interventricular
septum
Superior views of these valves – next slide19-33
Right AV valve
Left AV valve
Aortic/pulmonary
valve
19-34
Heart valves (2)
2. Chordae tendineae—
– Structure–
• Fibrous cords anchor the cusps to
the ventricle walls via papillary
muscles
– Function–
• Prevent valves from being _________
Figure 19.7, 19.8
19-35
Right atrium
Chordae
tendineae
Right AV
valve
Direction of
backflow of
blood
Septum
Right ventricle
Papillary
muscle
19-36
Right AV valve seen from within the
right ventricle
19-37
§ Heart
valves (3)
3.Semilunar valves include: One
______ valve and one __________ valve
A. Where are they located respectively?
• Major arteries leave the ventricles
B. How to prevent them from everting?
• Anatomical structure— leakproof “seam”
C. Function– (of all valves)
• Ensure unidirectional flow of blood
Figure 19.7 and Fig. Z
19-38
Aorta
Superior vena cava
Pulmonary valve
Pulmonary veins
Right atrium
Right AV valve
Right ventricle
Inferior vena cava
Next slide
Pulmonary artery
Pulmonary veins
Left atrium
Left AV valve
Aortic valve
Chordae tendineae
Papillary muscle
Left ventricle
Interventricular
septum
19-39
(Pulmonary trunk
or Aorta)
Direction of backflow of blood
Leakproof
“seam”
Aortic valve
(Right or Left
Ventricle)
19-40
§ Valve Mechanics (Fig. 19.9, 19.19)
Ventricles filling & isovolumetric contraction
– AV valves open (semilunar valves close);
blood flows from atria to ventricles (v. fillings)
– AV valves open/closed (circle one)—S1
– ventricle pressure continues to rise
– Momentarily before ventricle ejection
Ventricles ejection & isovolumetric relaxation
– semilunar valves open (AV valves close);
– ventricle ejection; ventricle pressure drops
– semilunar valves open/closed (circle one)—S2
– Isovolumetric relaxation
19-41
Operation of Atrioventricular Valves
S1
19-42
Operation of Semilunar Valves
S2
19-43
Before You Go On (p. 730)
• Reminder: Remember to go over each
question of Before You Go On in the
text.
• P. 730– Trace the flow of blood through
the heart, naming each chamber, valve,
and the great vessels in order (from the
superior vena cava to the aorta). Do it
yourself. Fig. 19.9 is a great figure to
help you with this.
44
Fig. 19.9 Pathway of blood flow through the heart
Figure 19.10
III. The Coronary Circulation
19-46
§ Coronary arteries
Right C.A.
Left C.A.
19-47
§ Coronary Arterial Supply
• 1. Left coronary artery (LCA)– 2 branches
– 1A--anterior interventricular branch
• supplies blood to interventricular septum and
anterior walls of both ventricles
– 1B--circumflex branch (Fig. 19.10 a+b)
• passes around left side of heart in coronary sulcus,
supplies left atrium and posterior wall of left
ventricle; it gives off a left marginal branch (1C)
• 2. Right coronary artery (RCA)– 2 branches
– 2A--right marginal branch
• supplies lateral side of R atrium and ventricle
– 2B--posterior interventricular branch
• supplies posterior walls of ventricles
19-48
1B
2A
1A
19-49
1B
1C
2A
2B
19-50
§ Anastomoses of coronary arteries
1. Definition (Anastomosis) – a point where
two blood vessels join/merge; this is
arterial anastomoses
2. Where? Anterior interventricular branch
of LCA joins the posterior interventricular
branch of RCA
3. Function– provide collateral (alternative)
routes of blood supply to a tissue (the
heart)
Fig. x
19-51
Chest pain and Heart Attack
• Angina pectoris-– partial obstruction of coronary blood flow can
cause chest pain
– pain caused by ischemia, often activity
dependent
• Myocardial infarction (heart attack)-– complete obstruction causes death of cardiac
cells in affected area
– pain or pressure in chest that often radiates
down left arm
19-53
§ Venous Drainage of Heart
• 10% drains directly into right atrium and
ventricle via multiple thebesian veins
• 90% returns to right atrium via: (Fig. 19.10)
– A. great cardiac vein
• blood from anterior interventricular sulcus
– B. middle cardiac vein (post. interventricular v.)
• from posterior sulcus
– C. left marginal vein
The above three (A, B, C) empty into the
coronary sinus before emptying into the
____________ (which chamber of the heart?)
19-54
A
19-55
A
C
B
or posterior interventricular v. 19-56
IV. Cardiac conduction
system
19-57
§ 19.3 Cardiac muscle &
conduction system
Heart has its own pacemaker, nerves
MODIFY the heart rate & contraction
strength.
• Beat rhythmically, _________beats per
min.
– Pacemaker? Where? (next slide)
– Myogenic and autorhythmic
– Regulation by autonomic nerve system
19-58
§ Cardiac Conduction System (1)
I. Properties
– myogenic - heartbeat originates from within
____________________
– Originated from what cells (1% of heart cells)?
cardiac muscles become specialized into
autorhythmic cells (cardiac conduction system)
– What do autorhythmic cells do?–
regular, spontaneous depolarization
II. Components
– next slide
19-59
Cardiac Conduction System (2)–
Autorhythmic cells
1. SA (sinoatrial) node: pacemaker, initiates
heartbeat, sets heart rate; where?
2. AV node: electrical gateway to ventricles;
where?
• fibrous skeleton– insulates atria from ventricle
3. AV bundle: pathway for signals from AV node
4. Right and left bundle branches: divisions of
AV bundle that enter interventricular septum
5. Purkinje fibers: upward from apex spread
throughout ventricular myocardium
Fig. 19.12 + X
19-60
Cardiac Conduction System
1
2
3
5
4
19-61
Students-- work on
this one at home
Interatrial
pathway
3. Atrioventricular
(AV) node
1. Sinoatrial
(SA) node
4. Bundle of His
or AV bundle
Right
atrium
5b. Left branch
of bundle of His
2. Internodal
pathway
5a. Right
branch
of bundle
of His
Left
ventricle
Right
ventricle
6. Purkinje
fibers
19-62
Checkpoint Question
Which chamber of the heart is first to
receive the electrical signal that
induces the heart to contract?
63
V. Cardiac muscle
19-64
§ Cardiac vs. skeletal m.(1)
Skeletal M.
Cardiac M.
(cardiocyte)
Fibers & their
control
•Fibers
independent
•Voluntary
•Interlocking
cells; (next)
•Involuntary
Nervous
control by
•Somatic motor • Autonomic
neurons
nervous sys.
Initiation of
contraction
•Requires input • by
from motor
autorhythmic
neurons
cells in heart
65
§ Cardiac vs. skeletal m.(2)
1. Cardiac myocytes—size,
thickness etc.
2. T (transverse) tubules– smaller
3. Presence of intercalated discs–
(see next slide)
4. Mitochondria—
5. Myoglobin and glycogen-66
§ Intercalated discs (of
cardiac muscle cells)
• Def. specialized zigzag structures
joining cardiac muscle cells end to end
• Containing three distinctive features
not found in skeletal muscle; what are
they?
Figure 19.11 a-c
67
Figure 19.11a light micrograph
Next slide
19-68
One myocyte is shown
(colored).
19-69
2
1
3
Structure of
an
intercalated
disc
1-- interdigitating folds
2—mechanical junctions– two types; fascia
adherens and desmosomes
3—electrical (gap) junctions-19-70
Plasma membranes of adjacent
cardiac muscle fibers
Desmosome
Fascia adherens
Gap junction
Intercalated disc
Action
potential
19-71
§ Intercalated discs
1. Function of interdigitating folds--
2. Functions of fascia adherens and
desmosome –
• Types of adhering junction
• Mechanically, hold cells together
72
§ Intercalated discs
3. Functions of gap junction (connexons):
• Allows action potentials to spread . . .
• Therefore, cardiac cells form functional
syncytia— cardiac cells excited and
contract as a single unit
Q--Does the atria and the ventricle each
form a separate unit?
73
VI. Electrical activity of
heart (autorhythmic cells)
19-74
§ 19.4 Heart Autorhythmic Cells
1. Two types of cardiac muscle cells:
A. 1% are autorhythmic cells (our focus
on this section)–
– Function?
• AP— Yes
• Contraction– No
B. 99% --contractile cells
– Function?
• AP— No initiation of own Action
Potential
• Contraction– Yes
19-75
§ Heart autorhythmic cells
2.Autorhythmic cells act as pacemaker:
• How? Their m. potential slowly
depolarizes (drifts) between AP, until . .
.…
Figure 19.13
19-76
B
C
A
Pacemaker potentials &
action potentials of the
SA node
19-77
§ Heart autorhythmic cells
3.
Details of pacemaker activity: (vs.
AP in nerve and skeletal m.):
A. Slow depolarization:
i. K+ voltage-gated channels slowly close
ii. (No voltage-gated Na+ channels),
instead sodium leak channels are
used; So, sodium ions move in/out
iii. Transient Ca+2 channels open—Calcium
ions move inward
All these make the inside becomes
depolarized Thus, pacemaker p. toward
19-78
threshold
§ Heart autorhythmic cells
B. Rising phase of the action potential:
•
Once, reach threshold p., longlasting Ca+2 channels open; . . .
•
Influx of calcium ions
C. The falling phase:
•
as usual, potassium ions efflux
19-79
§ Heart autorhythmic cells
4.Autorhythmic cells are self excitable:
– Without nervous stimulation
– They initiate AP cyclically, which
trigger rhythmic beating
– Each depolarization of SA node sets
off one heartbeat (every 0.8 sec.)
– They form the conduction system of
the heart (see Figure 19.12)
– It excites the other components in the
system
19-80
§ Heart autorhythmic cells
5. The spread of cardiac excitation:
In a coordinated sequence:
A-First, atrial excitation– From SA node to
atria;
How? through gap junctions;
via internodal and interatrial pathways as
well; Result– a single smooth contraction
of the pair of atria (Fig. Y)
B-Second, from the atria to the ventricles—
AV node is the only point of electrical contact
from the atria to the ventricles
C-Finally, ventricular excitation-from AV node to the bundle of His, . . .
Result– a single smooth contraction in
19-81
ventricles
Interatrial pathway
Right atrium
Left atrium
1st
beat
SA node
Internodal
pathway
Bundle
of His
AV node
2nd
beat
Purkinje
fibers
Right ventricle
Left ventricle
19-82
VII. contractile activity of heart
19-83
Our focus
19-84
§ Cardiac contractile cells
1. Action
potential is
initiated by:
the
pacemaker
cells
3 phases:
– Rising
– Plateau
–…
85
§ Cardiac contractile cells
2.The detail of action potential:
A.Rising phase
• Massive sodium ions influx causes
depolarization and AP
B.Plateau phase
• Primarily caused by opening of calcium
channels
• Also caused by temp. reduction in outflow of
_____________ ions
86
§ Cardiac contractile cells
C.Falling phase
• Primarily caused by ____________ outflow
• Closing of calcium channels contribute to
this as well
87
Review slide— ID A, B, C, D, E below
B
C
A
D
E
19-88
§ Cardiac contractile cells
3.Contractile
response
Compare to skeletal
muscle:
• Longer period of
cardiac contraction
• Longer refractory
period
How? Why? (next)
Action
potential
Contractile
response
Refractory
period
89
§ Cardiac contractile cells
A.Longer period of cardiac contraction
– 3x longer compared to skeletal m.
– Caused by entry of calcium ions which
induce more calcium ions release from the
sarcoplasmic reticulum
– Purpose– this increased contractile time
ensures emptying blood into ventricles and
arteries
Fig. 11.13 (skeletal muscle)
90
Latent
period
Contraction Relaxation
time
time
In skeletal
muscle
Muscle
twitch
Contractile
response
Action
potential
19-91
Stimulation
§ Cardiac contractile cells
B.Longer refractory period
• Caused chiefly by inactivation of the
sodium ion channels
• Consequences/Purpose– Cardiac
muscle cannot be re-stimulated until
contraction is almost over, therefore
summation and tetanus of cardiac m. is
impossible
• This ensures . . .
Compared to Fig. 11.13 (Shown previously; in
skeletal m.)
92
§ ECG (Electrocardiogram)
1. Def. A record of the overall electrical
activity in all the cardiac muscle cells from
the body surface
– NOT a recording of a single action
potential in a single cell
– ECG recording represents . . .electrical
activity detected by electrodes at 2
different points
Figure 19.15 (ECG)
93
§ ECG (Electrocardiogram)
2.Components of the ECG correlate to
cardiac events (Fig. 19.16 in the next slide)
• P wave— atrial depolarization when the
electrical impulse spreads across the atria
• QRS complex—
• T wave— ventricular repolarization
R
T
P
P
Q S
95
P
T
QRS
19-96