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The Heart
Contents:
• Functions of the heart – heart as a double
pump
• Why do we need a heart?
• Location of heart in the thorax
• Anatomy of the heart
• Flow of blood through the heart
• Flow of action potentials through the heart
• Vascularization of the heart
• Common diseases
Function
• Heart Function
• https://www.youtube.com/watch?v=oHMmtqKgs50
• Capillary beds
https://www.youtube.com/watch?v=Q530H1WxtOw
Why do we need a Heart?
• If you’ll remember from biology, you learned that multicellular
organisms are composed of cells. Humans contain approximately
70 trillion cells. Each of these cells are individual lives! They need
food, water, vitamins, hormones and they excrete waste. Unicellular
animals get all of that from their environment. Mulitcellular
organisms need mechanisms which mimic an external environment.
This is there the cardiovascular system comes in. Most of the cells
in our body are surrounded by fluid which mimics a natural
environment. Capillary beds are where cells are fed. It is crucial
that all cells receive what they need to survive. The CVS is
responsible for circulating fluid which contains nutrients, including
oxygen and also carry waste products away from capillary beds.
The pressure coming out of the heart is approx. 120/80. It needs to
get below 10mmHg in a capillary bed because it is only 1 cell thick
and would blow out with high pressure. Conversely, if pressure is
too low, perfusion of the capillary bed may not be sufficient.
Landmarks
• I. Orientation
• The heart is approximately the size of your fist.
It lies deep to the sternum in the inferior
mediastinum.
• Borders: Superiorly: great vessels, aorta,
superior vena cava
• Inferiorly: diaphragm
• Laterally: lungs
• Anteriorly: sternum
• Posteriorly: spinal column
Orientation of the Heart in the Thorax
Spinal cord
Body of vertebra
Right lung
Descending aorta
Esophagus
Left lung
Left atrium
Bronchi
Left AV valve
Rib (cut)
Inferior vena cava
Left pleural cavity
Right pleural cavity
Parietal pleura
Right atrium
Papillary muscle of left ventricle
Parietal pericardium
Pericardial cavity
Interventricular septum
Right ventricle
Body of sternum
Superior view of a horizontal section through the trunk at the level of
vertebra T8
Figure 21.2a Location of the Heart in the Thoracic Cavity
Trachea
Thyroid gland
Right lung
First rib (cut)
Left lung
Base of
heart
Diaphragm
Parietal pericardium
(cut)
Apex of
heart
Anterior view of the open chest cavity showing the position
of the heart and major vessels relative to the lungs. The
sectional plane indicates the orientation of part (c).
Figure 21.4 Position and Orientation of the Heart (Part 1 of 2)
Base of heart
1
1
Ribs
2
3
4
5
6
7
2
3
4
5
6
7
8
8
9
9
10
10
Apex
of heart
Figure 21.1 A Generalized View of the Pulmonary and Systemic Circuits
Pulmonary Circuit
Systemic Circuit
Pulmonary arteries
Systemic arteries
Pulmonary veins
Systemic veins
Capillaries in
head, neck,
upper limbs
Capillaries
in lungs
Right atrium
Right
ventricle
Capillaries in
trunk and
lower limbs
Left atrium
Left
ventricle
Figure 21.5a Superficial Anatomy of the Heart, Part I
Left common carotid artery
Left subclavian artery
Arch of aorta
Brachiocephalic trunk
Ligamentum
arteriosum
Descending
aorta
Ascending
aorta
Left pulmonary
artery
Superior
vena cava
Auricle
of right
atrium
Fat in
coronary
sulcus
Pulmonary
trunk
Auricle of
left atrium
RIGHT
ATRIUM
RIGHT
VENTRICLE
LEFT
VENTRICLE
Fat in
anterior
interventricular
sulcus
APEX
Anterior view of the heart and great
vessels
Figure 21.5b Superficial Anatomy of the Heart, Part I
Arch of aorta
Left pulmonary artery
Right pulmonary
artery
Left pulmonary veins
Superior
vena cava
LEFT
ATRIUM
Fat in
coronary
sulcus
Right
pulmonary
veins (superior
and inferior)
Coronary
sinus
RIGHT
ATRIUM
LEFT
VENTRICLE
Inferior
vena cava
RIGHT
VENTRICLE
Fat in posterior
interventricular sulcus
Posterior view of the heart and great
vessels
Figure 21.7b Sectional Anatomy of the Heart, Part I
Left common carotid artery
Brachiocephalic
trunk
Left subclavian artery
Ligamentum arteriosum
Superior
vena cava
Aortic arch
Pulmonary trunk
Pulmonary valve
Right
pulmonary
arteries
Left pulmonary
arteries
Ascending
aorta
Fossa ovalis
Opening of
coronary sinus
Left pulmonary
veins
LEFT
ATRIUM
Interatrial septum
Aortic valve
RIGHT ATRIUM
Pectinate muscles
Cusp of left AV
(mitral) valve
Conus arteriosus
LEFT VENTRICLE
Cusp of right AV
(tricuspid) valve
Chordae tendineae
Interventricular
septum
Papillary muscle
RIGHT VENTRICLE
Trabeculae
carneae
Inferior vena cava
Moderator
band
Descending
aorta
Diagrammatic frontal section through the relaxed heart shows the major
landmarks and the path of blood flow through the atria and ventricles (arrows).
See real heart valves in motion
Figure 21.8a Sectional Anatomy of the Heart, Part II
Ascending aorta
Cusp of aortic valve
Left coronary artery
branches (red)
and great cardiac
vein (blue)
Inferior vena cava
Fossa ovalis
Pectinate muscles
Coronary sinus
RIGHT ATRIUM
Cusps of right AV
(tricuspid) valve
Trabeculae carneae
RIGHT VENTRICLE
Anterior view of a frontally sectioned heart showing internal
features and valves. The cardiac arteries and veins have been
injected with latex; the arteries are red, the veins blue.
Cusp of left AV
(bicuspid) valve
Chordae tendineae
Papillary muscles
LEFT VENTRICLE
Interventricular
septum
II. Walls of Heart
A. Endocardium: endothelium, simp. squamous epith., lines inside
of heart & covers heart valves.
Endocarditis: inflammation of this internal lining.
B. Myocardium
Cardiac muscle, intercalated discs, branched,
striated. Organized by CT in networks called
bundles. Requires O2, has many mitochondria, myoglobin
& glycogen reserves
C. Pericardium.
1) visceral pericardium “epicardium”
2) parietal pericardium
3) fibrous pericardium
-Inferiorly: attaches to diaphragm,
Superiorly: attaches to large vessels of
heart.
D. Pericardial fluid- found between the epicardium and parietal
pericardium. Reduces friction between the two
serous membranes in beating heart
Figure 21.3ab Histological Organization of Muscle Tissue in the Heart Wall
Base of heart
Pericardial
cavity
Cut edge of pericardium
Apex of heart
Anterior view of the heart showing
several important landmarks
Pericardial cavity
Dense fibrous layer
Areolar tissue
MYOCARDIUM
(cardiac muscle tissue)
Parietal
pericardium
Mesothelium
Artery
Vein
A diagrammatic section
through the heart wall showing
the structure of the epicardium,
myocardium, and endocardium
Connective tissues
Mesothelium
Areolar tissue
ENDOCARDIUM
Areolar
connective
tissue
Endothelium
EPICARDIUM
(visceral pericardium)
Figure 21.3d Histological Organization of Muscle Tissue in the Heart Wall
Cardiac muscle cell
Mitochondria
Intercalated
disc (sectioned)
Nucleus
Cardiac muscle
cell (sectioned)
Bundles of
myofibrils
Diagrammatic three-dimensional
view of cardiac muscle cells
Intercalated
disc
Horse, heart. The pericardial sac contains excessive, slightly
turbid straw-colored fluid
Disease Images: African Horse Sickness
Which structures associated with the
atrioventricular (AV) valves play an important
role in the normal function of the AV valves
during the cardiac cycle?
a. pectinate muscles and papillary muscles
b. chordae tendineae and pectinate
muscles
c. trabeculae carneae and papillary
muscles
d. chordae tendineae and papillary muscles
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IV. Heart Contraction
A. Heart Beat
Systole= heart muscle contraction (atrial systole, ventricular systole)
Diastole= heart muscle relaxation
(for blood pressure, systolic vs diastolic pressure refers to
ventricles.)
- Heart beat “lub-dup” sounds are caused when valves close.
Heart murmur: ineffective valves that cause blood to pass back into
atria or ventricles
B. Conduction system - Heart beats approx 2.5 billion times in a lifetime!
- Nodal tissue: has both muscle & nervous characteristics.
1. SA node (sinoatrial node): Pacemaker generates impulse
every 0.85 seconds
2. AV node (atrioventricular node)
3. atrioventricular bundle (bundle of His) found in
interverntricular septum
4. Perkinje fibers * ventricles contract from bottom up; good for blood
flow direction
Figure 21.12a The Conducting System of the Heart
Will the heart beat
outside the body?
Sinoatrial
(SA) node
Internodal
pathways
Atrioventricular
(AV) node
AV bundle
Left bundle branch
Right bundle branch
Moderator band
Purkinje fibers
The stimulus for contraction is generated by pacemaker cells at
the SA node. From there, impulses follow three different paths
through the atrial walls to reach the AV node. After a brief delay,
the impulses are conducted to the bundle of His (AV bundle), and
then on to the bundle branches, the Purkinje fibers, and the
ventricular myocardial cells.
C. Modification of heart beat
Cardioregulatory center in medulla oblongata carried
out by sympathetic &parasympathetic fibers via vagus nerve)
D. Echocardiogram (ECG, EKG)
- measures the depolarization of the heart’s chambers.
1. Bradycardia: slow heartbeat: (Fewer than 60
heartbeats/min.)
2. Tachycardia: fast heart beat (more than 100
beats/min.)
3. Fibrillation: heart beats rapidly, but in an
uncoordinated manner- heart can be defibrillated by
applying a strong electrical current to chest.
Figure 21.13 The Autonomic Innervation of the Heart
Vagal nucleus
Cardioinhibitory
center
Cardioacceleratory
center
T/F
If sympathetic
fibers are active, it
will increase heart
rate.
Medulla
oblongata
Vagus (N X)
Spinal cord
Sympathetic
Sympathetic
preganglionic
fiber
Sympathetic ganglia
(cervical ganglia and
superior thoracic
ganglia [T1–T4])
Sympathetic
postganglionic fiber
Cardiac nerve
https://www.youtube.com/watch?v=RYZ4d
aFwMa8
© 2012 Pearson Education, Inc.
Parasympathetic
Parasympathetic
preganglionic
fiber
Synapses in
cardiac plexus
Parasympathetic
postganglionic
fibers
Clinical Note 21.2 Cardiac Arrhythmias, Artificial Pacemakers, and Myocardial Infarctions
An artificial pacemaker
© 2012 Pearson Education, Inc.
ECG/EKG
Which of the following statements
regarding the cardiovascular system is/are
true?
a.The right atrium collects blood from the
pulmonary circuit.
b.The right ventricle ejects blood into the
systemic circuit.
c.When the heart beats, the atria contract
first, followed by the ventricles.
d.All of these statements are true.
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V. Blood supply to the heart
A. Right coronary artery: from right side of aorta, descends in coronary
sulcus- marks border btwn atria & ventricles.
1. Branches to form the right marginal artery
2. Posterior: large branch, posterior interventricular (descending)
artery, (in posterior interventricular sulcus) Serves right atrium &
ventricle. SA Nodal branch (supplies SA node)
B. Left coronary artery: from left side of aorta, under pulmonary trunk;
forms 2 branches:
1. anterior interventricular (descending) artery ( in anterior
interventricular sulcus)
branches to serve both ventricles
2. circumflex artery (in coronary sulcus) serves left
ventricle and atrium.
C. Cardiac veins
- Draining into the coronary sinus:
1) great cardiac vein: in anterior interventricular sulcus
2) middle cardiac vein in posterior interventricular sulcus
3) small cardiac vein: running along heart’s inferior right margin.
4) anterior cardiac veins in anterior surface of Rt. Ventricle, small
horizontal veins. empty directly into right atrium.
https://www.youtube.com/watch?v=Kv-MN-Gv6jw
Figure 21.10c Coronary Circulation
Left common
carotid artery
Brachiocephalic
trunk
Left subclavian artery
Aortic arch
Superior
vena cava
Pulmonary trunk
Ascending
aorta
Diagonal branch
of LCA
Right auricle
Right coronary
artery
Great
cardiac vein
Anterior cardiac
vein
Anterior
interventricular
branch of LCA
RIGHT ATRIUM
Small cardiac
vein
LEFT
VENTRICLE
Right marginal
branch of RCA
RIGHT VENTRICLE
A cast of the coronary vessels showing the complexity and extent of the coronary circulation. Coronary vessels are also seen in Figure 21.6.
Which of the following statements regarding heart
contraction is true?
a.
A.The atria contract together, before the ventricles
b.
B. The ventricles contract together in a wave that
begins at the base and spreads toward the apex.
c.
C The stimulus for a contraction is generated at the
atrioventricular bundle.
d.
D Cardiac muscle tissue contracts only in the
presence of neural or hormonal stimulation.
• VI. Common Coronary Artery Disease
Procedures
•
1. balloon angioplasty: plastic tube is
threaded into the arteries & balloon is
inflated to open up the vessel. A stent
holds the vessel open.
•
2. Bypass surgery:
•
Use a vessel from another part of
the body to re-route blood around the
blockage.
For Occluded Coronary Arteries…
See heart surgery explained pt 1 7min
balloon angioplasty animation
Heart surgery pt 2 7min