Transcript Cardiovascular System: The Heart A

The Heart
Part 1
Slides by Vince Austin and W. Rose.
figures from Marieb & Hoehn 8th and 9th eds.
Portions copyright Pearson Education
Heart Anatomy
• Approximately the size of a fist
• Location
• In the mediastinum between second rib and fifth
intercostal space
• On the superior surface of diaphragm
• Two-thirds to the left of the midsternal line
• Anterior to the vertebral column, posterior to the
sternum
• Enclosed in pericardium, a double-walled sac
PLAY
Animation: Rotatable heart
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Superior
vena cava
Aorta
Parietal
pleura (cut)
Pulmonary
trunk
Left lung
Pericardium
(cut)
Diaphragm
Apex of
heart
(c)
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Figure 18.1c
Pericardium
Two layers
Parietal layer (“pericardium”) a clear fibrous
“bag” protecting & anchoring heart. Limits
filling beyond a certain volume.
Visceral layer (epicardium) on external surface
of the heart
Very thin layer of fluid between the layers decreases friction
Layers of the heart wall
• Epicardium
(visceral
pericardium)
• Myocardium
(muscle)
• Endocardium
(inner lining)
http://dev.biologists.org/content/139/18/3277/F1.large.jpg
Cardiac Chambers: 2 ventricles, 2 atria
Two atria
• Separated internally by interatrial septum
• Coronary sulcus (atrioventricular groove)
encircles junction of atria and ventricles
• Auricles increase atrial volume
Two ventricles
• Separated by interventricular septum
• Anterior & posterior interventricular sulci on
external surface suggest location of septum
inside
Brachiocephalic trunk
Superior vena cava
Right pulmonary
artery
Ascending aorta
Pulmonary trunk
Right pulmonary
veins
Right atrium
Right coronary artery
(in coronary sulcus)
Anterior cardiac vein
Right ventricle
Right marginal artery
Small cardiac vein
Inferior vena cava
(b) Anterior view
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Left common carotid
artery
Left subclavian artery
Aortic arch
Ligamentum arteriosum
Left pulmonary artery
Left pulmonary veins
Auricle of
left atrium
Circumflex artery
Left coronary artery
(in coronary sulcus)
Left ventricle
Great cardiac vein
Anterior interventricular
artery (in anterior
interventricular sulcus)
Apex
Figure 18.4b
Atria: The Receiving Chambers
Vessels entering right atrium
• Superior vena cava
• Inferior vena cava
• Coronary sinus
Vessels entering left atrium
• Right and left pulmonary veins
Ventricles: The Discharging
Chambers
Walls are ridged by trabeculae carneae
Papillary muscles project into the
ventricular cavities
Pulmonary trunk leaves right ventricle
Aorta leaves left ventricle
Aorta
Superior vena cava
Right pulmonary
artery
Pulmonary trunk
Right atrium
Right pulmonary
veins
Fossa ovalis
Pectinate muscles
Tricuspid valve
Right ventricle
Chordae tendineae
Trabeculae carneae
Inferior vena cava
Left pulmonary
artery
Left atrium
Left pulmonary
veins
Mitral (bicuspid)
valve
Aortic valve
Pulmonary valve
Left ventricle
Papillary muscle
Interventricular
septum
Epicardium
Myocardium
Endocardium
(e) Frontal section
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Figure 18.4e
Pathway of Blood Through the Heart
The heart is two side-by-side pumps
Right side pumps blood to & through pulmonary
(lung) arteries & veins
Left side pumps blood to & through systemic
arteries & veins (everything but lungs)
Pulmonary
Circuit
Pulmonary arteries
Venae cavae
Capillary beds
of lungs where
gas exchange
occurs
Pulmonary veins
Aorta and branches
Left atrium
Left ventricle
Right atrium
Right ventricle
Oxygen-rich,
CO2-poor blood
Oxygen-poor,
CO2-rich blood
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Heart
Systemic
Circuit
Capillary beds of all
body tissues where
gas exchange occurs
Figure 18.5
Blood pathway through right side of heart
Systemic veins  Right atrium  tricuspid valve 
right ventricle
Right ventricle  pulmonary (semilunar) valve 
pulmonary trunk  pulmonary arteries  lung
capillaries
Blood pathway through left side of heart
Pulmonary veins  Left atrium  mitral valve  left
ventricle
Left ventricle  aortic (semilunar) valve  ascending
aorta  systemic arteries  systemic capillaries
Pathway of Blood Through the Heart
• Equal volumes of blood are pumped to the
pulmonary and systemic circuits
• Pulmonary circuit is a short, low-pressure
circulation
• Systemic circuit blood encounters much
resistance in the long pathways
• Anatomy of the ventricles reflects these
differences
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Left
ventricle
Right
ventricle
Interventricular
septum
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Figure 18.6
Coronary Circulation
• The functional blood supply to the heart
muscle itself
• Arterial supply varies considerably and
contains many anastomoses (junctions)
among branches
• Collateral routes provide additional routes for
blood delivery
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Coronary Circulation
• Arteries
• Right and left coronary (in atrioventricular
groove), marginal, circumflex, and anterior
interventricular arteries
• Veins
• Small cardiac, anterior cardiac, and great
cardiac veins
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Superior
vena cava
Anastomosis
(junction of
vessels)
Right
atrium
Aorta
Pulmonary
trunk
Left atrium
Left
coronary
artery
Circumflex
artery
Right
coronary
Left
artery
ventricle
Right
ventricle
Anterior
Right
interventricular
marginal Posterior
artery
artery
interventricular
artery
Major coronary arteries
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Figure 18.7a
Superior
vena cava
Anterior
cardiac
veins
Great
cardiac
vein
Coronary Sinus
(on the back wall,
drains into RA)
Small cardiac vein
Middle cardiac vein
Major cardiac veins
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Figure 18.7b
Aorta
Left pulmonary
artery
Superior vena cava
Left pulmonary
veins
Auricle of left
atrium
Left atrium
Great cardiac
vein
Right pulmonary veins
Posterior vein
of left ventricle
Left ventricle
Apex
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Right pulmonary artery
Right atrium
Inferior vena cava
Coronary sinus
Right coronary artery
(in coronary sulcus)
Posterior
interventricular
artery (in posterior
interventricular sulcus)
Middle cardiac vein
Right ventricle
(d) Posterior surface view
Figure 18.4d
Homeostatic Imbalances
• Angina pectoris
• Thoracic pain caused by temporarily
inadequate blood flow to the myocardium
• Cells are weakened
• Myocardial infarction (heart attack)
• Prolonged coronary artery blockage
• Dead muscle cells are replaced with noncontractile scar tissue
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Heart Valves
• Ensure unidirectional blood flow through the heart
• Atrioventricular (AV) valves
• Prevent backflow into the atria when ventricles
contract
• Tricuspid valve (right)
• Mitral valve (left)
• Chordae tendineae anchor AV valve cusps to
papillary muscles
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Heart Valves
• Semilunar (SL) valves
• Prevent backflow into the ventricles when
ventricles relax
• Aortic semilunar valve
• Pulmonary semilunar valve
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Myocardium Pulmonary valve
Aortic valve
Tricuspid
Area of cutaway
(right atrioventricular)
Mitral valve
valve
Tricuspid valve
Mitral
(left atrioventricular)
valve
Aortic
valve
Myocardium
Tricuspid
(right atrioventricular)
valve
Mitral
(left atrioventricular)
valve
Aortic valve
Pulmonary
valve
Fibrous
skeleton
(a)
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Pulmonary valve
Aortic valve
Area of cutaway
(b)
Pulmonary
valve
Mitral valve
Tricuspid
valve
Anterior
Figure 18.8a
Opening of inferior
vena cava
Tricuspid valve
Mitral valve
Chordae
tendineae
Myocardium
of right
ventricle
Myocardium
of left ventricle
Papillary
muscles
(d)
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Interventricular
septum
Pulmonary
valve
Aortic valve
Area of
cutaway
Mitral valve
Tricuspid
valve
Figure 18.8d
Cardiac MRI of a
preserved human
heart.
Short axis view at
the level of the
valves.
The short axis view is a plane perpendicular to a line from the apex of the heart along the
interventricular septum to the approximate middle of the base of the heart.
“This short axis slice of the specimen beautifully shows the annulus of the mitral valve.
Additionally, the left circumflex artery can be seen curving around heart above the mitral
annulus and the left anterior descending artery diving down into the myocardium adjacent to
the pulmonary valve annulus.” Note how the mitral, aortic, and tricuspid valves share parts of
their annuli.
Source: Atlas of Human Cardiac Anatomy, heart 0053, http://www.vhlab.umn.edu/atlas/cardiac-mri/short-axis-valve/index.shtml, retrieved 20150228.
1 Blood returning to the
Direction of
blood flow
heart fills atria, putting
pressure against
atrioventricular valves;
atrioventricular valves are
forced open.
Atrium
Cusp of
atrioventricular
valve (open)
2 As ventricles fill,
atrioventricular valve flaps
hang limply into ventricles.
Chordae
tendineae
3 Atria contract, forcing
additional blood into ventricles.
Ventricle
Papillary
muscle
(a) AV valves open; atrial pressure greater than ventricular pressure
Atrium
1 Ventricles contract, forcing
blood against atrioventricular
valve cusps.
2 Atrioventricular valves
close.
3 Papillary muscles
contract and chordae
tendineae tighten,
preventing valve flaps
from everting into atria.
Cusps of
atrioventricular
valve (closed)
Blood in
ventricle
(b) AV valves closed; atrial pressure less than ventricular pressure
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Figure 18.9
Aorta
Pulmonary
trunk
As ventricles
contract and
intraventricular
pressure rises,
blood is pushed up
against semilunar
valves, forcing them
open.
(a) Semilunar valves open
As ventricles relax
and intraventricular
pressure falls, blood
flows back from
arteries, filling the
cusps of semilunar
valves and forcing
them to close.
(b) Semilunar valves closed
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Figure 18.10
Microscopic Anatomy of Cardiac Muscle
• Cardiac muscle cells are striated, short, fat,
branched, and interconnected
• Connective tissue matrix (endomysium)
connects to the fibrous skeleton
• T tubules are wide but less numerous; SR is
simpler than in skeletal muscle
• Numerous large mitochondria (25–35% of cell
volume) – these cells need energy & never
rest!
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Nucleus
Intercalated discs
Gap junctions
Cardiac muscle cell
Desmosomes
(a)
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Figure 18.11a
Microscopic Anatomy of Cardiac Muscle
• Intercalated discs: junctions between cells
anchor cardiac cells
• Desmosomes prevent cells from separating
during contraction
• Gap junctions allow ions to pass; electrically
couple adjacent cells
• Heart muscle behaves as a functional
syncytium
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Cardiac
muscle cell
Mitochondrion
Intercalated
disc
Nucleus
T tubule
Mitochondrion
Sarcoplasmic
reticulum
Z disc
Nucleus
Sarcolemma
(b)
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I band
A band
I band
Figure 18.11b