3. 1-Size, Location, and Orientation1-Size, Location, and Orientation
• About the size of a fist, hollow, cone-shaped heart has a mass of
between 250 and 350 grams
• Mediastinum, the medial cavity of the thorax, the heart extends
obliquely for 12 to 14 cm (about 5 inches) from the second rib to
the fifth intercostal space.
• As it rests on the superior surface of the diaphragm, the heart lies
anterior to the vertebral column and posterior to the sternum.
• Approximately two-thirds of its mass lies to the left of the
midsternal line.
• Its broad, flat base, or posterior surface, is about 9 cm (3.5 in) wide
and directed toward the right shoulder.
• Its apex points inferiorly toward the left hip. If you press your
fingers between the fifth and sixth ribs just below the left nipple,
you can easily feel your heart beating where the apex contacts the
chest wall. Hence, this site is referred to as the point of maximal
intensity (PMI).
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5. 2-Coverings of the heart2-Coverings of the heart
• The heart is enclosed in a double-walled sac called the
pericardium
• The loosely fitting superficial part of this sac is the
fibrous pericardium. This tough, dense connective tissue
layer
(1) protects the heart,
(2) anchors it to surrounding structures
(3) prevents overfilling of the heart with blood.
• Deep to the fibrous pericardium is the serous
pericardium, a thin, slippery, two-layer serous
membrane.
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6. Coverings of the heartCoverings of the heart
Its parietal layer lines the internal surface of the fibrous
pericardium.
At the superior margin of the heart, the parietal layer attaches to
the large arteries exiting the heart, and then turns inferiorly and
continues over the external heart surface as the visceral layer,
also called the epicardium (“upon the heart”), which is an
integral part of the heart wall.
Between the parietal and visceral layers is the slitlike
pericardial cavity, which contains a film of serous fluid. The
serous membranes, lubricated by the fluid, glide smoothly past
one another during heart activity, allowing the mobile heart to
work in a relatively friction-free environment.
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8. 3-Layers of the heart wall3-Layers of the heart wall
The superficial epicardium is the visceral layer of the serous
pericardium.
The middle layer, the myocardium (“muscle heart”), is composed
mainly of cardiac muscle and forms the bulk of the heart. It is the layer
that contracts.
In this layer, the branching cardiac muscle cells are tethered to one
another by crisscrossing connective tissue fibers and arranged in spiral
or circular bundles
The third layer, the endocardium (“inside the heart”), is a glistening
white sheet of endothelium (squamous epithelium) resting on a thin
connective tissue layer.
Located on the inner myocardial surface, it lines the heart chambers
and covers the fibrous skeleton of the valves. The endocardium is
continuous with the endothelial linings of the blood vessels leaving and
entering the heart.
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10. 4-Chambers & great vessels4-Chambers & great vessels
The heart has four chambers two superior atria and two inferior
ventricles
The internal partition that divides the heart longitudinally is called
the interatrial septum where it separates the atria, and the
interventricular septum where it separates the ventricles.
The right ventricle forms most of the anterior surface of the heart.
The left ventricle dominates the inferoposterior aspect of the heart
and forms the heart apex.
Two grooves visible on the heart surface indicate the boundaries of
its four chambers and carry the blood vessels supplying the
myocardium. The coronary sulcus, or atrioventricular groove,
encircles the junction of the atria and ventricles like a crown.
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11. Chambers & great vesselsChambers & great vessels
The anterior interventricular sulcus, cradling the anterior
interventricular artery, marks the anterior position of the
septum separating the right and left ventricles.
It continues as the posterior interventricular sulcus, which
provides a similar landmark on the heart’s posteroinferior
surface.
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13. Chambers & great vesselsChambers & great vessels
Atria: The Receiving Chambers.Atria: The Receiving Chambers.
•Right atrium has two basic parts
1.a smooth-walled posterior part
2.anterior portion in which the walls are ridged by bundles of muscle
tissue. Because these bundles look like the teeth of a comb, these
muscle bundles are called pectinate muscles
•The posterior and anterior regions of the right atrium are separated
by a C-shaped ridge called the crista terminalis (“terminal crest”).
• In contrast, the left atrium is mostly smooth and undistinguished
internally.
•The interatrial septum bears a shallow depression, the fossa ovalis
that marks the spot where an opening, the foramen ovale, existed in
the fetal heart 13
14. Chambers & great vesselsChambers & great vessels
Blood enters the right atrium via three veins
The superior vena cava returns blood from body regions
superior to the diaphragm;
The inferior vena cava returns blood from body areas
below the diaphragm; and
The coronary sinus collects blood draining from the
myocardium.
Four pulmonary veins enter the left atrium, which makes up
most of the heart’s base. These veins, which transport blood
from the lungs back to the heart, are best seen in a posterior
view
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15. Right anterior view of the internal aspect of the right atrium.Right anterior view of the internal aspect of the right atrium.
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17. Chambers & great vesselsChambers & great vessels
Ventricles: The Discharging chambersVentricles: The Discharging chambers
•The right ventricle forms most of the heart’s anterior surface
•Left ventricle dominates its posteroinferior surface.
•Marking the internal walls of the ventricular chambers are irregular
ridges of muscle called trabeculae carneae “crossbars of flesh”).
•Still other muscle bundles, the cone like papillary muscles, which
play a role in valve function, project into the ventricular cavity.
•The ventricles are the discharging chambers or actual pumps of the
heart When the ventricles contract, blood is propelled out of the heart
into the circulation.
•The right ventricle pumps blood into the pulmonary trunk, which
routes the blood to the lungs where gas exchange occurs.
•The left ventricle ejects blood into the aorta the largest artery in the
body. 17
19. Anatomical differences in right and left ventricles. The left ventricle
has a thicker wall and its cavity is basically circular; the right ventricle
cavity is crescent shaped and wraps around the left ventricle.
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21. 5-Coronary circulation5-Coronary circulation
• The coronary circulationcoronary circulation, the functional blood supply of the
heart, is the shortest circulation in the body.
• The arterial supply of the coronary circulation is provided by
the right and left coronary arteries, both arising from the base
of the aorta and encircling the heart in the coronary sulcus .
• The left coronary artery runs toward the left side of the heart
and then divides into its major branches:
1.1. Anterior interventricular arteryAnterior interventricular artery (also known clinically as the
left anterior descending artery), which follows the anterior
interventricular sulcus and supplies blood to the
interventricular septum and anterior walls of both ventricles;
2.2. Circumflex arteryCircumflex artery, which supplies the left atrium and the
posterior walls of the left ventricle.
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23. Coronary arteriesCoronary arteries
• The right coronary artery courses to the right side of the
heart, where it also divides into two branches:
1.1. Marginal arteryMarginal artery, which serves the myocardium of the
lateral right side of the heart,
2.2. Posterior interventricular arteryPosterior interventricular artery, which runs to the heart
apex and supplies the posterior ventricular walls.
• Near the apex of the heart, this artery merges
(anastomoses) with the anterior interventricular artery.
• Together the branches of the right coronary artery supply
the right atrium and nearly all the right ventricle.
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24. Coronary veinsCoronary veins
• After passing through the capillary beds of the myocardium, the
venous blood is collected by the cardiac veins, whose paths
roughly follow those of the coronary arteries.
• These veins join together to form an enlarged vessel called the
coronary sinus, which empties the blood into the right atrium.
• The coronary sinus is obvious on the posterior aspect of the heart.
• The sinus has three large tributaries:
1. the great cardiac veingreat cardiac vein in the anterior interventricular sulcus;
2. the middle cardiac veinmiddle cardiac vein in the posterior interventricular sulcus;
3. the small cardiac veinsmall cardiac vein, running along the heart’s right inferior
margin.
• Additionally, several anterior cardiac veins empty directly into
the right atrium anteriorly.
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26. 6-Heart valves6-Heart valves
• Blood flows through the heart in one direction: from atria
to ventricles and out the great arteries leaving the superior
aspect of the heart.
• This one-way traffic is enforced by four valves that open
and close in response to differences in blood pressure on
their two sides.
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27. Atrioventricular ValvesAtrioventricular Valves
• The two atrioventricular (AV) valves, one located at each
atrial-ventricular junction, prevent backflow into the atria when
the ventricles are contracting.
• The right AV valve, the tricuspid valve, has three flexible
cusps (flaps of endocardium reinforced by connective tissue
cores).
• The left AV valve, with two flaps, is called the mitral valve. It
is sometimes called the bicuspid valve.
• Attached to each AV valve flap are tiny white collagen cords
called chordae tendineae (“tendonous cords”), “heart strings”
which anchor the cusps to the papillary muscles protruding
from the ventricular walls.
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28. The valves open when the blood pressure exerted on their atrialThe valves open when the blood pressure exerted on their atrial
side is greater than that exerted on their ventricular side.side is greater than that exerted on their ventricular side.
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29. The valves are forced closed when the ventricles contract andThe valves are forced closed when the ventricles contract and
intraventricular pressure rises, moving the contained bloodintraventricular pressure rises, moving the contained blood
superiorly. The action of the papillary muscles and chordae tendineaesuperiorly. The action of the papillary muscles and chordae tendineae
keeps the valve flaps closed.keeps the valve flaps closed.
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30. Semilunar ValvesSemilunar Valves
The aortic and pulmonary (semilunar, SL) valves guard the
bases of the large arteries issuing from the ventricles (aorta and
pulmonary trunk, respectively) and prevent backflow into the
associated ventricles.
Like the AV valves, the SL valves open and close in response to
differences in pressure.
In the SL case, when the ventricles are contracting and
intraventricular pressure rises above the pressure in the aorta and
pulmonary trunk, the SL valves are forced open and their cusps
flatten against the arterial walls as the blood rushes past them.
When the ventricles relax, and the blood (no longer propelled
forward by the pressure of ventricular contraction) flows backward
toward the heart, it fills the cusps and closes the valves.
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32. When the ventricles relax, the back flowing blood closes theWhen the ventricles relax, the back flowing blood closes the
valves.valves.
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33. Superior view of the two sets of heart valves (atria removed). The pairedSuperior view of the two sets of heart valves (atria removed). The paired
atrioventricular valves are located between atria and ventricles; the twoatrioventricular valves are located between atria and ventricles; the two
semilunar valves are located at the junction of the ventricles and the arteriessemilunar valves are located at the junction of the ventricles and the arteries
issuing from them.issuing from them.
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34. Photograph of the tricuspid valve. This bottom-to-top view begins in thePhotograph of the tricuspid valve. This bottom-to-top view begins in the
right ventricle and faces toward the right atrium.right ventricle and faces toward the right atrium.
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