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Cardiovascular System
Prof. Abdulameer Al-Nuaimi
E-mail: [email protected]
E. mail: [email protected]
LOCATION AND SURFACE PROJECTION OF THE
HEART
• The cone-shaped heart is relatively small, roughly the same size as a closed fist.
• The heart rests on the diaphragm, near the midline of the thoracic cavity in the
mediastinum (an anatomical region that extends from the sternum to the
vertebral column, the first rib to the diaphragm, and between the coverings
(pleurae) of the lungs).
• About two-thirds of the mass of the heart lies to the left of the body’s midline.
• Visualize the heart as a cone lying on its side.
• The pointed end of the heart, the apex, is formed by the tip of the left ventricle
(lower chamber of the heart and rests on the diaphragm).
• The apex is directed anteriorly, inferiorly, and to the left
• The base faces posteriorly, it is square in outline.
• The heart has many surfaces
• The posterior surface of the heart is the base, it is formed mainly by the left
atrium which receives four pulmonary veins.
• The anterior surface of the heart is deep to the sternum and ribs. It is formed
mainly by the right ventricle which is separated from right atrium by
coronary sulcus and anterior interventricular sulcus from the left ventricle.
• The inferior surface rests on the diaphragm. It is formed by the left and
right ventricles anteriorly and part of the right atrium posteriorly
• The right surface is formed by the right atrium which receives the superior
vena cava above and inferior vena cava below. It is in contact with the right
lung.
• the left surface is formed by the left ventricle and small part of the left
atrium. It is in contact with the left lung and extends from the base to the
apex.
The Heart
The Pericardium
• Pericardium: Is a membranous flask shaped sac that surrounds and
protects the heart.
• It is formed by two principal portions:
• An outer fibrous pericardium: Is tough, inelastic, dense irregular
connective tissue. It blends inferiorly with the central tendon of the
diaphragm and superiorly with the adventitia of the great vessels
• An inner serous pericardium: is a thin, more delicate membrane that
forms a double layer around the heart.
• The outer parietal layer of the serous pericardium is fused with the
fibrous pericardium.
• The inner visceral layer of the serous pericardium, called the
epicardium. It is combined with the underlying delicate areolar tissue and
adipose tissue and adheres tightly to the surface of the heart.
• Between the parietal and visceral layers of the serous pericardium is a
thin film of lubricating fluid known as pericardial fluid.
• The space that contains the few milliliters of pericardial fluid is called
the pericardial cavity.
• The heart is suspended freely inside the pericardial cavity. It is only
fixed by the junction between fibrous pericardium and the adventitia
of the aorta, pulmonary trunk and superior vena cava superiorly and
adventitia of pulmonary veins posteriorly
Mediastinum
Layers of the Heart Wall
• The wall of the heart consists of three layers: epicardium, the
myocardium, and the endocardium.
• Epicardium (external layer): is composed of two tissue layers. The
outermost is the visceral layer of the serous pericardium (mesothelium).
Beneath the mesosthelium is a variable amount of delicate areolar tissue
and adipose tissue. It contains blood vessels, lymphatics, and nerves that
supply the myocardium.
• The middle myocardium (muscle 95% of the heart) is responsible for the
pumping action of the heart and is composed of cardiac muscle tissue.
• Endocardium (innermost layer): is a thin layer of endothelium
overlying a thin layer of connective tissue. Provides a smooth lining for
the chambers of the heart and covers the valves of the heart. The smooth
endothelial lining minimizes the surface friction.
Chambers of the Heart
• The heart is a dual pump that contains four chambers, two upper or
receiving chambers called the atria and the two lower or pumping
chambers called the ventricles.
The paired atria receive blood from blood vessels returning blood to the
heart, called veins,
while the ventricles Eject the blood from the heart into blood vessels
called arteries.
• Thickness of myocardium varies according to the function of the chamber
Atria are thin walled, deliver blood to adjacent ventricles.
• Ventricle walls are much thicker and stronger.
Right ventricle supplies blood to the lungs.
Left ventricle wall is the thickest to supply systemic circulation.
Atria of the Heart
• Atria are the receiving chambers of the heart.
• Each atrium has a protruding auricle
• Pectinate muscles mark the anterior wall of the right atrium.
Left atrium has smooth walls
• Blood enters right atria from superior and inferior venae cavae and coronary
sinus.
• Blood enters left atria from pulmonary veins
Left atrium
right atrium
Ventricles of the Heart
• Ventricles are the discharging chambers of the heart.
• Papillary muscles and trabeculae carneae
muscles mark ventricular walls.
• Right ventricle pumps blood
into the pulmonary trunk.
• Left ventricle pumps blood
into the aorta.
Fibrous Skeleton of the Heart
• the heart wall contains dense connective tissue that forms the fibrous
skeleton of the heart.
• fibrous skeleton consists of: four dense connective tissue rings that
surround the valves of the heart, fuse with one another, and merge
with the interventricular septum.
• Fibrous skeleton prevents overstretching of the valves as blood
passes through them.
• Serves as a point of insertion for bundles of cardiac muscle
fibers.
• Acts as an electrical insulator between the atria and ventricles.
Heart Valves
• The heart has four valves that open and close in response to pressure changes as
the heart contracts and relaxes.
• Each of the four valves helps to ensure one-way flow of blood by opening to let
blood through and then closing to prevent its backflow.
• Atrioventricular Valves: they are located between the atria and ventricles.
Chordae tendineae anchor AV valves to papillary muscles.
• The tricuspid valve (on the right side of the heart between right atrium and
right ventricle) has three cusps.
• The bicuspid valve (on the left side of the heart between left atrium and left
ventricle )has two cusps
• Semilunar Valves: Each valve has three semilunar cusps
• The aortic valve: lies between the left ventricle and the aorta.
• The pulmonary valves: lies between the right ventricle and pulmonary trunk.
Systemic and Pulmonary Circulations
• With each beat, the heart pumps blood into two circuits:
• The systemic circulation.
• The pulmonary circulation.
• The amount of blood pumped out from a ventricle per each beat is 7o
ml (stroke volume)
• The two circuits are arranged in series so that the output of one becomes
the input of the other.
The systemic circulation
• The left side of the heart, which receives bright-red freshly oxygenated
(oxygen-rich) blood from the lungs, is the pump for systemic circulation.
• The left ventricle ejects blood into the aorta, which branches into smaller
systemic arteries that carry the blood to all organs throughout the body (except
for the air sacs (alveoli) of the lungs, which are supplied by the
pulmonary circulation).
• In systemic tissues, arteries give rise to smaller-diameter arterioles, which
lead into extensive beds of systemic capillaries.
• Exchange of nutrients and gases occurs across the thin capillary walls: In the
tissues, blood unloads O2 (oxygen) and picks up CO2.
• In most cases, blood flows through only one capillary and then enters a
systemic venule.
• Venules carry deoxygenated blood away from tissues and merge to form larger
systemic veins, and ultimately the blood flows back to the right atrium
The pulmonary circulation
• The right side of the heart is the pump for pulmonary circulation
• It receives all the dark-red deoxygenated blood returning from the
systemic circulation.
• Blood ejected from the right ventricle flows into the pulmonary
trunk, which branches into pulmonary arteries that carry blood to
the right and left lungs.
• In pulmonary capillaries, blood unloads CO2, which is exhaled, and
picks up O2 from inhaled air.
• The freshly oxygenated blood then flows into pulmonary veins and
returns to the left atrium.
Coronary Circulation
• The flow of blood through the vessels that pierce the myocardium is called
the coronary circulation.
• It is called coronary because the arteries encircle the heart like a crown.
• Arterial blood runs through the right and left coronary arteries (branches
of ascending aorta) and returns back to the right atrium through the
coronary sinus
• While it is contracting, the heart receives little oxygenated blood by way of
the coronary arteries.
• When the heart relaxes, the high pressure of blood in the aorta propels
blood through the coronary arteries, into capillaries, and then into
coronary veins.
Conductive system of the heart
The system is formed of specialised cardiac muscle cells which are difficult to
distinguish from cardiac muscle. It comprises the Sinuatrial (SA) node, the
Atrioventricular (AV) node, the Atrioventricular bundle (AV bundle, or bundle of
His), its right and left branches and a terminal subendocardial plexus (Purkinje
fibres).
This system initiates the complex
cardiac muscle contractions comprising
the cardiac cycle, and controls its
regularity.
Conductive system of the heart
Purkinje fibres
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