Download The Heart (cont`d)

Chapter 22
The Cardiovascular System
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The Cardiovascular System
• Designed for transportation and communication
throughout the body
• Vital in maintaining homeostasis within the body
• Composed of the heart and blood vessels
• Functions
– Pumping blood
– Transporting gases, nutrients, hormones, and wastes
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The Heart
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The Heart (cont’d)
• The heart lies in the thoracic cavity in the mediastinal
space.
• Layers of the heart wall
– Endocardium
– Myocardium
– Epicardium
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The Heart (cont’d)
• The pericardium is a sac that surrounds and protects the
heart.
– Epicardium portion of the heart wall also makes up
the pericardium’s visceral layer.
– Parietal layer is the inner serous pericardium.
– The space between the visceral and parietal layers is
called the pericardial space or cavity.
– The outermost layer is called the fibrous pericardium.
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Heart Chambers and Valves
• Chambers
– Atria and ventricles
• Valves
– Atrioventricular valves
• Tricuspid valve and mitral valve
– Overflow valves
• Semilunar valves: Pulmonic valve and aortic valve
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Heart Chambers and Valves (cont’d)
• Chordae tendineae
– Tendon-like strands attached to tissue flaps of the
valves
– Anchored to papillary muscles
– As the ventricles contract, the papillary muscles also
contract at this time, tightening the chordae
tendineae, to prevent the valve cusps from everting.
• If the AV valves, chordae tendineae, or papillary muscles
become damaged, backflow of blood (regurgitation) into
the atria can occur with ventricular contraction.
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Question
Is the following statement true or false?
The left ventricle contains the thickest layer of muscles in
the heart.
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Answer
True
The left ventricle must pump strongly enough to send
blood out to the entire body.
The right ventricle also has thick muscles; the muscles in
the atria are thinner than those of either ventricle.
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Route of Blood Flow Through the Heart
• The right atrium receives venous blood from the body via
the superior and inferior vena cavae and the coronary
sinus.
• Blood then passes through the tricuspid valve into the
right ventricle.
• It moves on through the pulmonic valve during
ventricular contraction to enter the pulmonary artery and
then the lungs, where it exchanges carbon dioxide for
oxygen.
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Route of Blood Flow Through the Heart
(cont’d)
• Oxygenated blood returns to the left atrium via four
pulmonary veins.
• It travels through the mitral (bicuspid) valve into the left
ventricle.
• During ventricular contraction, the blood from this
chamber exits through the aortic semilunar valve into the
aorta and out to the systemic circulation.
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Blood Vessels of the Heart
• Coronary Arteries
– Two coronary arteries branch off the ascending aorta
to provide blood to heart muscle.
• Left coronary artery/left main coronary artery
• Left anterior descending (LAD) artery
• Left circumflex (LCX) artery
• Right coronary artery
• Marginal branch
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Blood Vessels of the Heart (cont’d)
• Collateral circulation
– When two vessels that nourish the same area
interconnect
– In coronary obstruction, these vessels can enlarge to
nourish endangered heart muscle.
• Ischemia: A reversible cell injury due to decreased blood
and oxygen supply
• Myocardial infarction (MI): A localized area of dead tissue
caused by a lack of blood supply
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Blood Vessels of the Heart (cont’d)
• Coronary Veins
– Drain into capillaries in the myocardium, where
delivery of oxygen and nutrients occurs, along with
waste removal.
• Great cardiac vein
• Middle cardiac vein
– These vessels transport blood into the coronary
sinus, which returns blood to the right atrium.
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Systemic Blood Vessels
• Arteries
– They carry blood away from the heart. Aorta is the
largest artery.
– Ascending aorta, aortic arch, thoracic aorta, and
abdominal aorta.
• The smallest arteries are called arterioles.
• Capillaries
– They make up most of the great length of the body’s
blood vessels. They serve as “in-between” channels.
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Systemic Blood Vessels (cont’d)
• Veins and venules
– They carry blood toward the heart.
– The largest veins in the body are the superior vena
cava (SVC) and inferior vena cava (IVC).
– Venous blood return
• Venodilation
• Vasoconstriction
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Question
Is the following statement true or false?
The pulmonary veins carry deoxygenated blood.
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Answer
False
The pulmonary veins are the only veins that carry
oxygenated blood.
The pulmonary arteries are the only arteries in the body
that carry deoxygenated blood.
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Tissue Layers Within Blood Vessels
• Tunica adventitia—the outermost layer
– Composed of connective tissues, nerve cells, and
nutrient capillaries; protects the outside of the vessel
• Tunica media—the middle layer
– Contains the thickest elastic fibers, as well as
connective tissue composed of polysaccharides;
covered by a thick elastic band and smooth muscle
fibers, which control the caliber of the vessel
• Tunica intima—the innermost layer
– Thinnest layer held together by an intercellular matrix
surrounded by connective tissue
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Cardiac Conduction
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Cardiac Conduction (cont’d)
• Conduction system of the heart
– SA (sinoatrial) node (pacemaker)
– AV (atrioventricular) node
– Bundle of His (AV bundle)
– Right and left bundle branches
– Purkinje fibers to muscles of ventricles
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Cardiac Cycle
• Cardiac cycle or one heartbeat
– In less than 1 second, both atria contract as both
ventricles relax. Immediately after this, both
ventricles contract as both atria relax.
• Systole: Sequence of dual contractions—the atria
followed by the ventricles
• Diastole: Atrial relaxation, followed by ventricular
relaxation
• One complete cardiac diastole
– Ventricular diastole + atrial diastole
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Cardiac Cycle (cont’d)
• (S1)
– The first normal heart sound is called the “lub” and is
produced by closure of the AV valves when the
ventricles contract.
• (S2)
– The second normal heart sound is called the “dub” or
“dup” and is produced by the closure of the aortic
and pulmonary semilunar valves when the ventricles
relax.
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Cardiac Cycle (cont’d)
• Abnormal heart sounds
– Gallops, rubs, or murmurs
• Pulse
– Rhythmic expansion of the arterial walls as the heart
pumps blood to the body
– Average of 72 beats per minute in an adult
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Cardiac Output
• Cardiac output (CO)
– Amount of blood pumped by the ventricles in 1 minute
• Stroke volume (SV)
– Volume of blood ejected with each heartbeat.
• Factors affecting CO
– Body’s metabolic needs, autonomic nervous system’s
influence on heart rate, effect of preload and afterload
on SV, norepinephrine and epinephrine released by the
sympathetic nervous system
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Blood Pressure
• Blood pressure
– The force that blood exerts against the walls of blood
vessels
– Systolic blood pressure (sBP)
– Diastolic blood pressure (dBP)
• Pulse pressure
– Difference between systolic and diastolic pressure
• Average blood pressure in an adult is 120/80.
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Blood Pressure Regulation
• Factors other than the force and rate of the pumping
heart that help to maintain or regulate blood pressure
include
– Amount and contents of circulating blood
– Elasticity and ability of smooth muscles in arterial
walls to dilate and constrict
– Plaque build-up on arterial walls
– Kidney functioning
– Hormones
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Question
Which of the following heart sounds are caused by the
narrowing of a valve?
a. Lub
b. Dub
c. Rub
d. Murmur
e. Gallop
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Answer
d. Murmur
Murmurs are most typically caused by narrowing (stenosis)
of a valve or by blood regurgitating through a valve that
does not close properly.
Gallop sounds occur when ventricular filling creates audible
vibrations during a normally silent diastolic phase.
Rubs may be heard when layers of the pericardium rub
together due to inflammation, as in pericarditis.
Normal heart sounds are “lub” and “dub.”
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Effects of Aging
• Increased rigidity of vessels from decreased elasticity
• Dilation of blood vessels due to weakening muscle tone
• Fibrosis in the conduction system and heart
• Calcification of the valves
• Increased size of myocardium and atria
• Decreased cardiac output
• Decreased ability of cells to absorb oxygen
• Decreased sensitivity to stimuli
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Effects of Aging (cont’d)
• Blood vessel disorders can cause other problems such as
– Downstream ischemia (insufficient blood supply)
– Vessel damage or hemorrhage
– Atherosclerosis
– Vasculitis
– Edema
– Varicose veins or obstructed blood flow
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End of Presentation
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