Download Cardiovascular System Notes

Chapter 15
Cardiovascular System
1
Size of Heart
• Average Size of Heart
• 14 cm long
• 9 cm wide
•250-350 grams
•About size of your
closed fist
2
Location of Heart
• Posterior to sternum
• Medial to lungs
• Anterior to vertebral column
• Base lies beneath 2nd rib
• Apex at 5th intercostal space
• Lies upon diaphragm
•2/3 of mass lies left of midline
3
Coverings of Heart
4
Coverings of Heart
• Pericardium
– Surrounds heart
– Fibrous
pericardium
• Resembles bag
that sits on the
diaphragm
• Provides tough
protection &
anchors heart to
mediastinum
5
Coverings of Heart
• Pericardium
– Serous pericardium
• Thinner & delicate
• Parietal layer
– Attached to fibrous
pericardium
• Visceral layer
– Attached to
myocardium
6
Coverings of Heart
• Pericardial Fluid
– Between parietal and
visceral layers of
serous pericardium
– Reduces friction from
beating
7
Wall of the Heart
8
Wall of the Heart
•3 Parts of the wall
•Epicardium
•Visceral layer of
serous pericardium
•Myocardium
•Muscle layer
•Endocardium
•Thin layer of
endothelial tissue
that is continuous
with the remainder
of the cardiovascular
system
9
Heart Chambers
•Right Atrium
• Receives blood
from
• Inferior vena
cava
• Superior vena
cava
• Coronary sinus
•Right Ventricle
• Receives blood
from right atrium
10
Heart Chambers
• Left Atrium
• receives blood
from pulmonary
veins
• Left Ventricle
• receives blood
from left atrium
11
Heart Chambers
• Separations
– Atria
• Each atrium has an
auricle
• Separated by interatrial
septum
– Ventricles
• Interventricular septum
• Sulci show the location
of septum
– Contain blood
vessels and store fat
12
Heart Valves
•Atrioventricular Valves
•Separate atria from
ventricles
•Tricuspid Valve
•Right side
•3 cusps
•Bicuspid valve
•Left side
•2 cusps
•Chordae Tendineae
•Fibrous cord that
connects cusps to
papillary muscles
13
Heart Valves
• Atrioventricular
Valves
– Papillary Muscles
• Anchor chordae
tendineae to ventricle
walls
– Chordae Tendineae &
Papillary Muscles
• Function to keep AV
valves from being
pushed into the atria
during ventricular
contraction
14
Heart Valves
• Semilunar Valves
– Pulmonary semilunar
• Between right ventricle
and pulmonary trunk
• Blood leaves heart
toward lungs
– Aortic semilunar
• Between left ventricle
and aorta
• Blood leaves heart
toward body
– Prevent backflow to keep
blood flowing in one
direction
15
Coronal Sections of Heart
16
Heart Valves
Tricuspid Valve
Pulmonary and Aortic Valve
17
Path of Blood
Through the Heart
18
Path of Blood
Through the Heart
• Superior/Inferior Vena Cava/Coronary
Sinus bring blood to right atrium
• Blood flows through tricuspid valve to
right ventricle
• Right ventricle pumps blood through
pulmonary semilunar valve to pulmonary
trunk/pulmonary arteries
19
Path of Blood
Through the Heart
• Pulmonary arteries take blood to lungs
• Blood returns to heart through pulmonary
veins to left atrium
• Blood flows through bicuspid valve to left
ventricle
• Blood leaves left ventricle through aortic
semilunar valve to ascending aorta
• Aorta takes blood to body
• Blood returns to heart through veins leading to
inferior vena cava & superior vena cava
20
Path of Blood
Through the Heart
21
Blood Supply to Heart
22
Blood Supply to Heart
• Left & right coronary arteries originate from
the ascending aorta
– Carry oxygenated blood to myocardium
• Coronary Sinus carries deoxygenated blood to
right atrium
• Anastomosis
– 2 different arteries connecting & supplying an area
with blood flow
– Found throughout body, many in heart
– Provides collateral circulation for blood to reach an
organ
23
Blood Supply to Heart
24
Blood Supply to Heart
25
Angiogram of Coronary
Arteries
26
Heart Actions
•Systole
•Phase of contraction
•Diastole
•Phase of relaxation
•Cardiac Cycle
•One complete heart beat
•Consists of
•systole & diastole of both atria
•Systole & diastole of both ventricles
27
Cardiac Cycle
•Atrial
Systole/Ventricular
Diastole
•blood flows passively
into ventricles
•remaining 30% of
blood pushed into
ventricles
•A-V valves
open/semilunar valves
close
• ventricles relaxed
• ventricular pressure
increases
28
Cardiac Cycle
•Ventricular Systole/Atrial
diastole
• A-V valves close
• chordae tendinae
prevent cusps of valves
from bulging too far into
atria
• atria relaxed
• blood flows into atria
• ventricular pressure
increases & opens
semilunar valves
• blood flows into
pulmonary trunk & aorta
29
Heart Sounds
Lubb
• first heart sound
• occurs during ventricular systole
• A-V valves closing
Dupp
• second heart sound
• occurs during ventricular diastole
• pulmonary and aortic semilunar valves closing
30
Heart Sounds
• Clinical Application
• Murmur – any condition that causes unusual sounds
to heard before or after the lubb-dupp
• Noises caused by turbulent blood flow
• Mitral and Aortic Stenosis
– Narrowing of either valve by scar formation or
congenital defect
• Mitral and Aortic insufficiencies
– Backflow of blood because the cusp doesn’t close
properly
31
Heart Sounds
• Clinical Application
• Mitral Valve Prolapse
– Inherited disorder in which the mitral valve is
pushed back too far during contraction
– Usually asymptomatic
– About 10% of population has this disorder
32
Heart Sounds
33
Cardiac Conduction System
34
Cardiac Conduction System
• 4 main parts
– Sinoatrial node (SA node)
• “pacemaker”
• Found in right atrial wall inferior to the opening of the
vena cava
– Atrioventricular node (AV node)
• Found near inferior portion of the interatrial septum
– Impulse from SA node travels across atria
(stimulates atrial contraction) then stimulates AV
node
35
Cardiac Conduction System
• AV bundle
– Conducting fibers run from the AV node to top of
interventricular septum and branches into two
– Distributes potential over medial surface of the
ventricles
• Purkinje Fibers (conduction myofibers)
– Pass from bundle branches into the myocardium
– Stimulates the contraction of the ventricles
36
Cardiac Conduction System
37
Muscle Fibers in
Ventricular Walls
38
Electrocardiogram
• Recording of electrical changes that occur in the myocardium
• Used to assess heart’s ability to conduct impulses
39
Electrocardiogram
P wave
• Atrial depolarization
• Fraction of a second after atria contract
40
Electrocardiogram
QRS wave
•
•
•
•
•
Ventricular depolarization
Downward deflection (Q)
Large upward peak (R)
Ventricular depolarization
Fraction of a second after the completion of this wave,
ventricles may contract again
41
Electrocardiogram
• T wave – ventricular repolarization
42
Electrocardiogram
A prolonged QRS complex may result from damage to the A-V
bundle fibers
43
Regulation of Cardiac Cycle
Autonomic nerve impulses alter the
activities of the S-A and A-V nodes
44
Regulation of Cardiac Cycle
Additional Factors that Influence HR
• physical exercise
• body temperature
• concentration of various ions
• potassium
• calcium
• parasympathetic impulses decrease heart action
• sympathetic impulses increase heart action
• cardiac center regulates autonomic impulses to the heart
45
Blood Vessels
• Arteries
• Carry blood away from ventricles of heart
• Arterioles
• Receive blood from arteries
• Carry blood to capillaries
• Capillaries
• Sites of exchange of substances between blood
and body cells
• Venules
• Receive blood from capillaries
• Veins
• Carry blood toward atria of heart
•Vasa Vasorum
•Blood vessels in vascular tissue walls
•Nourish vascular tissue
46
Arteries and Arterioles
Artery
• thick strong wall
• endothelial lining
• middle layer of smooth
muscle and elastic tissue
• outer layer of
connective tissue
• carries blood under
relatively high pressure
Arterioles
• thinner wall than
artery
• endothelial lining
• some smooth muscle
tissue
• small amount of
connective tissue
• helps control blood
flow into a capillary
47
Walls of Artery and Vein
48
Walls of Artery and Vein
• Composed of 3 layers
(tunics)
– Tunica Interna
• Inner wall (tunic)/
Endothelium
• Simple squamous
epithelium
• Layer of elastic tissue
(internal elastic
lamina)
• Extremely thin in
veins
49
Walls of Artery and Vein
– Tunica media
• Middle tunic
• Thickest smooth
muscle
• Elastic fibers
• Thinner in veins
50
Walls of Artery and Vein
– Tunica Externa
• Outer tunic
• Composed of elastic
and collagenous fibers
• Thicker in veins
51
Walls of Artery and Vein
52
Walls of Artery and Vein
53
Types of Arteries
• Elastic conducting arteries
– Conduct blood from the heart to the medium
sized arteries
– Large diameter with relatively thin walls
• Tunica media has more elastic fibers and less
smooth muscle
– Must be able to withstand high blood
pressures
– Aorta, Common carotid
54
Types of Arteries
• Muscular Distributing Arteries
–
–
–
–
–
Distribute blood to the rest of the body
More smooth muscle in tunica media
Regulate blood needs of structures they serve
Anastomoses likely to occur in this type of artery
Axillary, brachial, femoral, popliteal
55
Types of Arteries
• Arterioles
– Smallest arterioles only have a few smooth muscle
fibers
– Capillaries lack muscle fibers
– Deliver & regulate blood to capillaries
56
Metarteriole
• Connects arteriole directly to venule
57
Capillaries
• Smallest diameter blood vessels
•Only one RBC at a time
• Extensions of inner lining of arterioles
• Walls are endothelium only
•Only 1 cell layer thick
• Semi-permeable
• Found near almost every cell in the body
• The higher the tissue’s activity, the more
capillaries present
• Sinusoids – leaky capillaries
58
Capillaries
59
Capillary Network
60
Regulation of Capillary
Blood Flow
• Precapillary
sphincters
• may close a
capillary
• respond to
needs of the cells
• low oxygen and
nutrients cause
sphincter to
relax
61
Exchange in the Capillaries
• Water
and other substances leave capillaries because of
net outward pressure at the capillaries’ arteriolar ends
• Water enters capillaries’ venular ends because of a net
inward pressure
• Substances move in and out along the length of the
capillaries according to their respective concentration
gradients
62
Exchange in the Capillaries
63
Venules and Veins
Venule
• thinner wall than arteriole
• less smooth muscle and elastic tissue than arteriole
• collects blood from capillaries & drain into the veins
Vein
• thinner wall than artery
• three layers to wall but middle layer is poorly developed
• some have flaplike valves
• carries blood under relatively low pressure
• serves as blood reservoir
64
Venous Valves
65
Venous Valves
• Disorders
– Varicose Veins
• Valves are weak allowing gravity to force large
quantities of blood into distal parts of the veins
• Pressure stretches vein and causes it to lose
elasticity
• Veins become stretched and flabby
• Deep veins are not susceptible
66
Blood Volumes in Vessels
67
Arterial Blood Pressure
Blood Pressure – force the blood exerts against the
inner walls of the blood vessels
Arterial Blood Pressure
• rises when ventricles contract
• falls when ventricles relax
• systolic pressure – maximum pressure
• diastolic pressure – minimum pressure
68
Blood Flow Factors
• Blood Pressure (BP)
– Pressure on arterial wall due to the left ventricle
contraction
– Blood flows from high to low pressures
– Average aorta pressure is 100mmHg
– Average right atrium pressure is nearly 0 mmHg
– Normal resting BP is 120 mmHg (systolic)
80 mmHg (diastolic)
– Measured with a sphygomanometer
69
Blood Flow Factors
70
Blood Flow Factors
• Resistance
– Friction as blood travels
– Related to
• Viscosity
– Ratio of RBC and solutes to liquid
– Anything that decreases viscosity (dehydration)
increases BP
• Blood Vessel Length
– Longer vessel = higher resistance
• Blood Vessel Radius
– Resistance inversely proportional to the 4th power, the
radius of the vessel
71
Pulse
• alternate expanding and recoiling of the arterial wall
that can be felt
72
Factors That Influence
Arterial Blood Pressure
73
Factors That Influence
Arterial Blood Pressure
• Cardiac Output
– Amount of blood ejected by the left ventricle into
the aorta each minute
– Main factor of BP
• Blood Volume
– Average is about 5 liters
– Decreased volume = decreased pressure
– Increased volume = increased pressure
• High salt intake  retain water increased blood volume
74
Factors That Influence
Arterial Blood Pressure
• Peripheral Resistance
– All of the vascular resistance offered by the
cardiovascular system
– Major function of arterioles is to control resistance
• Capillary Exchange
– Blood flow is at its slowest to aid in exchange of
gases and nutrients
– Depends on concentration differences
75
Control of Blood Pressure
Controlling cardiac output and peripheral resistance
regulates blood pressure
76
Venous Blood Flow
• Not a direct result of heart
action
• Dependent on
• Skeletal muscle
contraction
• Breathing
• Venoconstriction
77
Venous Blood Flow Factors
• Velocity of blood flow
• Skeletal muscles and valves in veins
– Venous milking
• Muscle contracts and “squishes” blood upward
• Valves keep blood from flowing backward with
gravity
• Breathing
– Decreases pressure in thoracic cavity and
increases pressure in abdominal cavity
78
Central Venous Pressure
• pressure in the right atrium
• factors that influence it alter flow of blood into
the right atrium
• affects pressure within the peripheral veins
• weakly beating heart increases central venous
pressure
• increase in central venous pressure causes blood
to back up into peripheral vein
79
Pulmonary Circuit
• consists of vessels that carry blood from right ventricle of the
heart to the lungs and back to the left atrium of the heart
80
Blood Flow Through Alveoli
• cells of alveolar wall are tightly joined together
• the high osmotic pressure of the interstitial fluid draws
water out of them
81
Systemic Circuit
• Composed of vessels that lead from the
heart to all body parts (except the lungs)
and back to the heart
• Includes the aorta and its branches
• Includes the system of veins that return
blood to the right atrium
82
Additional Circuits
• Coronary
– Circulation through blood vessels supplying
the heart
• Hepatic Portal
– Runs from GI tract to the liver
83
Circulation Time
• Time required for blood to travel from
the right atrium through pulmonary
circulation and systemic circulation and
back to the right atrium
• Average is about 1 minute
84
Pulse
• Alternating expansion and recoil of an
arterial wall
• Stronger closer to the heart
• Measured by counting for 15 seconds and
multiplying by 4
• Most commonly used artery is the radial
artery
85
Pulse
• Other commonly used arteries
–
–
–
–
–
–
–
–
Temporal
Facial
Common carotid  lateral to the larynx
Brachial artery  medial sides of biceps brachii
Femoral
Popliteal  behind the knee
Posterial Tibial  posterior to medial malleolus
Dorsalis Pedis  superior to the longitudinal arch of
the foot
86
Life-Span Changes
• cholesterol deposition in blood vessels
• heart enlargement
• death of cardiac muscle cells
• increase in fibrous connective tissue of the heart
• increase in adipose tissue of the heart
• increase in blood pressure
• decrease in resting heart rate
87
Clinical Application
Arrhythmias
Ventricular fibrillation
• rapid, uncoordinated
depolarization of ventricles
Tachycardia
• rapid heartbeat
Atrial flutter
• rapid rate of atrial
depolarization
88
Clinical Application
• Angina Pectoris
– Chest pain
– Reduced oxygen supply weakens cardiac cells but
doesn’t kill them
– Symptoms
• Tightness of choking sensation
• Squeezing pressure type of sensation for short durations
– Causes
• Stress, exertion, hypertension
89
Clinical Application
• Myocardial Infarction (MI)
– Heart attack
– Infarction means death of tissue due to lack
of blood supply
– Myocardial tissue behind blocked arteries
dies
– Dead tissue may disturb conducting system
of the heart which could lead to sudden
death (ventricular fibrillation)
90
Clinical Application
• Shock
– Failure of cardiovascular system to deliver
adequate amounts of oxygen and nutrients to
meet the metabolic needs of body cells
because of inadequate cardiac output
91
Clinical Application
• Shock Signs and Symptoms
– Systolic PB lower than 90 mmHg as a result
of vasodilation and decreased cardiac output
– Clammy, cool, pale skin due to
vasoconstriction of blood vessels in the skin
– Sweating due to increased levels of
epinephrine
– Rapid heart rate
92
Clinical Application
• Signs and Symptoms
–
–
–
–
Lactic acid build-up
Weak pulse
Altered mental state
Thirst due to extra-cellular fluid loss
93