Transcript vascular notes goood copy ppt

The Cardiovascular System
1
The Cardiovascular System
• A closed system of the heart and blood
vessels
– The heart pumps blood
– Blood vessels allow blood to circulate to all
parts of the body
• The function of the cardiovascular system
is to deliver oxygen and nutrients and to
remove carbon dioxide and other waste
products
2
The Heart
• Location
– Thorax
between the
lungs
(mediastinum)
– Pointed apex
directed
toward left hip
& rests on the
diaphragm
• About the size
of your fist
3
The Heart: Coverings
• Pericardium – a double serous membrane
– Visceral pericardium (epicardium)
• Next to heart
– Parietal pericardium
• Outside layer
• Serous fluid fills the space between the
layers of pericardium, decreases friction
• Pericarditis – inflammation of pericardium
causes a decrease in serous fluid
– Pericardial layers touch, stick and form painful
adhesions
4
The Heart: Heart Wall
• Three layers
– Epicardium
• Outside layer
• This layer is
the parietal
pericardium
• Connective
tissue layer
– Myocardium
• Middle layer
• Mostly cardiac
muscle
– Endocardium
• Inner layer
• Endothelium
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External Heart Anatomy
6
The Heart: Chambers
• Right and left side act as
separate pumps
• Four chambers
– Atria
• Receiving chambers
– Right atrium
– Left atrium
– Ventricles
• Discharging chambers
– Right ventricle
– Left ventricle
» Thick walled
» Contract
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Figure 11.2c
The Heart: Associated Great Vessels
• Aorta
– Leaves left ventricle
– Largest artery in the body
• Pulmonary arteries
– Leave right ventricle
– Carry deoxygenated
blood
• Vena cava
– Enters right atrium
– Largest veins of the body
• Pulmonary veins (four)
– Enter left atrium
– Carry oxygenated blood
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Blood Circulation – Both sides events occur simultaneously!
1. Blood low in O2 from
body returns to the
heart via veins
flowing into the
Superior & Inferior
Vena Cava returning
blood to RA.
2. Through Tricuspid
(AV) valve into RV
(atria contracts).
3. RV contracts forcing
AV valve shut.
Blood flows out
pulmonary
semilunar valve into
pulmonary arteries
and to the lungs for
gas exchange.
1. Blood high in O2
returns via the
pulmonary veins
to the LA.
2. LA contracts
pushing blood
through the
bicuspid (mitral or
AV) valve into LV.
3. LV contracts
forcing AV valves
shut. Blood flows
out aortic
semilunar valve
into Aorta and
artery network to
the body.
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Figure 11.3
The Heart: Valves
• Allow blood to flow in only one direction
• Four valves
– Atrioventricular valves (AV) – between atria and ventricles
• Bicuspid valve (left) (mitral) – 2 flaps
• Tricuspid valve (right) – 3 flaps
– Chordae tendinae anchor the valve flaps to the ventricle to keep them
from being pushed inside the atria during ventricular contraction.
» Called your “heart strings”
– Semilunar valves between ventricle and artery
• Pulmonary semilunar valve
• Aortic semilunar valve
– Valvular Stenosis – valve flaps become stiff, usually due to
infection.
• Valves may not close completely, allowing backflow.
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Operation of Heart Valves
Figure11
11.4
Coronary Circulation
• Blood in the heart chambers does not nourish the
myocardium (NO O2, nothing)
• The heart has its own nourishing circulatory system
– Coronary arteries branch from the base of the aorta
• They are compressed during ventricular contraction and fill during
relaxation.
– Cardiac veins empty blood into the right atrium via the
coronary sinus
• Rapid heart beat can lead to a decrease of oxygen to
the myocardium. This may cause pain called angina
pectoris.
– If the heart muscle goes without oxygen long enough,
damage occurs or an infarct.
– This results in a myocardial infarction or heart attack.
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The Heart: Conduction System
• Intrinsic conduction system
(nodal system)
– Heart muscle cells contract, without nerve
impulses, in a regular, continuous way
– Composed of special tissue, a cross of muscle
and nervous tissue.
– Forces a coordinated depolarization in one
direction, about 75 bpm
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The Heart: Conduction System
• Special tissue sets
the pace
– Sinoatrial (SA)
node
• Located in the right
atrium
• Pacemaker
– Atrioventricular
(AV) node
– Atrioventricular
bundle (Bundle of
His)
– Bundle branches
(R & L – in septum)
– Purkinje fibers
(Muscle of
Ventricular Walls)
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Heart Contractions
1. Contraction is initiated by the sinoatrial
node – the pacemaker
2. Impulse spreads through atria to AV
Node, both atria contract
3. Impulse pauses at AV node. Then goes
through the AV bundle, bundle branches
and purkinje fibers.
4. This causes the “wringing action” of the
ventricles. This starts at the apex and
moves up towards the atria.
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Heart block – damage to AV node causes
ventricles to contract on their own at a slower
rate
Artificial Pacemaker – needed when there is
damage to SA node causing the heart to slow
Ischemia – lack of blood flow to heart which leads
to fibrillation – shuddering of heart, no
pumping, can lead to death
Tachycardia - >100 bpm, can become fibrillation
Bradycardia - < 60 bpm
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Cardiac
Cycle
• Atria
contract simultaneously
• Atria relax, then ventricles contract
• Systole = contraction, Diastole = relaxation (of the
ventricles)
• Cardiac cycle – events of one complete heart beat
• Lub is AV valves closing
• Dub is semilunar valves closing
• Murmur – unusual heart sound caused by faulty
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valves and a back flow of blood
Cardiac Output Regulation
Figure18
11.7
The Heart: Regulation of Heart Rate
• Increased heart rate
– Sympathetic nervous system
• Crisis
• Low blood pressure
– Hormones
• Epinephrine
• Thyroxine
– Exercise
– Decreased blood volume
– Increased Temperature
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Regulation of Heart Rate
• Cause Decreased heart rate
– Parasympathetic nervous system
– High blood pressure or blood volume
– Decreased venous return
– Decreased temperature
• CHF (Congestive Heart Failure)
– Left Side Dec. Function causes pulmonary
congestion, blood backs up in lungs, causing
fluid to leak into lungs
– Right Side Dec. Function causes peripheral
congestion, blood backs up in systemic
circulation, causing edema in extremities.
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Blood Vessels: The Vascular
System
• Taking blood to
the tissues and
back
– Arteries
– Arterioles
– Capillaries
– Venules
– Veins
Figure21
11.8a
The Vascular System
Figure22
11.8b
Differences Between Blood Vessel Types
• Walls of arteries are the thickest
• Lumens of veins are larger & have
valves
• Skeletal muscle “milks” blood in veins
toward the heart
• Walls of capillaries are only one cell
layer thick (tunica intima) to allow for
exchanges between blood and tissue
(capillary beds)
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Movement of Blood Through
Vessels
• Most arterial blood
is pumped by the
heart
• Veins use the
milking action of
muscles to help
move blood
Figure24
11.9
Capillary beds consist of
two types of vessels
Capillary Beds
1. Vascular shunt – directly
connects an arteriole to a
venule
2. True capillaries – exchange
vessels
• Oxygen and nutrients
cross to cells
• Carbon dioxide and
metabolic waste
products cross into
blood
http://www.youtube.com/watch?v=Q530H1
WxtOw&safe=active
Figure25
11.10
• Blood may move
through shunt or true
capillaries.
• Precapillary sphincters
close off the true
capillaries when blood
flow is needed
elsewhere.
• Varicose veins- valves
are faulty, blood pools &
vein twists
• Thromobphlebitis – clot
forms in a vein
Capillary Beds
Figure26
11.10
Major
Arteries of
Systemic
Circulation
Figure27
11.11
Major Veins
of Systemic
Circulation
Figure28
11.12
Hepatic Portal Circulation
• Veins
from digestive
organs, spleen and
pancreas take blood to the
liver
• After a meal, this blood is
nutrient rich.
• Liver stores glucose and
further processes nutrients.
• This is why blood goes
here from the digestive
system BEFORE going out
to “feed” the body.
Figure29
11.14
Pulse
• Pulse – pressure
wave of blood
• Monitored at
“pressure points”
where pulse is
easily palpated
Figure30
11.16
Blood Pressure
• Measurements made on the pressure in
large arteries
– Systolic – pressure at the peak of ventricular
contraction
– Diastolic – pressure when ventricles relax
• Pressure exerted on inner walls of blood
vessels
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Blood Pressure: Effects of
Factors
• Neural factors
– Autonomic nervous system adjustments
(sympathetic division) – causes
vasocostriction - BP
• Renal factors
– Regulation by altering blood volume – retain
water
BP & Blood Volume
– Renin – hormonal control, vasoconstriction
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Blood Pressure: Effects of Factors
• Temperature
– Heat has a vasodilation effect
– Cold has a vasoconstricting effect
• Chemicals
– Alcohol – vasodilator
– Nicotine - constrictor
• Diet – low in salt, saturated fats &
cholesterol help prevent hypertension
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Factors
Determining
Blood
Pressure
Figure34
11.19
Variations in Blood Pressure
• Human normal range is variable
– Normal
• 140–110 mm Hg systolic
• 80–75 mm Hg diastolic
– Hypotension
• Low systolic (below 110 mm HG)
• Often associated with illness
• Orthostatic hypotension – positional
drop in BP
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– Hypertension
• High systolic (above 140 mm HG)
• Can be dangerous if it is chronic
– Strains the heart & damages arteries
– Eventually myocardium enlarges, heart
weakens & walls become flabby
– Causes small tears in arteries where clots can
form, leading blockage
– Atherosclerosis
• Damage to tunica interna & clot response
• Continual injuries to area & plaque begins to form
• Fats & cholesterol enter & collect, eventually
protrude into the lumen
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Capillary Exchange
• Substances exchanged due to
concentration gradients
– Oxygen and nutrients leave the blood
– Carbon dioxide and other wastes leave the
cells
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Capillary Exchange: Mechanisms
• Direct diffusion across plasma membranes
• Endocytosis or exocytosis
• Some capillaries have gaps (intercellular
clefts)- not in brain
– Plasma membrane not joined by tight
junctions
• Fenestrations of some capillaries
– Fenestrations = pores w/ a thin membrane
covering
– Found where absorption is a priority or
filtration occurs (kidney, intestine, endocrine) 38