Transcript ST120 Peripheral Vascular System

The Peripheral Vascular System
ST120: Basic Sciences II
Concorde Career College, Portland
Cardiovascular System
Objectives:
• Discuss the relevant vessels of the peripheral vascular
system
• Compare and contrast the structure of an artery and a
vein
• Describe the mechanisms that regulate blood pressure
• Describe the etiology of atherosclerosis and arterial
embolism and their treatments
• Compare and contrast bypass grafting and
endarterectomy
Cardiovascular System
Blood Vessels and Circulation
Types of Blood Vessels
• Arteries
– Arterioles
• Veins
– Venules
• Capillaries
Blood Vessels
• Arteries: blood is pumped from the heart
through a series of large distribution
vessels. Largest artery = aorta
• Arteries divide into vessels that become
progressively smaller and finally become
tiny arterioles that control the flow into
microscopic exchange vessels called
capillaries
• Gas exchange occurs in capillary beds
Blood Vessels
• Blood exits capillary beds and enters
venules
• Venules steadily increase in size to
eventually become veins
• Largest veins are the superior and inferior
vena cava
Blood Vessels
• Arteries carry blood away from the heart
• Veins carry blood toward the heart
• So do all arteries carry oxygen rich blood
and all veins carry oxygen poor blood?
Structure
• 3 tunics (coats) or layers of veins and arteries
– Tunica adventitia- outermost – made of connective tissue,
which reinforce the vessel wall so it will not burst
– Tunica media- middle – contains smooth muscle
– Tunica intima- inner – endothelial cells --- endothelium
lines the entire circulatory system
Structure
• Only arteries, arterioles, veins, and venules
can be seen during surgery- capillaries are
microscopic
• Capillaries are only one layer thick and
thin-walled- only tunica intima
• This allows for easy exchange of gases and
nutrients
Systemic and Pulmonary Circulation
• Systemic circulation: blood flow from left
ventricle of the heart through blood vessels to all
parts of the body and back to the right atrium
• Pulmonary circulation: venous blood moves from
the right atrium to the right ventricle to the
pulmonary artery to lung arterioles and capillaries.
There the exchange of gases between the blood
and the air takes place. This oxygenated blood
then flows through lung venules into four
pulmonary veins and returns to the left atrium
Pulmonary and Systemic
Blood Circuits
Cardiovascular System
Veins contain valves to
prevent the backward
flow of blood:
A. External view of the
vein shows wider area
of valve.
B. Internal view with the
valve open as blood
flows through.
C. Internal view with the
valve closed.
Blood Vessel Structure
Note the valve and the
comparison of the
artery, vein, and
capillary
Cardiovascular System
Ascending Aorta
• Right Coronary
• Left Coronary
Aortic Arch
• Brachiocephalic
– Right Common Carotid
– Right Subclavian
• Left Common Carotid
• Left Subclavian
Cardiovascular System
Major veins and
arteries of the neck
Branches of the Thoracic and
Abdominal Aorta
Arterial System
Venous System
Blood Pressure
• Pressure on the blood vessel walls
• Highest in arteries, Lowest in Veins
• Blood pressure gradient: the graph looks like a
hill… aorta is highest point and the venae cavae
are the lowest. Defined as the difference between
the mean BP in the aorta and the mean BP in the
venae cavae.
Blood Pressure
• Blood pressure keeps the blood circulating
• No blood pressure = No blood circulating = death
• Average pressure is the MEAN BP
• Hypertension- high blood pressure; could rupture blood
vessels
• Hypotension- low blood pressure; circulation can be too
low to sustain life - Hemorrhage can cause hypotension
Factors That Influence Arterial
Blood Pressure
• Blood volume
• Strength of ventricular
contractions
• Resistance
• Blood viscosity
• Heart rate
Blood Pressure
• Blood Volume- volume of blood in the vessels
– Direct cause of blood pressure
• Arterial blood volume is determined by how much the
heart pumps into them, which determines how much the
arterioles drain out of them; the size of the arterioles are
important in determining how much blood is drained
from the arteries
• Larger the volume, the higher the pressure; conversely,
lower blood volume, lower blood pressure; thus
hemorrhage = lower blood pressure = not corrected =
death
• Drop in BP is a major sign of hemorrhage
Strength of ventricular
Contractions
–the strength and rate of the
heartbeat affects the stroke
volume (amount of blood ejected by the LV into the aorta
with one contraction), which in turn affects
cardiac output, which affects
blood volume, therefore the BP
Blood Pressure
• Blood Viscosity- aka thickness. Blood that is too
diluted causes BP to drop
– Less viscous than normal, BP decreases, so for
hemorrhage treatment, whole blood or plasma is
preferred
– More viscous than normal, BP increases
• Polycythemia increases viscosity thereby
increasing BP
Blood Pressure
 As blood leaves the LV and
enters the aorta, its pressure falls
progressively as the distance from
the heart increases
 Once in the venae cavae, the
pressure is near zero
Blood Pressure
• Resistance is the hindrance of blood flow
with in the CV system due to friction of the
blood against the walls of the vessels
• Most resistance is in the aterioles,
capillaries, and venules
• Vasoconstriction and vasodilation influence
resistance
Blood Pressure
• Heart rate affects BP
• As the heart beats faster, each contraction of
the LV leaves less time for the ventricle to
refill, thus less blood is pumped into the
aorta. This means less blood volume which
is less blood pressure
Fluctuations in BP
• Doesn’t stay the same all the time.
• Increases during exercise, fear, etc.
• Decreases at night, while sleeping or
relaxing.
• Normal is 120/80 for healthy adults
(average)
Central venous pressure
• BP within the RA
• CVP is low as it enters the RA
• If the heart is weakened, the CVP increases
5 mechanisms that keep venous
blood moving
• Continued beating of the heart
• Adequate BP in the arteries
• Semilunar valves preventing backflow thus
moving blood in the right direction
• Contraction of skeletal muscles squeezing
veins with assistance of venous valves
• Changing pressures in the chest cavity
during breathing acting as a pump
Pulse
• An artery expanding and then recoiling
– alternately is what you are feeling when you
take a pulse.
• Provides information on the rate, strength,
and rhythm of the heartbeat
Major pulse points
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Temporal – over the temple anterior to the ear
Facial – lower margin of the mandible
Carotid – neck, along the sternocleidomastoid muscle
Axillary – inferiolateral axillary wall
Brachial – medial aspect of upper arm
Radial – at the wrist
Femoral – groin
Popliteal – behind and proximal to the knee
Dorsalis – dorsal surface of the foot
Apical – 5th left intercostal space (requires
auscultation)
Hepatic Portal System
• Veins from the spleen, stomach,
pancreas, gallbladder, and
intestines send their blood to the
liver by means of the hepatic
portal vein.
Hepatic Portal Circulation
• Refers to the route of blood flow through
the liver.
• Liver cells remove and detoxify various
poisonous substances.
• This is a variation (detour) of the normal
blood route
• This means that this blood is sent through a
second set of capillaries (in the liver)
Pathology
• Arteriosclerosis -thickening & loss of
elasticity of the walls of the arteries
Hardening of the arteries
– Atherosclerosis -collection of fatty & other
substances on the inner lining of arteries,
forming plaques, which progressively occlude
the passageways; obstruction of the flow of
blood
• Atheroma – prototypical lesion of atherosclerosis
Arteriosclerosis Obliterans
Diagnostic Procedures and
Equipment
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Plethysmography
Doppler probe
Phleborheography
CAT scan, MRI, and ultrasonography
Angiography
Angiography
Pathology
• Arterial embolism
– Treatment - Fogarty
catheter
Pulmonary Emboli Following
Fogarty Embolectomy
– Carotid Endarterectomy - removal of
arteriosclerotic plaque from an obstructed carotid artery
in order to restore circulation.
Endarterectomy