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Cardiovascular System: VesselsChapter 20 – Lecture Notes
to accompany
Anatomy and Physiology: From Science to Life
textbook by
Gail Jenkins, Christopher Kemnitz, Gerard Tortora
Chapter Overview
20.1 Arterial Blood Flow Overview
20.2 Capillaries
20.3 Venules and Veins
20.4 Capillary Exchange
20.5 Blood Flow
20.6 Blood Pressure Regulation
20.7 Pulse
20.8 Systemic and Pulmonary Circuits
Essential Terms
artery blood vessel carrying blood away from the
heart
vein vessel carrying blood toward the heart
capillaries smallest vessels that function in exchange of
nutrients and wastes between blood and body cells
Introduction Blood vessels transport materials
throughout body carry nutrients to cells carry wastes away for excretion
From heart to arteries to arterioles to capillaries to venules to veins to heart
Concept 20.1
Arteries
Arteries Two main types
elastic arteries muscular arteries
Three coats tunic interna
endothelium, basement membrane, internal elastic lamina
tunica media elastic fibers and smooth muscle fibers
tunic externa elastic and collagen fibers
Innervated by sympathetic fibers of ANS
Figure 20.1ab
Figure 20.1c
Figure 20.1d
Figure 20.1e
Elastic Arteries largest diameter highest proportion of elastic fibers in tunica
media help propel blood onward while ventricles
are relaxing stretch with surge of blood recoil when pressure decreases
Figure 20.2
Muscular Arteries medium-sized arteries tunica media has more smooth muscle and
fewer elastic fibers than elastic arteries adjust blood flow capable of greater vasoconstriction and
vasodilation most named arteries are muscular arteries
Arterioles muscular arteries divide into smaller arteries smaller arteries divide into arterioles arterioles feed capillaries tunics minimize as they near capillary beds regulate resistance
contraction of smooth muscle increases resistance
can significantly affect blood pressure
Figure 20.3
Concept 20.2 Capillaries
Capillaries microscopic vessels that connect arterioles to
venules exchange vessels fed by metarterioles found near almost every cell in the body number varies with metabolic activity of
tissue they serve center vessel is thoroughfare channel all others have precappillary sphincters that
can constrict and restrict flow
Figure 20.3
Three Capillary TypesFrom least leaky to most leaky
1. continuous
2. fenestrated
3. sinusoids
If blood passes from one capillary network to another through a vein
– vein is called portal vein– second network is called portal system
Figure 20.4a
Figure 20.4b
Figure 20.4c
Concept 20.3 Venules and Veins
Venules capillaries unite to form venules drain into veins tunica interna and tunica media
Veins venules unite to form veins return blood to the heart tunica interna, media, and externa thinner than arteries many have valves to prevent back flow low pressure system
Figure 20.5
Veins venules unite to form veins return blood to the heart tunica interna, media, and externa thinner than arteries many have valves to prevent back flow low pressure system
Table 20.1
Blood Reservoirs about 64% of blood is in systemic veins and
venules at any given moment brain stem can vasoconstrict these vessels
allowing greater blood flow to skeletal muscles
Figure 20.6
Concept 20.4 Capillary Exchange
Capillary Exchange exchange mechanisms include
diffusion transcytosis bulk flow
Hydrostatic pressure influences exchange Blood colloid osmotic pressures helps blood
retain fluid in vessels resisted by interstitial fluid osmotic pressure
Figure 20.7
Filtration and Reabsorption filtration
pressure driven movement of fluid and solutes FROM blood into interstitial fluid
reabsorption pressure driven from interstitial fluid INTO blood
vessels net filtration pressure (NFP)
difference between filtration pressure and reabsorption pressure is
Figure 20.7
Concept 20.5 Blood Flow
Blood Pressure hydrostatic pressure exerted by blood on
walls of blood vessel measured in mm Hg systolic blood pressure
highest pressure attained in arteries during systole
diastolic blood pressure lowest pressure during diastole
mean arterial pressure average of systolic and diastolic pressures useful when considering blood flow
Figure 20.8
Vascular Resistance opposition to blood flow due to friction between
blood and walls of vessels increase in resistance increases BP decrease in resistance decreases BP Systemic vascular resistance depends on three
things1. size of lumen
larger lumen less resistance
2. blood viscosity thinner blood less resistance
3. vessel length shorter length less resistance
Venous Return mechanisms that “pump” blood from lower
body to heart
1. skeletal muscle pump figure 20.9
2. respiratory pump during inhalation the diaphragm moves
downward increasing pressure in abdominal cavity and decreasing pressure in thoracic cavity
– abdominal veins are compressed and blood forced upward
Figure 20.9
Velocity of Blood Flow Inversely related to cross-sectional area of
vessel slowest where area is greatest velocity slows as blood moves into larger veins
Circulation time time required for a drop of blood to pass from
right atrium through pulmonary and systemic circulation back to right atrium
normally about 1 minute
Figure 20.10
Concept 20.6 Blood Pressure Regulation
Cardiovascular Center in medulla oblongata controls neural and hormonal negative
feedback systems input
from cerebral cortex, limbic system and hypothalamus
sensory receptors proprioceptors, baroreceptors, chemoreceptors
output ANS sympathetic & parasympathetic neurons vasomotor nerves throughout body
especially skin and abdominal visceral
Figure 20.11
Neural Regulation of BP Baroreceptor Reflexes
pressure sensitive sensory receptors in aorta, internal carotid arteries in neck and chest
two most important carotid sinus reflex (BP in brain) aortic reflex (BP in ascending arch of aorta)
if pressure drops sympathetic stimulation increases parasympathetic stimulation decreases
Chemoreceptor Reflexes monitor carbon dioxide, oxygen gas, pH
Figure 20.12
Figure 20.13
Hormonal Regulation of BP Renin-angiotensin-aldosterone system
endocrine response Epinephrine and norepinephrine
sympathetic nervous system ADH ANP
Table 20.2
Autoregulation of BP tissue level automatic regulation of BP to
match metabolic needs Two general types of stimuli
physical changes chemicals
Concept 20.7 MeasuringPulse and BP
Pulse alternate expansion and recoil of arteries rate same as heart rate strongest close to heart faintest most distally may be felt in any artery that lies near the
surface of body and runs over a bone or other firm structure
Blood Pressure measured in mm Hg using
sphygomanometer when pressure in cuff exceeds systolic
blood pressure sounds cut off as pressure is released sounds return when
pressure in cuff is equal to systolic pressure and disappears again as it is equalized with diastolic blood pressure
Figure 20.15
Concept 20.8 Systemic and Pulmonary Circulation
Figure 20.16
Circulatory Routes anastomosis
union of two or more arteries that supply the same body region
provide collateral circulation alternate routes for blood to reach a tissue or organ
end arteries arteries that do not anastomose
Concept 20.9 Pulmonary Circulation
Pulmonary Circulation heart to lungs and back again heart to pulmonary trunk to right and left pulmonary arteries to lungs (arteries, arterioles, capillaries
surrounding alveoli, to venules to pulmonary veins to left atrium blood leaves the heart deoxygenated and
returns oxygenated resistance is very low in pulmonary circuit
(low pressure system)
Figure 20.17a
Figure 20.17b
Concept 20.10 Systemic Circulation
Systemic Circulation all arteries and arterioles that carry blood
containing oxygen and nutrients from left side of heart throughout the body and back to the right atrium via vena cava
leaves through aorta returns through superior and inferior vena
cava or coronary sinus
Figure 20.18a
Figure 20.18b
Figure 20.18c
Figure 20.24
Table 20.3 pt 1
Table 20.3 pt 2
Figure 20.20a
Figure 20.20b
Figure 20.20c
Figure 20.20d
Table 20.4 pt 1
Table 20.4 pt 2
Table 20.4 pt 3
Figure 20.21a
Figure 20.21b
Table 20.5
Figure 20.22a
Figure 20.22b
Figure 20.22c
Figure 20.22d
Figure 20.22e
Table 20.6 pt 1
Table 20.6 pt 2
Figure 20.23a