Chapter 21: Blood Vessels and Circulation Biol141 A

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Chapter 21Blood Vessels and CirculationBiol141
A PR.L. Brashear-Kaulfers
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5 Classes of Blood Vessels

• Arteries
• carry blood away from heart
• Arterioles
• Are smallest branches of arteries
• Capillaries
• are smallest blood vessels
• location of exchange between blood and
  interstitial fluid
• Venules
• collect blood from capillaries
• Veins
• return blood to heart

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The Largest Blood Vessels

• Attach to heart
• Pulmonary trunk
• carries blood from right ventricle
• to pulmonary circulation
• Aorta
• carries blood from left ventricle
• to systemic circulation

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The Smallest Blood Vessels

• Capillaries
• Have small diameter and thin walls
• Chemicals and gases diffuse across walls

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Structure of Vessel Walls
Tunica Externa In arteries contain
collagen elastic fibers In veins contain elastic
fibers smooth muscle cells
Figure 21-1
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Arteries vs. Veins

• Arteries and veins run side-by-side
• Arteries have thicker walls and higher blood
  pressure
• Collapsed artery has small, round lumen
• Vein has a large, flat lumen
• Vein lining contracts, artery lining does not
• Artery lining folds
• Arteries more elastic
• Veins have valves

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Arteries and Pressure

• Elasticity allows arteries to absorb pressure
  waves that come with each heartbeat
• Contractility -Arteries change diameter
• Controlled by sympathetic division of ANS

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Vasoconstriction and Vasodilation

• Vasoconstriction -The contraction of arterial
  smooth muscle by the ANS
• Vasodilatation- The relaxation of arterial smooth
  muscle
• Enlarging the lumen
• Both Affect
• afterload on heart
• peripheral blood pressure
• capillary blood flow

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Structure of Blood Vessels
Artery Characteristics From heart to capillaries,
arteries change from elastic arteries to
muscular arteries to arterioles
Figure 21-2
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Arterioles

• Are small
• Have little or no tunica externa
• Have thin or incomplete tunica media

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Artery Diameter

• Small muscular arteries and arterioles
• changes with sympathetic or endocrine stimulation
• constricted arteries oppose blood flow
• Resistance (R) -The force opposing blood flow
• Resistance vessels
• arterioles

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Aneurysm

• A bulge in an arterial wall
• Is caused by weak spot in elastic fibers
• Pressure may rupture vessel

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Capillaries

• Are smallest vessels with thin walls
• Microscopic capillary networks permeate all
  active tissues
• Capillary Function
• Location of all exchange functions of
  cardiovascular system
• Materials diffuse between blood and interstitial
  fluid

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Capillary Structure
Figure 21-4
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2 Types of Capillaries

• 1. Continuous capillaries-Have complete
  endothelial lining
• Are found in all tissues except epithelia
  and cartilage
• Permit diffusion of
• Water, small solutes, Lipid-soluble materials
• Block
• blood cells, plasma proteins
• Are in CNS and thymus, Have very restricted
  permeability e.g., the bloodbrain barrier
• 2. Fenestrated capillaries-Have complete
  endothelial lining
• Are found in all tissues except epithelia and
  cartilage, in choroid plexus, endocrine organs,
  kidneys,intestinal tract

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Capillary Networks
Capillary bed or capillary plexus Connect 1
arteriole and 1 venule
Figure 21-5
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Capillary Sphincter

• Guards entrance to each capillary
• Opens and closes, causing capillary blood to flow
  in pulses
• Vasomotion -Contraction and relaxation cycle of
  capillary sphincters
• Causes blood flow in capillary beds to constantly
  change routes

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Veins

• Collect blood from capillaries in tissues and
  organs
• Return blood to heart
• Veins vs. Arteries
• Are larger in diameter
• Have thinner walls
• Carry lower blood pressure

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3 Vein Categories

• Venules
• very small veins
• collect blood from capillaries
• Medium-sized veins
• thin tunica media and few smooth muscle cells
• tunica externa with longitudinal bundles of
  elastic fibers
• Large veins
• have all 3 tunica layers
• thick tunica externa
• thin tunica media

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Valves in the Venous System
Vein Valves Folds of tunica intima Prevent blood
from flowing backward Compression pushes blood
toward heart
Figure 21-6
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Blood Distribution
Heart, arteries, and capillaries 3035 of blood
volume Venous system 6065
Figure 21-7
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Venous Blood Distribution

• 1/3 of venous blood is in the large venous
  networks of the liver, bone marrow, and skin

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Cardiovascular Physiology
Figure 21-8
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Cardiovascular Regulation

• Maintains capillary blood flow in peripheral
  tissues and organs

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Capillary Blood Flow

• Equals cardiac output
• Is determined by
• pressure and resistance in the cardiovascular
  system

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Measuring Pressure

• Blood pressure (BP)
• arterial pressure (mm Hg)
• Capillary hydrostatic pressure (CHP)
• pressure within the capillary beds
• Venous pressure
• pressure in the venous system

InterActive Physiology Cardiovascular System
Measuring Blood Pressure
PLAY
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Viscosity

• R caused by molecules and suspended materials in
  a liquid
• Whole blood viscosity is about 4 times that of
  water

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Turbulence

• Swirling action that disturbs smooth flow of
  liquid
• Occurs in heart chambers and great vessels
• Atherosclerotic plaques cause abnormal turbulence

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Pressures in the Systemic Circuit

• Systolic pressure
• peak arterial pressure during ventricular systole
• Diastolic pressure
• minimum arterial pressure during diastole
• Pulse pressure
• difference between systolic pressure and
  diastolic pressure
• Mean arterial pressure (MAP)
• MAP diastolic pressure 1/3 pulse pressure

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Abnormal Blood Pressure

• Hypertension
• abnormally high blood pressure
• greater than 140/90
• Hypotension
• abnormally low blood pressure

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Venous Return

• Amount of blood arriving at right atrium each
  minute
• Determined by venous pressure
• Low effective pressure in venous system
• Low venous resistance Is assisted by
• muscular compression of peripheral veins
• the respiratory pump
• Compression of skeletal muscles
• pushes blood toward heart (one-way valves)

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Capillary Exchange

• Vital to homeostasis
• Moves materials across capillary walls by
• diffusion, filtration, and reabsorption

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5 Diffusion Routes

• Water, ions, and small molecules such as glucose
• diffuse between adjacent endothelial cells
• or through fenestrated capillaries
• Some ions ( Na, K, Ca2, Cl)
• diffuse through channels in cell membranes
• Large, water-soluble compounds
• pass through fenestrated capillaries
• Lipids and lipid-soluble materials such as O2 and
  CO2
• diffuse through endothelial cell membranes
• Plasma proteins
• cross endothelial lining in sinusoids

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Capillary Filtration
Figure 21-11
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Capillary Exchange

• At arterial end of capillary
• fluid moves out of capillary
• into interstitial fluid
• At venous end of capillary
• fluid moves into capillary
• out of interstitial fluid

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The Transition Point

• Between filtration and reabsorption
• is closer to venous end than arterial end
• Capillaries filter more than reabsorb
• Excess fluid enters lymphatic vessels

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4 Functions of Blood and Lymph Cycle

• Ensures constant plasma and interstitial fluid
  communication
• Accelerates distribution of nutrients, hormones,
  and dissolves gases through tissues
• Transports insoluble lipids and tissue proteins
  that cant cross capillary walls
• Flushes bacterial toxins and chemicals to immune
  system tissues

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Capillary Dynamics

• Hemorrhaging
• reduces CHP and NFP
• increases reabsorption of interstitial fluid
  (recall of fluids)
• Dehydration
• increases BCOP
• accelerates reabsorption
• Increase in CHP or BCOP
• fluid moves out of blood
• builds up in peripheral tissues (edema)

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KEY CONCEPT

• Blood flow is the goal
• Total peripheral blood flow equals cardiac output
• Blood pressure overcomes friction and elastic
  forces to sustain blood flow
• If blood pressure is too low
• vessels collapse, blood flow stops
• tissues die
• If blood pressure is too high
• vessel walls stiffen, capillary beds may rupture

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How do central and local control mechanisms
interact to regulate blood flow and pressure in
tissues?
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Tissue Perfusion

• Blood flow through the tissues
• Carries O2 and nutrients to tissues and organs
• Carries CO2 and wastes away
• Is affected by
• cardiac output
• peripheral resistance
• blood pressure

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3 Regulatory Mechanisms

• Control cardiac output and blood pressure
• 1. Autoregulation
• causes immediate, localized homeostatic
  adjustments
• Neural mechanisms
• respond quickly to changes at specific sites
• 3. Endocrine mechanisms
• direct long-term changes

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Vasodilators

• Dilate precapillary sphincters
• Local vasodilators
• accelerate blood flow at tissue level
• Low O2 or high CO2 levels
• Low pH (acids),Nitric oxide (NO)
• High K or H concentrations
• Chemicals released by inflammation (histamine)
• Elevated local temperature

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Patterns of Cardiovascular Response

• Blood, heart, and cardiovascular system
• work together as unit
• respond to physical and physiological changes
  (e.g., exercise, blood loss)
• to maintain homeostasis

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Blood Distribution during Exercise
Table 21-2
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3 Effects of Light Exercise

• Extensive vasodilation occurs
• increasing circulation
• Venous return increases
• with muscle contractions
• Cardiac output rises
• due to rise in venous return (FrankStarling
  principle) and atrial stretching

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5 Effects of Heavy Exercise

• Activates sympathetic nervous system
• Cardiac output increases to maximum
• about 4 times resting level
• Restricts blood flow to nonessential organs
  (e.g., digestive system)
• Redirects blood flow to skeletal muscles, lungs,
  and heart
• Blood supply to brain is unaffected

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Training and Cardiovascular Performance
Effects of Exercise Regular moderate
exercise lowers total blood cholesterol
levels Intense exercise can cause severe
physiological stress
Table 21-3
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Responses to Blood Loss
Figure 21-17
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Responses to Severe Blood Loss

• Also called hemorrhaging
• Entire cardiovascular system adjusts to
• maintain blood pressure
• restore blood volume
• To prevent drop in blood pressure
• 1. carotid and aortic reflexes
• increase cardiac output (increasing heart rate)
• cause peripheral vasoconstriction
• Sympathetic nervous system
• triggers hypothalamus
• further constricts arterioles
• venoconstriction improves venous return

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3 Short-Term Responses to Hemorrhage

• To prevent drop in blood pressure
• 1. carotid and aortic reflexes
• increase cardiac output (increasing heart rate)
• cause peripheral vasoconstriction
• 2. Sympathetic nervous system
• triggers hypothalamus
• further constricts arterioles
• venoconstriction improves venous return
• 3. Hormonal effects
• increase cardiac output
• increase peripheral vasoconstriction (E, NE, ADH,
  angiotensin II)

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Shock

• Short-term responses compensate up to 20 loss of
  blood volume
• Failure to restore blood pressure results in shock

Circulatory Shock
PLAY
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4 Long-Term Responses to Hemorrhage

• Restoration of blood volume can take several
  days
• Recall of fluids from interstitial spaces
• 2. Aldosterone and ADH promote fluid retention
  and reabsorption
• 3. Thirst increases
• 4. Erythropoietin stimulates red blood cell
  production

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What are the principle blood vessels and
functional characteristics of the special
circulation to the brain, heart, and lungs?
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Blood Flow to the Brain

• Is top priority
• Brain has high oxygen demand
• When peripheral vessel constrict, cerebral
  vessels dilate, normalizing blood flow

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Stroke

• Also called cerebrovascular accident (CVA)
• Blockage or rupture in a cerebral artery
• Stops blood flow

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Blood Flow to the Heart

• Through coronary arteries
• Oxygen demand increases with activity
• Lactic acid and low O2 levels
• dilate coronary vessels
• increase coronary blood flow
• Epinephrine
• dilates coronary vessels
• increases heart rate
• strengthens contractions

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Heart Attack

• A blockage of coronary blood flow
• Can cause
• angina
• tissue damage
• heart failure
• death

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Blood Flow to the Lungs

• Regulated by O2 levels in alveoli
• High O2 content
• vessels dilate
• Low O2 content
• vessels constrict
• Pulmonary Blood Pressure
• In pulmonary capillaries
• is low to encourage reabsorption
• If capillary pressure rises
• pulmonary edema occurs

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Circulation Patterns
3 Distribution Patterns 1. Peripheral artery and
vein distribution is the same on right and left,
except near the heart 2. The same vessel may
have different names in different locations 3.
Tissues and organs usually have multiple arteries
and veins vessels may be interconnected by
anastomoses
Figure 21-18
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The Pulmonary Circuit
Figure 21-19
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The Pulmonary Circuit

• Deoxygenated blood arrives at heart from systemic
  circuit
• passes through right atrium and ventricle
• enters pulmonary trunk
• At the lungs
• CO2 is removed
• O2 is added
• Oxygenated blood
• returns to the heart
• is distributed to systemic circuit

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Pulmonary Vessels

• Pulmonary arteries
• carry deoxygenated blood
• Pulmonary veins
• carry oxygenated blood

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Pulmonary Arteries

• Pulmonary trunk
• branches to left and right pulmonary arteries
• Pulmonary arteries
• branch into pulmonary arterioles
• Pulmonary arterioles
• branch into capillary networks that surround
  alveoli

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Pulmonary Veins

• Capillary networks around alveoli
• join to form venules
• Venules
• join to form 4 pulmonary veins
• Pulmonary veins
• empty into left atrium

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Major Systemic Arteries
The Systemic Circuit Contains 84 of blood
volume Supplies entire body except for pulmonary
circuit
Figure 21-20
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Arteries of the Chest and Upper Limbs
3D Peel-Away of Arteries of the Upper Limbs
PLAY
Figure 21-21a, b
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Systemic Arteries

• Blood moves from left ventricle
• into ascending aorta
• Coronary arteries
• branch from aortic sinus

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The Aorta

• The ascending aorta
• rises from the left ventricle
• curves to form aortic arch
• turns downward to become descending aorta
• Branches of the Aortic Arch deliver blood to head
  and neck
• brachiocephalic trunk
• left common carotid artery
• left subclavian artery

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• The Brachiocephalic Trunk Branches to form
• right subclavian artery
• right common carotid artery
• The Subclavian Arteries Branches within thoracic
  cavity
• internal thoracic artery
• vertebral artery
• thyrocervical trunk

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The Subclavian Arteries

• The Subclavian Arteries Branches within thoracic
  cavity
• internal thoracic artery
• vertebral artery
• thyrocervical trunk
• Leaving the thoracic cavity
• become axillary artery in arm
• and brachial artery distally- Divides at coronoid
  fossa of humerus
• into radial artery and ulnar artery

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Arteries of the Neck and Head
3D Peel-Away of Arteries of the Head and Neck
PLAY
Figure 21-22
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The Common Carotid Arteries

• Carry blood to head and neck
• Each common carotid divides into
• external carotid artery-Supplies structures of
  Neck, lower jaw, face
• internal carotid artery-Enters skull and divides
  into opthalmic artery, anterior cerebral artery,
  middle cerebral artery

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Arteries of the Brain
Figure 21-23
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The Vertebral Arteries

• Also supply brain with blood supply
• Left and right vertebral arteries
• arise from subclavian arteries
• enter cranium through foramen magnum
• fuse to form basilar artery

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Arteries of the Trunk
Descending Aorta - is divided by diaphragm
into thoracic aorta abdominal aorta
Figure 21-24a
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Arteries of the Trunk
Thoracic Aorta branches are anatomically grouped
into visceral parietal
3D Peel-Away of Arteries of the Trunk
PLAY
Figure 21-24b
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4 Visceral Branches

• Supply organs of the chest
• bronchial arteries
• pericardial arteries
• esophogeal arteries
• mediastinal arteries

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The Abdominal Aorta

• Divides at terminal segment of the aorta into
• left common iliac artery
• right common iliac artery

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Branches of the Abdominal Aorta

• Unpaired branches
• major branches to visceral organs
• Paired branches
• to body wall
• kidneys
• urinary bladder
• structures outside abdominopelvic cavity

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Arteries of the Abdominopelvic Organs
Figure 21-25
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3 Unpaired Branches of the Abdominal Aorta

• Celiac trunk, divides into
• left gastric artery
• splenic artery
• common hepatic artery
• Superior mesenteric artery
• Left mesenteric artery

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5 Paired Branches of the Abdominal Aorta

• Inferior phrenic arteries
• Suprarenal arteries
• Renal arteries
• Gonadal arteries
• Lumbar arteries

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The Abdominal Aorta

• Divides to form
• right and left common iliac arteries Divide
  to form internal iliac artery, external iliac
  artery
• middle sacral artery-

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Arteries of the Lower Limbs
3D Peel-Away of Arteries of the Lower Limbs
PLAY
Figure 21-26
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Major Systemic Veins
All Systemic Veins Drain into either superior
vena cava (SVC) or inferior vena cava (IVC)
Figure 21-27
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Complementary Arteries and Veins

• Run side by side
• Branching patterns of peripheral veins are more
  variable

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Differences in Artery and Vein Distribution

• In neck and limbs
• 1 set of arteries (deep)
• 2 sets of veins (1 deep, 1 superficial)
• Venous system controls body temperature

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Veins of the Head, Neck, and Brain
Figure 21-28
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The Superior Vena Cava (SVC)

• Receives blood from
• head
• neck
• chest
• shoulders
• upper limbs

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Veins of the Neck

• Temporal and maxillary veins
• drain to external jugular vein
• Facial vein
• drains to internal jugular vein

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Veins of the Abdomen and Chest
Figure 21-29
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Deep Veins of the Forearm

• Deep palmar veins drain into
• radial and ulnar veins
• which fuse above elbow to form brachial vein
• Veins of the Upper Arm Cephalic vein joins
  axillary vein
• to form subclavian vein

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The Subclavian Vein

• Merges with external and internal jugular veins
• to form brachiocephalic vein
• which enters thoracic cavity

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Veins of the Thoracic Cavity

• Brachiocephalic vein receives blood from
• vertebral vein
• internal thoracic vein
• Merge to form the superior vena cava (SVC)

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Tributaries of the Superior Vena Cava
Figure 21-30a
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Tributaries of the Inferior Vena Cava

• Inferior Vena Cava collects blood from organs
  inferior to the diaphragm

Figure 21-30b
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Veins of the Lower Limbs
Figure 21-31
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The Femoral Vein

• Before entering abdominal wall, receives blood
  from
• great saphenous vein
• deep femoral vein
• femoral circumflex vein
• Inside the pelvic cavity
• becomes the external iliac vein
• The Right and Left Common Iliac Veins Merge to
  form the inferior vena cava

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Veins of the Abdomen
6 Major Tributaries of the Abdominal Inferior
Vena Cava Lumbar veins Gonadal veins Hepatic
veins Renal veins Suprarenal veins Phrenic veins
Figure 21-29
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The Hepatic Portal System
Figure 21-32
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The Hepatic Portal System

• Connects 2 capillary beds
• Delivers nutrient-laden blood
• from capillaries of digestive organs
• to liver sinusoids for processing

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5 Tributaries of the Hepatic Portal Vein

• Inferior mesenteric vein
• drains part of large intestine
• Splenic vein
• drains spleen, part of stomach, and pancreas
• Superior mesenteric vein
• drains part of stomach, small intestine, and part
  of large intestine
• Left and right gastric veins
• drains part of stomach
• Cystic vein
• drains gallbladder

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Blood Processed in Liver

• After processing in liver sinusoids, blood
  collects in hepatic veins and empties into
  inferior vena cava

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Fetal Circulation

• Embryonic lungs and digestive tract nonfunctional
• Respiratory functions and nutrition provided by
  placenta

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Placental Blood Supply
Blood flows to the placenta through a pair of
umbilical arteries which arise from internal
iliac arteries and enter umbilical cord Blood
returns from placenta in a single umbilical
vein which drains into ductus venosus Ductus
venosus empties into inferior vena cava
Figure 21-33a
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The Neonatal Heart
Before Birth -Fetal lungs are collapsed O2
provided by placental circulation
At Birth -Newborn breathes air Lungs
expand Pulmonary circulation provides O2
Figure 21-33b
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2 Fetal Pulmonary Circulation Bypasses

• Foramen ovale
• interatrial opening
• covered by valve-like flap
• directs blood from right to left atrium
• Ductus arteriosus
• short vessel
• connects pulmonary and aortic trunks

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Cardiovascular Changes at Birth

• Pulmonary vessels expand
• Reduced resistance allows blood flow
• Rising O2 causes ductus arteriosus constriction
• Rising left atrium pressure closes foramen ovale

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Congenital Cardiovascular Problems
Develop if proper circulatory changes do not
occur at birth
Figure 21-34
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Aging and the Cardiovascular System

• Cardiovascular capabilities decline with age
• Age-related changes occur in
• blood
• heart
• blood vessels

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3 Age-Related Changes in Blood

• Decreased hematocrit
• Blood clots (thrombus)
• Blood-pooling in legs
• due to venous valve deterioration

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5 Age-Related Changes in the Heart

• Reduced maximum cardiac output
• Changes in nodal and conducting cells
• Reduced elasticity of fibrous skeleton
• Progressive atherosclerosis
• Replacement of damaged cardiac muscle cells by
  scar tissue

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3 Age-Related Changes in Blood Vessels

• Arteries become less elastic
• pressure change can cause aneurysm
• Calcium deposits on vessel walls
• can cause stroke or infarction
• Thrombi can form
• at atherosclerotic plaques

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Integration with Other Systems
Figure 21-35
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Clinical Patterns

• There are many categories of cardiovascular
  disorders
• Disorders may
• affect all cells and systems
• be structural or functional
• result from disease or trauma

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SUMMARY (1)

• 3 types of blood vessels
• arteries
• veins
• Capillaries
• Structure of vessel walls
• Differences between arteries and veins
• Atherosclerosis, arteriosclerosis, and plaques
• Structures of
• elastic arteries
• muscular arteries
• arterioles

118
SUMMARY (2)

• Structures of capillary walls
• continuous
• Fenestrated
• Structures of capillary beds
• precapillary sphincters
• vasomotion
• arteriovenous anastomoses
• Functions of the venous system and valves
• Distribution of blood and venous reserves

119
SUMMARY (3)

• Circulatory pressures
• blood pressure
• capillary hydrostatic pressure
• venous pressure
• Resistance in blood vessels
• viscosity
• turbulence
• Vasoconstriction
• The respiratory pump
• Capillary pressure and capillary exchange
• osmotic pressure
• net filtration pressure

120
SUMMARY (4)

• Physiological controls of cardiovascular system
• Autoregulation, neural controls
• hormonal controls
• Cardiovascular responses to exercise and blood
  loss
• Special circulation to brain, heart, and lungs
• Distribution of arteries in pulmonary and
  systemic circuits
• Distribution of veins in pulmonary and systemic
  circuits
• Fetal circulation and changes at birth
• Effects of aging on the cardiovascular system