Anatomy & Physiology 34B Lecture
Chapter 19 - Blood Vessels & Circulation
I.
Overview
A. General Anatomy of Blood Vessels
B. Blood Pressure, Resistance & Flow
C. Capillary Exchange
D. Venous Return & Circulatory Shock
E. Special Circulatory Routes
F. Principal Arteries of the Body
G. Principal Veins of the Body
H. Blood Vessel Disorders
II. General Anatomy of Blood Vessels
A. Circulatory Routes – blood leaving the heart passes through a ____________ route in the
body
1.
2.
3.
Blood moves away from the heart to body tissues through _________ to arterioles to
capillaries
Blood moves back to the heart from capillaries to venules to _______
Exceptions to the above include portal systems and anastomoses
a. In a ________ system, blood flows through two consecutive ____________
systems before returning to the heart
b. An _____________ is a point where two blood vessels merge
1) In an ______________ anastomosis (shunt), blood flows from an artery directly
into a ______; found in fingers, palms, toes, and ears
2) In an arterial anastomosis, two ________ merge and form collateral routes of
blood supply to a tissue (e.g., between coronary arteries)
3) Venous anastomoses, in which two _____ merge, are more common than
arterial anastomoses
B. The walls of arteries & veins are composed of three _____ (layers)
1. Tunica ________ (adventitia) - outermost layer, composed of loose fibrous CT that
anchors the vessel, and provides a passage way for nerves, lymph vessels, and smaller
blood vessels (____ _______)
2.
3.
4.
Tunica ______ - middle layer, composed of smooth _______, collagen and elastic
fibers; smooth muscle contraction = vaso________; muscle relaxation =
vaso_________
Tunica _______ (interna) - innermost layer, of endothelium and a basement
membrane (capillaries consist solely of this layer)
The _______ is the central blood-filled space within the vessel.
C. Some differences between arteries & veins:
1. Arteries have a thicker T. _____ and are rounder than veins in cross section
2. Veins are usually partially collapsed, and many have ______ that are absent in
arteries
D. Arteries and Metarterioles - carry blood (usually oxygenated) _____ ______ the heart.
Three categories are
2
1.
Conducting (_______) arteries (e.g.: aorta & major branches) have many ______
fibers in their smooth muscle, thus expand when BP rises during systole, then recoil
during diastole
2.
Distributing (_________) arteries are smaller medium sized arteries, with less
elastic and a thick tunica ______ in relation to their diameters; these distribute blood
to specific organs
3.
___________ arteries are small with little elastic and relatively thick tunica media;
__________ are the smallest of these, with only 1-2 layers of smooth muscle over
endothelium
E. ___________ - narrowest of the blood vessels; the functional units of the circulatory
system
1.
Capillary walls are thin, composed of just one layer of _____________ in a basement
membrane (of CT)
2.
It is across capillary walls that gases (___ & ___), nutrients, and wastes are exchanged
with tissues
3.
Blood flow from arteriole into a capillary bed is controlled by precapillary
___________ muscles
a. When sphincters are open, blood flows into the ________ bed
b. When sphincters close, blood from arterioles enters venules directly via
thoroughfare _________
Types of capillaries include
4.
a.
______________ capillaries are the most common; have endothelial cells with
_______ junctions, found in muscles, lungs, & the CNS (e.g.: the blood brain
barrier); some small molecules can diffuse through, but large molecules can’t
b.
____________ capillaries have wide intercellular pores That allow rapid passage
of small molecules; found in organs engaged in rapid absorption & filtration (e.g.,
________ and intestines)
c.
_____________ capillaries are irregular, blood filled spaces, found in the ______,
bone marrow & spleen; large materials, such as proteins and blood cells can exit
sinusoids
F. Veins - vessels that carry blood (usually deoxygenated) _________ the heart
1. Capillaries converge to form ______, which converge into veins
2. Venous ________ are veins with very thin walls, no smooth muscle, and large
lumens (e.g., coronary & dural sinuses)
3.
BP is very ____ in veins & venules (compared to arteries) due to their distance from
the heart, which influences vein structure
a. Veins have _______ walls, with less smooth muscle, than arteries
b. Veins _______ more easily than arteries and hold more blood
c. The upward flow of blood in veins depends mainly upon
1) _________________ pump: skeletal muscles contract and squeeze associated
veins, pushing blood toward the heart
2) One way venous ______ prevent blood backflow in veins (varicose veins occur
when these valves break down)
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3) ______ pump – during inhalation, the diaphragm contracts, which decreases
intrathoracic pressure and increases intraabdominal pressure, pulling blood
toward the heart
III. Blood Pressure, Resistance, and Flow
A. Blood ______ is the amount of blood flowing through an organ, tissue or blood vessel in a
given time (mL/min)
1. __________ is blood flow per given unit of tissue (mL/min/gm), which governs the
speed of O2 and nutrient delivery to the tissue and the speed of waste removal
2. Although total blood flow equals _______ _________ in a resting person, blood flow
and perfusion vary with the metabolic needs of a tissue (greater metabolic needs 
greater blood flow)
3. ______________, the principles of blood flow, are based mainly on pressure and
resistance [FP/R]
a. The greater the _______ difference (P) between two points, the ____________
the flow
b. The greater the ____________ (R), the ____ the flow.
B. Blood _________- force exerted by the blood on inner vessel walls
1.
Blood pressure (__) is much higher in arteries & arterioles than in capillaries, venules
& veins (Why?)
2.
3.
Arterial BP can be measured with a _________________ meter and a stethoscope
4.
Normal adult BP is about ___/__, where 120 mm Hg is the _________ pressure and
80 mm Hg is the _________ pressure
a.
Systolic pressure is created by blood flow through arteries during ventricular
systole (____________)
b.
Diastolic pressure is a measurement of arterial pressure during ventricular
diastole (____________)
c.
The difference between the systolic & diastolic pressures is the ________
pressure (usually about ___ mm Hg)
d.
Mean arterial pressure (____) is the “average” pressure in the arteries during the
cardiac cycle
1) Calculated by: [MAP = diastolic pressure + 1/3 pulse pressure]
2) MAP is the _____ that propels the blood to the tissues during the cardiac cycle
________________ is an elevated BP, dangerous because of the damage to heart and
other vital organs due to weakening of small blood vessels in the organs
C. Expansion and contraction of elastic arteries during systole and diastole reduces the _____
pressure and eases the strain on smaller arteries.
D. Factors affecting blood _________ and ______ are cardiac output, blood volume, and
peripheral resistance
1. As cardiac _______ increases, blood flow and blood pressure increase (What factors
influence cardiac output?)
2. As blood ________ increases, blood flow and pressure increase
3. Peripheral _____________ is affected by 3 major factors
a. Blood ___________ – the thickness or “stickiness” of blood; more viscosity =
greater resistance = higher BP
b. Total blood vessel _________ – longer vessels have greater resistance. As we gain
weight, blood vessel length increases, leading to increased BP
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c. Blood vessel ____________ (vaso_______ = larger diameter;
vaso______________ = smaller diameter)
1) The _________ the vessel, the greater the resistance of the blood against the
vessel walls, causing slower blood flow
2) In _______ vessels, blood near the wall moves slowly, but blood in the middle
moves rapidly (_________ flow); less resistance = faster blood flow
3) Blood vessel _________ changes have the greatest effect on resistance (as width
increases, resistance __________), and thus on blood flow
4) Blood flow is fastest in the ______ and its branches (higher pressure), and
slowest in _____________ (lowest pressure)
4. Poiseuille’s equation describes the relationship between blood pressure, vessel radius,
viscosity, and vessel length on blood flow:
Blood flow (ΔQ) = πΔP r4
8ηl
ΔP = pressure differences between two ends of a blood vessel
r = blood vessel radius
η = blood viscosity; l = blood vessel length
Which of the above factors would have the greatest effect?
E. __________ of blood pressure and blood flow is controlled mainly by local, neural, and
hormonal control of vessel constriction and dilation (___________)
1. Local control involves _____________, the ability of a tissue to regulate its own blood
supply.
a. Short term local vasomotion is stimulated by vasoactive chemicals; (e.g.,
__________ and nitric oxide dilate vessels)
b. Long term autoregulation can be achieved by _____________, the growth of new
blood vessels (e.g., in coronary arteries)
2. _________ control of blood vessels is based on the vasomotor center in the medulla
_________, which integrates baroreflexes, chemoreflexes, and the medullary ischemic
reflex
a. _____receptors in the aorta and carotid arteries sense changes in blood ______ and
signal the medulla to restore homeostasis
b. _______receptors in the aorta and carotid arteries sense changes in pH, O2, and
CO2 and signal the medulla
1) Low O2, high CO2, and low pH cause vaso_____________, which increases ___
and blood flow to lungs for increased gas exchange
c. The medullary ________ reflex involves a decrease in blood flow to the brain; the
vasomotor center responds by sending sympathetic signals to the heart and blood
vessels
1) Heart _____ and contraction force increases
2) Blood vessels vaso_________
3) All increase blood __________ and flow to the brain
3. Hormonal control involves the following ___________:
a. ________________ – vasoconstricts vessels and raises BP
b. _____________ – “salt retaining hormone” that promotes Na+ retention by kidneys
and in the blood vessels; water flows into the blood, increasing blood volume and
pressure
c. Antiduretic hormone (____) also promotes water retention, as well as
vasoconstriction
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d. Atrial natriuretic peptide (___), secreted by the heart, causes increased Na+
excretion by kidneys and vasodilation
e. ________________ & Norepinephrine
1) Cause vasodilation in vessels of __________ muscle and ________ arteries,
increasing blood flow during exercise
2) Cause vasoconstriction in other vessels, increasing blood pressure
4. Vasomotion can ______ blood flow from organs with less need to organs with more
need at a given time (e.g., from intestines to skeletal muscle during exercise)
IV. Capillary Exchange – the movement of water and solutes across ___________ walls to and
from surrounding tissues
A. Substances pass between the _______ stream and ____________ fluid via
1. Intercellular ________ between endothelial cells
2. Fenestrations (pores) within _______________ capillaries
3. ________________ cell cytoplasm
B. _____________ mechanisms include diffusion, trancytosis, filtration, and reabsorption
1. _____________ is the movement of molecules from high concentration to a lower
concentration.
a. ______, uncharged molecules (O2, CO2, H20) and _________ soluble molecules
(steroids) can diffuse freely through capillary walls
b. Glucose and _______ diffuse out of the blood stream into surrounding tissues
c. ______ and wastes diffuse from tissues into the blood stream
d. In the lungs, O2 and CO2 diffuse in the _______________ directions
e. Lipid insoluble molecules, such as _________, and _______________ must pass
through membrane channels, fenestrations, or intercellular clefts of capillaries
2. Trancytosis – endocytosis and ___________ of larger molecules, such as fatty acids,
proteins, and some hormones, across capillary endothelial walls
3. Filtration & Reabsorption
a. ______________ - fluid is forced out of capillaries at the arterial end of a capillary
via higher blood (______________) pressure than surrounding tissues
b. ________________ – fluid is drawn back into capillaries at the venous end of a
capillary via colloid _________ pressure, because blood has higher __________
than tissues, due to plasma proteins
c. About 15% of tissue fluid is reabsorbed by the ________________ system
d. Overall, the volume of fluid reabsorbed into the blood is almost ________ to the
volume filtered out (Starling’s Law)
e. Fluid exchange ____ from place to place in the body and from moment to moment
1) Some capillaries engage solely in ______________ (e.g., kidney glomeruli)
2) Some capillaries participate solely in _________ (e.g., lung alveolar capillaries)
3) Reabsorption dominates in __________ tissues in which precapillary sphincters
are _______________ and BP is low in capillaries
4) Filtration dominates in ______ tissues in which precapillary sphincters are ____
and capillary blood flow and pressure ___________
C. ________ is an accumulation of excess tissue fluid resulting from increased capillary
filtration, reduced reabsorption, or obstructed lymphatic drainage
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1. Increased capillary _____________ can result from increases in capillary BP or
permeability due to poor venous return, water retention, and increased capillary
permeability
2. Reduced capillary _____________ can result from hypoproteinemia (low plasma
protein concentration)
3. Obstructed ____________ drainage can occur with certain diseases, advanced age,
and surgical removal of lymph nodes
4. Severe edema can lead to __________ _______, due to low BP, impaired O2 delivery
and waste removal, and tissue necrosis
V. Venous Return & Circulatory Shock
A. ______________ is the flow of blood back to the heart, and is achieved by 5 mechanisms
1. _________ gradient – movement of blood from higher pressure vessels (i.e., venules)
to lower pressure vessels (veins). Pressure decreases with venoconstriction and
increases with venodilation
2. ___________ – blood from head and neck flows “downhill” to heart
3. Skeletal _________ pump – limb veins are surrounded by muscles that squeeze blood
upward as they contract and relax
4. __________ pump – inspiration flattens the diaphragm, causing a decrease in thoracic
pressure and increasing abdominal pressure, which pulls blood upward
5. __________ suction – expansion of the artial space during ventricular systole creates
suction that draws blood into the atria
V. B. Venous Return & _____________
1. Exercise ________ venous return because the vessels dilate, the thoracic and skeletal
muscle pumps work harder, and cardiac output is elevated
2. Inactivity allows blood to accumulate in low points in the body (_________________).
It can result in ___________ (fainting) if too much blood flows away from the brain
C. ___________ __________ occurs when cardiac output is not sufficient to meet the body’s
metabolic needs. Two major categories are
1. __________ shock – caused by inadequate pumping of the heart, usually due to
myocardial infarction
2. Low venous return (____) shock – caused by too little blood returned to the heart.
Three types of LVR are
a. _____________ shock most common, produced by a loss of blood volume due to
bleeding or dehydration
b. _______________ ______ return shock due to tumor or aneurysm
c. _________ ________ (vascular) shock occurs when a body has a normal blood
volume, but blood pools in the limbs due to prolonged sitting, standing, or
widespread vasodilation
d. _______ shock and ___________ shock both result from general vasodilation and
increased capillary permeability, combining hypovolemia and venous pooling
VI. Blood Vessel Disorders
A. ___________________ (hardening of the arteries) - thickening and loss of elasticity of
arterial walls
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B. ___________________ - most common type of arteriosclerosis; the arterial tunica intima
thickens with atherosclerotic plaques that narrow and can eventually block the artery
lumen, causing
1.
2.
Cerebrovascular Accident (CVA = _________) if an artery to the brain is blocked
Myocardial _______________ (MI) if a coronary artery is blocked
C. An _____________ is a bulge in an artery or vein that puts the vessel at risk of rupturing
1. May result from a congenital defect, _________________, or arteriosclerosis
2. Usually occurs in the abdominal aorta and arteries of the _______ & kidneys