CV Study Guide Flashcards
1
Q
Thecardiovascularsystemconsistsofthe
A
heartandallthebloodvessels.Functionally,
2
Q
theheartislikea
A
doublepumpwitheachpumpconnectedtotheotherthroughalongseriesofbloodvessels
3
Q
heart consists of how many chambers
A
4
4
Q
tworeceivingchamberscalled
A
atria
5
Q
twopumpingchamberscalled
A
ventricles.
6
Q
Theleftsideoftheheartalwayspumps
A
oxygenatedblood,
7
Q
andtherightsidealwayspumps
A
deoxygenatedblood.
8
Q
Thepulmonarycircuitrefersto
A
allthebloodvesselsthattakedeoxygenatedbloodfromtherightventricleofthehearttothelungs,andthenreturnoxygenatedbloodtotheleftatrium.
9
Q
systemiccircuit.
A
bloodvesselsthattransportthisoxygenatedbloodtothebody
10
Q
gasexchangeoccurswithin
A
capillaries
11
Q
capillaries
A
microscopicbloodvesselsonlyonecelllayerthick
12
Q
capillaries wall made up of
A
simplesquamousepithelium.
13
Q
Theseflatcellseasilypermitthediffusionofgases,suchasoxygen(O2)andcarbondioxide(CO2)
A
simplesquamousepithelium.
14
Q
normalby-productofcellularrespirationandgraduallybuildsupwithinbodycells
A
Carbondioxide
15
Q
Carbondioxidediffusesfromthebodycellsintothe
A
capillary.
16
Q
pathwaythatbeginsandendswiththe
A
right atrium
17
Q
whichatrioventricularvalve—bicuspidortricuspid—comesfirst
A
Yourideyourtricycle(tricuspid)beforeyourbicycle(bicuspid).
18
Q
Coronarycirculationreferstothe
A
bloodsupplytotheheart
19
Q
oronaryarteriessupplyoxygenatedbloodtothe
A
heart
20
Q
cardiacveinscarrydeoxygenatedbloodbackto
A
the heart
21
Q
flowchartsummarizescoronarycirculationthroughthebloodvessels
A
Baseofaortaleftandrightcoronaryarteriesbranchesofcoronaryarteries(circumflexa.,anteriorinterventriculara.,marginala.,posteriorinterventriculara.)coronarycapillariescardiacveinscoronarysinusrightatrium
22
Q
coronaryarteriesbecomeblocked
A
bloodsupplytotheheartisreduced
23
Q
coronaryarteriesbecomeblocked deprives cardiac muscles cells of
A
oxygen
24
Q
if coronary arteries remain blocked for many years, it can lead to
A
myocardialinfarction(heartattack)
25
To distinguish the anterior from the posterior view of the heart
use the coronary sinus as a landmark for the posterior view
26
Good landmarks for the anterior view include
pulmonary trunk, anterior interventricular artery, circumflex artery, and ascending aorta.
27
heart is divided into
left and right halves and has four chambers, two atria and two ventricles.
28
first chambers to receive blood from the body.
atria
29
what happens in the atria
fill with blood, contract, and transfer blood to the pumping chambers, or ventricles
30
which are the pumping chambers
ventricles.
31
right ventricle pumps
deoxygenated blood to the lungs
32
left ventricle pumps
oxygenated blood to the rest of the body
33
heart has two different types of valves
atrioventricular (AV) valves and semilunar valves
34
atrioventricular (AV) valves and semilunar valves.
The AV valves are located between the atria and the ventricles. The one on the right side of the heart has three valve flaps, so it is called the tricuspid valve, and the one on the left side has two valve flaps, so it is called the bicuspid (mitral) valve. These valves permit a one-way flow of blood from atria to ventricles.
35
semilnar valves
??
36
chordae tendineae
Long, fibrous, cord-like structures anchor the valve flaps to the papillary muscles
37
papillary muscles
long, cone-shaped, muscular extensions of the inner ventricles
38
chordae tendineae and papillary muscles help
keep the AV valves closed during ventricular contraction.
39
semilunar valves are located at
the base of each major artery that leaves each ventricle
40
On the right side is the pulmonary semilunar valve, and on the left is the aortic semilunar valve
??
41
Semilunar valves prevent
backflow of blood into the ventricles
42
From outermost to innermost, the wall of the heart is made of three layers
epicardium, myocardium, and endocardium
43
The epicardium (visceral pericardium) is made of
fibrous connective tissue and is the innermost layer of the pericardial sac that surrounds the heart
44
myocardium is composed of
multiple layers of cardiac muscle and many blood vessels and nerves
45
endocardium is made of
simple squamous epithelium and lines the inside of all the heart chambers and valves
46
endocardium is continuous with the
endothelium of blood vessels that enter and exit the heart, such as the aorta and the pulmonary veins.
47
The semilunar valves resemble a modified
peace sign when closed
48
To distinguish between the left and right ventricles, note that the wall of the left ventricle is
thicker than the wall of the right ventricle
49
The atrioventricular valves and associated structures resemble a
parachute; The valve flaps are the parachute, ventricle. the parachute cords are the chordae tendineae, and the paratrooper is the papillary muscle
50
The heart has its own internal regulation system to achieve two important functions:
(1) triggering the heartbeat, and (2) coordinating the timing between contraction of the atria and contraction of the ven tricles
51
intrinsic conduction system
The heart has its own internal regulation system to achieve two important functions
52
without the intrinsic conduction system to ensure that the heart chambers do what
completely fill with blood before contracting, the heart would be a very inefficient pump
53
intrinsic conduction system consists of the following six structures
sinoatrial (SA) node; Internodal pathway; atrioventricular node; atrioventricular (AV) bundle; bundle branches (right and left); purkinje fibers
54
intinsic conduction system cann be structurally divided into two main parts
the nodes (SA and AV nodes) and the pathway (internodal pathway, AV bundle, bundle branches, and Purkinje fibers).
55
the nodes
(SA and AV nodes)
56
the pathway
(internodal pathway, AV bundle, bundle branches, and Purkinje fibers)
57
The nodes consist of
clusters of specialized cardiac muscle cells that contain very few contractile proteins—myosin and actin—found in normal cardiac muscle cells
58
nodes are the only cells in the body that are
autorhythmic muscle cells
59
Instead of contracting, nodes serve as a kind of
“spark plug,” or stimulus, to establish the heartbeat
60
SA node is located
within the wall of the right atrium and is referred to as the primary pacemaker.
61
AV node is located in the
septum between the two atria and is referred to as the secondary pacemaker
62
Like smooth muscle cells, cardiac muscle cells can
stimulate adjacent cells.
63
because cardiac muscle cells interdigitate with each other like pieces of a jigsaw puzzle, stimulating the first cell will
quickly stimulate all the others in the pathway.
64
The internodal pathway radiates from the
SA node and extends to the left and right atria and AV node.
65
AV bundle is a relatively short segment of cells that extends from
the AV node and penetrates into the top of the interventricular septum
66
AV BUNDLE IS THE ONLY
electrical connection between the atria and the ventricles.
67
AV bundle splits into two pathways at the interventricular septum
the right and left bundle branches, which extend through the interventricular septum toward the apex of the heart
68
The flow of the impulse for contraction always moves in the following sequence:
SA node internodal pathway AV node AV bundle bundle branches Purkinje fibers
69
the autorhythmic cells within the SA node trigger the
impulse to spread to the left and right atria through the internodal pathway.
70
The impulse causes the _____ to contract, which forces blood into the ventricles.
atria
71
A delay in ventricular contraction is needed to allow
the ventricles to fill with blood. This delay comes in the form of the time it takes to stimulate the AV node and send the impulse down the AV bundle and bundle branches. By the time the impulse has spread to the Purkinje fibers, the ventricles have finished filling with blood, and the ventricles are stimulated to contract.
72
The intrinsic conduction system is an ___________that leads to the contracting of the heart chambers, a mechanical event Impulse Pathway Specialized cardiac
ELECTRICAL EVENT
73
An electrocardiogram (ECG or EKG)
graph of the heart’s electrical activity as expressed in millivolts (mV) over time.
74
instrument used to obtain an ECG is called an
electrocardiograph
75
An ECG is used to detect if
electrical conduction pathway within the heart is normal and if any damage has been done to the heart
76
In a typical lead II recording, three different waves appear:
P, QRS complex, and T; Each wave represents an electrical event called a depolarization or a repolarization.
77
electrical events stimulate
cardiac muscle within the heart wall to either contract or relax. Consequently, these events lead to the contraction and relaxation of the heart chambers—atria and ventricles.
78
P WAVE
atrial depolarization—at the end of the P wave, both atria have depolarized, which causes the atria to contract.
79
QRS COMPLEX
ventricular depolarization—at the end of the QRS complex, both ventricles have depolarized, which causes the ventricles to contract. Note: Atrial repolarization also occurs during this period, but it is masked by the ventricular depolarization.
80
T WAVES
ventricular repolarization—at the end of the T wave, both ventricles have repolarized, which causes the ventricles to relax.
81
Two types of variations IN AN ECG may signal abnormalities:
Variation in wave height (they may be elevated or depressed) ; 2. Variation in normal time intervals
82
if a P wave is elevated, it may indicate
atrial enlargement.
83
If the QRS complex is elevated, it may indicate
ventricular enlargement.
84
A tall and pointed T wave may indicate
myocardial ischemia.
85
The heart is essentially
two pumps that work together as one synchronized unit.
86
The left side pumps only
oxygenated blood, and the right side pumps only deoxygenated blood
87
The cardiac cycle refers to all the
pumping actions that occur within the heart during one entire heartbeat. It consists of both the atria and the ventricles filling with blood and then contracting. It begins with contraction of the atria and ends with refilling of the atria. On average, this continuous cycle takes about 800 msec. to complete in an adult.
88
The atria and the ventricles have repeated patterns of contraction _____ and relaxation ________.
SYSTOLE AND DIASTOLE
89
The atria function as the
receiving chambers of blood from the body. After they fill with blood, they contract and force blood downward into the true pumps—the more powerful ventricles.
90
TRUE PUMPS OF THE HEART
THE VENTRICLES
91
Because these chambers have the more difficult task of pumping the blood to the body, they have a thicker layer of cardiac muscle in their walls and a larger volume.
THE VENTRICLES
92
Recall that the heart has two pairs of
valves: atrioventricular (AV) valves and semilunar valves.
93
The AV valves function as
one-way valves to permit blood to flow from the atria to the ventricles. The closing of the semilunar valves prevents blood from flowing back into the ventricles after being ejected.
94
The electrocardiogram (ECG) is related to the
cardiac cycle.
95
An ECG measures
atrial contraciton; sovolumetric ventricular contraction ; Ventricular ejection; Isovolumetric ventricular relaxation; Passive ventricular filling
96
, the cardiac cycle has been divided into five steps, as follows:
atrial contraciton; sovolumetric ventricular contraction ; Ventricular ejection; Isovolumetric ventricular relaxation; Passive ventricular filling
97
atrial contraciton;
ECG connection: from P wave to Q wave ; AV valves open ; Semilunar valves closed; Description: The left and right atria contract simultaneously, causing the atrial pressure to increase. This forces blood through the AV valves and into the ventricles. The ventricles are relaxed and filling with blood. The semilunar valves are closed because the pressure in the ventricles is too low to force them open.
98
sovolumetric ventricular contraction ;
ECG connection: begins with R wave ● AV valves closed ; Semilunar valves closed ● Description: The ventricles begin contracting in this phase, causing the ventricular pressure to increase. Higher ventricular pressure relative to the atria closes the AV valves. The volume of blood in the ventricles remains constant (isovolumetric). All heart valves are closed.
99
Ventricular ejection;
ECG connection: from S wave to T wave ● AV valves closed ● Semilunar valves open ● Description: The ventricles continue contracting during this phase. Like wringing out a wet rag, the ventricles wring the blood out, beginning at the apex and moving upward. This allows for the maximum volume of blood to be ejected - about 70ml per ventricle. The high ventricular pressure forces the semilunar valves to open, and blood is ejected into the pulmonary arteries and the aorta
100
Isovolumetric ventricular relaxation;
ECG connection: begins at end of T wave ● AV valves closed ● Semilunar valves closed ● Description: The ventricles are relaxing, and the heart valves are all closed. The volume of blood in the ventricles remains constant (isovolumetric). Because ventricular pressures are higher than atrial pressures, no blood flows into the ventricles. Ventricular pressure is quickly decreasing during this phase.
101
Passive ventricular filling
ECG connection: after T wave to next P wave ; ● AV valves open ● Semilunar valves closed ; ● Description: As blood flows into the atria, the atrial pressure increases until it exceeds the ventricular pressure. This forces the AV valves open, and blood fills the ventricles. This is the main way the ventricles are filled. At the end of this phase, the ventricles will be about 70–80% filled.
102
The CARDIAC CYCLE is a
MECHANICAL EVENT like squeezing a bottle of water. Just as the pressure in the bottle rises when squeezed, so does the pressure in a heart chamber when it is contracted.
103
In the central nervous system (CNS), the cardiovascular (CV) center in the medulla oblongata is
the command-and-control center for regulating heart function. It uses reflex pathways to control heart rate.
104
The three major peripheral sensory receptors that provide input to the CV center are:
1. Proprioceptors; 2. Chemoreceptors—; 3. Baroreceptors;
105
1. Proprioceptors—
measure tension changes in muscles and joints
106
2. Chemoreceptors—
detect changes in blood acidity by sensing changes in CO2 and H levels
107
3. Baroreceptors—
located in the carotid sinus, aortic arch, and other arteries; detect changes in blood pressure
108
The CV center sends its motor output to the heart through two different nerves:
1. Vagus nerve—to decrease heart rate ; 2. Cardiac accelerator nerve—to increase heart rate
109
VAGUS NERVE
TO DECREASE HEART RATE
110
CARDIAC ACCELERATOR NERVE
TO INCREASE HEART RATE
111
The internal pacemakers within the heart—
the SA node and AV node—
112
The internal pacemakers within the heart helps set the
its normal rate and rhythm
113
The vagus nerve (cranial nerve X) is part of the
parasympathetic division of the ANS and sends impulses to the heart to decrease heart rate
114
why is the vagus nerve a mixed nerve
meaning that it contains both sensory and motor neurons. Baroreceptors, located in the carotid sinus, aortic arch, and other arteries, detect changes in blood pressure
115
As blood pressure increases above normal levels, impulses are sent along sensory neurons to the
CV center and then carried along motor neurons within the vagus nerve to the heart.
116
The vagus nerve innervates the heart at the
SA node and AV node.
117
THE VAGUS NERVE FUNCTIONS TO INHIBIT THE HEART, THEREBY ….
reducing the heart rate and strength of contractions. This, in turn, decreases cardiac output, which lowers blood pressure back to normal. At the same time, impulses also are sent out along vasomotor nerves (not shown in illustration) that stimulate vasodilation, thereby further lowering the blood pressure.
118
The cardiac accelerator nerve is part of the
sympathetic division of the ANS and sends impulses to the heart to increase the heart rate.
119
As blood pressure decreases below normal levels, this is detected by
baroreceptors that send impulses along a neural network over to the CV center, then to the spinal cord and to the heart. The final nerve in this pathway—the cardiac accelerator nerve—
120
the cardiac accelerator nerve—innervates the heart at the
SA node, AV node, and cardiac muscle in the ventricular wall (ventricular myocardium). The response is that both the heart rate and strength of contractions increase. This, in turn, increases cardiac output, which increases blood pressure. At the same time, impulses are sent out along vasomotor nerves (not shown in illustration) that stimulate vasoconstriction and thereby further increase blood pressure.
121
The body has five fundamental types of blood vessels:
arteries, arterioles, capillaries, venules, and veins. All of them connect in the following predictable pattern:
122
PATH OF BLOOD
Heart TO artery (larger) TO artery (smaller) TO arteriole TO capillary TO venule TO vein (smaller) TO vein (larger)
123
Arteries always carry blood
away from the heart.
124
ARTERIES ARE THICKER WALLED THAN VEINS BECAUSE
because the blood within them is at a higher pressure.
125
All veins always carry blood
BACK TO THE HEART
126
WHY ARE VEINS THINNER WALLED
BECAUSE PRESSURE WITHIN THEM IS LOWER
127
LARGER VEINS CONTAIN
valves—similar to one way semilunar valves in the heart—that assist the low-pressure venous blood return to the heart.
128
When a person is standing, gravity works against
venous blood flow.
129
valves break up larger veins into
smaller segments.
130
Arteries and veins connect at the microscopic level by
capillary networks.
131
Capillaries are
the smallest blood vessels in the body and are important functionally because gas and fluid exchange occurs here. Their entire wall is often a single cell layer in thickness.
132
Arterioles and venules are microscopic vessels that feed and drain
Capillaries
133
ATERIOLOES AND capillaries are structurally similar to a capillary except
they have small amounts of smooth muscle around them. The smooth muscle around an arteriole can be stimulated to either constrict (vasoconstriction) or relax (vasodilation). This, in turn, causes changes in blood flow to a capillary and systemic blood pressure.
134
Vasoconstriction of arterioles
decreases blood flow and increases blood pressure, and vasodilation does just the opposite.
135
Arteries and veins have three major layers in their walls:
tunica externa, tunica media, and tunica interna:
136
tunica externa,
connective tissue layer made mostly of collagen fibers
137
tunica media,
layers of smooth muscle and some elastic fibers
138
tunica interna:
endothelial layer (simple squamous epithelium) with underlying loose connective tissue
139
some arteries/veins carry oxygenated blood and others carry deoxygenated blood. TRUE OR FALSE
TRUE
140
Arteries Away!
Arteries always carry blood away from the heart.
141
● To recall one structural difference between arteries and veins:
Veins have Valves (arteries do not have valves).
142
● To distinguish an artery from a vein under the microscope,
remember that arteries always have a thicker tunica media.
143
Blood always follows a predictable circuit through blood vessels. There are five fundamental types of blood vessels in the body:
arteries, arterioles, capillaries, venules, and veins. All of them connect in the following pattern:
144
PATH OF BLOOD
HEART TO LARGE ARTERY TO SMALLER ARTERY TO ARTERIOLOE TO CAPILLARY TO VENULE TO SMALLER VEIN TO LARGER VEIN TO HEART
145
AS ARTERIES MOVE FARTHER AWAY FROM THE HEART (DISTANCE INCREASES) WHAT HAPPENS TO BLOOD PRESSURE
As distance from the heart increases, blood pressure decreases.
146
Arteries and veins connect together at the microscopic level by
capillary networks.
147
Capillaries are the smallest
blood vessels in the body and are
148
Capillaries very important functionally because
gas exchange and fluid exchange occurs here. Oxygen exits the blood to be used by body cells, and carbon dioxide enters the blood from cells. The liquid plasma is filtered out of the blood to become interstitial fluid (tissue fluid).
149
Veins carrY WHAT TO WHERE
low-pressure, deoxygenated blood drain into the vena cava, which drains into the heart’s right atrium (RA)
150
WHAT IS THE RIGHT ATRIUM
receiving chamber fills with blood, contracts, and forces blood into the right ventricle (RV).
151
WHAT HAPPENS IN THE RIGHT VENTRICLE
All this deoxygenated blood is then pumped out of the right ventricle to go to the lungs to get oxygenated.
152
WHAT HAPPENS IN THE LUNGS
the pulmonary capillaries function only for gas exchange, in which oxygen diffuses into the blood and carbon dioxide diffuses out. The oxygenated blood is then transported through veins to the left atrium (LA)
153
WHAT HAPPENS IN THE LEFT ATRIUM
LA fills with blood, contracts, and forces blood into the left ventricle (LV).
154
WHAT HAPPENS IN THE LEFT VENTRICLE
his oxygenated blood is then pumped out to the body via the aorta.
155
The heart feeds its own cardiac muscle first through
coronary capillaries so it can continue pumping blood every minute of every day
156
Arteries carry
oxygenated blood above the heart to the capillaries in the brain, trunk, and upper limbs. Other arteries carry blood below the heart
157
ARTERIES CARRY BLOOD BELOW THE HEART TO THE FOLLOWING MAJOR AREAS
Digestive organs and spleen; Kidney; Gonads; Liver, lower limbs
158
WHAT HAPPENS AT THE Digestive organs and spleen—
After gas and fluid exchange occurs at the splenic and mesenteric capillaries, deoxygenated blood is carried by veins to the hepatic portal system in the liver. Note that capillaries in this system are not for the typical purpose of gas and fluid exchange. Instead, these highly permeable capillaries are specialized for delivering nutrients absorbed by the digestive tract to liver cells before entering the general circulation. The liver cells serve as special processing centers that perform many functions. For example, they store glucose as glycogen and detoxify alcohols.
159
WHAT HAPPENS AT THE KIDNEY
Another unique group of permeable capillaries is the glomerular capillaries. Like the capillaries in the hepatic portal system, these are also not for the typical purpose of gas and fluid exchange. Instead, they are specialized to filter only the blood plasma, place it in a separate tubular system, and process this liquid into urine. These capillaries lead into the peritubular capillaries, where gas and fluid exchange does occur.
160
WHAT HAPPENS AT THE GONAD
In the male, gas and fluid exchange occurs at capillaries in the testes, whereas in the female, this occurs at capillaries in the ovaries.
161
The two types of flow patterns are:
(1) laminar flow, and (2) turbulent flow.
162
1 Laminar (lamina 4 layer) flow is the
normal flow pattern in healthy blood vessels; The concentric layers of fluid flow together, but not at the same rate. As shown in the illustration, the outer layers travel more slowly than the inner layers. Why? As the fluid in the outermost layer rubs against the vessel wall, it is hindered by the force of friction and moves the slowest. In contrast, the fluid in the center of the tube is interfered with the least, so it moves the fastest. Normal, healthy blood vessels are smooth on their inner surface. Like the smooth surface on the inside of a garden hose or a drainpipe, this allows the fluid to flow through most easily.
163
As another clinical example, turbulent blood flow
is heard moving through a defective heart valve as a “murmur.”
164
2 Turbulent flow is the result of any disruption in the normal,
laminar flow.
165
Some low levels of turbulent flow are normal
as blood flows through all the vessels in the body, but high levels may indicate an abnormality.
166
What causes TURBULENCE? Two things:
(1) physical change in a vessel (ex.: constriction, sharp turn, or narrowing of a vessel) or (2) Disease state (ex.: atherosclerosis). Because large blood vessels connect to smaller ones, some narrowing is normal, but it is a gradual change that doesn’t usually result in turbulent flow.
167
(1) physical change in a vessel (ex.:
constriction, sharp turn, or narrowing of a vessel) or
168
(2) Disease state (ex.:
atherosclerosis). Because large blood vessels connect to smaller ones, some narrowing is normal, but it is a gradual change that doesn’t usually result in turbulent flow.
169
The heart generates the blood pressure by
ejecting blood into the arterial system.
170
Blood pressure (BP) is a type of
hydrostatic pressure—or force of a fluid against the wall of a tube.
171
As the ventricles contract and force blood out into the arteries, these vessels
expand, and the pressure rises to a maximum pressure. As the ventricles relax, and no more blood is ejected into the arteries, the arteries recoil, and pressure falls to a minimum pressure.
172
the source of our pulse.
constant cycle of rising and falling blood pressure is
173
When blood pressure is taken, it is measured in
mm Hg and expressed numerically as the maximum pressure over the minimum pressure. This is referred to as the systolic pressure over the diastolic pressure. For example, a normal blood pressure reading might be 120/70, read as “120 over 70.”
174
Blood pressure has to be homeostatically maintained at a normal level. If blood pressure exceeds normal levels, it can cause
smaller vessels to rupture, leading to anything from a stroke even to blindness.
175
If BLOOD PRESSURE levels fall too low, this also can lead to numerous problems. For example, filtration is totally dependent on pressure.
The kidneys constantly filter the blood to remove waste products, and the capillaries in all our organs filter the blood to form tissue fluid. No pressure, no filtration. The body has numerous physiological mechanisms to increase BP when it falls too low.
176
blood pressure results from
the force of blood against the wall of the blood vessel.
177
1 When a blood pressure cuff is wrapped around the upper arm, the intended purpose is to
compress the brachial artery, which delivers oxygenated blood to the arm.
178
Blood pressure (BP) is a type of
hydrostatic pressure (HP) or fluid force against the wall of a tube.
179
The heart generates the blood pressure by ejecting blood into
the arterial system
180
the most microscopic blood vessels in the body, join arterioles to venules
Capillaries, Their diameter is so small that red blood cells must pass through single file. These vessels form an interconnecting network or mesh of vessels called capillary beds.
181
capillary beds.
interconnecting network or mesh of vessels
182
. All the various tissues in the body depend on these to remove wastes and to deliver nutrients and fluid.
capillary beds.
183
The tubelike structure of each capillary is simple. The wall of the vessel is made up of
endothelial cells or simple squamous epithelial cells. Each of these cells is flat to allow for easy diffusion of solutes from blood to tissue cells and vice versa.
184
basement membrane
Wrapped around the outside of these cells like a thin blanket are protein fibers called the basement membrane.
185
intercellular clefts
Gaps between adjacent endothelial cells called allow for passage of fluid and small solutes.
186
The three types of capillaries are:
(1) continuous capillaries, (2) fenestrated capillaries, and (3) sinusoidal capillaries.
187
(1) continuous capillaries,
most common; least permeable; skin, connective tissues, skeletal muscle, smooth muscle and lungs
188
(2) fenestrated capillaries,
most permeable, found in kidneys, small intestines, choroid plexus in brain and some endocrine glands
189
(3) sinusoidal capillaries.
most permeable, found in liver, red bone marrow, spleen, and some endocrine glands
190
fenestrations
endothelial cells contain small holes called fenestrations that increase permeability
191
Blood flow through a capillary bed is controlled by
bands of smooth muscle called precapillary sphincters.
192
precapillary sphincters.
When they are closed, blood bypasses the capillary bed by going through the shunt. When they are open, blood moves through the entire capillary bed (as illustrated). This allows the body to respond to different situations. For example, during exercise, the sphincters have to be opened in the capillaries in skeletal muscles to meet the muscle’s increased oxygen demand and deal with increased production of carbon dioxide. During the digestion of a heavy meal, more blood has to be shunted to the capillaries in the digestive tract rather than to the skeletal muscles.
193
Capillary beds are the sites of
nutrient and waste exchange between the blood and body cells. Nutrients move from the blood into tissue cells, and wastes move from tissue cells into the blood. For example, the respiratory gases—oxygen and carbon dioxide—diffuse across the wall of the capillary.
194
Oxygen is a vital nutrient that diffuses out of the blood and into
tissue cells, and carbon dioxide is a waste product that diffuses from tissue cells into the blood.
195
Recall that diffusion depends on a
gradient (see pp. 78–79). The rule for simple diffusion is that a solute moves from a region of higher solute concentration to a region of lower solute concentration. Oxygen is carried in the blood primarily by the protein hemoglobin. As cells consume oxygen to metabolize glucose in the cellular respiration process, this ensures that the gradient for oxygen is maintained. Carbon dioxide is a by-product of cellular respiration, so it maintains a gradient as it constantly accumulates within body cells.
196
Gas exchange occurs across
capillary beds.
197
This is how oxygen is delivered to your cells and how carbon dioxide is removed from tissues.
capillary beds.
198
Two processes are occurring simultaneously with diffusion:
filtration and reabsorption.
199
filtration process is completely dependent on a
force. NO FORCE, NO FILTRATION
200
(CHP)
capillary hydrostatic pressure
201
capillary hydrostatic pressure
the blood pressure inside the capillarieS
202
THIS drives the filtration process and is measured in millimeters of mercury (Hg).
capillary hydrostatic pressure (CHP)
203
Across a capillary bed, the CHP quickly drops as
blood moves from the higher pressure arteriole end (35 mm Hg) to the lower pressure venule end (18 mm Hg).
204
Working against the CHP is a counterforce called the
blood colloidal osmotic pressure (BCOP).
205
Osmotic pressure represents
the force from water’s tendency to move across a semipermeable membrane toward the solution with the greater concentration of nonpenetrating solutes (primarily proteins)
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osmotic pressure is proportional to the
solute concentration. The higher the solute concentration, the greater is the osmotic force.
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Because the concentration of nonpenetrating solutes in the blood is greater than the tissue fluid within the interstitial spaces, water’s tendency is to
move back into the blood.
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Unlike the CHP, the BCOP remains
constant across the capillary bed at 25 mm Hg. Why? Because the concentration of nonpenetrating solutes does not change from one end of the capillary bed to the other.
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Filtration occurs only at the
arteriole end of the capillary bed.
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This process of filtering the blood plasma is the only way the body has to
create interstitial fluid.
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The interstitial fluid is then drained into the
lymphatic system to become lymph
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Reabsorption of water occurs only at the
venule end.
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some water is always reabsorbed at the venule end of the capillary because of
osmosis.
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The capillary hydrostatic pressure (CHP) is the
blood pressure inside the capillary.
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Venous return refers to
the volume of blood returning to the heart through the veins.
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Veins are under much lower pressure than arteries, which makes it difficult to return venous blood to the heart. TRUE OR FALSE
TRUE
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Veins contain________ at regular intervals, which allow for blood flow in one direction and prevent backflow.
semilunar valves
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Venous return is easier when a person is lying down because
the force of gravity is not a factor. But when someone is standing up, consider how long a journey it is for the venous blood in your foot to return to the heart while moving against gravity.
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Although the heart’s normal pumping action helps move the venous blood back to the heart, the body has two other mechanisms
(1) skeletal muscle “pump,” and (2) respiratory “pump.”
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When you are walking, the normal muscle contractions in your legs greatly aid
in venous return. They actually squeeze blood up through the peripheral veins toward the heart in an action called “milking.”
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milking
Here is how it works: The illustration shows a short segment of a vein with two semilunar valves. The proximal valve is nearer the heart, and the distal valve is farther from the heart. As the skeletal muscle around this vein contracts, the vessel is squeezed, thereby increasing the pressure inside the vein. This increased pressure forces the proximal valve to open, but the distal valve remains closed because of back pressure. The end result of this action is that some venous blood is moved up into the next section of the vein. By repeating this pattern, venous blood is given an extra push on its journey back to the heart.
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If you have to stand for a long time, it is good to flex your gastrocnemius muscles (calf muscles) to prevent
fainting.
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Fainting is caused by a
decrease in venous return, which leads to decreased cardiac output, which causes a decrease in the blood supply to the brain. This means that less oxygen and glucose are being delivered to neurons in the brain, which causes fainting.
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By flexing your gastrocnemius muscles after standing still for a long time, you will put your __________ to work for you.
skeletal muscle “pump”
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Normal breathing facilitates
venous return. The deeper the breathing, the greater is the assistance in this regard.
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Normal breathing involves a repeating cycle of
contraction and relaxation of the diaphragm.
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When this diaphragm contracts for a normal inspiration, it moves downward and
compresses the contents of the abdominal cavity, which increases the abdominal pressure. Simultaneously, the volume in the thoracic cavity increases, causing a decrease in pressure. This pressure gradient forces blood out of the various veins in the abdominal region and into the inferior vena cava (IVC) to allow blood to move back into the right atrium of the heart.
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Cardiac output (CO) is
the amount of blood pumped out of a ventricle in 1 minute and is expressed as milliliters of blood per minute. It is mathematically defined as the product of the stroke volume (SV) times the heart rate (HR)
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A normal stroke volume is the amount of
blood pumped out of each ventricle in one beat—about 70 mL for an adult heart.
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A healthy adult male has a resting heart rate of about
70 beats per minute
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In general, factors that effect SV also affect
HR. For example, during exercise, both SV and HR increase
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Factors affecting SV
preload, contractility; afterload
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Preload:
defined as the amount of tension in the ventricular cardiac muscle cells prior to contracting. The rule is that the greater the tension on the cells, the more forcefully they contract.
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Frank-Starling Law.
This relationship is referred to as the For example, during exercise, more blood is returned to the heart through the venous return. As more blood enters the heart, it stretches cardiac muscles cells, resulting in a more forceful ejection of blood. For this reason, exercise increases SV.
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Contractility: defined as
the degree to which cardiac muscle cells can shorten when stimulated by a specific chemical substance. For example, calcium ions have a positive influence on cardiac muscle contraction. Abnormally low levels of calcium result in an irregular heartbeat, decreasing the SV.
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Afterload: defined as
the amount of force needed from ventricular cardiac muscle cells to eject blood from the ventricles and past the semilunar valves. Anything that impedes blood flow can increase afterload. For example, any blockage in the peripheral blood vessels (such as atherosclerosis) would restrict blood flow and increase the afterload. Hypertension (high blood pressure) also increases the afterload. As the afterload increases, the SV decreases.
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Factors affecting HR
age, sex, state of activity, endurance training, stress, anxiety
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Age:
HR gradually decreases from childhood to adulthood. A newborn may have an HR of 120 bpm, whereas an adult male may have 70 bpm. In the elderly, the HR increases again relative to that of a young adult.
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● Sex:
On average, females have slightly higher resting HRs than males. The difference is about 5 bpm.
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● State of activity:
During certain phases of the sleep cycle, the HR decreases. But during exercise the HR temporarily increases.
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● Endurance training:
Marathon runners may have a resting HR of 50 bpm. This type of training increases heart size as well as SV. This allows for a normal CO with a lower HR.
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● Stress, anxiety:
Stress and anxiety increase HR.
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The CO does not remain constant. True or False
It regularly rises and falls.
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Maintaining the CO in a normal range is primarily the job of the
cardiovascular (CV) center in the medulla oblongata of the brain.
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Using reflex pathways in the
autonomic nervous system, the CV center regulates the rhythm and force of the heart rate.
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Hormones also help to control
cardiac activity.
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For example, epinephrine and norepinephrine are powerful
cardiac stimulators.
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In short, the nervous system and hormonal regulators work together to regulate
heart activity, thereby indirectly ensuring that a normal CO is achieved.
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Heart rate (HR) is the number of
heartbeats per unit time, typically expressed as beats per minute (bpm). A normal average is 70 bpm.
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Stroke volume (SV) is the amount of
blood pumped out of each ventricle in one beat (BPM), expressed in milliliters (mL) of blood. A normal value is 70 mL.
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Cardiac output (CO) is the amount of
blood pumped out of the left ventricle in one minute, expressed in milliliters (mL) of blood per minute. A normal value is 4,900 mL/min.
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The following four regulatory mechanisms are used to control blood pressure (BP):
cardiovascular center, neural regulation, hormonal regulation, and autoregulation.
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1 Neural regulation through the cardiovascular center
Neural regulation uses reflex pathways to regulate normal blood pressure. As its name implies, the cardiovascular center (CV), in the medulla oblongata, is the nervous system’s command-and-control center for regulating the heart rate and vasoconstriction.
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the cardiovascular center (CV), in the medulla oblongata receives peripheral sensory input from three major sources:
proprioceptors, chemoreceptors, and baroreceptors. The CV responds by sending the appropriate motor output to the heart and blood vessels. Depending on the stimulus, the heart rate (HR) either increases or decreases, and blood vessels are stimulated to constrict. The end result is that the BP either increases or decreases back to normal levels. For details of these reflex pathways
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proprioceptors
(detect changes in muscle tension),
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chemoreceptors
(detect changes in blood acidity),
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and baroreceptors
(detect changes in blood pressure)
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Hormonal regulation involves the use of
chemical messengers called hormones that bind to receptors at a target tissue in order to induce a response.
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● Renin-angiotensin-aldosterone (RAA) system
When blood pressure decreases, it stimulates the kidney to release the enzyme renin into the blood. This leads to the production of a powerful vasoconstrictor called angiotensin II. This, in turn, stimulates the adrenal cortex to produce the hormone aldosterone. The net result is an increase in blood pressure.
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renin
??
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angiotensin II
vasoconstrictor
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● Epinephrine (EPI)/norepinephrine (NE) EPI and NE are produced by
cells in the adrenal medulla in response to emergency or stressful situations. Two of the organs they target are the heart and blood vessels. The result is that heart rate increases and blood vessels constrict, respectively. Together, these two responses lead to an increase in blood pressure.
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Water loss from the blood, like what occurs during excessive sweating, stimulates the
posterior lobe of the pituitary gland to produce ADH. This hormone targets the nephrons in the kidneys and causes more water to be reabsorbed into the blood, thus restoring normal blood pressure.
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As blood volume increases, this stretches the atria in the heart, which stimulates cells in the atria to produce
● Atrial natriuretic peptide (ANP) ; ANP. By increasing vasodilation, sodium ion excretion, and urine production and blocking the release of hormones like ADH and aldosterone, ANP decreases BP.
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3 Autoregulation—
the automatic control of blood flow to a tissue ;
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These mechanisms are normally not as significant as the neural and hormonal mechanisms
physical changes; chemical changes
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● Physical changes
Changes in body temperature affect BP. For example, cold causes superficial blood vessels to constrict, which increases BP. In contrast, heat causes blood vessels to dilate, leading to a decrease in blood pressure.
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● Chemical changes
Different types of body cells, such as smooth muscles cells, endothelial cells, and macrophages, produce various chemicals that signal blood vessels to either dilate or constrict. For example, smooth cells produce lactic acid, which causes blood vessels to dilate. Other vasodilating chemicals include nitric oxide (NO), H, and K.
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What is the hepatic portal system?
The term hepatic refers to the liver and the term portal refers to a portal vessel which is defined as a blood vessel that carries blood from one capillary network to another. All the blood vessels associated with this network constitute a system.
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The first capillary network is found in
all the digestive organs
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Second capillary network is located in
the liver (the capillaries here are called sinusoids). The vessel that links them together is the hepatic portal vein. This wide vessel is labeled as #1 in the illustration on the facing page. Place your finger on it and notice that
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sinusoids
capillaries found in the liver
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hepatic portal vein
??
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??
there are many vessels draining deoxygenated blood from the digestive organs and carrying it through the hepatic portal vein and into the liver. The blood vessels in this system carry nutrient-rich blood to the liver so the nutrients can be processed in liver cells before entering the general circulation. The deoxygenated venous blood in this system is different from normal venous blood in that the level of nutrients such as glucose and amino acids is much higher. For example, after a meal, blood glucose levels rise and excess glucose needs to be delivered to liver cells where it is stored as glycogen. After all these nutrients have been processed in liver cells, then the deoxygenated blood is drained by the heptic veins (#2 in the illustration) which carry blood to the inferior vena cava (labeled in the illustration) where it enters the general circulation.
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There are three major veins that drain the blood into the hepatic portal vein: ●
Superior mesenteric vein (#10) ; ● Inferior mesenteric vein (#9) ; ● Splenic vein (#8)
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Superior mesenteric vein (#10)
blood vessels to the left that are draining blood from part of the large intestine. Also notice the blood vessels draining blood from the pancreas and the bottom of the stomach. Do you see the words duodenum and ileum in the illustration? These are two of the three parts of the small intestine and blood is being drained from both of them. The third part, the jejunum, is not shown in the illustration. Even so, you can see blood vessels branching off the right side of the superior mesenteric vein that have been cut. These are draining the rest of the small intes tine that is not shown.
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● Inferior mesenteric vein (#9)
Notice that it drains blood from the rectum and the distal portion of the large intestine. As you follow it upwards, notice that it merges with the splenic vein (#
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● Splenic vein (#8)
The name splenic obviously informs us that it drains blood from the spleen, but if you look near its terminus, you will see that it also drains blood from part of the stomach. Lastly, if you look at the pancreas, you can see that it also drains blood from the pancreas via the pancreatic veins (#7).
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The Fetal circulation is different from
adult blood circulation. This is to be expected if you give it some thought. Although the fetal heart is functioning and pumping the fetal blood, the fetal lungs are collapsed and filled with fluid, so they are not functioning for gas exchange. The kidneys are also not functioning to remove fetal waste products from the blood. None of the digestive organs are functioning because no food is being ingested, so nutrients cannot be obtained. What replaces these nonfunctional organs in the fetus? The placenta, the organ in the mother’s uterus, is the site for exchang ing blood gases (O2 and CO2), removing waste products, and obtaining nutrients. This is why it is so important for a pregnant woman to maintain a healthy diet. The fetus’s lifeline is the umbilical cord, a bendable, cable-like structure that connects the fetus to the placenta.
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pathway that blood flows in fetal circulation.
pair of umbilical arteries that branch off the internal iliac arteries and carry the fetal blood to the placenta to become oxygenated. The newly oxygenated blood from the placenta flows through the single umbilical vein to the non functional liver where it connects to the ductus venosus that drains into the inferior vena cava. The deoxygenated blood from the inferior vena mixes with the oxygenated blood from the ductus venosus to become mixed blood entering the heart. Blood then drains from both the superior vena cava and the inferior vena cava into the right atrium (RA). Blood in the RA follows two different paths. Some of the blood in the RA goes through an opening with a flap called the foramen ovale and enters the left atrium (LA). The remaining blood enters the right ventricle, and then flows into the pulmonary trunk. Interestingly enough, both pathways end up bypassing the nonfunctional lungs. Blood in the left atrium is pumped into the left ventricle, flows through the aortic arch, and moves into the systemic circuit. While a small amount of blood in the pulmonary trunk goes to the lungs, almost all of it is pumped through the ductus arteriosus—a short fetal blood vessel that connects the pulmonary trunk to the aorta and diverts the blood into the systemic circuit. As the mixed blood moves through the common iliac artery and into the internal iliac artery, it enters the umbilical arteries once again to repeat the cycle.
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After birth, the umbilical cord is tied off and blood doesn’t flow through it anymore. The following key changes occur:
● Umbilical arteries close and become fibrous cords at their distal ends.
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● Foramen ovale closes and seals off to become a
shallow depression in the interatrial septum called the fossa ovalis.
283
● Ductus arteriosus—closes to become the
fibrous ligamentum arteriosum.
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The umbilical vein closes to become the
fibrous ligamentum teres (round ligament). ●
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Ductus venosus closes to become the
fibrous ligamentum venosum.
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The arterial system in the head and neck feeds oxygenated blood to the
brain, face, eyes, neck, larynx, pharynx, esophagus, and other important structures.
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The arteries branching off the abdominal aorta feed oxygenated blood to
the digestive organs, kidneys, spleen, gonads, urinary bladder, and other important structures in the abdominopelvic cavity and the lower limbs.
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The arterial system in the upper limbs feeds oxygenated blood to
all the tissues in the arms.
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The arterial system in the lower limbs feeds oxygenated blood to
all the tissues in the legs.
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The venous system in the head and neck drains deoxygenated blood from
the brain, face, eyes, neck, larynx, pharynx, esophagus, and other important structures.
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The venous system in the abdominopelvic cavity drains deoxygenated blood into the
inferior vena cava, which empties into the right atrium of the heart.
292
The venous system in the upper limbs drains deoxygenated blood from
all the tissues in the arms.
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The venous system in the lower limbs drains deoxygenated blood from
all the tissues in the legs.
