Blood Vessels: The Vascular System Transport blood to the
tissues and back Carry blood away from the heart Arteries
Arterioles Exchanges between tissues and blood Capillary beds
Return blood toward the heart Venules Veins Arterioles Venules
Slide 3
Cross-section of Artery & Vein Figure 11.9a Assume you are
viewing a blood vessel under the microscope. It has a lopsided
lumen, relatively thick externa, and a relatively thin media. Which
kind of blood vessel is this?
Slide 4
TunicDescriptionFunction Tunica intimaA single layer of
squamous epithelium provides a smooth, friction-reducing lining for
the vessel. Tunica mediaA middle layer, consisting of smooth muscle
and connective tissue (primarily elastic fibers) The smooth muscle
is activated by the sympathetic nervous system when
vasoconstriction (and increases in blood pressure) is desired. The
elastic fibers provide for stretching and then passive recoil of
vessels close to the heart, which are subjected to pressure
fluctuations Tunica externaThe outermost layer, made of fibrous
connective tissue basically a protective and supporting layer Name
and describe from the inside out the three tunics making up the
walls of arteries, and veins, and give the most important function
of each
Slide 5
Blood Vessels: The Vascular System Figure 11.9b
Slide 6
Figure 11.9a Arteries are much closer to the pumping action of
the heart and must be able to withstand the pressure fluctuations
at such locations. Veins, on the distal side of the capillary beds
of the tissues, are essentially low-pressure vessels that need less
strength/support/ elasticity than do arteries. Why are artery walls
so much thicker than those of corresponding veins?
Slide 7
Skeletal Muscles and Valves Figure 11.10 1.The presence of
valves, 2.the milking action of skeletal muscles against the veins
as the muscles contract, 3.the respiratory pump (pressure changes
in the thorax during breathing) 1.The presence of valves, 2.the
milking action of skeletal muscles against the veins as the muscles
contract, 3.the respiratory pump (pressure changes in the thorax
during breathing) Name three factors that are important in
promoting venous return.
Slide 8
Breathing in pulls blood into right atrium from vena cava the
thoracic pump which generates negative pressure in the lungs during
inhalation causing blood to rush through the vena cava and right
heart filling the dense The thoracic pump draws blood from the
extremities on inhalation and sends blood throughout the body on
exhalation
Slide 9
Arteries are often described as vessels that carry oxygen-rich
blood, and veins are said to carry oxygen poor (carbon
dioxide-rich) blood. Name two sets of exceptions to this rule that
were discussed in this chapter. Pulmonary arteries carry
oxygen-poor blood and pulmonary veins carry oxygen-rich blood.
Umbilical arteries carry oxygen-poor blood from the fetus and the
umbilical vein carries the most oxygen-rich blood to the fetus.
Pulmonary arteries carry oxygen-poor blood and pulmonary veins
carry oxygen-rich blood. Umbilical arteries carry oxygen-poor blood
from the fetus and the umbilical vein carries the most oxygen-rich
blood to the fetus.
Slide 10
Arteries lack valves, but veins have them. How is the
structural difference related to blood pressure? Blood pressure in
veins is much lower in arteries because veins are farther along in
the circulation pathway. Veins need extra measures to force blood
back to the heart.
Slide 11
Describe the structure of capillary walls Capillary walls are
essentially just the tunica intima (endothelium plus the basement
membrane); thus, they are exceedingly thin.
Slide 12
Capillary Beds Capillary beds consist of two types of vessels
Vascular shuntvessel directly connecting an arteriole to a venule
True capillariesexchange vessels Oxygen and nutrients cross to
cells Carbon dioxide and metabolic waste products cross into
blood
Slide 13
How is the structure of capillaries related to their function
in the body? Capillary walls consist only of the innermost intima
layer which is very thin. Capillaries are the exchange vessels
between the and tissue, thus, thin walls are desirable
Slide 14
Figure 11.12 Left ventricle to ascending aorta aortic arch
brachiocephalic artery subclavian artery axillary artery brachial
artery radial (or ulnar) artery capillary network of wrist radial
(or ulnar) vein brachial vein axillary vein subclavian vein right
brachiocephalic vein superior vena cava right atrium of the
heart.
Slide 15
Figure 11.12 Left ventricle ascending aorta aortic arch
descending aorta right common iliac artery external iliac artery
femoral artery popliteal artery anterior tibial artery dorsalis
pedis artery capillary network anterior tibial vein popliteal vein
femoral vein external iliac vein common iliac vein inferior vena
cava right atrium of the heart.
Slide 16
In what part of the body are the femoral, popliteal, and
arcuate arteries found ? Lower Limb
Slide 17
In what part of the body are the axillary, cephalic, and
basilic arteries found? Upper Limb
Slide 18
What is the function of the hepatic portal circulation? In what
way is a portal circulation a strange circulation? Figure 11.16 The
hepatic portal circulation carries nutrient-rich blood from the
digestive viscera to the liver for processing before the blood
enters the systemic circulation. A portal circulation involves a
capillary bed that is both fed and drained by veins; the usual
circulation has a capillary bed that is fed by arteries and drained
by veins. The hepatic portal circulation carries nutrient-rich
blood from the digestive viscera to the liver for processing before
the blood enters the systemic circulation. A portal circulation
involves a capillary bed that is both fed and drained by veins; the
usual circulation has a capillary bed that is fed by arteries and
drained by veins.
Slide 19
Which vessel the hepatic portal vein, hepatic vein, or hepatic
artery- has the highest content of nutrients after a meal? The
hepatic portal vein carries nutrient-rich blood from the digestive
viscera to the liver for processing before the blood enters the
systemic circulation. The liver removes nutrients (and toxins) from
blood.
Slide 20
Comparison of Blood Pressures in Different Vessels Figure
11.19
Slide 21
Capillary Exchange Substances exchanged due to concentration
gradients Oxygen and nutrients leave the blood Carbon dioxide and
other wastes leave the cells
Slide 22
Direct diffusion across plasma membranes Endocytosis or
exocytosis Some capillaries have gaps (intercellular clefts)
Fenestrations (pores) of some capillaries Capillary Exchange:
Slide 23
What is the different about the capillary exchanges seen in a
capillary with fenestrations and intracellular clefts and the
exchanges seen in a capillary lacking those modifications? Figure
11.22 Intercellular clefts allow limited passage of solutes and
fluid. Fenestrated capillaries allow very free passage of small
solutes and fluids. Capillaries lacking these modifications are
relatively impermeable. Intercellular clefts allow limited passage
of solutes and fluid. Fenestrated capillaries allow very free
passage of small solutes and fluids. Capillaries lacking these
modifications are relatively impermeable.
Slide 24
Capillary Types Continuous basement membrane is continuous and
intercellular clefts are tight; these capillaries have the lowest
permeability.; Fenestrated perforations (fenestrae) in endothelium
result in relatively high permeability. Discontinuous large
intercellular gaps and gaps in basement membrane result in
extremely high permeability Continuous basement membrane is
continuous and intercellular clefts are tight; these capillaries
have the lowest permeability.; Fenestrated perforations (fenestrae)
in endothelium result in relatively high permeability.
Discontinuous large intercellular gaps and gaps in basement
membrane result in extremely high permeability
Slide 25
Fluid Movements at Capillary Beds Blood pressure forces fluid
and solutes out of capillaries Osmotic pressure draws fluid into
capillaries Blood pressure is higher than osmotic pressure at the
arterial end of the capillary bed Blood pressure is lower than
osmotic pressure at the venous end of the capillary bed
Slide 26
Would you expect fluid to be entering or leaving the
capillaries at the venous end of a capillary bed? Figure 11.23
Venous end of capillary bed: Fluid entering capillary Venous end of
capillary bed: Fluid entering capillary Arterial end of capillary
bed: Fluid leaving capillary Arterial end of capillary bed: Fluid
leaving capillary
Slide 27
Explain why blood flow in arteries is pulsatile* and blood flow
in veins is not. Blood flow in arteries is pulsatile because it is
under a greater amount of pressure compared to veins. Arteries are
located closer to the ventricles, so their walls must be capable of
expanding and contracting under the changes in pressure when the
ventricles contract. When blood reaches the veins, the pressure is
very low, and so instead of veins having a pulsatile ability to
maintain pressure, they instead have valves to prevent backflow
*beating rhythmically; pulsating or throbbing
Slide 28
What is the relationship between cross-sectional area of a
blood vessel and velocity (speed) of blood flow in that vessel? The
greater the cross-sectional area in a blood vessel, the faster that
blood can flow through that vessel. Smaller vessels, like
capillaries, are only one cell thick in diameter, which slows down
blood flow and allows nutrient and gas exchange to occur.
Slide 29
Which type of blood vessel is most important in regulating
vascular resistance*, and how does it achieve this? Arterioles are
the blood vessels that are most important in regulating vascular
resistance. These vessels can constrict as a result of activity
from the sympathetic nervous system, which alters blood pressure.
(Arterioles are enervated by the sympathetic nervous system.
Sympathetic nerve fibers secrete norepinephrine to receptors on the
smooth muscles of arterioles causing contraction and thus leads to
vasoconstriction.) Atherosclerosis in these vessels also causes
narrowing due to plaque deposits, which also affects blood pressure
Arterioles are the blood vessels that are most important in
regulating vascular resistance. These vessels can constrict as a
result of activity from the sympathetic nervous system, which
alters blood pressure. (Arterioles are enervated by the sympathetic
nervous system. Sympathetic nerve fibers secrete norepinephrine to
receptors on the smooth muscles of arterioles causing contraction
and thus leads to vasoconstriction.) Atherosclerosis in these
vessels also causes narrowing due to plaque deposits, which also
affects blood pressure *Resistance of blood flow through blood
vessels
Slide 30
In a fetus, the liver and lungs are almost entirely bypassed by
blood. Why is this? Name the vessel that bypasses the liver. Name
two lung bypasses. Three vessels travel in the umbilical cord;
which of these carries oxygen and nutrient rich blood. In a fetus,
both liver and lungs are nonfunctional (the liver relatively so).
The ductus venosus bypasses the liver. The ductus arteriosus and
the foramen ovale bypass the lungs. The umbilical vein carries
nutrient-rich and oxygen- rich blood to the fetus through the
umbilical cord. In a fetus, both liver and lungs are nonfunctional
(the liver relatively so). The ductus venosus bypasses the liver.
The ductus arteriosus and the foramen ovale bypass the lungs. The
umbilical vein carries nutrient-rich and oxygen- rich blood to the
fetus through the umbilical cord.
Slide 31
Ductus venosus BYPASS LIVER Liver What is the ductus venosus,
and what is its function? The ductus venosus is the liver bypass in
the fetus. Since the mothers liver is working for the fetus as
well, the entire fetal liver need not be continuously suffused with
blood. The ductus venosus is the liver bypass in the fetus. Since
the mothers liver is working for the fetus as well, the entire
fetal liver need not be continuously suffused with blood.
Slide 32
Foramen ovale & Ductus arteriosus BYPASS LUNGS
Slide 33
Umbilical Cord- contains three blood vessels: two arteries and
one vein. Umbilical vein- bright red = high oxygenation Umbilical
arteries pink = low oxygenation
Slide 34
Define pulse. Pulse: The alternate expansion and recoil of an
artery that occur with each heartbeat.
Slide 35
Which artery is palpated at the wrist? A At the groin? B At the
side of the neck? C At the front of the ear? D At the back of the
knee? E A B C D E
Slide 36
Define systolic and diastolic pressure. Systolic
pressurepressure in the arteries at the peak of ventricular
contraction Diastolic pressurepressure in the arteries when
ventricles relax Systolic pressurepressure in the arteries at the
peak of ventricular contraction Diastolic pressurepressure in the
arteries when ventricles relax
Slide 37
Two elements define blood pressure the cardiac output of the
heart and the peripheral resistance, or friction, in the blood
vessels. Name two factors that increase cardiac output. Name two
factors that increase peripheral resistance. Cardiac output is
increased by increased venous return increased heart rate.
Peripheral resistance is increased by decreased diameter of the
blood vessels increased blood viscosity. Cardiac output is
increased by increased venous return increased heart rate.
Peripheral resistance is increased by decreased diameter of the
blood vessels increased blood viscosity. Increased blood viscosity
Increased venous return
Slide 38
How does blood pressure change throughout the systemic
circulatory pathway? It decreases from heart to vena cavae
Slide 39
What is the effect of hemorrhage on blood pressure? Why?
Hemorrhage reduces blood pressure initially because blood volume
drops...Then the heart begins to beat more rapidly as it tries to
compensate. However because blood loss reduces venous return, the
heart beats weakly and inefficiently. In such cases, the
sympathetic nervous system causes vasoconstriction to increase
blood pressure so venous return increases and circulation can
continue.
Slide 40
In which position sitting, lying down, or standing- is the
blood pressure normally highest? Lowest? Blood pressure is normally
highest in the recumbent position and lowest immediately after
standing up; however, the sympathetic nervous system quickly
compensates in a healthy individual. Very often an individual can
become hypotensive after remaining still in the sitting position
for an extended period. Blood pressure is normally highest in the
recumbent position and lowest immediately after standing up;
however, the sympathetic nervous system quickly compensates in a
healthy individual. Very often an individual can become hypotensive
after remaining still in the sitting position for an extended
period. Both systolic BP and diastolic BP were significantly higher
in the supine than in the sitting position. When you stand, gravity
causes blood to pool in your leg veins, reducing the amount of
blood that returns to your heart. This causes your blood pressure
to drop