LAB T O P I C 29
Investigating Circulatory Systems
Supplies
Preparator's guide available on WWW at
http://www.mhhe.com/dolphin
The role of capillaries in exchange
General patterns of mammalian circulation to the
lungs, brain, gut, and body muscles and return
path to heart
As a result of this review, you most likely have
questions about terms, concepts, or how you will do
the experiments included in this lab. Write these
questions in the space below or in the margins of the
pages of this lab topic. The lab experiments should
help you answer these questions, or you can ask your
instructor during the lab.
Equipment
Dissecting microscopes
Compound microscopes
Stethoscope
Sphygnomanometer
Materials
Fetal pig
Demonstration dissection of beef heart
Dissection pans and instruments
Microscope slides
Cross section artery
Cross section vein
Wright-stained human blood smear
Live guppies, tadpoles, or frogs
Live crayfish
Small petri dishes
Coverslips
Absorbent cotton
Solutions
Ringers invertebrate saline
Student Prelab Preparation
Before doing this lab, you should read the introduction
and sections of the lab topic that have been scheduled
by the instructor.
You should use your textbook to review the
definitions of the following terms:
aorta
artery
atrium
capillary
carotid artery
erythrocyte
hemolymph
jugular vein
-<*
leucocyte
lymphatic system
lymphocyte
pulmonary artery
pulmonary vein
vein
vena cava
ventricle
You should be able to describe in your own words
the following concepts:
Open and closed circulatory systems
The pumping action of a four-chambered heart
29-1
Objectives
1. To dissect the heart and major vessels of the
mammalian circulatory system
2. To be able to distinguish between a cross section
of an artery and vein and between a red blood
cell and a white blood cell
3. To observe blood flow in capillary beds of a fish
4. To measure human blood pressure, using a
Sphygnomanometer.
5. To contrast the pumping mechanism of a
mammalian heart with that of an arthropod
Background
Invertebrates, such as cnidarians, flatworms, and roundworms, lack circulatory systems. Simple diffusion is sufficient for the necessary exchanges of respiratory gases, waste
products, and nutrients. Larger, more complex animals require a circulatory system to supply the needs of their tissues.
The circulatory system consists of a special internal
body fluid called blood or hemolymph, a pumping system,
and a vascular system consisting of vessels for moving the
blood rapidly from one location to another within an animal. The circulating fluid often contains a respiratory pigment, a protein that aids in transporting oxygen and carbon
393
dioxide between the tissues and the respiratory surface.
Hemocyanin and hemoglobin (which in vertebrates occurs
in red blood cells) are common pigments. Blood also contains cells or proteins that protect against invasion by microorganisms and proteins that are involved in clotting, the
sealing of leaks. The blood-vessel system often has
anatomical provisions so that the blood is brought into
close contact with three other physiological systems: lung
or gill, where gas exchange occurs; excretory, where salt,
water, and waste exchange occur; and digestive, where nutrients are absorbed.
Circulatory systems may be either open or closed. In
open circulatory systems, found in molluscs and arthropods, the arterial system is not connected to the venous system through capillary beds. Instead, the small arteries simply terminate, emptying their contents into the tissue spaces,
and the blood (properly called hemolymph) directly bathes
the tissues, eventually finding its way back to the heart.
In closed circulatory systems, found in some invertebrates and all vertebrates, the flow of blood is always
within blood vessels. The arterial system is connected to
the venous system by means of capillaries which have very
thin walls only one cell thick. Blood entering the capillaries
is under relatively high pressure, and part of the fluid portion is filtered through the capillary walls, entering the tissue spaces. On the venous side of the capillary bed, most of
this fluid flows back into the capillaries due to osmosis.
Gaseous, waste, and nutrient exchanges between the blood
and tissues occur by way of this fluid exchange as well as
by diffusion. Blood flow in each capillary bed is regulated
by the opening and closing of the precapillary sphincter,
as seen in figure 29.1.
The capillary bed, and only the capillary bed, is the
functional site of the closed circulatory system where all
exchanges take place. The lymphatic system consists of
small open-ended lymphatic capillaries that conduct fluid
into larger lymphatic ducts. Fluid that does not return to the
blood capillaries enters the lymphatic capillaries. This fluid
is collected in lymphatic ducts and returns to the venous
system near the heart.
Vertebrate circulation is summarized in figure 29.2.
Consider the changes that occur in the blood as it passes
through the various circuits. It is more important to understand the purpose of the circulatory system than to know a
long list of names of vessels.
You will observe the gross and microscopic features of
the mammalian circulatory system and circulation in
the capillary beds of a living vertebrate. You will learn
how to measure the blood pressure of a human. Finally, you will observe a living arthropod heart in
order to compare open and closed circulatory systems.
Figure 29.1
Anatomy of a capillary bed. Fluid leaves
the capillaries because of the pumping force of the heart,
raising the osmotic pressure of the blood. Pumping pressure
falls across the capillary bed due to drag and volume loss. On
the venous side, fluids are drawn into the capillary by osmosis.
Excess fluids enter the lymphatic capillaries.
Metarteriole
(forming
arteriovenous
shunt)
Precapillary
sphincter
Arteriole
Vein
Blood
flow
Figure 29.2
Schematic of major mammalian blood
vessels and their relationship to one another.
Carotid artery
Jugular
vein
Pulmonary artery
Aortic arch
Left atrium
Dorsal aorta
Left ventricle
Right ventricle
Right atrium
Caudal
vena cava
Hepatic artery
Hepatic
vein
Hepatic
portal
vein
Coeliac plus
mesenteric
arteries
Renal artery
Extremities
and other tissues
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Investigating Circulatory Systems
29-2
Invertebrate Circulatory System
Mammalian Circulatory System
Most molluscs, arthropods, and many other invertebrates
(but not all) have open circulatory systems. Of these, the
crayfish's is most easily observed. See figure 22.7 for a diagram showing the crayfish's circulatory system.
your fetal pig has not previously been opened, make a series of cuts as diagramed in the figure I.I, page 378. If you
have followed the lab sequence in this manual, complete
the opening as follows:
1. Make a longitudinal cut 1 cm to the left of the sternum
Optional Demonstration of Open Circulation
from the lower ribs to the region of the forelimbs and
E^ To observe the heart of a crayfish, first anesthetize an animal
parallel to the previous cut. Sever all ribs.
by packing it in crushed ice in a glass finger bowl. Cover the
2. Lift up the center section, labeled (A) in figure 1.1
abdomen with wet cotton. The dorsal part of the carapace,
(page 378), and cut any tissues adhering underneath.
the exoskeleton covering the thorax, should be removed by
A transverse cut at the anterior end will detach this
inserting scissors under its posterior edge 1 cm to the left of
center piece, which should be discarded.
the midline and cutting forward to the region of the eye. This
3. The heart and lungs will be easier to observe if the
procedure should be repeated on the right side, and the strip
diaphragm is cut away from the rib cage on the
of exoskeleton should be carefully lifted and removed, so
animal's left side only. Cut close to the ribs.
that none of the underlying membranes are torn.
4. In the region of the throat, remove the thymus glands,
The heart can now be seen beating in the pericardial
thyroid, and muscle bands, but do not cut or tear any
sinus covered by the epidermal and pericardium membranes.
major blood vessels.
These membranes can be removed to expose the heart, which
should be bathed in Ringer's solution to keep it from drying.
In an open circulatory system such as this one, heThe Heart and Its Vessels
molymph, the circulating fluid, leaves the heart in arteries 3)-Find the heart encased in the pericardial sac. Remove the
but returns in open sinuses instead of veins. Under a dissac and identify the four heart chambers. The paired atria,
secting microscope, you will be able to see the fluid surthin-walled, distensible sacs, collect blood as it returns to
rounding the heart enter it through three pairs of slitlike
the heart. The two ventricles are the large, muscular pumpopenings called ostia. These ostia open when the heart reing chambers of the heart.
laxes and allow hemolymph to flow in. When the heart
Blood returning from the systemic circulation enters
contracts, flaps of tissue inside the heart close the ostia, and
the right atrium from the cranial and caudal vena cavae.
hemolymph is forced out of the heart through the arteries.
After passing into the right ventricle, it is pumped to the
You should be able to see the dorsal abdominal arlungs through the pulmonary trunk, which divides into
tery, which carries hemolymph to the tail, and the ophthe left and right pulmonary arteries. The trunk is visible
thalmic and antennary arteries, which carry hemolymph
passing from the heart's lower right to upper left and passto the head region. Other arteries lie beneath the heart.
ing between the two atria (fig. 29.3). In the mammalian
Make a diagram of how the crayfish heart works.
fetus, the pulmonary trunk and aorta are connected by a
short, shunting vessel, the ductus arteriosus. Find this vessel in your animal. During the intrauterine life, when the
lungs are not functional, most blood entering the pulmonary circuit does not pass to the lungs. Instead, it is
shunted to the aorta. At birth, the shunting vessel constricts
so that blood enters the lungs. The constricted vessel fills
with connective tissue to become a solid cord seen in adults
as the arterial ligament.
Trace the pulmonary arteries to the lungs. Following
gas exchange in the capillaries of the lungs, blood collects
in the pulmonary veins and flows to the left atrium. These
veins enter on the dorsal side of the heart and will be difficult to find. If you remove some of the lung tissue from the
left side, you may be able to locate these vessels.
From the left ventricle, blood is pumped at high pressure through the aorta to the systemic circulation. Find the
aorta. It will be partially covered by the pulmonary trunk
but can be identified as the major vessel that curves 180° to
the pig's left, forming the aortic arch (fig. 29.3).
m*
1—«
29-3
Investigating Circulatory Systems
395
Figure 29.3
External ventral and dorsal views of the fetal pig's heart.
Left subclavian
artery
Brachiocephalic
artery
Cranial vena cava
Aortic arch
- Ductus arteriosus
Brachiocephalic
artery
Right pulmonary
artery
Aorta
Cranial vena
cava
Right pulmonary
vein
Right atrium
Right ventricle
Left pulmonary
vein
Caudal vena
cava
Coronary artery
and vein
Dorsal View
Ventral View
Vessels Cranial to the Heart
Veins
ecause the venous system is generally ventral to the arterial system, it will be studied first in the congested region
of the heart. Refer to figure 29.4 and place a check next to
each vein identified.
Trace the cranial vena cava forward from the heart to
where it is formed by the union of the two very short brachiocephalic veins. Each of these in turn is formed by the
union of the five major veins: the internal and external
jugular veins, which drain the head and neck; the cephalic
vein, which lies beneath the skin anterior to the upper forelimb and typically enters at the base of the external jugular;
the subscapular vein from the dorsal aspect of the shoulder; and the subclavian vein from the shoulder and forelimb. As the latter passes into the forelimb, it is known as
the axillary vein in the armpit and the brachial vein in the
upper forelimb. Caudal to the union of the brachiocephalic
veins, is a pair of internal thoracic veins that drain the
chest wall. These veins were most likely cut when you
opened the animal.
„
from the aorta is the brachiocephalic artery. It gives rise
to the two carotid arteries, which pass anteriorly to supply
the head, and the right subclavian artery, which passes to
the right forelimb. Just to the left of the brachiocephalic artery, find the left subclavian artery arising as a separate
branch from the aortic arch. Blood in this vessel goes to
which region of the body?
Once the aorta runs posteriorward along the dorsal
wall of the thorax, it gives rise to intercostal arteries, which
supply the walls of the chest. The aorta then passes through
the diaphragm to become the abdominal aorta.
Return to the left subclavian artery and trace it into
the forelimb, removing skin and separating muscles as
necessary. In the armpit it is known as the axillary artery, and in the upper forelimb as the brachial artery.
Arteries
The subscapular artery branches from the axillary artery
the aortic arch and trace it back to the heart. Note the
and supplies the shoulder muscles. The brachial artery diseveral arteries that branch off to supply the anterior region
vides in the lower forelimb to give rise to the radial and
of the animal. Refer to figures 29.4 and 29.5 to identify the
ulnar arteries.
vessels. Check off the arteries as they are identified.
6
Find another student in the lab who is at the same stage
Find the small coronary arteries that arise from the
in the dissection as you are. Quiz one another about the
base of the aorta behind the pulmonary trunk. They supply
path blood takes as it flows from the forelimb through the
the muscles of the heart. The first major artery to branch
heart to the head.
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Investigating Circulatory Systems
29-4
Figure 29.4
Ventral view of the fetal pig's major arteries (a) and veins (v).
Internal jugular v
Common carotid a
External jugular v
Thyrocervical a
Brachiocephalic v
Cephalic v
Axillary a
Internal thoracic v
Cranial vena cava
Brachial a
Radial a
Dinar a
Subscapular v
Radial v
Ulnar v
Axillary v
Right atrium
Brachial v
Subclavian v
Aortic arch
Ductus arteriosus
Pulmonary trunk
L. pulmonary a
Hepatic v
Caudal vena cava
Diaphragm
Coronary a
Right ventricle
Hepatic a
Abdominal aorta
Allantoic duct
Umbilical a
Renal a
Kidney
Renal v
Caudal mesenteric a
External iliac a
Femoral v
Femoral a
External iliac a
Internal iliac v
Gonadal a
Internal iliac a
Median sacral a
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Median sacral v
Investigating Circulatory Systems
397
Figure 29.5
Major arteries in the region of the fetal pig's heart.
Left
common
carotid
artery
Trachea
Vagus
nerve
Esophagus
Right
subclavian
artery
Lung
Left
subclavian
artery
Brachiocephalic
trunk
Atria
Aorta
Pulmonary
artery
Ductus
arteriosus
Pulmonary
trunk
Ventricle
Hemiazygous
vein
Dorsal
aorta
Lung
Vessels Caudal to the Heart
Veins
£>If the heart is lifted and tilted forward, the caudal vena
cava can be viewed at the point where it enters the right
atrium. As this vein is traced caudally, several veins will be
found flowing into it. After it passes through the diaphragm,
the paired hepatic veins and single umbilical vein enter
first. The umbilical vein carries oxygenated, nutrient-laden
blood from the placenta. This vein passes through the liver
where it is known as the ductus venosus.
The hepatic portal vein runs next to the common bile
duct under the lobes of the liver. It will be difficult to find.
Nutrient-laden blood flows through this vein to the liver
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Investigating Circulatory Systems
where exchanges occur between the blood and the liver
across the walls of the portal system capillaries. The blood
then flows into the hepatic veins, which enter the caudal
vena cava.
Follow the vena cava caudally to where the renal veins
enter from the kidneys. In the male, the spermatic veins,
and in the female, the ovarian veins, enter next. On the left
side, these veins may enter the renal vein first. Below the
kidneys, the vena cava splits into the internal and external
iliac veins and the median sacral vein, a small vein that
comes from the tail. The external iliac veins collect blood
from the femoral veins in the hind legs, whereas the internal iliacs collect blood from the pelvic area.
29-6
Figure 29.6
Lateral view of circulatory system in fetal pig (arteries—red, veins—blue). Label the major arteries and veins.
Heart
Aorta
Lu n
,9
Caudal vena cava
Liver
Kidney
Small intestine
Hepatic portal system
Large intestine
Arteries
£> After the aorta enters the abdominal cavity, a large, single
coeliac artery arises from it at the cranial end of the kidneys. You will have to remove some connective tissues to
obtain a full view of this artery. The coeliac artery eventually divides into three arteries supplying the stomach,
spleen, and liver. The mesenteric artery next arises from
the aorta and supplies the pancreas, small intestine, and
large intestine. The renal arteries are short, paired arteries
supplying the kidneys. The next large arteries arising from
the aorta are the external iliacs, which supply the hind legs
with a branch to the lower back. In the fetus, the umbilical
arteries branch from the caudal end of the abdominal aorta
and pass out through the umbilical cord. They form a capillary bed in the placenta for nutrient, gas, and waste exchange with the maternal circulatory system.
Find another student in the lab who is at the same stage
in the dissection as you are. Quiz one another about the circulation paths to the major organs and hind limbs.
Look at the diagram in figure 29.6 and add labels to the
major arteries and veins that you identified in your dissection.
Internal Heart Structure
1J^ Study the orientation of the heart so that you can later identify it in isolation. Now, free the heart from the body by cutting through all the vessels holding it in place. Be careful to
29-7
leave enough of each vessel so that they can be identified in
the isolated heart. Alternative to removing the fetal pig's
heart, your instructor may have a demonstration dissection of
a beef heart or heart models for you to study. Whichever
specimen you are using, orient yourself by identifying the
aorta, pulmonary artery, pulmonary vein, and vena cava.
Place the heart in your dissecting pan, ventral side up.
Make a razor cut along the pulmonary trunk down through
the right ventricle. Spread the tissue open, pin it down, and
remove the latex. You may wish to use a dissecting microscope to observe the open ventricle.
Identify the semilunar valves at the junction of the artery and ventricle. Consider how these valves work. The
open flaps face into the pulmonary trunk, and any backflow
in the pulmonary trunk fills the valve flaps with blood and
closes the valve. You may have to cover the heart with water
to float the valve flaps so that you can see them (fig. 29.7).
Now cut through the right atrium and remove the latex
and coagulated blood. The tricuspid valves are between the
atrium and ventricle. These valves also work on the backflow principle, allowing blood to flow only one way from
the atrium into the ventricle. In the ventricle, fine fibers
called chordae tendinae are attached to the valve flaps.
These cords prevent the flaps from "blowing back" from
high pressures developed when the ventricle contracts.
Cut into the left atrium and ventricle as you did on the
right side. Identify the bicuspid or mitral valve between
Investigating Circulatory Systems
399
Figure 29.7
from above.
Human heart: (a) the path of blood flow through the major chambers and vessels; (Jb) valves of the heart viewed
Aorta
Cranial vena cava
Left pulmonary artery
Pulmonary trunk
Right pulmonary veins
Left pulmonary veins
»•"*•
Left atrium
Pulmonary semilunar valve
Aortic semilunar valve
Right atrium
Bicuspid valve
Tricuspid valve
Chordae tendineae
Papillary muscle
Left ventricle
Right ventricle
Caudal vena cava
(a)
Pulmonary semilunar
Aortic semilunar valve
Opening of
coronary artery
Bicuspid valve
(b)
400
Investigating Circulatory Systems
Jricuspid valve
Figure 29.8
Histology of arteries and veins: (o) tissues in the wall of an artery; (b) tissues in the wall of a vein; valves in veins
prevent backflow of blood in the venous sytem.
Artery
Vein
Endothelial lining
Valve
Connective tissue
Elastic tissue
Muscle layers
the atrium and ventricle with its associated chordae tendinae. After cutting into the ventricle and cleaning it, find the
aortic semilunar valve. Blood flow through the human
heart is shown in figure 29.7.
Pair off with another student and describe how blood returning to the heart from the foreleg travels to the lungs and
then to the hindleg. Describe the operation of the heart valves.
Clean your dissecting instruments and tray and return
your fetal pig to the storage area.
Histology of Vessels
tain prepared slides of cross sections of arteries and
veins and observe them under low power with a compound
microscope. Note that arteries have thicker walls than veins
of the same size. Most of the difference in thickness is due
to the increased amounts of muscle and connective tissue in
the artery. Since arteries carry blood from the heart, they
operate under relatively high pressure (average 120 mm of
mercury equivalent). Veins experience only one-twentieth
as much pressure.
Blood flows through veins because skeletal muscles
press on them and move the blood along. Valves in the
veins prevent backflow and make the passage of blood unidirectional (fig. 29.8).
Observe the tissues of a blood vessel under lOx. Endothelial cells are epithelial cells that line both arteries and
veins; capillary walls consist of only endothelial cells.
When the muscle layers are contracted in the smallest arter29-9
Figure 29.9
Scanning electron micrograph of a broken
blood vessel, showing the smooth endothelial lining and
several red blood cells (RBC).
BB
RBC
Vessel wall
ies, the total volume of the vascular system is reduced and
the blood pressure rises.
Figure 29.9 shows the nature of the endothelial lining
of blood vessels and red blood cells in an arteriole. The
complexity of the microvasculature is evident in scanning
electron micrographs of casts of the circulatory system.
Note the capillaries and their relationship to arterioles in
figure 29.10.
Investigating Circulatory Systems
401
Figure 29.10
Scanning electron micrograph of a plastic
cast of a capillary bed from skeletal muscle in which individual
arterioles can be traced to capillaries. From R. G. Kessel and
R. H. Kardon. Tissues and Organs: A Text-Atlas of Scanning
Electron Microscopy. 1 979. W. H. Freeman and Company.
Figure 29.11
Human blood stained with Wright's stain
shows red blood cells and different types of white blood cells;
(a) neutrophil; (b) lymphocyte.
Arteriole
Capillary
Blood
Human blood consists of 55% plasma and 45% cells by
volume. Plasma is the fluid portion of the blood containing
dissolved proteins, salts, nutrients, and waste products.
Several different types of cells and cell fragments are contained in blood. By far the most common (about 95% of
the cells) are erythrocytes (red blood cells) which are red
because they contain hemoglobin. The other 5% are collectively called leukocytes (white blood cells) and platelets
that are important in blood clotting. There are several types
of leukocytes. The most common, neutrophils and lymphocytes, representing 95% of the white blood cells, are
shown in figure 29.11. The remaining types of cells, basophils and monocytes, represent only 5% of the white
blood cells.
Get a prepared slide of a Wright-stained human blood
smear from the supply area and look at it with your compound microscope under medium power. Note the large
A number of red blood cells. Can you see a nucleus in these
cells?_
. Why do you think that the red blood cells are
lighter in color in the center and darker at the periphery?
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Investigating Circulatory Systems
As you look carefully at the slide, you will see occasional cells that look different. These are leukocytes and
because of the staining they have a blue/purple color. Center a leukocyte in the field of view and observe it with high
power. What structure in the cell is stained?
.
Return to medium power and scan the slide to locate other
leukocytes. Try to find examples of each of the types
shown in figure 29.11.
Neutrophils leave the blood early in the inflammation
process and become phagocytic cells consuming cell debris
and bacteria. Lymphocytes are important in the immune
response. Some are involved in cellular immunity and others secrete antibodies that neutralize foreign proteins and
other macromolecules.
Return your slide to the supply area.
29-10
L
IF
Figure 29.12
Method for observing microcirculation in
a fish tail.
t
Mi
(1) Wrap the fish (except for the
head and tail) with dripping
wet cotton. Place fish in
half of a petri dish.
Place coverslip over tail.
Place the dish on a compound microscope stage and
observe the tail under scanning power. Sketch your observations, answering the following questions:
1. Can you identify capillaries, venules, and arterioles?
2. Is blood flow faster in certain vessels compared to
others?
(2) Place dish on microscope so that
fish's tail is over hote in stage.
3. Is blood flow continuous in all vessels? What might
control this?
Dilute solutions of nicotine, caffeine, and adrenalin are
available in the lab in dropper bottles. Devise an experiment to determine the effects of these chemicals on capillary circulation.
(3) Examine with low- and medium-power
objectives of your microscope.
Circulation in Capillaries
o observe circulation in capillaries, net a small fish or
tadpole from an aquarium and wrap it in dripping wet cotton, as shown in figure 29.12, being careful not to cover
the head or the tail. Lay the wrapped fish in an open petri
dish. About every five minutes return the fish to water.
Place a few drops of water on the tail and add a coverslip
over the tail.
29-11
Measuring Blood Pressure
Blood pressure is the pressure that the blood exerts on the
walls of blood vessels and is usually measured in arteries.
Because of the contraction cycle of the heart, pressure varies
from a high (systolic) to a low (diastolic) pressure during a
cycle. Pressures are reported in mm of mercury (Hg) with
the systolic pressure appearing first. Thus a blood pressure
reading of 120/60 means that the pressure just following
maximum contraction is 120 and just following maximum
relaxation is 60 mm of Hg. In this section, you will learn
how to take a blood pressure reading by the indirect method.
Method An instrument called a sphygmomanometer
and a stethoscope are used in this method. An inflatable
cuff is placed around a person's arm (fig. 29.13) and inflated until the pressure exerted is greater than the systolic
Investigating Circulatory Systems
403
Figure 29.13
Method to be used in measuring blood pressure.
column of mercury
indicating pressure
in mm Hg
No sounds
1 (artery is closed)
•<- systole =
<- diastole =
0
•
Sounds heard
(artery is opening
and closing)
o
No sounds
(artery is open)
=
inflatable
rubber cuff
brachial
artery
sounds are heard
with stethoscope
I
air valve
S
-squeezable bulb
inflates cuff with air
pressure, thus collapsing the arteries in the upper arm. The
pressure in the cuff is gradually reduced while the operator
listens for resumption of blood flow in the arteries with a
stethoscope (fig. 29.13). The pressure at which faint tapping sounds are heard is taken as the systolic pressure. As
pressure in the cuff is further reduced, louder sounds are
heard because of turbulent blood flow through the partially
compressed artery. There is a pressure at which these
sounds stop when blood flow becomes laminar. This pressure is considered the diastolic pressure.
16
Work with a partner to measure these pressures. The
subject should sit with the arm extended and resting on a
table. Your instructor may explain in more detail how to do
the following procedures.
Results
Record your results below:
First trial
Systollic pressure
Diastolic pressure
Second trial
Systolic pressure
Diastolic pressure
What range of pressure values were observed in the class?
Were there any differences between genders? Were there
any differences between athletes and non-athletes?
1. Wrap the cuff around the upper arm in such a way that
the inflatable area is over the inner surface of the arm
where the brachial artery is located.
2. Don the stethoscope and place the end over the pulse
point located on the inside of the elbow joint (fig. 29.13).
3. Inflate the cuff to about 160 mm of pressure. DO NOT
OVER INFLATE!
4. Slowly release the pressure by opening the valve on
the squeeze bulb as you listen for the first thudding
sounds of blood flow. Note the pressure when you hear
them. Continue to reduce pressure until the sounds are
no longer heard. Note the pressure reading when this
happens.
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Investigating Circulatory Systems
29-12
T2^Blood Pressures under Experimental Conditions
Assuming that you now can measure blood pressures rather
quickly, try doing so under these experimental conditions:
Have a fully cuffed subject recline on a table for two or
three minutes and then quickly stand as you inflate the cuff.
Take your measurements and record below:
Does this measurement have any relationship to lightheadedness that is sometimes felt when getting up quickly?
Explain?
First trial
Systolic pressure
Diastolic pressure
Second trial
Systolic pressure
Diastolic pressure
Learning Biology by Writing
Your instructor may ask you to answer the Lab Summary
and Critical Thinking questions that follow.
Internet Sources
Many medical schools have extensive collections of
pictures of pathological conditions. These collections
are available over the WWW. Use your browser
program and a search engine to locate pictures of a
blood vessel with arteriosclerosis. Compare this
picture to your observations of a normal artery in the
lab. Describe the differences.
Lab Summary Questions
—*
E
1. Create a flowchart showing the major vessels and heart
chambers that a drop of blood passes through as it
returns from the arm and passes to the back leg.
2. Create a flowchart showing the major vessels and heart
chambers that a drop of blood passes through as it
returns from the small intestine and passes to the brain.
3. List the valves of the heart and describe how they
operate.
29-13
4. What are the structural differences between an artery
and a vein? How do capillaries differ?
5. How does the open circulatory system of a crayfish
differ from the closed system of a mammal? Describe
how blood returns to and enters the heart of both types
of animals.
6. Trace a molecule of oxygen from when it enters the
pig's nostril to when it enters the tissues of the upper
hind leg. Then trace a carbon dioxide molecule as it
passes from the leg back to the nostril.
7. Explain what blood pressure is and what it means
when a person says their blood pressure is 125/70.
Critical Thinking Questions
1. What are the roles of the lymphatic system and the
venous system in returning fluid filtered through the
microcirculation?
2. Since a giraffe's head is 15 feet above the ground,
what circulation adaptations are necessary to allow
adequate blood supply to the head?
3. If arthropods such as insects have open circulatory
systems that lack veins, how does hemolymph return
from the tissues to the heart?
4. Based on your lab observations, give an opinion on the
following situation: A person has a blood pressure of
150/90.
Investigating Circulatory Systems
405