Download Heart Parts Activity - Delaware Access Project

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ACTIVITY OVERVIEW
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Heart Parts
BO RA
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SUMMARY
Students investigate the functions of the blood vessels and the major structures of the
heart. This activity offers an excellent opportunity for students to compare models
and diagrams to real structures. After developing an understanding of the structures
and function of the circulatory system, students can explore the structure of an actual heart in an optional dissection.
KEY CONCEPTS AND PROCESS SKILLS
1.
Human body systems are composed of organs. The structure of an organ is
adapted to perform specific functions within one or more systems.
2.
Each system within the human body is defined by the functions that it
performs. For example, the heart, blood, arteries, veins, and capillaries are a
part of the circulatory system, whose function is to transport gases (oxygen
and carbon dioxide), nutrients, and wastes within the body.
3.
Blood is pumped around the human body by the heart.
4.
Valves control the direction of flow and allow liquid to move under pressure
in both a pressure bulb and in the human heart.
5.
The human heart is a double pump, which increases the efficiency of blood
circulation.
6.
The human heart is divided into four chambers (right ventricle, right atrium,
left ventricle, left atrium). One side of the heart pumps blood directly to the
lungs, while the other side of the heart pumps blood to the rest of the body.
7.
The greater the surface area available for contact, the faster oxygen and carbon
dioxide can diffuse from blood vessels into and out of the body’s tissues. The
capillary network provides surface area for this diffusion to take place.
Teacher’s Guide
B-143
Activity 23 • Heart Parts
KEY VOCABULARY
arteries
function
atrium (plural: atria)
structure
blood vessels
valves
capillaries
veins
circulatory system
ventricle
MATERIALS AND ADVANCE PREPARATION
For the teacher
*
1
Transparency 23.1, “Circulation in Mammals and Fish”
1
transparency of Student Sheet 23.1, “Heart Diagram”
1
overhead projector
For the class
*
2–3 stethoscopes (optional)
*
alcohol swabs
For each student
1
*
Student Sheet 23.1, “Heart Diagram”
red and blue colored pencils
For the Extension
For the teacher
*
1
video camera hooked up to a TV monitor (optional)
For the class OR For each pair of students
*
1
sheep heart
*
soap
*
paper towels
*
disinfectant spray
*
sponges
*
supply of water
*
1
quart-size plastic bag with airtight seal
*
1
pair of large dissection scissors
*
1
thick paper plate (or a foam meat-packing tray)
For each student
*
B-144
Science and Life Issues
1
pair of non-latex gloves
1
Student Sheet 23.2, “Heart Dissection”
*Not supplied in kit
Heart Parts • Activity 23
MATERIALS AND ADVANCE PREPARATION
(CONT.)
To find sheep hearts, look in your phone directory under “Meat–Wholesale”
or “Meat Packers.” You can also use other mammalian hearts, such as deer
hearts. One heart per two students is ideal, but one heart per four students
also works. If you are pressed for time and funds, do the dissection as an interactive, whole-class demonstration. This works best if you have a video camera that can hook up to a TV monitor. If not, consider splitting the class in
half, with another activity for half of the class while you perform the dissection with the other half.
TEACHING SUMMARY
Getting Started
1.
Introduce the relationship between the heart’s structure and its
function in providing continuous blood flow.
Doing the Activity
2.
Students use Student Sheet 23.1, “Heart Diagram,” to investigate
concepts presented in a reading.
Follow-Up
3.
The class reviews key concepts and discusses the Analysis Questions.
Extension
Students perform or the teacher demonstrates the dissection of a heart.
Teacher’s Guide
B-145
Activity 23 • Heart Parts
BACKGROUND INFORMATION
Circulatory System
around the body. This is essential to supply the high
In the human heart, blood enters through the atria.
oxygen and nutrition requirements of the cells of
The right atrium receives blood from the body and
homeotherms such as birds and mammals.
the left atrium receives blood from the lungs.
Although they appear smaller than the ventricles,
the atria contain the same volume of blood during a
heartbeat as the ventricles. The walls of the atria are
thinner and more elastic than the walls of the ventricles, so they have a greater capacity to expand as
they fill with blood. (If you do the dissection, students will be able to feel this difference in chamberwall thickness for themselves.)
The heart valves work in opposition. When the
right atrium is filled with blood, the valve between
the atrium and ventricle is closed. As it opens to
allow blood to flow into the ventricle, the valve
between the ventricle and pulmonary artery closes.
Occasionally a valve is not formed correctly at birth
or deteriorates due to medications or disease and
does not close completely. This can be heard
through a stethoscope and is known as a heart mur-
Ventricles pump blood to all parts of the body. Ven-
mur. Heart murmurs can also be caused by other
tricle walls are thicker than the walls of the atria
defects, such as a hole in the septum (wall) between
because they exert a much greater force than do the
the ventricles.
walls of the atria. The right ventricle pumps blood
to the lungs for oxygenation, while the left ventricle pumps blood to the rest of the body. The body
tissues contain far more capillaries for blood to
move through than the lungs do. This means that
the blood leaving the left ventricle needs to be
pumped harder in order to get it through the exten-
Arteries always carry blood away from the heart. All
arteries in the body except the pulmonary arteries
carry oxygenated blood. Since the pulmonary arteries are carrying blood away from the heart to the
lungs, they are carrying deoxygenated blood. In pictures, arteries are always red. In reality, arterial
blood is bright red.
sive capillary beds of the body’s tissues. For this reason, the wall of the left ventricle is thicker and
Veins always carry blood to the heart. All veins in the
stronger than the wall of the right ventricle.
body except the pulmonary veins carry deoxygenated blood. Since the pulmonary veins are carrying
This double-pump system (present in mammals and
birds) is more efficient than a single-pump system,
such as in fish. In mammals, the blood pressure is
boosted after the blood gets back from the lung cap-
blood to the heart from the lungs, they are carrying
oxygenated blood. In pictures, veins are always
shown as blue—and vessels seen through the skin do
appear blue. In reality, venous blood is dark red.
illaries, allowing it to be pumped much faster
REFERENCES
Smith, Anthony. The Body. George, Allen and Unwin, 1985.
B-146
Science and Life Issues
Heart Parts • Activity 23
TEACHING SUGGESTIONS
n
GETTING STARTED
If you have stethoscopes, let students take turns trying to hear the lub-dub sound (described in the read-
1.
Introduce the relationship between the
ing) of their own hearts. Wipe the earpieces with an
heart’s structure and its function in provid-
alcohol swab between students. Tell them that they
ing continuous blood flow.
will investigate heart sounds in more detail by lis-
n Teacher’s Note: You can greatly enhance this reading by using heart models, showing video clips of
the heart pumping blood, and/or doing the dissec-
tening to an audio tape in Activity 26, “Heart
Sounds.”
tion extension.
n
Ask, How does the heart maintain a one-way flow of
3.
blood through your body? Students are likely to men-
FOLLOW-UP
The class reviews key concepts and discusses
the Analysis Questions.
tion the pressure bulb and valves investigated in the
Make a transparency of Student Sheet 23.1 to display
previous activities. Ask, Do you think heart valves
while you review students’ ideas about how the heart
will be similar to or different from the valves in the
works. Review the four-chambered double-pump
pressure bulb? Explain that they will be looking
structure of the heart. The left side of the heart func-
more closely at the structure of the heart and think-
tions as one pump to circulate oxygenated blood to
ing about how the structure helps the heart to per-
the organs. The right side of the heart functions as a
form its pumping function.
second pump to circulate deoxygenated blood to the
lungs for oxygenation. The presence of two separate
n
2.
DOING THE ACTIVIT Y
pumps for these separate functions increases the efficiency of the heart. The structure and location of the
Students use Student Sheet 23.1, “Heart
valves help to maintain the continuous, one-way flow
Diagram,” to investigate concepts
of blood through the system. Large arteries and veins
presented in a reading.
allow the blood to enter and leave the heart, while
Provide each student with a copy of Student Sheet
small capillaries allow for close proximity between the
23.1, “Heart Diagram.” Have students read the activ-
blood and tissues of the organs.
ity, stopping periodically to complete the Stopping
to Think sections by using their student sheets.
Refer students to Student Sheet 23.1, which they
colored in oxygenated and deoxygenated blood.
Use Transparency 23.1, “Circulation in Mammals
Discuss the Stopping to Think questions, especially
vs. Fish,” to review the double-pumped double loop
3b and 3c. The pulmonary arteries, unlike other
of the circulatory system in mammals and birds.
arteries in the human body, carry deoxygenated
Contrast this with the single loop of the circulatory
blood. The right atrium receives deoxygenated
system in fish, which requires only a single pump.
blood from the body. The blood then enters the
Teacher’s Guide
B-147
Activity 23 • Heart Parts
right ventricle, from which it is pumped to the
perform a dissection of a sheep heart. Students often
lungs via the pulmonary arteries. (The mnemonic
react strongly to dissections. Some consider it the
“Arteries come from the heart-ery” may help stu-
most memorable and interesting thing they have
dents identify the function of arteries.) The pul-
ever done in science. Others find it unpleasant or feel
monary veins, unlike other veins in the human
that it is unethical. Dissecting organs from animals
body, carry oxygenated blood. The left atrium
already used to provide meat is more likely to be
receives oxygenated blood from the lungs. The
acceptable to individuals who object to sacrificing
blood then enters the left ventricle, from which it is
animals solely for dissection. Be prepared to have an
pumped to the body via the aorta.
alternative assignment for students who do not want
As you discuss Analysis Question 2, some students
may point out that nothing prevents the valves from
flapping backward into the atria. You could then show
students how attachments prevent this from happening, as shown in Figure 2 of Activity 26, “Heart
Sounds,” on page B-73 in the Student Book. Heart
to participate. Some students may be more comfortable wearing latex gloves as they perform the dissection. (Make sure they are not allergic to latex. If a student shows an allergic reaction to latex, get medical
attention immediately.) In all dissections or activities
involving animals, model respect for life.
valves can be damaged from rheumatic heart disease
Dissections demonstrate structure and function rela-
or from calcification due to old age. Damaged valves
tionships and allow students to see how models relate
allow some blood to leak backward and, although the
to the real object. Heart dissections are fairly straight-
damaged heart continues to work hard, the output of
forward, although it is best to practice ahead of time
blood is reduced. This results in a decreased oxygen
if you have never done one (see Student Sheet 23.2).
supply to the tissues. People with serious heart valve
disease are likely to feel chronically tired and are often
unable to physically exert themselves. Inform students that they will be listening to the effects of valve
failure in Activity 26, “Heart Sounds.”
Decide whether students are ready to be assessed on
the function of the heart. You can score student
responses to Question 3 using the “Applying Relevant Content” element of the UNDERSTANDING CONCEPTS
(UC) variable.
Safety Note: Before students start, discuss
how to use the scissors safely. Students should take
turns cutting. Warn students against trying to work
together, with one holding the heart while the other
cuts. This can easily result in cut fingers.
Distribute Student Sheet 23.2, “Heart Dissection.”
Students can use as this as a guide to record their
notes during a class demonstration or to guide their
own dissections. It is designed to minimize the time
you have to spend demonstrating what to do and to
Extension
Students perform or the teacher demonstrates
maximize their time exploring this organ.
the dissection of a heart.
Distribute the hearts. Have students feel the thick-
Depending on your school, community, and person-
ness of different parts of the heart and think about
al policies with regard to dissection, you may wish to
the functional reasons for any differences they feel.
B-148
Science and Life Issues
Heart Parts • Activity 23
At the end of the class period, students should put
ciently in one direction. If the heart were like a
the dissected heart into a large, seal-able plastic bag.
siphon bulb, it would not be able to maintain
They should wash and dry the scissors, wipe the
the one-way flow of blood. In order for the
desk tops with disinfectant, and wash their hands
heart to pump blood around the body in one
with soap after the dissection.
direction only, it has to have valves. Students
may also note the greater thickness of the ven-
To review the dissection extension, discuss Analysis
tricular walls, especially the left ventricle,
Question 1 on Student Sheet 23.2 (“What did the
which pumps blood to the body.
dissection teach you that would have been hard to
learn in other ways?”) with the class. At this point,
2.
What structures prevent blood in the ventricles from
you may also wish students to discuss the trade-offs
backing up into the atria? Why is it important for
involved in classroom dissections. Student respons-
your heart to have these structures?
es may include that they would not have realized
The valves prevent backup of the blood from
the toughness of the valves, vessels, and cords in the
the ventricles to the atria. When the ventricles
heart if they had not dissected one. They could also
contract, the valves close and prevent blood
feel for themselves the elasticity and strength of the
from flowing back into the atria. The valves are
heart muscle. In addition, the dissection may also
important for the heart to be able to pump
have helped them understand the three-dimen-
blood in one direction only.
sional structure of the heart.
3.
Students should begin to develop an understanding
of how real structures are represented in diagrams
Explain what is meant by the statement: “The heart
is two pumps.” You may want to draw a diagram to
support your explanation.
and models. Many characteristics of actual structures cannot be fully represented and, in many
A level 3 response follows. A level 4 response
cases, have been simplified. Some students may also
may include a reference to the difference
have enjoyed practicing “surgical skills” during the
between the double circulation of mammals
dissection.
and the single circulation of fish, as presented
on Transparency 23.1.
SUGGESTED ANSWERS
TO ANALYSIS QUESTIONS
1.
How is the structure of the heart related to
its function?
UC
arc
The heart pumps blood to the body. The
blood goes through the body and comes
back to the heart. The heart then pumps this
blood to the lungs. The blood comes back to the
heart before it goes through the body again.
The function of the heart is to pump blood
One pump pumps blood to the body, and the
around the body. In order to perform this func-
other pump pumps blood to the lungs. This is
tion, it has to be able to move the blood effi-
why the heart is really two pumps.
Teacher’s Guide
B-149
Circulation in Mammals and Fish
Mammal Circulation
blood to body
blood from lungs
capillaries
in lungs
heart
capillaries
in body
Fish Circulation
©2006 The Regents of the University of California
capillaries
in gills
heart
Science and Life Issues Transparency 23.1
capillaries
in body
B-151
Name
Date
Heart Diagram
Arteries to head and arms
Vein from head
Aorta
Pulmonary artery
Pulmonary artery
Pulmonary veins
Left atrium
Right atrium
Left ventricle
Right ventricle
©2006 The Regents of the University of California
Vein from body
Science and Life Issues Student Sheet 23.1
B-153
Name
Date
Heart Dissection
Safety: Use caution when cutting with the scissors. Hold the heart carefully.
Do not try to have one partner hold the heart while another cuts. This
can result in cut fingers.
1.
Before you cut, examine the outside of the heart as described below.
a.
Find the main area of muscle at the base of the heart. These are the ventricles.
Record how they feel.
__________________________________________________________________________________________________
©2006 The Regents of the University of California
__________________________________________________________________________________________________
b.
Find the small arteries that supply the muscles of the ventricles with blood.
Draw a few of the arteries on the diagram below.
c.
Find the floppy-looking sacks at the top of the ventricles. Use your diagrams
from the Reading in Activity 23 to help you decide what these sacks are. Record
your ideas below.
__________________________________________________________________________________________________
2.
Put a finger through one of the large tubes coming out of the top of the heart and
feel around inside one of these sacks. Record your observations in the space below.
Think about how the structure of these tubes helps them do their job.
________________________________________________________________________________
________________________________________________________________________________
Science and Life Issues Student Sheet 23.2a
B-155
Name
Date
Heart Dissection (cont.)
3.
Now cut the heart as shown in the diagram.
4.
Decide which of the vessels (large tubes) at the top of the
heart carry blood into the heart. Hint: Look for the flap-like
valves that will let your finger move more easily in one
direction than the other. Label these vessels as “veins” on the
diagram shown in Step 1.
5.
Identify an atrium and a ventricle. Identify and describe the
structures that prevent blood from flowing back into the
atrium when the ventricle squeezes.
__________________________________________________________
__________________________________________________________
__________________________________________________________
6.
Look again at the atrium and ventricle. Find where the blood leaves the heart. Put
your finger through this opening. Label these vessels (large tubes) as “arteries” on
the diagram shown in Step 1.
7.
If you have time, dissect the other half of the heart.
a.
Compare the thickness of the ventricles.
________________________________________________________________________________
b.
Explain which side of the heart will pump blood more forcefully.
________________________________________________________________________________
c.
Based on their functions in pumping blood to the body and to the lungs,
explain any differences you observe between the left and right ventricles.
©2006 The Regents of the University of California
________________________________________________________________________________
ANALYSIS
1.
Reflection: What did the dissection teach you that would have been hard to learn
in other ways?
Science and Life Issues Student Sheet 23.2b
B-157