Dissection as a Culminating Activity
Thursday, October 27th, 2011 2:00–3:00 PM
Hilton Hartford, Connecticut Salon A
Presenter: Michael J.V. Lazaroff
E-mail: Michael_Lazaroff@westport.k12.ct.us
Staples High School, Westport, CT
SUBJECT: Biology
GRADE LEVEL: High School & Middle School
End your year with dissection! Find out ways to get all students involved,
make the most out of it, and use it as a culminating activity.
Learn strategies to create a safe environment, engage your students,
and eliminate the need for alternative assignments.
Value of Dissection:
If you are attending this session, then you clearly know the value of dissection. Your students, on the other
hand, may need convincing. A strong argument, presented with conviction, and compassion, will win the
day. In that spirit, I will show you how I approach this subject in my classroom.
If you also teach in Connecticut, you know that state standardized testing (i.e., the C.A.P.T.) has all but
eliminated body systems in biology classrooms. Going beyond the time lost to administer the tests, the test
designers, in their infantile infinite wisdom have removed body systems from the exam. (To be fair,
Connecticut is not the only state which has dropped body systems from their state standardized tests, as our
next door neighbor, New York, has done the same.) When looking at the Connecticut state science
standards, all body systems fall under one standard regarding structure and function. Imagine an Anatomy &
Physiology class, which I also teach, in which the entire curriculum falls under a single standard.
What makes these state decisions all the more interesting is that 1/3 of all jobs in Fairfield County, in which I
teach, are related to health care. Of all the courses students take in high school, one of the ones that will be
of the most use to them in later life is biology. The reason for this is that every student will have to face
serious health issues, if not for themselves, then for family members, friends, and pets. The knowledge they
gain in the class will help them not only to understand better what is going on, but it will also make it
possible for them to ask the right questions.
On a personal note, I put my high school biology knowledge to good use in my freshman year in
college when I was diagnosed with Type I Diabetes (a.k.a. Juvenile Onset, Insulin-dependent). The
combined symptoms of excessive thirst and excessive urination were beautifully explained when I
combined my knowledge of osmosis with my knowledge of the cardiovascular and excretory systems!
Every year, biology teachers must face students who are resistant to dissection. In their concern for animal
rights, they ignore the benefits our society has reaped as a result of animal dissection and animal testing. A
knowledge of animal anatomy is the most important to the students in the things they can learn about their
own bodies. Every doctor, every veterinarian, every nurse, every paramedic started out with dissection. The
concept that medicine for humans is entirely separate from that for animals is short-sighted.
On another personal note, I owe my life to the dozen or so dogs that died when Dr. Frederick
Banting and his medical student Charles Best discovered insulin. The dogs, however, did not die
solely to save humans, for there are many pet owners who have used the life-saving insulin on their
own pets. The medicine that saves us also saves our animal friends.
The Discovery of Insulin: http://nobelprize.org/educational/medicine/insulin/discovery-insulin.html
With that in mind, I would hate to have a surgery planned, knowing that the doctor had not had ample
experience with dissection.
Dissection Specimens vs. Computer Resources:
In our technology driven world, there is a bit of a battle cry echoing around school hallways: It's better when
you do ___ (insert activity here) with a computer! Although that is often true, it is often not! Given that you
will likely encounter an argument in favor of computer resources over actual dissection, it is important that
you be prepared.
As you can see by the web resources I have designed, I am no stranger to the computer, and I use it
extensively in my classroom. In addition to an extensive website for all three of my classes (Biology,
Anatomy & Physiology, and Forensics), I also use digital cameras, digital microscopy, an interactive white
board, and resources to collect data digitally, as well as for the students to share information when involved
in cooperative projects. Given that, I do not take avoiding the computer lightly. In terms of dissection,
technology should be used as a supplemental resource only. In fact, I have my student do online dissections
for homework the night before they do the same dissection in the lab; in this way, the student are not only
better prepared, but they also learn that the online dissection is only a starting point for the more detailed
dissection they will be doing in the lab. There truly is no replacement for actual dissection.
Have you ever tried to make origami, using photos as your only resource? It is extremely difficult (some
even say impossible), as one has to translate two dimensional images into a three dimensional object. When
using computers, one has similar issues. One cannot truly explore an organism unless that exploration is in
three dimensional space. The actual organism allows the student to see how the different areas of the body
are actually connected (e.g., in the bullfrog, the connection between external and internal nares, between the
Eustachian tube and the tympanic membrane, and between the glottis and the lungs, to name but a few).
In addition, electronic resources give you only one specimen at a time. The only time a second specimen is
introduced is when exploring the reproductive system. Comparisons should not, however, end there. It is a
valuable experience to have students compare individual specimens. When the students see that, despite the
similarities, there can be many differences, they learn to appreciate the tough job of a surgeon. Despite a
general knowledge of anatomy, a surgeon must quickly identify structures in each patient, for differences do,
indeed exist. In addition, surgeons must be able to recognize normal vs. abnormal structures in order to
direct their incisions.
Beyond all of that, there is an incredible power to the kinesthetic role of dissection. To actually feel the
structures (e.g., why, in the earthworm, is there a difference in the feel of the crop vs. the gizzard), either
through gloves or the use of a blunt probe, to make the delicate cuts, make a profound impression. If
handled correctly, dissection can be a positive learning experience that will stay with the students for years to
come.
Student Issues, and how to Overcome them (Setting Boundaries, and more):
Having been through many classrooms over the years, and observed dissection being run by various teachers,
I have a good idea as to what works and what doesn't. The horror stories I have heard, but never witnessed
in my classroom, are usually the result of too much down time. When students either don't know what to do,
or are finished early, then their imaginations wander. That is a recipe for trouble. So, what's the cure?
Simple: give them too much to do!
A quick look at the three dissection lab pages below
Earthworm:
Crayfish:
Bullfrog:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthworm.htm
http://shs.westport.k12.ct.us/mjvl/biology/dissect/crayfish.htm
http://shs.westport.k12.ct.us/mjvl/biology/dissect/frog.htm
Note: There is a printer-friendly link at the top of each of the pages.
will show that there is a great deal to do. The labs are laid out in terms of systems, with plenty of detail for
each system, including the creation of multiple labeled student diagrams. In addition, the many detailed
images on the lab, as well as the use of the online dissections (which I always have up and running on an
interactive white board during the labs), give the students multiples frames of reference. In addition, a
comparison of the online dissections and the dissection we do in class will illustrate the value of doing the
actual dissection, for I routinely go far beyond what is explored online.
I typically spend at least two full weeks, and often more, doing the dissection of all three specimens (in my
school, that works out to three regular periods and one lab period a week, for a total of 224 minutes a week).
Despite this, there are often areas that we don't have time to complete (especially if you use dissection as a
culminating activity, which then leaves the end of the school year as an absolute deadline). The importance
of the activity is thus reinforced with greater depth than would be surmised if the entire dissection were to be
confined to a single lab period, as is the case with many school classrooms across the country.
Given that students may be at very different points before starting a dissection, one needs to be aware of that
and prepare accordingly. In any classroom there will be students who would never touch a specimen with a
39 1/2 foot pole, and others who can't wait to get elbow deep in them. How do you make a rewarding
experience for such a disparate group of students? That, it turns out, is easier than it sounds. My solution is
a simple one: let the students choose their own partners. If that sounds like a recipe for disaster, let me
elaborate:
(1) Given that the dissection is at the end of the year, the students will have a better sense of your
standards, and are less likely to take advantage of the situation.
(2) Then, give them a very specific limitation: at least one of the two must be willing to do the
physical dissection. Both students must be there to observe, diagram, and answer questions, but no
student will be required to physically dissect. That takes a tremendous pressure off the hesitant
student, many of whom, in my experience, end up participating in the dissection before the two
weeks are up!
(3) Choosing their own partners also has a divide and conquer effect, as the students are not alone
with another reluctant student, and their partner, once again a partner of their choice, will be
supportive of the hesitant student.
In order to make dissection the positive learning experience it should be, it is crucial to set some strong
boundaries. I have heard negative stories regarding dissection, situations which have never happened in my
classroom. All of them seem to follow a lack of preparation prior to the dissection (it is not merely another
lab), and above all, far too much free time on the students' part. A well planned dissection experience is
extremely rewarding, and is also less likely to produce some of the problems other teachers may have.
I always tell my students that there are three ways that I can fail them for the dissection. (NOTE: Although
the threat is quite serious, I have never had to come even close to carrying out the threat. Forewarned is,
indeed, forearmed!) The three things, any one of which will cause student failure, are a follows:
(1) Using the tools improperly (i.e., a scalpel is not a sword). These are serious tools, and they need
to be approached with great care.
NOTE: This is valuable in that the students start off their first dissection with the earthworm. In
essence, after the initial variation in the first several sections (pharynx, crop, gizzard, reproductive
organs, etc., etc.), the earthworm is basically one long intestine! If the students start their initial cut
near the posterior end, then they have a ways to go before they get to the anterior end. Even though
their initial cut will be with a scalpel, subsequent cuts are with rounded dissecting scissors. This
being said, it is still not an easy task to cut the skin without damaging the delicate intestine. As there
is very little variation from segment to segment, any damage they do will not interfere with what they
need to learn from the specimen. This gives them time to work their way forward, and to learn from
their mistakes, to learn to use greater care with the tools.
(2) Treating the animals with disrespect, anywhere from making improper noises to the extreme of
mutilating the specimen. In teaching about life we examine a dead creature, but given that the animal
gave its life so that we might learn, we need to treat the animals with the utmost respect.
(3) Treating EACH OTHER with disrespect. Given that some students are not comfortable with the
idea of dissection, it is important that the classroom environment be one in which the student feels
safe. If they need to stand aside near a window, or step outside for a moment to collect themselves, it
is important that they not be made to feel uncomfortable when they return to the lab station.
Order and Sequence (Organizing your course to lead up to dissection):
In order to have proper time for dissection, it is important that body systems be integrated in one's approach
throughout the year. For example, a unit on cell organelles should include reference to cell differentiation,
and how the number and arrangement of organelles, as well as the form the cell membrane takes, explain
much of the functional difference in cells. This is, of course, best illustrated through examples: the profusion
of golgi bodies in the goblet cells of mucus membranes, the numerous cilia in the tracheal epithelium
pushing the balls of mucus and dust up towards the esophagus, etc.). In each of these examples, the
importance of these structures in the organs themselves help explain the function of the organ (e.g., the
goblet cells humidify the air to help with gas exchange in the alveoli, and the cilia help to clear inhaled
debris before it reaches the alveoli, etc.).
Prior to performing the dissection, I review the body systems. Having incorporated the body systems
throughout the year, however, the review is a reinforcement, rather than a barrage of new information. If
you are approaching body systems for the first time right before dissection, there are some excellent coloring
sheets for body systems in The Biology Coloring Book, by Robert D. Griffin. By connecting every unit to
body systems, I prefer to approach the specimens as individuals, and the students learn through the
evolutionary approach to the specimens how body systems evolved out of simpler structures. In doing so, I
use the coloring sheets for each of the specimens from The Zoology Coloring Book, by Lawrence M. Elson.
I am sure there are other resources out there as well.
In the act of coloring, I give the students the following instructions:
1. All coloring should be done with colored pencils. Crayons are not advisable because they can be
rather mess; felt-tipped pens should never be used because they bleed through the paper, and I copy
onto both sides of the page to save paper. I strongly suggest that you find a brand that is erasable.
Given the fact that there are often a large number of terms to color on any given page, a large set of
colors is helpful, but if you have only a small set, you can distinguish terms and portions of the
diagram using stripes and/or polka dots.
2. The terms have subscript letters that identify the location on the diagram. Each term should be
colored the same color as the appropriate portion of the diagram. Check the diagram carefully, for
more than one area may have the same identifying letter. Also, identical structures, even if unlabeled,
need to be colored in as well.
3. Each term should be colored with a simple, broad swath of color; there is no need to carefully fill in
the terms. In the same sense, if you merely put a small dot to indicate the color, it will be extremely
hard to identify structures, thus making the coloring sheet extremely hard to study from.
4.
The text to the left of the diagrams have also been copied because I thought it too was important. The
same terms identified in the diagrams can be found in italics in the text. You need to color those
sentences or paragraphs that describe the terms with the same color that you used in the diagrams. As
such, you need to color all three places (term, diagram, and text) at the same time. If you go back to
the text, you will not only be less likely to absorb the information in the text, but you may find that
you do not have access to the correct color.
These instructions help to raise the bar well beyond the kindergarten level of coloring. I need to have the
students show me that they have learned something by completing the coloring sheets. Completing the
sheets can be time-consuming, so give the students the assignment at least two weeks in advance, and
perhaps more.
The dissection itself should proceed from external to internal - same as an autopsy. This has the added
benefit of giving the students time to become acquainted with the specimen before any actual cutting begins.
In addition, the features found externally will often generate questions that will be answered upon the
completion of the internal dissection. As you can see from the choice of specimens I made, I approach the
dissections in terms of the evolutionary order of the classes represented: (1) Clitellata - Earthworm, (2)
Crustacea - Crayfish, and (3) Amphibia - Frog. As for the order of the internal systems, that it up to you. I
tend to start with some that are easier to identify, such as the digestive. As they are identifying the organs,
they can do so mainly through moving the organs aside gently, using a blunt probe. To identify the finer
structures of the respiratory or cardiovascular systems, it is necessary to cut away some structures first,
which can damage other structures. Although you should make up your own mind, you can always follow
the order that I use by looking at the handouts listed in the web resources, and those posted on the NSTA
website next to the information for this presentation.
As the students learn more about the nature of the body systems, and the ways in which they fulfill the needs
of each species, needs which vary due to the varied environments in which they live, the students gradually
see the the nature of the evolutionary struggle that led to their existence. The entire experience should
illustrate the idea of evolution, and rather than use the experience as one in which the idea is hammered into
the students’ heads, I prefer to have the evolutionary theme develop slowly over the course of the dissection,
to evolve, as it were. When I have used this method, I have had years when almost every student in the class
deliberately speak of evolution in their conclusion, despite never mentioning it in the instructions for writing
the conclusion.
A Final Note:
At the NSTA Conference in San Francisco, in March of 2011, one of the attendees at this presentation was a
representative of Save The Frogs (http://www.savethefrogs.com). A number of valid points were made
regarding the source of the frogs used for dissection, not to mention the overall ecological threat to
amphibians around the world. Given this, I immediately suggested that another, non-amphibian specimen
might well be a better resource for dissection (an idea the representative accepted), especially if one wants to
use the specimen to highlight the anatomy of the human body. Although there were interesting points raised
by the representative from Save The Frogs, and they were raised in a non-combative manner, the
organization’s website was decidedly anti-dissection.
To me, any organization's anti-dissection crusade (http://www.savethefrogs.com/actions/dissections/) seems
rather like throwing the baby out with the bath water. To the credit of the representative who attended my
presentation, I appreciated that in our exchange of ideas (which is what it was, rather than a confrontation) he
was willing to accept the idea of dissection using other specimens. I can’t truly speak for the organization as
a whole (the anti-dissection message may actually be more of a means to garner support, rather than the
actual final outcome desired), but I can safely say that the representative I met, once again to his credit, did
not approach the issues as black and white.
I have to admit that my use of frogs in dissection was for no other reason than that I had dissected them
myself when I was in high school in the late 1970s, and that they were the preferred specimen at the schools
in which I have taught. Since I started teaching in 1991, I have learned to use some of the differences to my
advantage. For example, the size of the lungs, compared to those of the human, help illustrate not only the
difference between cold-blooded and warm-blooded metabolisms, it also shows the role of the skin in
breathing. The three-chambered amphibian heart, and the blood flow from the heart, illustrate a valuable
step in the evolution of the four-chambered mammalian heart. Also, the location of the testes and the
attachment for the ovaries in the frog, just anterior to the kidneys in the middle of the back, help illustrate a
quirky aspect of human anatomy that I teach in my Anatomy & Physiology course. The blood flow to/from
the ovaries and testes all connect to that same point in the upper back, close to the renal vessels near the
kidneys. The blood flow to/from the penis and the uterus, organs that all evolved much later with the
evolution of mammals and internal fertilization, connect to the pelvic blood flow off of the internal iliac
vessels. There are numerous other connections I make regarding evolution of humans through the dissection
of the frog.
Were my school to switch to a different specimen, and such a switch would require the agreement of all the
biology teachers in my school, I would suggest using a small mammal, such as a mouse or a rat. These
specimens have the value of being mammals themselves, and thus much closer to humans. For some, that
would make the comparison easier, for others, they would feel the loss of comparisons such as those that I
mentioned above, and how they illustrate evolution so beautifully (to be fair, there are beautiful examples of
evolution in a mammal to mammal comparison as well). In making the decision to switch to either a mouse
or a rat, it is helpful to consider factors such as size and cost. The mouse is smaller than many frogs
available, but also cheaper. The rat is a much better size, but a bit more expensive than some of the frogs.
As for my making an equivalent dissection lab page that illustrates the anatomy of a mouse or a rat, I
unfortunately do not yet have access to good image resources for use in building such a page at the moment,
and I would thus recommend using an outside resource.
For each of you, I would suggest following your own instincts before making your choice of specimen.
Regardless of what you decide to do, I suggest you look into using multiple specimens (as in the three
specimens I use, all of which belong to different phyla), for the use of such variety, in and of itself, is truly
the best way to showcase the wonders of evolution.
Web Resources:
Feel free to use these pages as is, or adapt as you see fit. (NOTE: If you adapt it, given that I paid a
subscription fee which allows me to use the images I included in the labs, you will need to include a link to
my original lab page). All of the following are web pages that I constructed:
A Note on Dissection in Biology and the Supplies Required:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/dissection.htm
Earthworm Dissection:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthworm.htm
Note: There is a printer-friendly link at the top of this page.
Crayfish Dissection:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/crayfish.htm
Note: There is a printer-friendly link at the top of this page.
Bullfrog Dissection:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/frog.htm
Note: There is a printer-friendly link at the top of this page.
Mouse and/or Rat Dissection:
Due to not having access to good labeled diagrams showing the dissection of
either of these specimens, I have not yet built a page for either specimen.
That may, however, happen at some point in the future.
Final Lab Report:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/dissectionlab.htm
Note: This page contains links to all the labs above,
including the printer-friendly links for each lab.
NSTA Presentations, both past and present:
http://shs.westport.k12.ct.us/mjvl/lazaroff/nsta.htm
Note: This page contains links to handouts from all my presentations
at NSTA Conferences (Boston 2008, New Orleans 2009, Philadelphia 2010,
and San Francisco 2011). Most are PDF files, and they cover courses
including Biology, Anatomy & Physiology, and Forensics.
Use them in good health!
A Note on Dissection in Biology
and a
Note on Supplies Required
Return to Mr. Lazaroff's Biology
DISSECTION
I require all my students to be present and participate during dissection labs. This does not, however, mean that
every student must physically dissect the specimens. I allow all of my students to choose their own dissection
partners, as long as at least one of you is willing to do the physical dissection work. In doing it this way, I have
found that it not only respects each student's comfort level, but that it also allows students who are uncomfortable to
observe, diagram, and, above all, learn, all the while near a trusted student!
NOTE: Students work in pairs; if there is an odd number of students (not to be confused with a number
of odd students . . .), then there will be one group of three.
I love animals, and I have two pets at home (one dog and one cat), and I got my start through studying animal
behavior at the San Francisco Zoo. I find that my appreciation of, and respect for the animals, increases every year,
as a result of the dissections. Your animals may get sick one day, and you will need to take them to the Vet.
Veterinarians, who clearly love animals, must learn all about their patients, and dissection is a crucial aspect of their
learning. Even if you don't have pets, you or someone you love will need to see a doctor someday, and an
understanding of your body, which is in many ways very similar to the animals we dissect (Earthworm, Crayfish, &
Frog), will be crucial to you. Students who dissect are more likely to understand their bodies, and will thus be better
prepared when future medical issues arise.
I want my classroom to be a place in which people feel comfortable, a place where people feel safe to return the next
day. Given that some students are uncomfortable with dissection, it is mandatory that we show some respect toward
our animal specimens. As such, anyone who purposefully mangles a specimen will fail that dissection . This also
holds true for anyone who uses tools unsafely, or, in any way, contributes to another student's discomfort. In the
past, I have never had to fail a student for breaking these rules, and I you are going to help me maintain that winning
streak. Student have always learned a tremendous amount from the experience, and they have had a lot of fun as
well. Remember, students who are uncomfortable may need more time to get used to the activity; let's all give each
other the respect we all deserve!
SUPPLIES FOR DISSECTION
REQUIRED:
(A) One Pair of Kitchen Gloves for dissection. The thicker rubber and the longer size is better protection for your
hands and wrists. Write your name on each glove with a permanent marker.
(B) One "Ziploc" or similar style plastic bag (for holding the gloves). Write your name on the bag with a permanent
marker.
(C) A pencil to leave in the classroom, to be used ONLY for dissection diagrams and notes! (That way you won't
absent-mindedly put that pencil in your mouth outside of class!)
(D) Your decision as to whom is in your group!
OPTIONAL:
(A) A small bottle of hand lotion. By applying hand lotion prior to dissection, you will be less likely to have any of
the odors attach themselves to your hands. Fear not; we will, of course, wash our hands prior to leaving the
classroom. The lotion, however, adds an extra barrier for your hands (i.e., hands . . . lotion . . . glove . . . specimen).
(B) An old shirt. We will have aprons for you to use, but this, once again, is an extra layer of protection.
http://shs.westport.k12.ct.us/mjvl/biology/dissect/dissection.htm
Earthworm (Oithwoim?) Dissection
Image purchased by Mr. Lazaroff, by subscription, from http://www.clipart.com
Return to Mr. Lazaroff's Biology
Earthworm
Crayfish
Frog
Final Lab Report
It costs me never a stab nor squirm
to tread by chance upon a worm.
"Aha, my little dear," I say,
"Your clan will pay me back one
day."
- from Thought for a Sunshiny
Morning
by
Dorothy Parker
Images purchased by Mr. Lazaroff, by subscription, from http://www.clipart.com
Virtual Earthworm Dissection
Image borrowed from the Virtual Dissection website above
By Day: Day 1 Day 2
By Topic/Region: External Anatomy Internal Anatomy
Skeletal
Lymphatic Integumentary
Cardiovascular
Muscular Endocrine Nervous
Reproductive
Respiratory Excretory Digestive
S L I C M E N R R E D
(SLIC Woims R RED?)
NOTE: The Systems in Italics above have their functions taken up by
other systems.
You must create a series of labeled drawings that ilustrate the structures outlined below:
Materials:
1.
2.
3.
4.
5.
6.
7.
Safety Goggles
Apron
A pair of medium thickness rubber Kitchen gloves (with your name on each), as per the Class Rules
A Ziploc-style bag (with your name on it) in which to keep your gloves, as per the Class Rules
A PENCIL (keep this in your Ziploc-style bag aboce, due to the chemicals)
An old small towel, as per the Class Rules
OPTIONAL An old long-sleeve shirt (for use under our lab aprons), as per the Class Rules
8. Tool Tray with:
(a) Forceps (your second-most valuable tool)
(b) Pointed Scissors (use with care, or you might damage your specimen)
(c) Rounded Scissors (use with the rounded end down)
(d) Scalpal (to be used very sparingly)
(e) Blunt Probe (your most valuable tool)
(f) Pins (use only a few)
(g) Bone Cutters (used the least, and only on the frog)
9. Dissection Tray
10. Plastic Dissection Tray Cover
11. Masking Tape & Pen (for labeling the tray cover)
12. Pencil & Paper (for making your diagrams) - NOTE: Pen will NOT be accepted!
13. Have I forgotten something . . . Oh, yes . . . an EARTHWORM!
Day 1
Image purchased by Mr. Lazaroff, by subscription, from http://www.clipart.com
External Anatomy
1. Place the specimen prone (ventral surface down, dorsal surface upon the
dissecting tray. (To what phylum does it belong? What is your evidence
for that?)
2. Note the difference in coloration. Why is the dorsal surface of the skin
darker?
3. Find the anterior and posterior ends and the clittellum (the wider portion,
which is closer to the anterior surface).
4. Count the number of segments. (How many are there in front of the
clittelum? In the clitellum? Behind the clitellum?)
5. Using the Dissecting Microscope, place the tray on the stage, and draw:
(a) the mouth (What do they eat? What does the soft texture of the
mouth
say about their diet?)
(b) the anus (What type of digestive system does it have, One-Way, or
Two-Way?)
(c) the setae, which are the dark projections on each section (How many
setae are there on each section? What purpose do the setae serve?)
(d) the sperm duct opening (Which segment is it on?)
(e) the oviduct opening (Which segment is it on? Given the existence of
both,
what type of creature is it? Given the location of both, is the
creature
likely to self-fertilize? What type of fertilization does it practice,
internal or external?)
6. CLEAN-UP CLEAN-UP CLEAN-UP CLEAN-UP CLEAN-UP
CLEAN-UP
7. Wipe off the dissecting microscope stage with a slightly moist paper towel
(if necessary) and dry it thoroughly.
8. Cover your entire specimen with a wet (not just moist) paper towel.
9. Using masking tape and a pen, write your name and your partner's name on
one of the plastic specimen tray lids.
10. Place the lid snugly on the tray and place the trays neatly on the middle
table in the back of the room.
11. Rinse off the tools and dry them thoroughly before returning them to the
Image purchased by Mr. Lazaroff, by subscription, from
tool tray.
http://www.clipart.com
NOTE: This clean up technique will be the same for all dissection days
except the last day for each specimen, described below.
Day 2
Image purchased by Mr. Lazaroff, by subscription, from http://www.clipart.com
Internal Anatomy
1. Place the specimen prone (ventral surface down, dorsal surface up)on the dissecting tray.
2. Using a scalpal, make a shallow medial incision only 1 cm long on the dorsal surface 1/3 of the way from the posterior
end.
3. Given that scalpals cut downward, and scissors can be lifted to cut upwards, you will use scissors to cut all the way
toward the anterior end. TAKE CARE NOT TO CUT INTO THE INTESTINE. (What do earthworms eat? Given that,
what color would you expect the contents of the intestine to be?)
o
4. Using dissection pins placed at a 45 angle from the tray, pin back the skin of the earthworm along the anterior third of
the specimen. (To what body system does the skin belong? Given the earthworm's form of locomotion, what else are
you pinnning back, and to what body system do they belong? Lastly, this system takes up the function of what other
system?)
NOTE: All subsequent diagrams need to use the dissecting microscope.
5. Identify and diagram the Nephridia (singular = Nephridium). (What is their function? What is the equivalent organ in
humans, and to what body system does it belong? Is the fact that they are in pairs in the worm at all retained in our
body?)
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6.
Identify and diagram the Pharynx & Esophagus. (What is the one function of the two organs? How is their function
similar in humans, and how is it different?)
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7. Identify and diagram the Gizzard & Crop. (Which of the two is harder? What does that say about its function?)
8. Identify and diagram the Doesal Blood Vessel and the 5 Aortic Arches. (What role do the arches play in the worm?
What is the equivalent organ - be careful here - in humans, and to what body system does it belong? Why do humans
have less than five?)
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9. Given that the earthworm's skin must be kept moist, and what organs that appear in humans appear to be missing in the
earthworm, what body system's function is taken up here by the skin?
10. Identify and diagram the Seminal Vessicles and the Seminal Receptacles. (What is the function of each? What are the
equivalent organs in humans, and to what body system do they belong?)
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11. Identify and diagram the Suprapharyngeal Ganglia. (What is its function? What is the equivalent organ in humans, and
to what body system dos it belong? Has the bilateral appearance been retained in humans? If so or if not, what is it
about the human organ that supports your statement? You will need to refer to specific structures in your answer
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12. Remove the intestine from the point where you started your incision. (It might help to gently cut the intestine at one end
with the scalpal; be careful not to cut all the way through the worm.) On either the underside of the intestine, or on the
bottom of the worm - depending on how gently you lifred up the intestine, you will find the Ventral Nerve Cord.
Diagram it. (What is - be specific as to direction - its function? What is the equivalent organ in humans, and to what
body system dos it belong? What aspect of this organ differentiates the earthworm from members of our phylum?)
Note the two layers of muscle, Circular and Longitudinal, that make up the wall of the organism. It is the
alternating contraction of these two layers that make it possible for the earthworm to propel itself through
the soil. As these two layers pull against each other (i.e., acting as an anchor for the opposing
contraction), what other body system's function is taken up my the muscles here?
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13.
14.
15.
16.
CLEAN-UP CLEAN-UP CLEAN-UP CLEAN-UP CLEAN-UP CLEAN-UP
Wipe off the dissecting microscope stage with a slightly moist paper towel (if necessary) and dry it thoroughly.
Dispose of the worm, and any worm parts in the one trash can specified by the teacher.
Rinse off the tools and dry them thoroughly before returning them to the tool tray.
Rinse off the lid and and the tray and stack them as seen in the picture below.
o
Note: the trays need to be placed upside down at 90 angles to each other, with one edge of the bottom tray over the
edge of the sink to allow all of the trays to air-dry!
Image by Mr. Lazaroff
NOTE: This clean up
technique will be the same
on the last day for each
specimen. At the end of
each regular dissection day
prior to the last day for
that specimen, you will be
using the clean up
technique described
above.
Clean up:
Normal Day Clean Up
Technique
Last Day Clean Up
Technique
Drawings:
1. Use a PENCIL!! NOTE: Pen will
NOT be accepted!
2. Make the drawings "larger than life" size, as the specimens are so small.
3. Draw the general shape (outline) and location of the organs, as the squiggles so many of you use to
"shade" your drawings make your drawings sloppy and hard to interpret.
4. Include Labels on all drawings.
Labels should start outside the drawing, and be connected to the structure by arrows
with tips (===>).
The Tip of the arow should be touching the structure.
Be sure to include the magnification for any drawings done with the dissecting
microscope.
Hang on to the drawings; they will all be handed in later, together with some questions to answer.
Day 2
Top
Return to Mr. Lazaroff's Biology
Day 1
Crayfish Dissection
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Return to Mr. Lazaroff's Biology
Earthworm
Crayfish
Frog
Final Lab Report
. . the term 'roaches of the
sea' reflects the behavior
of lobsters as omnivorous
scavengers.
Cockroaches will eat
almost anything organic
and so will lobsters . . .
. . . So much for the
delicious taste of lobster?
- Taken from the Biology
Department at the
University of
Massachusetts Amherst
http://www.bio.umass.edu
/biology/kunkel
/cockroach_faq.html#Q11
Image at right purchased
by Mr. Lazaroff, by
subscription, from
http://www.clipart.co
Virtual Crayfish Dissection - Cornell
Virtual Crayfish Dissection - Penn State
Just for Fun . . . visit The Crayfish Corner
Images borrowed from the virtual dissection websites above
By Day: Day 1
Day 2
Day 3
By Topic/Region: External Anatomy Internal Anatomy\
Skeletal
Lymphatic Integumentary
Cardiovascular
Muscular Endocrine Nervous
Reproductive
Respiratory Excretory Digestive
S L I C M E N R R E D
(SLIC Crayfish R RED?)
NOTE: The System in Italics above have their functions taken up
by other systems.
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You must create a series of labeled drawings that ilustrate the structures outlined below:
Day 1
I. Abdomen - Ventral View
(Day 1)
top
Place the crayfish supine (ventral surface up) on the dissecting tray and DRAW the following:
1. Telson (What is the telson's function?)
2. Uropod (Describe the location of the uropods to the telson. How do the add to the telson's
function?)
3. Anus (In which of the two structures above did you find the anus? 1 or 2 way digestive
system?)
4. Swimmerets -numbered in pairs, 1-5 w/ the 5th one the most posterior (What is their function,
and how is it different from the telson's function?)
5. Is your Crayfish a male or a female (Note the anterior-most swimmeret. In the male, its
function is to guide the sperm toward the female during copulation; as such, it will be
enlarged, and pointed anteriorly in the male. In the female there is no difference between the
swimmerets)? (Describe the appearance of the crayfish's swimmerets in your answer.)
6. Walking Legs (How many are there? In terms of this feature alone, is this organism closer to
an insect, or an arachnid?)
7. Chelipeds - some people like this meat the best . . . (What is their function?)
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II. Head - Ventral View
(Day 1-2)
top
1. Mandibles - 2 - hard & white (What are they equivalent to in
humans? How is their action - think direction of movement different from that of humans?)
2. Maxilla - softer w/ jagged edges (Given the difference in
texture, how is their function different from that of the
mandibles?)
3. Maxillapeds, or "mouth-feet" -3 pairs (What is their function?
Why not use the Chelipeds?)
4. Green Gland Ducts - (From what organ do they open out?
What is the equivalent organ in humans? What is the purpose
of the duct? Is its location at all disturbing to you?)
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II. Cephalothorax - Dorsal View
(Day 1-2)
top
1. Rostrum (What is cephalization? Given that, what organ would you expect to be inside the rostrum?)
2. Eyes (Does this organism have binocular vision - depth perception, why or why not?)
Eye
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3. Carapace (What is the function of the carapace? What two body systems in humans perform equivalent funtions? The support function is in reference to one
system in particular; given the external loaction of the carapace, explain the name of the type of system compared to our own, internal variety. The support
function implies specifically the attachment of organs of what body system to the inside of the carapace?
Day 2
Make a Dorsal Midline Incision from the posterior end of the thorax to the posterior end of the rostrum using the rounded scissors w/ the
rounded end down! Open the carapace and pin it back.
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III. Thorax - Dorsal View, Part I
(Day 2)
top
1. Heart & Ostia - the opening on the heart's superior surface (Is this a sign of an open or closed circulatory system? Differentiate between the two in your answer.)
2. Gills (What are they equivalent to in humans? To what body system do they belong? Why are the gills so feathery - i.e., how does this aid in their function?)
3. Cardiac Stomach -draw whole (There appear to be fibers attached to the outside of the stomach. What is their purpose in relation to the stomach and the
esophagus?)
IV. Thorax - Dorsal View, Part II
(Day 2)
top
1. Remove one gill and draw on high power (What is the red/pink material within each "finger" of each gill? How does this material relate to the function of the
gill?)
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2. GENTLY remove one walking leg, and you will see that a gill is attached to each walking leg. (How is this important to the function of the gills? In your answer
refer to the different requirements of the body during times of high physical activity, and how they are related to the gill-walking leg connection.)
3. Cut open the Cardiac Stomach and draw the Gastric Mill - reddish-browb lateral "teeth" - on high power (What is their function? What type of digestion involves
the gastric mill? Do we accomplish that type of digestion in our own stomach?)
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Day 3
V. Thorax - Dorsal View, Part III
(Day 3)
top
Gently remove the Heart.
1. The Intestine (Given its location posterior to the stomach, what is its function? What function of the stomach is lacking in the intestine?)
2. The Hepatopancreas Gland (What two organs is this equivalent to in humans? What are some of the functions of this gland? How is its location important to its
function?)
3. The Seminifierous Tubules or Ovaries (What is the function of each? To what body system do these belong? Which of the two does your spceimen contain? How
is this related to the swimmerets?)
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VI. Thorax - Dorsal View, Part IV
(Day 3)
top
Gently remove the Cardiac Stomach.
1. Esophagus (Describe how it's position relative to the stomach is different from the worm and the human.)
2. Green Gland (What is/are the equivalent organ(s) in humans? Do/does the analagous organ(s) appear in pairs in humans? To what body system do the green
glands belong? What organ in our equivalent body system is missing in the crayfish?)
3. Brain (Describe the appearance of the brain and the nerves in terms of the type of symmetry. There are nerves that are attached to the front and the back of the
brain. Describe the function of both the anterior and the posterior nerve pairs.)
VII. Abdomen - Dorsal View, Part I
(Day 3)
top
Make a Dorsal Midline Incision from the anterior end of the abdomen to the posterior end of the abndomen using the rounded scissors w/ the
rounded end down! Open the exoskeleton and pin it back.
In order for a Crayfish to determine BALANCE, it must insert a grain of sand in one of it's appendages.
Every time it molts and makes a new exoskeleton, it must get a new grain of sand!
(In what part of the body is that function taken up by the human body?)
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1. Dorsal Blood Vessel (Is this vessel sending the blood to, or away from, the heart? What name would we give to that type of vessel in our body?)
2. Large Intestine (How is the location of this organ related to the name of this section of the body [it is NOT a tail]? What is the function of the large intestine?
Given it's contents, is it wise, or unwise, to eat it when eating a lobster? Explain.)
3. Abdominal Flexor Muscles (How do muscles function, by shortening, lengthening, of both? Moving the abdominal flexor muscles will cause flexion, but what is
flexion? How will the abdomen - it is NOT a tail - change shape during flexion? What direction will the crayfish move during flexion? Given the size and strength
of the muscle, during what circumstances would the crayfish use this muscle over its walking legs?)
VIII. Abdomen - Dorsal View, Part II
(Day 3)
top
Gently remove the Abdominal Flexor Muscles.
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1. Ventral Blood Vessels (Given that there is no main ventral blood vessel, how does the blood return to the heart? Is this a sign of an open or closed circulatory
system?)
2. Ventral Nerve Cord (To what phylum does the crayfish belong? How is the location of the nerve cord different from creatures in our own phylum? Name our
own nerve cord. How is the protection of the nerve cord different in both phyla?)
Drawings:
1. Use a PENCIL!!
2. Make the drawings "larger than life" size, as the specimens are so small.
3. Draw the general shape (outline) and location of the organs, as the squiggles so many of you use to "shade" your drawings make
your drawings sloppy and hard to interpret.
4. Include Labels on all drawings.
Labels should start outside the drawing, and be connected to the structure by arrows with tips (===>).
The Tip of the arow should be touching the structure.
Be sure to include the magnification for any drawings done with the dissecting microscope.
Hang on to the drawings; they will all be handed in later, together with some questions to answer.
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Day 1
Day 2
Day 3
top
Return to Mr. Lazaroff's Biology
Bullfrog Dissection
Click Here to hear HOW MUCH IS THAT FROGGY IN THE WINDOW!
Return to Mr. Lazaroff's Biology
Earthworm
Crayfish
Frog
Final Lab Report
Click on the picture to hear me sing!
(from the WB Website)
Try These
Online Frog
Dissection Links:
The Virtual
The ONLINE
Frog Dissection
Frog Dissection:
Kit:
The Interactive Frog
Dissection (2002):
http://www-itg.lbl.gov
/vfrog/
http://www.aa.psu.edu/
biology/frog/
See a MOVIE from the
site above!
http://curry.edschool.virginia.
edu/go/frog/Frog2/
Cornell
University's
Frog Dissection
Froguts.com
The Interactive Frog
Dissection (1994):
DEMO only
(Click the DEMO Link)
http://www.froguts.com/
http://biog-101-104.bio.
http://curry.edschool.Virginia.
cornell.edu/Biog101_104
EDU/go/frog/menu.html
/tutorials/frog.html
BY DAY: Day 1 Day 2 Day 3 Day 4 Day 5 Day
6
BY TOPIC: External Anatomy Skin Removal Inside the
Mouth
Skeletal
Lymphatic Integumentary
Cardiovascular
Muscular Endocrine Nervous
Reproductive
Respiratory Excretory Digestive
SLIC MEN R RED
(SLIC Frogs R RED?)\
You must create a series of labeled drawings that illustrate the
structures outlined below:
Day 1
top
I. Head - Dorsal View
(Day 1)
top
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1. Eyes (What does their angle imply about depth perception? What can you say about the frog's niche by looking at its eyes?) More about the eyes.
2. Tympanum (What does the lack of pinna imply about hearing? What is the scientific term for the ear drum? Does the name "ear drum" make you think of the
Grinch?)
3. External Nares (Which implies the existence of . . .? What is their function? The tube - between the external and __ nares - in mammals is much longer; what
is accomplished in this longer tube? What is required on the inner surface of the tube to accomplish this?)
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II. Body - Dorsal View
(Day 1)
top
Skeletal System
top
SLIC MEN R RED
1. "Ribs" - it is not a ribcage! (What organs are within, and protected by, our ribcage?) NOTE: In reality, there are no ribs; these are merely the transverse processes of the vertebrae.
Our ribs attach
to the transverse process, and 7 of the 12 also attach directly to the sternum ["true" ribs], the next three attach indirectly ["false" ribs], and the last two do not attach to the sternum at all [also "false" ribs, but specifically "floating" ribs].
2. Pelvis - note the width and height up the back (The shape is very different from ours. Comparing the shape of our species and theirs, explain how certain body
characteristics - name them as well - account for this pelvic difference?)
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3. "Hand" (How many fingers? Looking at their arrangement, are the hands capable of much of a grip, or of detailed movement?)
4. Is your specimen a FEMALE or a MALE? Believe it or not, it is easier to tell by looking at the hands (See below)!
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5. Foot (How many toes? How are they different from the fingers? Which has more webbing, the hand or the foot? What does this say about their locomotion?)
6. Legs (What does their length and width imply about their use? In your answer, also make reference to the arms for comparisons sake.)
By the way . . .
. . . need a hand? Or a foot?
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Click on the Skeleton
to Enlarge and Print . . .
(from the Virtual Frog Dissection Kit: http://www-itg.lbl.gov/vfrog/)
III. Skin Removal - Ventral View
(Day 1 & 2)
top
Integumentary System
top
SLIC MEN R RED
Make a Ventral Midline Incision from the posterior end of the Abdomen to the Anterior end of the Thoracic Region using the rounded scissors with the
rounded end down!
Continue a Medial Incision, as above, along the Ventral surface of each limb as far as the wrists and ankles.
Using the forceps to lift the Skin, take a scalpal and gently cut the fascia with the blade parallel to the muscle beneath.
Remove the skin so as to leave the frog with a "hood," "gloves," and "socks." [sic]
It should be possible to remove the skin "in one piece!"
Pay Close Attention to the places on the body where the underside of the skin is much more firmly attached.
Pay Close Attention to the Blood Vessels on the underside of the skin. DIAGRAM THE PATTERN OF THE BLOOD VESSELS, AND THE
CONNECTION THROUGH THE MUSCLE TO THE SKIN!
Day 2
top
III. Skin Removal Continued- Ventral View
(Day 2)
top
Continue as above . . .
We will conclude this today so as to view the muscles beneath . . .
Draw the following:
1. The pattern of blood vessels on the underside of the frog's skin. (What does this say about the nature of the skin? What function does the frog's
skin have that ours lacks? How does that function impact upon the frog's choice of habitat? What is it about our skin, and our body as a whole,
that makes it impossible for us to have the same skin function?)
2. The pattern of coloration on the dorsal surface of the skin. (What does this say about one of the functions of the skin? How, and why, is the
coloration different on the ventral surface?)
3. The way the blood vessels, nerves, and lymphatics connect to the skin (i.e. passing through the muscle to get to the skin). (What are the nerves
for? What are the lymphatics for?)
4. (Why was the skin so much more firmly attached, stronger connective tissue, in some areas - e.g., the elbows, knees, and hips? Think in terms or
repetitive motion, and what would happen if the skin were not attached strongly in those places.)
Day 3
top
Muscular System top
Ventral Dorsal Arm Leg
. . . be able to describe how the body's position
changes whenever the muscle contracts . . .
SLIC MEN R RED
IV. Muscles - Ventral View, Part I
(Day 3)
muscles
top
1. Pectoralis (To what bones does it attach? Specifically, how does it move the body?)
2. Deltoid (To what bones does it attach? Specifically, how does it move the body?)
3. Rectus abdominus (To what bones does it attach? Specifically, how does it move the body?)
4. External oblique (To what bones does it attach? Specifically, how does it move the body?)
5. Submaxillary (To what bones does it attach? Specifically, how does it move the body?)
V. Muscles - Dorsal View, Part I
(Day 3)
muscles top
1. Depressor mandibulae (To what bones does it attach? Specifically, how does it move the body?)
2. Deltoid (To what bones does it attach? Specifically, how does it move the body?)
3. Latissimus dorsi (To what bones does it attach? Specifically, how does it move the body?)
4. External oblique (To what bones does it attach? Specifically, how does it move the body?)
5. Common extensors of the back (Why aren't there any flexors along the spine?) (To what bones does it attach? Specifically, how does it move the body?)
6. Gluteus (Yes . . . it's what you think it is . . . and why is it so small in comparison to us . . . it's related to the muscle's function . . .?) (To what bones does it attach?
Specifically, how does it move the body?)
VI. Muscles - Arm
(Day 3)
muscles top
1. Common flexors (ventral) (To what bones does it attach? Specifically, how does it move the body?)
2. Common extensors (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
3. Triceps brachii (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
VII. Muscles - Leg . . . to go!
(Day 3)
muscles top
1. Triceps femoris [. . . Quadriceps in humans . . .] (To what bones does it attach? Specifically, how does it move the body?)
2. Sartorius (ventral) (To what bones does it attach? Specifically, how does it move the body?)
3. Gracilis Major (ventral) (To what bones does it attach? Specifically, how does it move the body?)
4. Semimembranosus (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
5. Gracilis Minor (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
6. Biceps femoris (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
7. Tibialis Anterior (To what bones does it attach? Specifically, how does it move the body?)
8. Gastrocnemius (To what bones does it attach? Specifically, how does it move the body?)
9. Peroneus (dorsal) (To what bones does it attach? Specifically, how does it move the body?)
10. Achilles Tendon (Not a muscle, of course) (To what bones does it attach? Specifically, how does it move the body?)
Day 4
top
VIII. Abdomen - Vental View, Part I
(Day 3)
top
You will be making a Classic "I" Incision.
1. Make a Ventral Midline Incision through the abdominal muscles from the posterior end of the Abdomen to the Anterior end of the Thoracic Region using the rounded scissors with the
rounded end down!
2. Continue with a Lateral Ventral Incision through the abdominal muscles from "armpit to armpit," and along the base of abdomen from "hip to hip." [sic]
Using the forceps, open the abdomen by lifting the muscle flaps and pinning them against the dissection tray. The muscle flaps will thus appear as 2 "barn doors."
Make a diagram of the abdomen as you see it. Be sure to label (indicate also what system each organ belongs to)and locate the following:
1. Heart (The liver is right below the heart in your frog. In our bodies, what is between the heart and the liver? To what body system does this division provide
the most help? What function does this division perform? Given the lack of this division in the frog, what part of the frog's body performs this same function?)
2. Lungs (Why are they so much smaller, proportionately, than ours? Given the lack of a ribcage, how are the lungs protected - i.e., by what bones - in the frog?)
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3. Liver (How many lobes does it have? Explain why it is so big by referring to its functions.)
4. Stomach (What organ empties into the stomach? Into what organ does the stomach empty?)
5. Small Intestine (This implies the existence of ___? What is the first part of the small intestine called? What one basic function, among all of the digestive
organs, is found only in the small intestine?)
6. Fat Bodies (What is their function? To what area, and to what type of tissue, are they attached? Given that humans don't have them, where do we put most of
our fat?)
7. Any other organs you see (all of which will be discussed later) . . .
IX. Abdomen - Vental View, Part II
(Day 3 & 4)
top
Digestive System
top
SLIC MEN R RED
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Liver - Draw the following:
1. Gall bladder (Why is the organ hollow? What, and don't say gall, does it contain? What is the function of that substance?)
2. Cystic duct (What two organs does it connect? What material transports along the tube? What type of organ is it, endocrine or exocrine? Be sure
to define the two terms in your answer.)
3. Common bile duct (What three organs does it connect? Which of the three organs is the final organ - and hence the location of the substance's
action - for the substance above?)
Stomach
1. Make a Medial Incision along the stomach (DO NOT SEPARATE THE STOMACH FROM THE BODY!) and open it to view the inside.
2. Is your specimen "Packing a Lunch?" If so, can you identify it's "last meal?" Given the contents, what can you say about the animal's niche?
Does this agree with or contradict what you said about the eyes? How does your answer relate to food webs?)
3. Diagram the Rugae - folds (What is the purpose of the rugae? To best answer this question, compare the stomach of a "full" vs. a "hungry" frog.
Compare also the thickness of the walls in the full and empty stomach. What are the functions of the stomach? Given that, what type of tissue is
in the stomach walls.)
Small Intestine
1. Find the connective tissue between the loops of the small intestine - the Intestinal Mesentery (What is the function of the mesentery?)
2. Diagram the various structures within the mesentery (Blood vessels, lymphatics, and nerves: describe the function of each in terms of the small
intestine - and relate it to the function of the small intestine!)
Find my favorite organ . . . can you guess it? . . . the pancreas. Find also the pancreatic duct (a tube connecting the pancreas to the small intestine). (How is
this tube related to one of the functions of the pancreas? What other function of the pancreas makes that organ my favorite organ? What other system does
the pancreas connect two in fulfilling this latter function?)
Large Intestine (Why is it so much shorter than the small intestine? - Hint . . . it is related to the organ's function!)
Cloaca - Pay attention to where you see this organ again (What is its location, and how is this related to the final function of the large intestine?)
Day 5
top
X. Thoaracic Region - Ventral View
(Day 5)
top
Cardiovascular System
top
Removing the Heart
SLIC MEN R RED
Make a ventral, midline incision up to the base of the neck, using the rounded scissors as usual. It may be a bit tough due to the
sternum.
Make a ventral diagonal incision from the armpit region to the end of the incision above,using the rounded scissors as usual.
Remove all of the muscle and bone to reveal the heart and lungs.
Draw the following:
1. Heart - 3 chambered
a. Ventricle - there is only one (What sort of impact does this have on the function of the heart, compared to our four-chambred heart?)
b. Left & Right - remember: it's always the patient's left - Atria - singular = atrium (Why are the atria so much smaller than the ventricle? HINT:
Think in terms of the distance the pumped blood travels before it returns to the heart.)
c. (What are the three circuits in the frog's circulation? Do we have the same 3 circuits, or do ours differ?)
2. Lungs (Note the size. They are, unlike our lungs, smaller in comparison to the size of the heart. Explain the reasons - there are two - for this size
difference.)
3. Trachea (What is the function of the rings of cartilage? Why does no other tube - digestive, vascular, etc. - need these rings? The trachea divides
into two structures called ____; these structures go into the ____?)
Using the probe, gently remove the connective tissue surrounding the vessels above the heart. Then draw the following:
1. Pericardium (What is its function? HINT: it is related to the type of membrane of which it is made, and the specific fluid that the membrane
makes.)
2. Conus Arteriosus (To what chamber does it attach? To what circuit(s) does this vessel provide blood? What is the oxygen concetration of the
blood - high, medium, or low? What is the color of the blood?)
3. Coronary Artery (What is the oxygen concetration of the blood - high, medium, or low? What is the color of the blood? To what circuit(s) does
this vessel provide blood?)
4. Systemic Arch (What is the oxygen concetration of the blood - high, medium, or low? What is the color of the blood? To what circuit(s) does this
vessel provide blood?)
5. Pulmocutaneous Arch - to the lungs (What is the oxygen concetration of the blood - high, medium, or low? What is the color of the blood? To
what circuit(s) does this vessel provide blood?)
6. Pulmonary Artery - as above, but entering the lungs (What is the oxygen concetration of the blood - high, medium, or low? What is the color of
the blood? To what circuit(s) does this vessel provide blood?)
7. Pulmonary Veins - as above, but leaving the lungs (What is the oxygen concetration of the blood - high, medium, or low? What is the color of the
blood? To what circuit(s) does this vessel provide blood?)
8. Sinus Venosus (What is the oxygen concetration of the blood - high, medium, or low? What is the color of the blood? To what circuit(s) does this
vessel provide blood?)
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Inside the Mouth
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Using the rounded scissors, cut open the corners of the mouth and pin the mouth open. Draw the following:
1. Maxillary Teeth (Given the name, on what portion of the mouth are they found? What is their function?)
2. Vomerine Teeth (On what portion of the mouth are they found? What is their function?)
3. Internal Nares (Into what portion of the mouth do they open? Into what portion of the mouth do ours open? Given that the brain is above, and
behind, the eyes, what other function, besides breathing, do the nares have?)
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4. Underside of the Eyes
a. push gently upward from below and the eyes "bug out!"
b. more about the eyes.
c. (You were able to push the eyes up; the frogs are able to push them down into the oral cavity. What purpose does this serve? What body
system does this aid?
5. Glottis
a. place a blunt probe down this and you will see it move
into the trachea! (What is its function? To what body system does it belong?)
6. Esophagus
a. place a blunt probe down this and you will see it move
into the esophagus! (What is its function? To what body system does it belong?)
7. Eustachean tube
a. place a blunt probe up this and you will see it move
the tympanum! (What function does this tube provide? How does the function of this tube relate to the effectiveness of swallowing in
relieving ear pressure during airplane flights?)
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Day 6
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XI. Thoaracic Region - Ventral View, Part II
(Day 6)
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Remove the heart by cutting the blood vessels above it and removing it from the chest.
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1. Place it flat on your dissecting tray with the ventral surface up.
2. Make a cut parallel to the tray through the heart.
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3. Open up the heart and draw the inside under the dissecting microscope and label the three chambers. (Why are 4 chambers better? How can a
frog survive with only 3 [i.e. how are they different from us?]?)
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Draw the chest with the heart removed and label the trachea, the bronchi, and the lungs.
Respiratory System
SLIC MEN R RED
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Place a probe down the glottis to see it emerge in the trachea. Now remove a lung by cutting the trachea right before it branches to the two bronchi.
1. Place it flat on your dissecting tray with the ventral surface up.
2. Make a cut parallel to the tray through the lung.
3. Open up the lung and draw the inside under the dissecting microscope and label the bronchioles. (What are all the tubes within the heart? Other
than being proportionately larger, how do you think our lungs are different?)
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Draw the esophagus and show the connection to the top of the stomach. Place a probe down the opening to the esophagus - the glottis - to see it emerge in the
esophagus.
Using the scissors, cut the most anterior end of the esophagus and the most posterior end of the large intestine.
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1. Gently remove the digestive tract from the body, making sure not to danage the spleen or the testes - for those with a male frog - where it is
connected to the mesentery.
2. Gently cut all the mesentery from between the loops of the small intestine.
3. Stretch out the entire digestive tract and measure its length in centimeters. Now measure the frog's body length in centimeters from the tip of the
jaw to the bottom of the groin - "head to rump". Express the ratio as a GI - gastro-intestinal - tract to Body ratio (i.e. x : 1). (Would you expect
an herbivore to have a similr, larger, or smaller ratio? Explain.)
Cut open a section of the small intestine and draw the inside under the dissecting microscope. (How is it different from the inside of the stomach? How can
you explain those differences [i.e. in terms of the functions of the small intestine]?)
Lymphatic System
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The lymphatic system not only drains fluid in lymphatics, but it also fight infection in organs such as the tonsils and the spleen. (Why does a person infected
with mononucleosis run the risk of having her/his spleen rupture?)
Reproductive System
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Reproductive organs:
1. FEMALE: Draw the oviducts and where they connect to the posterior end of the abdomen. (Why do they connect there? To what structure do
they connmect?)
a. Compare a female frog with small, beige and black oviducts, to a female frog with large black and white oviducts. Explain the difference.
Through what structure are the eggs laid?)
2. MALE: Draw the testes and the vestigial oviducts. (Why are there vestigial oviducts? How is this related to Jurassic park? Where do the testes
connect? Through what structure are the sperm released?)
a. Cut open one of the testes and draw it under the dissecting microscope. (Why does a reproductively fertile male have such small and simple
testes? HINT: refer to the gametes.)
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Excretory System
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Draw the kidneys. NOTE: the kidneys are BEHIND the abdominal wall!!! Cut open the connective tissue so you can see the actual surface of the kidneys.
1. Find and draw the ureters. (Where do they go? What do they carry? Why isn't there a #1 and a #2 in a frog?)
2. Remove a kidney and pllace it flat on your dissecting tray with the ventral surface up
3. Make a cut parallel to the tray through the kidney
4. Open up the kidney and draw the inside under the dissecting microscope and label the renal pelvis (the open area inside. (What collects there?
What structures would you see with a more powerful microscope that do the actual work of the kidney? What is the function of the kidney?).
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Endocrine System
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On top of the other kidney - it's actually on both, but it will be easier to see with the kidney in position - is a pale organ. Renal means "kidney," and the prefix
"ad-" means "on top of." This organ is thus . . . the adrenal gland. Draw it. (What is its function? To what body system does it belong? Given the rapid
response, what body system must control the release of its contents?)
Another endocrine organ is the pancreas. This function of the pancreas is unrelated to the digestive system. The hormones produced are not released into the
small intestine; they are released directly into the bloodstream. (What are the two hormones? What do they do? NOTE: Given Mr. Lazaroff's chronic health
condition, it would behoove you to know the answer to this!)
Nervous System top
Peripheral Nervous System
Central Nervous System
Sensory Organs: Eye Ear
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SLIC MEN R RED
Remove ALL of the remaining organs as well as the connective tissue along the back of the abdominal wall (this is known as then parietal surface). Draw the
following:
1. The vertebrae. (What two basic functions do they perform? HINT: the two functions relate to separate body systems!)
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2. The Spinal Nerves. These travel laterally from either side of the spinal colomun between the vertebrae. (Where do the nerves go after they
disappear inbetween the vertebrae? Where does this - Is it dorsal? Is it ventral? - structure go?)
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Turn the frog onto its ventral surface, so that it's dorsal surface is up (this is known as prone, as in "being prone to fall flat on your face . . ." An organism on its
back, as our frog has been for so long, is known as supine.).
1. Using the scalpal, cut through the bone holding the scalpal parallel to the skull. It is necessary to cut throught the bone in order to expose the brain.
(What value is there to this brain-barrier? Is is related to the vertebrae in function? Which one evolved first: skull or spine?)
2. Note the two sides - dare we call them hemispheres? (Why are there two sides? Which side of the brain controls the left side of the body?)
3. Draw and label the following lobes (and be sure to describe the function of each):
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Forebrain (what else is in the forebrain that is not listed below? And beneath that area? [HINT: the prefix hypo = "below." What
other system is this area of the brain connected to?):
1. Olfactory bulbs (What is their function? Are ours proportionately larger, or smaller? What does this say about the
importance of this part of the brain to our survival?)
2. Cerebrum (What is its function? Is ours proportionately larger, or smaller? What does this say about the importance of
this part of the brain to our survival?)
Midbrain:
1. Optic lobes (Connected to what sensory organ? What area of the brain is the other sensory organ discussed above
connected to?)
Hindbrain:
1. Cerebellum (What does this portion of the brain control? Why does ours need to be proportionately larger than that of
the frog?)
2. Medulla oblongata (What basic body functions does this maintain? Why do we still have one?)
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What structure continues out the back of the brain? (What is the foramen magnum? Where is the frog's foramen magnum? What
does this say about the locomotion of the frog: quadruped or biped? Could you tell the form of locomotion without seeing the legs [i.e.
from the skull alone?]? Explain.)
(Which portion of the brain of those listed above has expanded the most in humans? Given the relative size of that structure in the
frog, what does it say about the mental capacity of the frog? After comparing it to the Earthworm and the Crayfish, do you care to
revise your answer?)
Remove one of the eyes. (What is the name of the nerve that connects to the back of the eyeball? What travels along it?)
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1. Make a cut from the front of the eye to the back, so that the eye is divided into top and bottom. Draw the inside of the eye under the dissecting
microscope. (Is the eye solid? If so, why? If not, why not? What is the eye filled with, and why? What is the back of the eye called? What does
it do? Is there any connection to the nerve? What is the lens like? What does it do?)
Drawings:
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1. Use a PENCIL!!
2. Make the drawings "larger than life" size, as the specimens are so small.
3. Draw the general shape (outline) and location of the organs, as the squiggles so many of you use to "shade" your drawings make
your drawings sloppy and hard to interpret.
4. Include Labels on all drawings.
Labels should start outside the drawing, and be connected to the structure by arrows with tips (===>).
The Tip of the arow should be touching the structure.
Be sure to include the magnification for any drawings done with the dissecting microscope.
Hang on to the drawings; they will all be handed in later,
together with some questions to answer.
Click Image to ENLARGE!
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 top
SLIC MEN R RED
Return to Mr. Lazaroff's Biology
The Final Lab on the Dissection of the Earthworm, Crayfish, and Frog!
The Final Lab
on the Dissection of the Following:
Earthworm, Crayfish, & Frog
Return to Mr. Lazaroff's Biology
Due: On the day of the FINAL EXAM!
That's right . . . there will be no more Bio LABS after this one. . .
You need to find the Earthworm Dissection Page:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthworm.htm
The PDF version below is the most printer-friendly with the images:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/earthworm_dissection.pdf
and the Crayfish Dissection Page:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/crayfish.htm
The PDF version below is the most printer-friendly with the images:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/crayfish_dissection.pdf
and the Frog Dissection Page:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/frog.htm
The PDF version below is the most printer-friendly with the images:
http://shs.westport.k12.ct.us/mjvl/biology/dissect/bullfrog_dissection.pdf
Throughout those three web pages there are questions.
They are usually written after each of the specific structures you were to identify and draw.
You have to search for the questions by reading the descriptions of the actual dissections;
this will actually help you to remember!
YOU DO NOT NEED TO DO A FULL LAB REPORT!!
Just include the following:
(A) answers to all the questions,
(B) your drawings, in the order you completed them, and
(C) write a conclusion comparing the three animals we dissected in class . . .
. . . In other words . . . what did you learn?
How are the animals similar to us?
How can you explain those similarities?
How are they different?
How can you explain those differences?
Good Luck, Have Fun, and I'll See You at the FINAL!
Return to Mr. Lazaroff's Biology
http://shs.westport.k12.ct.us/mjvl/biology/dissect/dissectionlab.htm