Download Cow Dissection Day - Virtual Homeschool Group

Cow Dissection Day
Wednesday, November 02, 2011
10:34 AM
The recording is an hour and 23 minutes
We had up to 40 attendees
Collaborate Recording https://sas.elluminate.com/site/external/jwsdetect/playback.jnlp?psid=
Link - please click the 2011-11-01.0641.D.0CEAEBBCD3AC15F59A671FF4F92804.vcr&sid=vclass
link to the right
VHSG Resource
http://www.virtualhomeschoolgroup.com/file.php/1/Home_Page_Resource
_Files/Cow_Dissection_Day.pdf
The recording will take some time to download enough for the recording the be playable, so while you wait, enjoy the still shots from the cow dissection and the pig eye dissections from
that day in the images and comments below. Then use them along with the recording to get additional background as well as get to see higher resolution images that came from the still
cameras. The webcam system in the online classroom must compress the video to enable it to go down the internet pipeline so some image clarity is lost in the video window of the online
classroom.
Slides
Comments
This image gives you a little bit of an idea as to
the setup that we used for the live, online
classroom presentation and for the hands on
dissection explorations that were done after
the online presentation ended.
The dissection specimens came from a local
farmer that slaughtered one of their cows for
their own family's winter meat supply. Brenda
Eatmon knew the family and asked if we could
use the cow heart and lungs for a home school
science. Timing was important because these
are fresh, not preserved specimens, so you
have to pull things together in less than a 24
hour window of time or the meat will spoil and
you will have a hazardous mess on your hands
(literally). We had three pig's eyes added in for
good measure. :0)
The setup is a wooden box with about 5 inch
sides. Layers on top of that is many layers of
plastic to protect the wood so that it can be
used again and to make clean up as easy as
drawing the sides together, tying up the sack,
and disposing of the left overs.
On the swing arm lamp you will see the
webcam that was used for the live, online
classroom presentation. There were also a
wide variety of scissors, the most useful of
which for an animal this size was the kitchen
shears which are dedicated solely to the use of
dissection. It is invaluable for the perch
dissection as well. The operculum is solid bone
and normal dissection scissors take forever to
get through it.
We began the live, online stage of the
dissection by having the student's view a video
of cow lungs being inflated. The links are …
Inflating the lungs YouTube link
http://www.youtube.com/watch?v=VX8JRZ7-3Q
or
Pureview of the video (no ads or video links
version):
http://viewpure.com/VX8JR-Z7-3Q
New Section 1 Page 1
Human lungs are structurally very similar to
cow lungs.
At rest, you will breathe about 14 to 16 times
per minute. After exercise it could increase to
over 60.
Newborns breathe 40 to 50/minute. By age 5 it
decreases to 25.
Surface area is about the size of a tennis court.
Floats in water
Produces a detergent like substance to prevent
surface tension in the fluid in the lungs
Bifurcation of the trachea
Bronchus - singular
Bronchi - plural
Pneumonia, asthma
Even if you are watching the Collaborate
recorded version of the dissection, you will
want to know how to make the webcam
window larger so that you can see the
dissection well. If you leave it docked,
everything will be too small to see well. So grab
it on up, tear it free, and use the lower corner
to expand it full size. You can later move the
window around as needed to see the slides on
the whiteboard screen by grabbing the top bar
again and, holding your left mouse button
down, move it around.
About the 6 minute mark in the recording:
New Section 1 Page 2
About the 6 minute mark in the recording:
The first task was to dissect the cow lungs.
We had initially thought that the cow had one
undersized lungs, but that was an error due to
having the specimen delivered just minutes
before we got started and we didn't have
much time to get familiar with it before we
needed to start.
Brenda Eatmon was our scalpel wielder. She
had previous experience dissecting a pig's
lungs, but this was her first time dissecting cow
lungs. She said that in the pig lungs you could
actually feel small air sacks in the lungs, but
not so in the cow lungs.
A view showing the trachea.
About the 10 min mark in the recording:
There are about 300 million alveoli in a typical
adult's lings.
These are covered with capillaries. Gasses are
exchanged between the capillaries and the
alveoli.
A serious lung disease associated with
cigarette smoking is emphysema. The damage
causes the alveoli to merge and the openings
to become large and coated with carbon. The
result is far less gas exchange leading to
difficulty in breathing.
About the 20 minute mark:
New Section 1 Page 3
About the 20 minute mark:
Here is the higher resolution image
It didn't take long to expose the bronchus
which is the large. Light-colored tube that you
see opened up in the image to the left. Look
closely at the lung tissue and you can also see
the openings of the bronchioles in that tube as
well as in the red tissue areas.
About the 29 minute mark:
As we transition from the lungs to the heart,
the students were sent out to watch a video of
the damage done by smoking.
You Tube version:
http://www.youtube.com/watch?v=
2glFau9ORAY
Pureview version of the video:
http://viewpure.com/2glFau9ORAY
4 chambers - note that left and right can get
New Section 1 Page 4
4 chambers - note that left and right can get
tricky. This is from the view of a person looking
at the heart as a spectator. The left and right
would be more normal from the perspective of
the heart being in your own chest, so this one
is a doctor's view style.
The tip at the bottom of the heart is called the
apex. It will be included in the left ventricle.
The diagram shows the two sides as being
roughly equivalent in size, but in reality the left
ventricle is larger.
That section of muscle that separates the left
and right ventricle is called the septum.
It is easy to get confused about what a vein
and artery is. An artery goes away from the
heart and veins always come to the heart. It
isn't dependent upon whether the blood is
oxygenated or non-oxygenated.
The pulmonary artery actually carries low
oxygen blood.
Note that the aorta goes in behind the heart
and sends blood to the lower body and it goes
up to supply oxygenated blood to the upper
body.
New Section 1 Page 5
Blood from the tissues → superior and inferior
vena cava → right atrium → tricuspid valve →
right ventricle → pulmonary semilunar valve
→ pulmonary artery → lungs → pulmonary
veins → left atrium → bicuspid (mitral) valve
→ left ventricle → aortic semilunar valve →
aorta → body tissue.
Those strings are the origin of the phrase "…
pull on my heartstrings". Those are chordae
tendona. They pull the heart valves open and
keep blood from back flowing.
The cow heart exterior view.
About 42 minute mark:
New Section 1 Page 6
About 42 minute mark:
Aorta shot The heart was cut away from the lungs to
make it easier to work with. As the aorta was
opened up, it really shows how much blood
that vessel is moving. It is the largest blood
vessel in the body. The blood will flow from the
heart out to the body through it.
If you work with an animal as large as a cow,
skip the scalpel and go for a pair of kitchen
shears dedicated to dissection and not kitchen
use.
The top of the heart after it has been removed
from the lungs. You can see the many veins
and arteries that lead in and out of the heart.
Up in the fatty area, you will find the auricle.
New Section 1 Page 7
Up in the fatty area, you will find the auricle.
Once the fat was trimmed out of the way, the
initial cut is done by following the superior
vena cava into the right atrium and on down
through the muscle wall to expose even the
ventricle.
51 minute mark:
Blood clot found in the right ventricle
The right atrium and ventricle have been
New Section 1 Page 8
The right atrium and ventricle have been
opened up exposing the tricuspid valve that
separates the two chambers. Those 'heart
strings' are called chorda tendona and they will
pull to open the valve during part of the heart
beat cycle.
53 minute mark:
Along the inner wall in the right ventricle are
openings that allow the blood that is used by
the heart itself to be deposited to be sent on
its way to the lungs for a fresh supply of
oxygen.
About 56 minute mark:
New Section 1 Page 9
About 56 minute mark:
Now the left atrium and ventricle are opened
up. This is the larger side of the heart and you
can see the thicker muscles of the heart that
are needed to send the blood out to the body.
The valve on this side is called the mitral valve.
This cow had some sort of yellow growth
attached to the mitral valve. Just as on the
other side, the 'heart strings' here are called
chordae tendona. Follow those down to near
the heart wall and you will see the muscular
papillary muscle.
I definitely recommend a set of kitchen shears
set aside only for dissection purposes. I bought
this pair for the purpose of cutting through the
perch operculum for the general bio perch
dissections, but the cow heart's thick, muscular
walls definitely called for them as well. Doing
this with a scalpel would have taken forever.
1 hour mark - valve names on the left atrium
and left ventricle side
About the 1:05 hour mark:
New Section 1 Page 10
About the 1:05 hour mark:
Next up is the pig eye dissection
New Section 1 Page 11
The eye as it appeared before dissection. There
is protective fat and muscle tissue connected
to the eye to allow smooth motion of the eye
in looking in a wide variety of angles.
1:07: The optic nerve
The optic nerve comes out from the back of
the eye. The eyes came to use with the optic
nerve pretty well trimmed down to the eye,
but it was still easy to make out where it was
located.
1:12 hour mark
New Section 1 Page 12
1:12 hour mark
A scalpel or razor blade is used to make a hole
in the area between the sclera (the white of
the eye) and the iris (the colored portion).
Then scissors are used to cut the cornea free
from the eye.
It is incredibly difficult to keep a firm grip on
the pig eye as you give the needed push with
the scalpel to make the initial incision. By
pinning the eye down to the dissection mat,
you can more easily stabilize the eye.
Abt 1:12 hour mark
Here, Maria is giving a gentle squeeze to expel
the lens and the vitreous humor. The shiny,
clear stuff coming out is the lens itself. In the
foreground on the dissection pad, you can see
another lens that was removed from one of
the previous dissections of an eye. If you are
dissecting a preserved specimen, the lens will
be solid and almost like a translucent rubber
material. In the fresh eye, it is clear and like a
firm bag of jelly-like water. It is easy to change
the shape with a gentle squeeze. In the eye,
there are muscles attached to this and the pull
causes the lens to change shape allowing your
eyes the ability to change focus from an object
that is close to one that is far away.
We didn't do this during the live, online
New Section 1 Page 13
We didn't do this during the live, online
session, but after the session was done and the
kids here at the house got a chance to work
hands-on, we explored the ability of the lens to
magnify.
Abt 1:21 hr
Here you can see the retina. This is the part of
the eye that converts the light and color (for
those organisms that can see in color) that
comes in to the eye into electrical signals that
get send down the optic nerve to the brain.
This we did later in the day, but I am posting it
New Section 1 Page 14
This we did later in the day, but I am posting it
here:
The retina is torn away now and it exposes the
tepetum. Though most animals have tapetums,
humans do not. The pig's eye that you see here
has a mildly opalescent tapetum. In a cow eye,
you will see a bright opalescence.
Here are some added shots from later on that
day when the kids here at the house got a
chance to get hands on.
You are seeing the backside of the iris here.
The muscles that line it makes the pupil dilate.
Timothy Moore and Maria Eatmonspent a bit
New Section 1 Page 15
Timothy Moore and Maria Eatmonspent a bit
over an hour exploring the lung and heart
before starting their individual eye dissections.
Maria Eatmon working on her eye dissection.
New Section 1 Page 16