Transcript Cut Above Front Legs

Frog Dissection
Place Frog in Pan
• Place him/her in the dissection pan. The
frog should be lying on his dorsal (back)
side with his belly facing up.
Pin the Frog
• To secure the frog for the dissection, pin
each of his four limbs to the pan.
Begin the First Skin Incision
• Once the legs of the frog are
securely pinned to the dissection
tray you can start your first
incision:
• Use the forceps to lift the skin
midway between the rear legs of
the frog.
• Using the scalpel, make a small
cut through the lifted skin.
• This cut should be made in the
along the center, or midline, of the
frog, bisecting it equally.
Continue Skin Incision
• Now, using the scissors, continue the
incision up the midline all of the way to the
frog's neck. Be very careful not to cut too
deeply.
Finish the First Skin Incision
• When your scissors reach the frog's neck,
you have cut far enough.
Cut Above Front Legs
• Using either the scissors or the scalpel,
make horizontal incisions through the skin
between the front legs.
Cut Above Rear Legs
• Still using either the
scissors or the scalpel,
make horizontal
incisions through the
skin just above the rear
legs.
Separate Skin & Muscle
• Once you have finished the
incisions between the front
and rear legs of the frog
you need to separate the
skin flaps from the muscle
below. To do this:
• Pick up the flap of skin with
the forceps, and
• Use a scalpel to help
separate the skin from the
muscle below.
Pin Skin Flaps
• Once you have finished
the incisions between the
front and rear legs of the
frog you need to separate
the skin flaps from the
muscle below. To do this:
Pick up the flap of skin
with the forceps, and
Use a scalpel to help
separate the skin from the
muscle below
Begin 1st Muscle Incisions
• Begin the incisions in
the abdominal muscles
in the same way as
when cutting through
the skin:
• Use the forceps to lift
the muscle midway
between the rear legs
of the frog.
• Use the scalpel to start
the incision in the
direction of the chin
Continue Muscle Incision
• Now, using the scissors,
continue the incision up the
midline all the way to the
frog's neck. Be careful not
to cut too deeply. The
muscle is thin and you
don't want to damage the
organs underneath
Turn Scissor Blades
• This is very important.
When you reach a point
just below the front legs,
turn the scissor blades
sideways to cut through
the bones in the chest.
This should prevent
damage to the heart or
other internal organs
Finish 1st Muscle Incision
• When your scissors
reach a point just
below the frog's
neck you have cut
far enough.
Make 2nd Muscle Incisions
• Next, using either
the scalpel or
scissors, make
horizontal incisions
through the muscle
between the front
legs.
Second Muscle Incisions
• Still using either the
scissors or scalpel,
make horizontal
incisions just above
the back legs.
Separate Muscle & Organs
• To open up the abdominal
area you need to pull back the
muscle flaps. To do this:
• Hold the flaps of the muscle
with forceps, and
• Use a scalpel to separate the
muscle from the tissues below.
Pin the Muscle Flaps
• Once the muscle flaps
have been separated
from the underlying
tissue, they must be
pinned back. This will
allow easy access to
the frog's internal
organs.
Open Triangular Flaps
• To finish opening up the
frog's body cavity, fold
back the triangular flaps
of skin and muscle which
are above the front legs.
To do this:
• Hold the flap of muscle
and skin with the forceps,
and
• Use a scalpel, if
necessary, to help
separate the flaps from
the underlying tissues.
Pin the Triangular Flaps
• As above, once the
muscle flaps have
been separated
from the underlying
tissue, they must
be pinned back to
allow access to the
body cavity.
Liver
• You are now at the first
layer of the dissection. At
this point you will be able
to see the entire liver
and heart.
• The liver is a large,
brownish colored organ
covering most of the
body cavity. In the
pictures above it is
circled by a yellow
border.
Heart
• The heart is a small
triangular shaped
organ between the
front legs and
anterior to the liver.
In the pictures above
it is circled by a
yellow border.
Stomach and Intestines
• The “J” shaped organ held by the forceps.
Gall Bladder
• When you raise the
liver up you will see a
small, greenish sac
underneath it. This is
the gall bladder. In
the pictures above it
is circled by a yellow
border.
Stomach
• The stomach is a
large, firm, sac-like
organ on the left
side of the frog. In
the pictures above
it is circled by a
yellow border.
Small Intestine
• The small intestine is a
long, folded, tube-like
organ that is posterior to
(below) the stomach. It
is similar in color to the
stomach, but smaller in
diameter. In the pictures
above it is circled by a
yellow border.
Lungs
• The lungs are at the
anterior end of the body
cavity on either side of
the heart. In a preserved
frog, they are small,
reddish-pink organs.
The frog's left lung is
circled in each of the
pictures above
Ovaries
• Found in female
frogs only. Locate
the ovaries. They
are dark organs
which may fill most
of the frog's body
cavity, depending on
the time of year that
the frog was
collected.
Frog Fat