Transcript Frog-Dissection

External Frog
To study the mouth,
scissors are used to
cut the corners of the
mouth at the angle
between the upper
and lower jaws on
each side of the head.
The Mouth
Maxilary
Teeth
Nasal
Nare
Typana
Nasal
Nare
Vomerine
Teeth
Glotis
Eustacian
Tubes
Gullet
Opening
Tongue
The Mouth
Just ventral to
the gullet is a
vertical slit
called the
glottis. The
glottis opens
into the
trachea, or
windpipe,
which leads to
the lungs.
gullet
glottis
Getting Under the Skin
The frog is laid
ventral side
up. Next,
beginning between
the hind legs, the
skin is cut along
the midline to the
middle of the
lower jaw. The
skin is loosely
attached to the
underlying
muscle. This
makes it easy to
explore the spaces
beneath it with a
dissecting
needle. The small,
yellowish knots
you may observe
under the skin are
lymph nodes.
r
Lymph nodes are
located beneath
the skin in this
area.
The skin is
cut laterally at
each end of
the incision
and then
spread open.
Lymph node.
Cutting Through the Muscles
The body cavity is opened by cutting through the abdominal
muscles and the muscles and bones of the chest and throat
regions. The same line is followed as with the skin, but at a
point just in front of the hind legs. The sternum, or breastbone,
was freed by cutting the bones joining it to the shoulders.
sternum
Here Is Your First Look Inside
The flaps of abdominal muscle are pinned back. As you
identify the organs in the body cavity, label Figure 2 in your
Record Book.
heart
pericardium
fat bodies
liver
small
intestine
The flaps of abdominal muscle are pinned
back. As you identify the organs in the body
cavity.
stomach
Oviducts and
Cloaca
In a female frog, the
abdomen may be filled
with small, black eggs
that would be
removed. The
oviducts can then be
located as two twisted
tubes that carry the
eggs to an excretory
organ, the cloaca, from
which they are passed
from the body.
spleen
egg mass
oviducts
spleen
egg mass
oviducts
The Heart
The heart lies along the
midline, just back of the
forelegs. Observe the large blood
vessels leading two and from the
heart.
heart
The heart is surrounded by a
thin tissue, the pericardium.
pericardium
Abdominal
Vein
The Heart
The pericardium
is opened to reveal
the lower part of
the heart, the
ventricle, and the
upper part, which
is composed of two
atria.
What is the
difference
between the
thickness of the
walls in the atria
and the
ventricle? What
is the reason for
this difference?
atria
ventricle
The walls of the
atria can be pushed
in easily.
The walls of the
ventricle are
sturdier.
The Heart
Truncous Arteriosus
Left Atrium
Conous Arteriosus
Right Atrium
Ventrical
The Liver and Gall
Bladder
Posterior to the heart
is a large, reddishbrown organ, the
liver. It is divided into
part called lobes. How
many lobes are there?
Liver
Underneath and
between the middle
and right lobes of the
liver, find a small
greenish sac, the gall
bladder.
The gall bladder
stores a liquid called
bile, which is
produced by the
liver. What is the
function of bile?
gall
bladder
The Small
Intestine and
Stomach
Find the small
intestine, a coiled
mass of tissue.
small
intestine
The small
intestine can be
traced anteriorly to
cloaca
the stomach, a
white, curved,
elongated
structure.
Small intestine
Of what
significance is
the constriction
Pyloric Valve
at the point
Constriction
where the
between the
stomach joins
small intestine
the intestine?
and the
stomach.
pancreas
stomach
The Small Intestine and Stomach
The stomach is
connected to the
mouth by the
esophagus. This
structure can be seen
by lifting the left lobe
of the liver.
esophagus
The Mesentery and Pancreas
Note the
mesentery, the thin,
delicate membrane
that supports the
intestines and other
organs of the
digestive tract.
Locate the
pancreas, a narrow,
whitish band of
tissue between the
stomach and the first
loop of intestines.
The function of
the pancreas is to
secrete digestive
enzymes.
mesentery
stomach
spleen
pancreas
mesentery
The Spleen and Fat
Bodies
Find the yellowish fat
bodies.
The spleen is a
reddish-brown body
which stores red
blood cells.
heart
liver
fat
bodies
spleen
stomach
The Kidneys
Lying along the dorsal body wall are two oblong, reddish bodies, the
kidneys. The other organs must be pushed aside to see them.
kidney
The Lungs
Covered
somewhat by the
other organs, the
lungs appear as
saclike organs on
either side of the
thorax, or chest
cavity.
lungs
stomach
lungs
cloaca
Review
stomach
mesentery
egg mass
small
intestines
oviducts
cloaca
spleen
atria
ventricle
Liver
Abdominal
Vein
pancreas