Frog Dissection - Remote

As you progress through the slides, you will be given descriptions and tasks to
complete. Be sure to complete all tasks! Some instructions may include links to
help you identify structures or answer questions.
All images are licensed Creative Commons 4.0 BY-NC, and linked where appropriate.
Complete frog album can be accessed through Google Photos.
External Anatomy
The dorsal surface of the frog is
darker than the ventral surface.
Note that the skin of the frog
appears smooth. Most of the
frogs in the class are about the
same size. The ruler shown
measures in centimeters.
1. Measure the length of the frog
from nose to tail (exclude legs).

10cm
If you flip the frog over, you should
notice differences in the color of
the frog on the ventral surface
(belly) compared to the dorsal
surface.
This type of coloration is called
countershading. This is
observed in fish species also.
2. Propose a reason for a frog
being lighter on the ventral side
and darker on the dorsal side.

Because of countershading,
frogs are lighter on the ventral
side and darker on the dorsal
side, which offers camouflage
from predators when viewed
from above or below and aids in
temperature management.
A careful examination of the forelimbs
and hindlimbs reveals that only the
back feet have webbing. Watch how
the frog swims in the water.

3. Describe how a frog swims.

Draw your back legs up and

drive yourself forward by firing
your back legs rearward in a
straight line.
Frogs have a clear membrane that
attaches to the bottom of the eye, called
nictitat
the nictitating membrane. It is clear and in
membr g
protects the eye while swimming. ane tympanic
Just behind the eye is a circular structure membrane
called the tympanic membrane. This is nostrils
the eardrum of the frog and is used for
hearing.
Toward the front of the frog is an opening
called the external nares, or the nostrils of
the frog. When floating, these stay above
water to allow the frog to breathe.
4. Drag the labels to the structures on the
frog image.
Opening the mouth can reveal several vomerin
e teeth
structures. Note that the tongue is
attached to the front of the mouth. It is tongue
sticky and will uncurl to capture prey.
ils
The internal nostrils are visible as str
no
openings, with two pointed teeth between
them called vomerine teeth. Frogs do not
chew, and use teeth to hold onto prey
before swallowing objects whole.
A ridge of teeth around the outside of the
mouth, called maxillary teeth will also hold
prey.
ma
xil lary
5. Label each of the underlined structures te e
th
on the frog image.

(Drag labels to image)

Removal of the tongue is necessary to view
the eustachian tubes, which are just above
the angles of the jaw. These pair of openings
lead to the tympanic membrane and help to
equalize pressure when the frog dives.
eustachian
At the back of the moth is the large opening tubes
of the esophagus. This tube leads to the
stomach.
Just in front of the esophagus (toward the
tongue) is a smaller opening called the
glottis. This opening leads to the lungs. This
esophagus
is how frogs take in air.
6. Label each of the underlined structures.
glottis

tongue
 Nictitating
7. Identify all of the structures of nostrils
membrane
the frogs you have just learned.
You will need to type them into tympanic maxillary teeth
the text fields. Refer back to membrane
vomerine teeth
previous slides for spelling and
names or use reference
this page.
eustachian tube

esophagus
Tongue
glottis
Internal Anatomy
To view internal structures, the frog is cut
from the lower stomach and up toward the
jaw. The sides of the frog are pinned back
to reveal the organs.
The most visible and largest organ of the
body cavity is the liver, which can be seen
as three green-ish lobes lying in the
center. Each lobe is named for its
location, from the frog’s perspective. The
left anterior lobe is on the frog’s left side.
Below it is the left posterior lobe. There is
a single right lobe on the frog’s right side.
8. Drag the colored circles to the correct
lobe.
Lying above the liver is the heart
(shown in yellow box), which is a um
atri
pink triangular structure. l e ft
rig
h ta
triu
The bottom area is the single m
ventricle and the top part
consists of a left atrium and right
atrium. ventricle

9. Label the chambers of the

heart.

Source: Giphy
On this image the liver has been
removed to show the spongy lungs
that lie close to the heart.
Blood travels to the heart, then to the
lungs and then back to the heart
before being pumped to the body.
10. Drag the green arrows to indicate
the left and right lung on either side of
the heart. Use the red arrow to
indicate the ventricle of the heart.
And the blue arrow to show the
atrium.
Use tweezers to lift the right lobe of
the liver and reveal the sac-like
gallbladder that lies underneath it.
One of the many jobs of the liver is to
produce bile. This bile is stored in the
gallbladder.
Also laying partially under the liver is Gallbladder
the curved stomach which leads to
the straight section of the small
intestine called the duodenum.
Within the interior curve of the Stomach
stomach is the pancreas, which is a
gland. It appears stringy or web-like in Duodenum
the preserved frog.
11. Label the underlined structures on
the image. Pancreas
In this image the stomach has been pyl
ori
removed to show the folds on the cs
ph
i nc
inside called rugae. Rugae allow for t er
the expansion of the stomach for
digestion. The layer of the stomach
on the inside, called the mucosa which
release enzymes to help digest food.
rug
ae
The lower end of the stomach where it
connects to the small intestine has a
circular valve (9) called the pyloric
sphincter. This valve opens and
Sometimes, the
closes to allow partially digested food remains of the frog’s
to enter the small intestine where last meal are found in
digestion will continue. the stomach, usually
insects or worms.
12. Label the rugae and pyloric
sphincter valve.

Source: Wikimedia Commons

In this view, the stomach has been
pushed up to reveal the small and stomach
large intestine. Recall that at the
stomach leads to the duodenum
The duodenum leads to a curly
portion of the small intestine. Near
the lower end of the abdomen the
small intestine widens and becomes small intestine
the large intestine (also known as
the colon).
13. Label the small and large
intestine. large intestine
The small intestine is coiled in the body
cavity and held together by a thin sm
membrane called the mesentery. This y all
e nt er int
e
membrane contains tiny blood vessels me
s sti
n e
that carry nutrients from digested food
into the bloodstream.
Embedding in these coils is the spleen,
shown as a reddish sphere. This organ sple
is responsible for filtering the blood and e n
replacing worn-out blood cells.

ch
14. Label the structures on the

ma
diagram.

s to
These are eggs, so we know this frog is female.
Removing most of the digestive system
and other internal organs, a pair of
flattened reddish organs can be seen
lying alongside the spine. These are the
kidneys.
Kidneys filter waste from the blood and
transport urine to the urinary bladder. In
this frog, it looks like a deflated balloon. kidney

Urine will then pass out of the frog

through the cloaca.
15. Label the structures on the diagram
bladder
On this frog, you can see the large
intestine and small intestine and the
reddish spleen embedded in the
mesentery.
To the right of the spleen is a cream small intestine
spleen
colored organ that sits on top of the
kidney. This is the testis, and it is only
found in male frogs. There is another testis
one that sits on the left side kidney (not
visible in this image).
Singular: Testis
Plural: Testes
large intestine
16. Label each of the underlined
kidney
structures.
This is a female frog without eggs.
You cannot see testes near the kidney,
but you can see a small curly structure
along the outside of the kidney. This is
the oviduct. Eggs produced by the
ovaries travel through the oviduct.
This frog also has a lot of fat bodies.
kidney
These are the orange structures being
pushed aside. Most frogs have fat
bodies, but underfed frogs may not
oviduct
have noticeable ones.
17. Label the fat bodies,oviducts, and
kidney. fat bodies
The body cavity of this female frog
is filled with eggs. They appear as
dark or speckled structures. You
can also see the curly oviducts to
the side of the eggs that appear
larger in frogs that are reproducing.
18. Label the eggs and oviducts. eggs

oviducts
19. The image shows the
female reproductive system.
Identify each of the following
by letter:

Urinary Bladder B

Cloaca E

Eggs A

Kidney D

Oviducts C
20. Now that you have learned all
the major structures. Practice heart
labeling the frog. You may need to
refer back to previous slides. liver esophagus

stomach

gallbladder

pancreas
small intestine

fat bodies duodenum

pyloric valve
large intestine

spleen

urinary bladder