1. Frog Dissection
Mr. Brothers Life Science Class
Discussion – Form and Function
External Dissection
Internal Dissection
Lab Wrap-up & Write-up
3. External Features
Legs
The rear legs are LONG. Record the length of
the leg, and the length of the foot. Calculate the
ratio of a frog’s leg to its foot, and compare this
to your OWN leg and foot.
Measure in centimeters!
Why do you think frogs have such long legs and
feet?
5. Something’s Missing!
Examine the ventral (belly) side of the frog with a probe,
without stabbing it.
What’s missing?
Birds, fish and mammals all have ribs.
Frogs don’t.
There are no ribs so
the chest is easily
squeezed together.
6. Something’s Missing!
Frogs breathe underwater by absorbing
oxygen through their skin, directly into
their bloodstream.
On land, adult frogs draw air into their lungs
using muscles in their mouth.
Frogs also don’t have necks.
10. External Features
The Mouth
Cutting time!!
With scissors, cut
the corners of the
mouth on each
side of the head.
Pry open the mouth
to expose the tongue,
teeth and throat tongue
11. External Features
Teeth
Frogs have teeth ??
Feel along the upper
and lower edges of the
mouth. Search for
maxillary teeth there.
Do frogs have teeth
up and down?
Next, find the two
vomerine teeth on the
upper jaw.
tongue
14. All Those Weird Holes…
Eustachian tubes
lead to the tympanic
membrane, to
equalize pressure
inside & outside the
ear.
When you yawn to
pop your ears you are
opening your own
Eustachian tubes!
15. All Those Weird Holes…
Nostrils
lead to the lungs,
allowing the frog to
breathe outside of
water.
16. All Those Weird Holes…
Gullet
leads to the stomach
Glottis
leads to the lungs
gullet
glottis
17. The Tongue
Use the probe to lift the tongue
Where does the tongue attach to the mouth?
Why does this make sense??
18. Let’s Look Inside!
Frogs have an amazing number of organs
that are similar to our own.
During the internal dissection we’ll identify the
- liver
- stomach
- heart
- spleen
- gall bladder
…and many more!
19. Getting Under the Skin
To reach the organs, you first cut through a thin
skin layer, and then through a layer of muscle.
20. Getting Under the Skin
Fold the abdominal muscles off to the sides,
and pin them.
heart
liver
small intestine
pericardium
fat bodies
stomach
21. Eeeeewwww, Gross!!
Your frog may be
filled with small,
black eggs.
These can be
removed carefully
with tweezers.
Try to locate the
oviducts! oviducts
oviducts
egg mass
egg
mass
22. Fat Bodies
The “yellow stuff” is actually stored fat.
This is food for the frog during its
winter hibernation.
fat bodies
23. The Liver
The most obvious organ is the liver.
Note that it is divided into 3 lobes
See if you can find a gall bladder beneath the liver
liver
gall
bladder
24. The Heart
The heart lies
just above the liver
It is lined with a
thin tissue called
pericardium
See if you can locate
the large blood vessel
leading away
from the heart.
heart
pericardium
blood
vessel
25. Chambers of the Heart
Frogs’ hearts have 3 chambers:
2 atria above, and 1 ventricle beneath
See if you can feel a difference between them
The walls of
the atria can be
pushed in easily.
The walls
of the
ventricle are
sturdier.
26. The Stomach
The stomach
lies sideways,
connecting the
esophagus to the
small intestine
Find the
esophagus by
lifting the left
lobe of the liver.
esophagus
small
intestine
stomach
pancreas
27. The Spleen
The spleen is a reddish-brown body
that stores red blood cells
spleen
