This document provides instructions for a frog dissection lab. It describes both the external and internal anatomy of frogs. Externally, it discusses identifying features like coloration, legs, eyes, ears, mouth, teeth and more. Internally, it guides students to locate major organs like the liver, heart, stomach, spleen and others through careful cutting and probing. The goal is to familiarize students with frog anatomy and how it compares with human anatomy.

1. Frog Dissection
Mr. Brothers Life Science Class
 Discussion – Form and Function
 External Dissection
 Internal Dissection
 Lab Wrap-up & Write-up

2. External Features
ventral
dorsal
 Coloration
Record the colors of the dorsal and ventral sides
of your frog. Why do you think a frog is colored
this way?

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?

4. Extended Rear Leg
Extended
Foot
Extended
Leg

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.

7. Frog Skeleton

8. External Features
 Eyes
Examine the eyes of the frog.
The clear lids that cover the eyes are called
nictitating membranes
eye

9. External Features
 Ears
Just behind the eyes,
a frog has an exposed
eardrum called a
tympanic membrane

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

12. Maxillary Teeth
maxillary
teeth
(upper jaw)
lack of
maxillary
teeth
(lower jaw)

13. Vomerine Teeth
vomerine teeth
(slanting inward)eye bulges

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

28. CHALLENGE
 The kidneys are two
reddish-brown organs
tucked back behind
other organs
kidney

29. CHALLENGE
 The lungs appear
as saclike organs
on either side of
the chest cavity.
lung