Frog Dissection

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Frog Dissection

• Why do we dissect frogs?

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Main Menu

• Terminology
• Background Information
• Materials
• External Anatomy
• Inside the Mouth
• Procedure
• Copy of Worksheet
• Concept Map
• Authors information
• Resources

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Terminology

• Dorsal-on or near the back
• Ventral-on or near the front (opposite of dorsal)
• Posterior-on or near the behind
• Anterior-on or near the top

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Background Information
Click on this video to learn about the
environmental threats on frogs
Click on this video to learn about frogs skin and
its qualities
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Materials

• A dissecting tray
• 
  Pins
• A frog
• Scalpel
• Scissors
• Forceps

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External Anatomy

• Identify
• Take notice of the skin
• The external Nares (nostrils)
• The eyes and the third eye-lid (which covers the
  eye when underwater.
• Locate the Tympanic membrane (ear drum) just
  posterior to the eye.
• Locate the shoulder, elbow, and wrist joints of
  the Forelimbs.
• How many Digits (fingers) are there to a
  Forelimb?
• At the posterior end of your frog is the Cloaca
  (feces, urine, and reproductive cells are
  expelled here).
• Examine the muscular hindlimbs
• Locate the thigh, knee, and ankle joints
• Examine the webs of the foot.
• How many Digits are there to each hindlimb?

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Inside the Mouth

• Identify
• Two large Muscular Pads are in the roof of the
  mouth (eyes retract here when it blinks)
• Locate Tongue.
• What unusual features do you notice?
• Find the two knobs that come out of the roof of
  the mouth. These are called Vomerine teeth.
• Rub your finger along the inside of the jaw, you
  will feel the maxillary teeth.

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Procedure

• Examine the exterior of the frog. (Follow the
  External Anatomy and Inside the Mouth slides)
• After answering the questions on the exterior,
  placing the frog on the tray ventral side up.
• Pin the forelimbs and hindlimbs to the tray.
• Make a cut down through the middle of the frog
  and then two perpendicular cuts (watch the video
  showing the process).

Click here to watch video
After you make your cut, pin the skin back to
the tray, now repeat the process and cut through
the muscle layer this time (exposing the internal
organs).
Go to next slide for further procedures
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Procedure2 Internal Anatomy

• Answer the appropriate questions on the worksheet
  as you go along.
• Carefully find the liver (large brown organ with
  3 lobes) and remove it.
• Your frog may have fat bodies and if you have a
  female it may contain a mass of eggs (you may
  need to remove these in order to examine the
  organs).
• Find and remove
• the stomach, intestines, pancreas (yellowish
  color), and gall bladder (greenish color).
• the heart, left lung, and right lung.
• the spleen and kidneys.
• the ovaries (female) or testes (male)

Go to the next slide for further procedures
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Procedure3Internal Anatomy

• After removing the necessary organs, unpin the
  frog and turn it dorsal side up. You are going
  to cut the skin on the neck and head to expose
  the cranium.
• Then cut open the cranium and expose the brain.
• Dispose of the frog and materials as directed in
  class. Clean all tools appropriately.

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Copy of the Worksheet worksheet will be given
out in class

• 1. Write down your observations of the skins
  texture and color.
• 2. Look at the hind limbsthere are __ toes on
  each foot.
• 3. Look at the front limbsthere are __toes on
  each foot.
• 4. When looking at the tongue, where is it
  attached (the back or front of the mouth)?
• 5. Is your frog male or female? How did you know
  it was male/female?

Click next to continue to page 2 of the worksheet
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Copy of Worksheet2

• 6. What is the livers function in the body?
• 7. Follow the digestive tract of the frog and
  briefly explain who food goes from the mouth and
  out of the anus.
• 8. There are __ chambers in the heart.
• 9. What is the small green sac that attaches to
  the liver?
• 10. Examine the cranium and brain, describe what
  you see.

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Lungs
Tympanum
External Nares
Liver
Internal Nares
Gall Bladder
Maxillary Teeth
Stomach
Vomerine Teeth
Small Intestine
Eustachian Tubes
Large Intestine
Tongue
Spleen
Esophagus
Kidney
Glottis
Oviducts/Eggs
Heart
Testis
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Tympanum
The tympanum, found just behind the eyes,
functions as the ears of the frog. They receive
sound waves both above and below water allowing
the frog to hear.
Home
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External Nares
The nares primary role is to let air into and out
of the frog. This is a view of the nares from
outside of the frog.
Home
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Internal Nares
The nares primary role is to let air into and out
of the frog. This is a view of the nares from
inside of the frog.
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Maxillary Teeth
This set of teeth is used for holding prey.
Home
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This set of teeth is also used for holding prey.
Vomerine Teeth
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The eustachian tubes function to equalize
pressure on both sides of the eardrum or tympanum
Eustachian Tubes
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Tongue
The tongue aids in swallowing and catching prey.
In humans the tongue also aids in speech and
taste.
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Glottis
The glottis is the opening between the vocal
chords at the upper part of the windpipe or
larynx.
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Esophagus
Food is swallowed through the esophagus where
peristalsis aids its movement to the stomach.
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Lungs
The lungs transport oxygen to the blood as well
as remove waste like carbon dioxide through a
process called respiration.
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Heart
Unlike the human heart the heart of a frog only
has three chambers (two atria and one ventricle)
however the role and function is the same. The
heart pumps blood throughout the body carrying
oxygen and nutrients and picking up waste to be
filtered by other parts of the body.
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Large Intestine
The main role of the large intestine is to absorb
water and store fecal material until it can be
excreted from the body.
Home
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Small Intestine
The small intestine receives the mixture of chyme
from the stomach through the pyloric valve. In
the small intestine nutrients are absorbed from
the tiny villi lining the inner walls of the
small intestine.
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Stomach
In the stomach food is further broken down by
gastric juices and peristalsis until it becomes a
liquid substance called chyme.
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Liver
The liver produces bile, a substance that
emulsifies fats contained within the food we eat,
and stores it in the gall bladder to be secreted
into the small intestine.
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Gall Bladder
The gall bladder stores bile that is received
from the liver. Bile is secreted from the gall
bladder into the first section of the small
intestine (duodenum) to help aid in digestion.
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Spleen
The spleen helps to destroy old red blood cells
and lymphocytes, which are cells that produce
antibodies to help fight infected and cancerous
cells.
Home
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Kidneys
The Kidneys filter out waste from the blood
through structures known as nephrons. The waste
removed is combined with water to form urine.
Home
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Oviducts Eggs
The oviducts are tubes that carry eggs from the
ovaries to the uterus. The eggs are the female
reproductive cell.
Home
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Testis
The testis are the male reproductive gland that
produce sperm and male hormones such as
testosterone.
Home
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Lungs
Tympanum
External Nares
Liver
Internal Nares
Gall Bladder
Maxillary Teeth
Stomach
Vomerine Teeth
Small Intestine
Eustachian Tubes
Large Intestine
Tongue
Spleen
Esophagus
Kidney
Glottis
Oviducts/Eggs
Heart
Testis
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Resources

• Video of Frog Dissection
• http//www.youtube.com/watch?vvK-YTwHZTSY
• Red Eyed Tree Frog Pictures
• animals.nationalgeographic.com
• Video of Frog Skin and Video of Environmental
  Threats
• http//www.unitedstreaming.com