Bullfrog Dissection
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Try These Online Frog Dissection Links:
The Virtual Frog Dissection Kit:	The ONLINE Frog Dissection:	The Interactive Frog Dissection (2002):
http://www-itg.lbl.gov/vfrog/	http://www.aa.psu.edu/ biology/frog/	http://curry.edschool.virginia. edu/go/frog/Frog2/
See a MOVIE from the site above!
Froguts.com	Cornell University's Frog Dissection	The Interactive Frog Dissection (1994):
DEMO only (Click the DEMO Link)
http://www.froguts.com/	http://biog-101-104.bio. cornell.edu/Biog101_104 /tutorials/frog.html	http://curry.edschool.Virginia. EDU/go/frog/menu.html

BY DAY:    Day 1    Day 2    Day 3    Day 4    Day 5    Day 6 BY TOPIC:    External Anatomy    Skin Removal    Inside the Mouth Skeletal    Lymphatic     Integumentary    Cardiovascular Muscular    Endocrine    Nervous Reproductive Respiratory    Excretory    Digestive S L I C   M E N   R   R E D (SLIC  Frogs  R  RED?)\ You must create a series of labeled drawings that illustrate the structures outlined below:

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Day 1   top 

I. Head - Dorsal View          (Day 1)         top

1. Eyes (What does their angle imply about depth perception?  What can you say about the frog's niche by looking at its eyes?)  More about the eyes.

2. Tympanum (What does the lack of pinna imply about hearing?  What is the scientific term for the ear drum?  Does the name "ear drum" make you think of the Grinch?)

3. External Nares (Which implies the existence of . . .?  What is their function?  The tube - between the external and __ nares - in mammals is much longer; what is accomplished in this longer tube?  What is required on the inner surface of the tube to accomplish this?)

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II. Body - Dorsal View             (Day 1)         top

Skeletal System     top

S L I C   M E N   R   R E D

1. "Ribs" - it is not a ribcage! (What organs are within, and protected by, our ribcage?) NOTE: In reality, there are no ribs; these are merely the transverse processes of the vertebrae.  Our ribs attach to the transverse process, and 7 of the 12 also attach directly to the sternum ["true" ribs], the next three attach indirectly ["false" ribs], and the last two do not attach to the sternum at all [also "false" ribs, but specifically "floating" ribs].

2. Pelvis - note the width and height up the back (The shape is very different from ours.  Comparing the shape of our species and theirs, explain how certain body characteristics - name them as well - account for this pelvic difference?)

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3. "Hand" (How many fingers?  Looking at their arrangement, are the hands capable of much of a grip, or of detailed movement?)

4. Is your specimen a FEMALE or a MALE?  Believe it or not, it is easier to tell by looking at the hands (See below)!
    

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5. Foot (How many toes?  How are they different from the fingers?   Which has more webbing, the hand or the foot?  What does this say about their locomotion?)

6. Legs (What does their length and width imply about their use?  In your answer, also make reference to the arms for comparisons sake.)

By the way . . .   . . . need a hand?  Or a foot? 
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Click on the Skeleton  to Enlarge and Print . . .
(from the Virtual Frog Dissection Kit: http://www-itg.lbl.gov/vfrog/)

III. Skin Removal - Ventral View         (Day 1 & 2)         top

Integumentary System     top

S L I C   M E N   R   R E D

• Make a Ventral Midline Incision from the posterior end of the Abdomen to the Anterior end of the Thoracic Region using the rounded scissors with the rounded end down!

• Continue a Medial Incision, as above, along the Ventral surface of each limb as far as the wrists and ankles.

• Using the forceps to lift the Skin, take a scalpal and gently cut the fascia with the blade parallel to the muscle beneath.

• Remove the skin so as to leave the frog with a "hood," "gloves," and "socks." [sic]

• It should be possible to remove the skin "in one piece!"

• Pay Close Attention to the places on the body where the underside of the skin is much more firmly attached. 

• Pay Close Attention to the Blood Vessels on the underside of the skin.  DIAGRAM THE PATTERN OF THE BLOOD VESSELS, AND THE CONNECTION THROUGH THE MUSCLE TO THE SKIN!

Day 2    top

III. Skin Removal Continued- Ventral View         (Day 2)         top

• Continue as above . . .

• We will conclude this today so as to view the muscles beneath . . .

Draw the following:

1. The pattern of blood vessels on the underside of the frog's skin. (What does this say about the nature of the skin?  What function does the frog's skin have that ours lacks?  How does that function impact upon the frog's choice of habitat?   What is it about our skin, and our body as a whole, that makes it impossible for us to have the same skin function?)

2. The pattern of coloration on the dorsal surface of the skin.  (What does this say about one of the functions of the skin?  How, and why, is the coloration different on the ventral surface?)

3. The way the blood vessels, nerves, and lymphatics connect to the skin (i.e. passing through the muscle to get to the skin).  (What are the nerves for?  What are the lymphatics for?)

4. (Why was the skin so much more firmly attached, stronger connective tissue, in some areas - e.g., the elbows, knees, and hips?  Think in terms or repetitive motion, and what would happen if the skin were not attached strongly in those places.)

Day 3    top

Muscular System    top
Ventral    Dorsal    Arm     Leg
. . . be able to describe how the body's position
changes whenever the muscle contracts . . .

S L I C   M E N   R   R E D

IV. Muscles - Ventral View, Part I          (Day 3)         muscles     top

V. Muscles - Dorsal View, Part I        (Day 3)         muscles   top

1. Depressor mandibulae  (To what bones does it attach?   Specifically, how does it move the body?)

2. Deltoid  (To what bones does it attach?  Specifically, how does it move the body?)

3. Latissimus dorsi  (To what bones does it attach?   Specifically, how does it move the body?)

4. External oblique  (To what bones does it attach?   Specifically, how does it move the body?)

5. Common extensors of the back (Why aren't there any flexors along the spine?)  (To what bones does it attach?  Specifically, how does it move the body?)

6. Gluteus (Yes . . . it's what you think it is . . . and why is it so small in comparison to us . . . it's related to the muscle's function . . .?)   (To what bones does it attach?  Specifically, how does it move the body?)

VI. Muscles - Arm             (Day 3)         muscles   top

1. Common flexors (ventral) (To what bones does it attach?   Specifically, how does it move the body?)

2. Common extensors (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

3. Triceps brachii (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

VII. Muscles - Leg . . . to go!          (Day 3)         muscles   top

1. Triceps femoris [. . . Quadriceps in humans . . .] (To what bones does it attach?  Specifically, how does it move the body?)

2. Sartorius (ventral)  (To what bones does it attach?   Specifically, how does it move the body?)

3. Gracilis Major (ventral) (To what bones does it attach?   Specifically, how does it move the body?)

4. Semimembranosus (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

5. Gracilis Minor (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

6. Biceps femoris (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

7. Tibialis Anterior (To what bones does it attach?   Specifically, how does it move the body?)

8. Gastrocnemius (To what bones does it attach?  Specifically, how does it move the body?)

9. Peroneus (dorsal) (To what bones does it attach?   Specifically, how does it move the body?)

10. Achilles Tendon (Not a muscle, of course) (To what bones does it attach?  Specifically, how does it move the body?)

Day 4    top

VIII. Abdomen - Vental View, Part I        (Day 3)         top

• You will be making a Classic "I" Incision.

1. Make a Ventral Midline Incision through the abdominal muscles from the posterior end of the Abdomen to the Anterior end of the Thoracic Region using the rounded scissors with the rounded end down!

2. Continue with a Lateral Ventral Incision through the abdominal muscles from "armpit to armpit," and along the base of abdomen from "hip to hip."  [sic]

• Using the forceps, open the abdomen by lifting the muscle flaps and pinning them against the dissection tray.  The muscle flaps will thus appear as 2 "barn doors."

• Make a diagram of the abdomen as you see it.  Be sure to label (indicate also what system each organ belongs to)and locate the following:

1. Heart (The liver is right below the heart in your frog.  In our bodies, what is between the heart and the liver?  To what body system does this division provide the most help?  What function does this division perform?   Given the lack of this division in the frog, what part of the frog's body performs this same function?)

2. Lungs (Why are they so much smaller, proportionately, than ours?   Given the lack of a ribcage, how are the lungs protected - i.e., by what bones - in the frog?)

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3. Liver (How many lobes does it have?  Explain why it is so big by referring to its functions.)

4. Stomach (What organ empties into the stomach?  Into what organ does the stomach empty?)

5. Small Intestine (This implies the existence of ___?  What is the first part of the small intestine called?  What one basic function, among all of the digestive organs, is found only in the small intestine?)

6. Fat Bodies (What is their function?  To what area, and to what type of tissue, are they attached? Given that humans don't have them, where do we put most of our fat?)

7. Any other organs you see (all of which will be discussed later) . . .

IX. Abdomen - Vental View, Part II         (Day 3 & 4)         top

Digestive System     top

S L I C   M E N   R   R E D

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• Liver - Draw the following:

1. Gall bladder (Why is the organ hollow?  What,  and don't say gall, does it contain?  What is the function of that substance?)

2. Cystic duct  (What two organs does it connect?  What material transports along the tube?  What type of organ is it, endocrine or exocrine?  Be sure to define the two terms in your answer.)

3. Common bile duct  (What three organs does it connect? Which of the three organs is the final organ - and hence the location of the substance's action - for the substance above?)

• Stomach

1. Make a Medial Incision along the stomach (DO NOT SEPARATE THE STOMACH FROM THE BODY!) and open it to view the inside.
   

2. Is your specimen "Packing a Lunch?"   If so, can you identify it's "last meal?"  Given the contents, what can you say about the animal's niche?  Does this agree with or contradict what you said about the eyes?  How does your answer relate to food webs?)

3. Diagram the Rugae - folds (What is the purpose of the rugae?  To best answer this question, compare the stomach of a "full" vs. a "hungry" frog.   Compare also the thickness of the walls in the full and empty stomach.  What are the functions of the stomach?  Given that, what type of tissue is in the stomach walls.)

• Small Intestine

1. Find the connective tissue between the loops of the small intestine - the Intestinal Mesentery (What is the function of the mesentery?)

2. Diagram the various structures within the mesentery (Blood vessels, lymphatics, and nerves: describe the function of each in terms of the small intestine - and relate it to the function of the small intestine!)

• Find my favorite organ . . . can you guess it?  . . . the pancreas.   Find also the pancreatic duct (a tube connecting the pancreas to the small intestine).  (How is this tube related to one of the functions of the pancreas?   What other function of the pancreas makes that organ my favorite organ?  What other system does the pancreas connect two in fulfilling this latter function?)

• Large Intestine (Why is it so much shorter than the small intestine? - Hint . . . it is related to the organ's function!)

• Cloaca - Pay attention to where you see this organ again (What is its location, and how is this related to the final function of the large intestine?)

Day 5    top

X. Thoaracic Region - Ventral View       (Day 5)        top

Cardiovascular System    top
Removing the Heart

S L I C   M E N   R   R E D

• Make a ventral, midline incision up to the base of the neck, using the rounded scissors as usual.  It may be a bit tough due to the sternum.

• Make a ventral diagonal incision from the armpit region to the end of the incision above,using the rounded scissors as usual.

• Remove all of the muscle and bone to reveal the heart and lungs.

• Draw the following:

1. Heart - 3 chambered
     a. Ventricle - there is only one (What sort of impact does this have on the function of the heart, compared to our four-chambred heart?)
     b. Left & Right - remember: it's always the patient's left - Atria - singular = atrium (Why are the atria so much smaller than the ventricle?  HINT: Think in terms of the distance the pumped blood travels before it returns to the heart.)
     c. (What are the three circuits in the frog's circulation?  Do we have the same 3 circuits, or do ours differ?)

2. Lungs  (Note the size.  They are, unlike our lungs, smaller in comparison to the size of the heart.  Explain the reasons - there are two - for this size difference.)

3. Trachea (What is the function of the rings of cartilage?  Why does no other tube - digestive, vascular, etc. - need these rings?  The trachea divides into two structures called ____; these structures go into the ____?)

• Using the probe, gently remove the connective tissue surrounding the vessels above the heart.  Then draw the following:

1. Pericardium (What is its function?  HINT: it is related to the type of membrane of which it is made, and the specific fluid that the membrane makes.)

2. Conus Arteriosus (To what chamber does it attach?  To what circuit(s) does this vessel provide blood?  What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?)

3. Coronary Artery (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?  To what circuit(s) does this vessel provide blood?)

4. Systemic Arch  (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?  To what circuit(s) does this vessel provide blood?)

5. Pulmocutaneous Arch - to the lungs  (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?   To what circuit(s) does this vessel provide blood?)

6. Pulmonary Artery - as above, but entering the lungs (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?  To what circuit(s) does this vessel provide blood?)

7. Pulmonary Veins - as above, but leaving the lungs  (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?  To what circuit(s) does this vessel provide blood?)

8. Sinus Venosus  (What is the oxygen concetration of the blood - high, medium, or low?  What is the color of the blood?  To what circuit(s) does this vessel provide blood?)

Inside the Mouth     top

S L I C   M E N   R   R E D

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• Using the rounded scissors, cut open the corners of the mouth and pin the mouth open.  Draw the following:

1. Maxillary Teeth  (Given the name, on what portion of the mouth are they found?  What is their function?)

2. Vomerine Teeth  (On what portion of the mouth are they found?   What is their function?)

3. Internal Nares (Into what portion of the mouth do they open?  Into what portion of the mouth do ours open?  Given that the brain is above, and behind, the eyes, what other function, besides breathing, do the nares have?)
                                                        
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4. Underside of the Eyes
      a. push gently upward from below and the eyes "bug out!"
      b. more about the eyes.
      c. (You were able to push the eyes up; the frogs are able to push them down into the oral cavity.  What purpose does this serve?  What body system does this aid?

5. Glottis
      a. place a blunt probe down this and you will see it move
          into the trachea!  (What is its function?   To what body system does it belong?)

6. Esophagus
      a. place a blunt probe down this and you will see it move
          into the esophagus!  (What is its function?   To what body system does it belong?)

7. Eustachean tube
      a. place a blunt probe up this and you will see it move
          the tympanum!  (What function does this tube provide?  How does the function of this tube relate to the effectiveness of swallowing in relieving ear pressure during airplane flights?)

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Day 6    top

XI. Thoaracic Region - Ventral View, Part II       (Day 6)        top

• Remove the heart by cutting the blood vessels above it and removing it from the chest.

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1. Place it flat on your dissecting tray with the ventral surface up.

2. Make a cut parallel to the tray through the heart.

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3. Open up the heart and draw the inside under the dissecting microscope and label the three chambers.  (Why are 4 chambers better?  How can a frog survive with only 3 [i.e. how are they different from us?]?)

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• Draw the chest with the heart removed and label the trachea, the bronchi, and the lungs.

Respiratory System     top

S L I C   M E N   R   R E D

• Place a probe down the glottis to see it emerge in the trachea.   Now remove a lung by cutting the trachea right before it branches to the two bronchi.

1. Place it flat on your dissecting tray with the ventral surface up.

2. Make a cut parallel to the tray through the lung.

3. Open up the lung and draw the inside under the dissecting microscope and label the bronchioles.  (What are all the tubes within the heart?  Other than being proportionately larger, how do you think our lungs are different?)

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• Draw the esophagus and show the connection to the top of the stomach.   Place a probe down the opening to the esophagus - the glottis - to see it emerge in the esophagus.

• Using the scissors, cut the most anterior end of the esophagus and the most posterior end of the large intestine.

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1. Gently remove the digestive tract from the body, making sure not to danage the spleen or the testes - for those with a male frog - where it is connected to the mesentery.

2. Gently cut all the mesentery from between the loops of the small intestine.

3. Stretch out the entire digestive tract and measure its length in centimeters.  Now measure the frog's body length in centimeters from the tip of the jaw to the bottom of the groin  - "head to rump".  Express the ratio as a GI - gastro-intestinal - tract to Body ratio (i.e. x  : 1).  (Would you expect an herbivore to have a similr, larger, or smaller ratio?   Explain.)

• Cut open a section of the small intestine and draw the inside under the dissecting microscope.  (How is it different from the inside of the stomach?   How can you explain those differences [i.e. in terms of the functions of the small intestine]?)

Lymphatic System     top

S L I C   M E N   R   R E D

• The lymphatic system not only drains fluid in lymphatics, but it also fight infection in organs such as the tonsils and the spleen.  (Why does a person infected with mononucleosis run the risk of having her/his spleen rupture?)

Reproductive System     top

S L I C   M E N   R   R E D

• Reproductive organs:

1. FEMALE: Draw the oviducts and where they connect to the posterior end of the abdomen.  (Why do they connect there?  To what structure do they connmect?)
     a. Compare a female frog with small, beige and black oviducts, to a female frog with large black and white oviducts.  Explain the difference.  Through what structure are the eggs laid?)

2. MALE: Draw the testes and the vestigial oviducts.  (Why are there vestigial oviducts?  How is this related to Jurassic park?  Where do the testes connect?  Through what structure are the sperm released?)
      a. Cut open one of the testes and draw it under the dissecting microscope.   (Why does a reproductively fertile male have such small and simple testes?   HINT: refer to the gametes.)

Excretory System     top

S L I C   M E N   R   R E D

• Draw the kidneys.  NOTE: the kidneys are BEHIND the abdominal wall!!!  Cut open the connective tissue so you can see the actual surface of the kidneys.

1. Find and draw the ureters.  (Where do they go?  What do they carry?  Why isn't there a #1 and a #2 in a frog?)

2. Remove a kidney and pllace it flat on your dissecting tray with the ventral surface up

3. Make a cut parallel to the tray through the kidney

4. Open up the kidney and draw the inside under the dissecting microscope and label the renal pelvis (the open area inside.  (What collects there?  What structures would you see with a more powerful microscope that do the actual work of the kidney?  What is the function of the kidney?).

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Endocrine System     top

S L I C   M E N   R   R E D

• On top of the other kidney - it's actually on both, but it will be easier to see with the kidney in position - is a pale organ.   Renal means "kidney," and the prefix "ad-" means "on top of."  This organ is thus . . . the adrenal gland.   Draw it.  (What is its function?  To what body system does it belong?   Given the rapid response, what body system must control the release of its contents?)

• Another endocrine organ is the pancreas.   This function of the pancreas is unrelated to the digestive system.  The hormones produced are not released into the small intestine; they are released directly into the bloodstream.  (What are the two hormones?   What do they do?  NOTE: Given Mr. Lazaroff's chronic health condition, it would behoove you to know the answer to this!)

Nervous System     top
Peripheral Nervous System
Central Nervous System
Sensory Organs:    Eye    Ear

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S L I C   M E N   R   R E D

• Remove ALL of the remaining organs as well as the connective tissue along the back of the abdominal wall (this is known as then parietal surface).  Draw the following:

1. The vertebrae.  (What two basic functions do they perform?   HINT: the two functions relate to separate body systems!)

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2. The Spinal Nerves.  These travel laterally from either side of the spinal colomun between the vertebrae.  (Where do the nerves go after they disappear inbetween the vertebrae?  Where does this - Is it dorsal?  Is it ventral? - structure go?)

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• Turn the frog onto its ventral surface, so that it's dorsal surface is up (this is known as prone, as in "being prone to fall flat on your face . . ."  An organism on its back, as our frog has been for so long, is known as supine.).

1. Using the scalpal, cut through the bone holding the scalpal parallel to the skull.  It is necessary to cut throught the bone in order to expose the brain.   (What value is there to this brain-barrier?  Is is related to the vertebrae in function?  Which one evolved first: skull or spine?)

2. Note the two sides - dare we call them hemispheres?  (Why are there two sides?  Which side of the brain controls the left side of the body?)

3. Draw and label the following lobes (and be sure to describe the function of each):

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• Forebrain (what else is in the forebrain that is not listed below?   And beneath that area? [HINT: the prefix hypo = "below."   What other system is this area of the brain connected to?):

1. Olfactory bulbs  (What is their function?  Are ours proportionately larger, or smaller?  What does this say about the importance of this part of the brain to our survival?)

2. Cerebrum  (What is its function?  Is ours proportionately larger, or smaller?  What does this say about the importance of this part of the brain to our survival?)

• Midbrain:

1. Optic lobes (Connected to what sensory organ?  What area of the brain is the other sensory organ discussed above connected to?)

• Hindbrain:

1. Cerebellum  (What does this portion of the brain control?  Why does ours need to be proportionately larger than that of the frog?)

2. Medulla oblongata  (What basic body functions does this maintain?   Why do we still have one?)

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• What structure continues out the back of the brain?  (What is the foramen magnum?  Where is the frog's foramen magnum?  What does this say about the locomotion of the frog: quadruped or biped?  Could you tell the form of locomotion without seeing the legs [i.e. from the skull alone?]?  Explain.)

• (Which portion of the brain of those listed above has expanded the most in humans?  Given the relative size of that structure in the frog, what does it say about the mental capacity of the frog?  After comparing it  to the Earthworm and the Crayfish, do you care to revise your answer?)

• Remove one of the eyes.  (What is the name of the nerve that connects to the back of the eyeball?  What travels along it?)

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1. Make a cut from the front of the eye to the back, so that the eye is divided into top and bottom.  Draw the inside of the eye under the dissecting microscope.  (Is the eye solid?  If so, why?  If not, why not?  What is the eye filled with, and why?  What is the back of the eye called?  What does it do?  Is there any connection to the nerve?  What is the lens like?  What does it do?)

Drawings:    top

1. Use a PENCIL!!

2. Make the drawings "larger than life" size, as the specimens are so small.

3. Draw the general shape (outline) and location of the organs, as the squiggles so many of you use to "shade" your drawings make your drawings sloppy and hard to interpret.

4. Include Labels on all drawings.

• Labels should start outside the drawing, and be connected to the structure by arrows with tips (===>).

• The Tip of the arow should be touching the structure.

• Be sure to include the magnification for any drawings done with the dissecting microscope.

Hang on to the drawings; they will all be handed in later,
together with some questions to answer.

Click Image to ENLARGE!

Day 1    Day 2     Day 3    Day 4    Day 5    Day 6    top
S L I C   M E N   R   R E D

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