Transcript Bio392-Frog Dissection

Which is a frog? Which is a toad?
How can you tell the difference?
How do frogs differ from toads?
Frogs
Toads:
• Need to live near water
• Have smooth, moist skin
that makes them look
“slimy”.
• Have a narrow body
• Have higher, rounder,
bulgier eyes
• Have longer hind legs
• Take long high jumps
• Have many predators
• Do not need to live near water
to survive
• Have rough, dry, bumpy skin
• Have a wider body
• Have lower, football shaped
eyes
• Have shorter, less powerful
hind legs
• Will run or take small hops
rather than jump
• Do not have many predators.
Skin lets out a bitter taste and
smell that burns the eyes and
nostrils of its predators.
Classification of the Frog
• Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Amphibia
Subclass: Lissamphibia
Order: Anura
Suborder: Neobatrachia
Family: Ranidae
Genus: Rana
Rules for Dissection
• 1. Do not mutilate the organism. Any unnecessary cutting or abuse of
the specimen will not be tolerated. Follow the directions and do not
go off on your own.
• 2. Do not even pretend to threaten classmates with any tool found in
the dissection kit. Any threat made will be taken as real and the
student will be turned into the school for violent intent.
• 3. Act accordingly. No horseplay. No throwing of anything. Once
you get started, stay in your seat with your group and focus on the
dissection. If you have questions – ask!
*Any violation of the above rules will result in the student being
instructed to put everything away, they will lose all dissection
privileges, they will get a zero on the dissection lab, and the will
have a visit to the local office and receive a detention*
Procedures for Dissection
• 1. You will be working with a partner
– If you do not want to dissect the frog, make sure that you a pick a
partner who will do the dissection
• 2. You will need to obtain the following materials before you
begin
–
–
–
–
Dissection tray
Scissors (Be careful, they are sharp)
Probe (Be careful, they are sharp)
Frog (Place the frog in your dissection tray)
• 3. We will be doing the lab together one section at a time.
When you have finished answering the questions for one
section, wait for instructions before beginning the next section.
Frog Dissection
Part 1: External Anatomy
A. Skin and Eyes
• 1. Observe the exterior of the
frog. Describe the texture and
color of the skin.
• 2. Observe the location of the
frog’s eyes relative to the head
-How might this be an
adaptation for its way of life?
B. Tympanic Membranes
#3 = ?
Tympanic membrane
• 3. Right behind the eyes are dark circular
structures called the tympanic membranes.
-What is their function?
D. Feet
• 4. Observe the frog’s feet.
Compare the frog’s feet to that of
humans. Develop a hypothesis as
to why the frog’s feet are shaped as
they are
-How is the structure of the frog’s
feet related to its function?
-How many toes are on the front
legs? How many toes are on the
back legs?
Part 2: Digestive System:
The Mouth
A. The Tongue
Cut the edges of the jaw with
scissors. Cut back till hear crack
(hit jaw bone)
• Compare the frog’s tongue to a
human’s
-1. How do the tip ends differ?
-2. How do the points of attachment to
the lower jaw different?
B. The Glottis and Esophagus
• Locate the slit-like glottis in the
center of the back of the mouth.
Use a probe to determine where
the glottis leads.
-3. To where does the glottis lead?
•Locate the esophagus. Using a
probe, determine where it leads
-4. To where does the esophagus
lead?
glottis
C. Teeth
Maxillary teeth
• Rub your fingers along the inside edge of the
frog’s upper jaw. You should feel the maxillary
teeth.
-5. Are any maxillary teeth also along the lower jaw
edge.
• Compare these teeth to human teeth
-6. How does their structures differ?
-7. Why do you think a frog’s teeth are this way
Vomerine teeth
•Extending from the roof of the mouth are two
vomerine teeth
-8. What is their function?
Part 3: Digestive System:
Internal Organs
Dissection Cuts
• 3 main cuts total
-1. Cut from abdomen up to neck
-2. Cut across front legs
-3. Cut across rear legs
*Have to perform cuts twice. Once to
cut through skin, then again to cut
through muscle*
*When finished, fold back skin flaps*
Dissection Cuts
http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin1_first.html
Skin First
1. Make the first incision in the skin along the center of
the frog between the rear legs.
(Take care to cut only the skin.)
2. Use the scissors to continue the incision up the midline
all the way to the frog's chin.
3. Stop cutting when your scissors reach the frog's chin.
Dissection Cuts
http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/skin2_horiz.html
Skin Horizontal
1. Use the scissors to make sideways incisions in the skin.
2. The first incisions are made between the front legs.
3. The next incisions are made just above the rear legs.
4. Be careful to only cut through the skin, not the muscle.
Dissection Cuts
http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle1_first.html
First Muscle Incision
1. Repeat the incisions, this time through the muscle
layer.
2. Make a small cut with the scissors at the rear legs of
the frog.
3. Using the scissors, continue the incision up the
midline to a point just below the front legs.
4. Be careful that you don't cut too deeply. The muscle is
thin. It is easy to damage the organs underneath.
Dissection Cuts
http://frog.edschool.virginia.edu/Frog2/Dissection/Incisions/muscle3_horiz.html
Muscle Horizontal
1. Make the horizontal incisions.
2. Just as you did with the skin, make a sideways
incision in the muscle with the scissors.
3. Make the first incision between the front legs.
4. The next incision is just above the rear legs.
Removal of Eggs
• If you have a female frog, you will have
many black circle shaped structures on
the inside of the frog when you it.
• These are eggs and need to be
removed so that you can see the organs
below them.
liver
A
Small
intestine
C
D
Large
intestine
General Structures
Inside Frog
B
stomach
A. Liver and Gall Bladder
Locate the liver and gall bladder
-1. How many lobes does the liver have?
-2. Describe the appearance and location of the
gallbladder.
Liver (large brown lobes)
Gall Bladder (greenish-brown sac)
-is located behind liver
B. Stomach
Locate the stomach and compare it to a human’s
-3. How do their shapes and locations compare?
Using scissor, cut along the outer curvature of the stomach toward the
pylorus. Examine the contents of the stomach and its lining
-4. Describe the lining of the stomach and compare to a human
-5. Describe the contents. Did the frog eat right before it was preserved?
What did it eat?
stomach
C. Small Intestine
Follow the stomach to the small intestine. The small intestine in the frog has
three portions just as in humans
-6. What are the three portions
The small intestine is surrounded by a thin membrane called the mesentery.
-7. What do you think is the function of the mesentery?
D. Large Intestine
Locate the large intestine
-8. To where does it lead?
Large intestine leads to cloaca.
-function of cloaca = collecting space
for urine, feces, and eggs or sperm
Remove the large intestine and cut it open
-9. Describe its interior
cloaca
Part 4: Circulatory System:
The Heart
A. The Heart
Remove the heart, leaving as much of the blood vessels attached as
possible. Examine the front side. Locate the right atrium, left atrium, and
ventricle. The large vessel arising from the ventricle and forming a “Y” at the
top of the heart is the conus arteriosus
-1. Make a sketch (below) of the heart, labeling the right and left atria,
ventricle, and conus arteriosus
*A frog heart only has 3 chambers: 2 atria and 1 ventricle*
Ventricle
Left atrium
Right atrium
Part 5: The Urogenital System
Is Your Frog a Girl or a Boy?
Female
Male
ovary/eggs
oviduct
Functions: transport
eggs, add jelly coating
Testes
Function: Make sperm
#1 = ?
Ovary with eggs
#2 = ?
oviducts
#2
#1
female
This frog is a ______________
female
male
?
?
testes
? = _______________
male
This frog is a ______________
male female
A. Urinary Bladder, Kidneys, and Oviducts
Locate the cream colored oviducts through which eggs pass from the anterior of the
body cavity to the posterior opening, the cloaca. Remove the oviducts to reveal the
brownish kidneys. The kidneys lie along the back of either side of the spine. Notice
they are covered by a thin, tough membrane, the peritoneum, which lines the body
cavity. Locate a small twisting tube, the ureter, leading from each kidney to the
cloaca. Attached to the cloaca is the urinary bladder.
-1. What is the function of the urinary bladder
-2. What is the function of the kidneys
-3. Make noteworthy observations of the following: oviducts and kidneys
kidney
Part 6: The Respiratory System
A. The Lungs
Locate the lungs situated near the heart. Make noteworthy observations of the
exterior of them. Now remove one lung and nearly slice it in half to expose the interior
surface. Make noteworthy observations of the interior.
-1. Lung observations: exterior and interior
Pink arrows
point to lungs
Frog Diagrams
THE END