Download Day 1 - TeacherWeb

Name: ______________________________
Life Science 7- Mr. Raucci
Frog Dissection
Date: ____________
Period ___________
Objectives & Purpose: To study the internal and external anatomy of a frog. Describe the appearance of various organs
found in the frog. Name the organs that make up various systems of the frog.
Materials:
safety goggles, gloves, and a lab apron
forceps
preserved frog
dissecting pins (6–10)
dissecting tray and paper towels
CLASSIFICATION:
Kingdom - Animalia
Phylum - Chordata
plastic storage bag
scissors
dissecting needle
probe
Class - Amphibia
Order – Ranidae
Genus - Rana
Species – pipiens
Background
As members of the class Amphibia, frogs may live some of their adult lives on land, but they must return to water to
reproduce. Eggs are laid and fertilized in water.
Day 1
External Anatomy:
On the outside of the frog’s head are two external nares, or nostrils; two tympani, or eardrums; and two eyes, each of which
has three lids. The third lid, called the nictitating membrane, is transparent. Inside the mouth are two internal nares, or
openings into the nostrils; two vomerine teeth in the middle of the roof of the mouth; and two maxillary teeth at the sides of
the mouth. Also inside the mouth behind the tongue is the pharynx, or throat. In the pharynx, there are several openings:
one into the esophagus, the tube into which food is swallowed; one into the glottis, through which air enters the larynx, or
voice box; and two into the Eustachian tubes, which connect the pharynx to the ear.
Identify the following structures:
1.
skin – dorsal and ventral
2.
external nares
3.
tympani
4.
eyes
a. eyelids (2)
b. nictitating membrane (1)
5.
mouth (cut corners open about 1 cm)
a. internal nares
b. vomerine teeth
c. maxillary teeth
d. esophageal opening
e. glottis to the larynx
f. Eustachian tubes
g. Tongue
6.
Cloaca
Procedures: (use only blunt probes)
1) identify your frog as male or female (male
tympani are larger than their eyes and
they have thick pads on their thumbs)
2) tap on the tympani externally and then internally
through the eustacian tube
3) stick the probe from the external nares in through
to the internal nares
4) Insert a straw into the glottis and gently blow
blow a small amount of air in
5) feel the tongues rough surface – lift the tongue
6) Carefully insert about 1 cm of the blunt probe
into the gullet (esophageal opening)
7) remove the upper palate skin to reveal muscles
of the eyes
Observations:
a)
b)
c)
d)
e)
f)
g)
What color was the frog’s belly and back? Why would this be beneficial?
How are the front legs/toes different from the back legs/toes?
Why does the frog’s eyes bulge upward?
Why is the frog’s tongue so rough?
How did the frog’s chest size change when you forced air into the glottis?
What are the 2 vomerine teeth for?
What is the eardrum connected to?
Day 2
The digestive system consists of the organs of the digestive tract, or food tube, and the digestive glands. From the
esophagus, swallowed food moves into the stomach and then into the small intestine. Bile is a digestive juice made by the
liver and stored in the gallbladder. Bile flows into a tube called the common bile duct, into which pancreatic juice, a
digestive juice from the pancreas, also flows. The contents of the common bile duct flow into the small intestine, where
most of the digestion and absorption of food into the bloodstream takes place. Indigestible materials pass through the large
intestine and then into the cloaca, the common exit chamber of the digestive, excretory, and reproductive systems.
The respiratory system consists of the nostrils (nares) and the larynx, which opens into two lungs, hollow sacs with thin
walls. The walls of the lungs are filled with capillaries, which are microscopic blood vessels through which materials pass
into and out of the blood.
The circulatory system consists of the heart, blood vessels, and blood. The heart has two receiving chambers, or atria, and
one sending chamber, or ventricle. Blood is carried to the heart in vessels called veins. Veins from different parts of the
body enter the right and left atria. Blood from both atria goes into the ventricle and then is pumped into the arteries, which
are blood vessels that carry blood away from the heart.
The urinary system consists of the frog’s kidneys, ureters, bladder, and cloaca. The kidneys are organs that excrete urine.
Connected to each kidney is a ureter, a tube through which urine passes into the urinary bladder, a sac that stores urine until
it passes out of the body through the cloaca.
The organs of the male reproductive system are the testes, sperm ducts, and cloaca. Those of the female system are the
ovaries, oviducts, uteri, and cloaca. The testes produce sperm, or male sex cells, which move through sperm ducts, tubes
that carry sperm into the cloaca, from which the sperm move outside the body. The ovaries produce eggs, or female sex
cells, which move through oviducts into the uteri, then through the cloaca outside the body.
The central nervous system of the frog consists of the brain, which is enclosed in the skull, and the spinal cord, which is
enclosed in the backbone. Nerves branch out from the spinal cord.
The frog’s skeletal and muscular systems consist of its framework of bones and joints, to which nearly all the voluntary
muscles of the body are attached. Voluntary muscles, which are those over which the frog has control, occur in pairs of
flexors and extensors. When a flexor of a leg or other body part contracts, that part is bent. When the extensor of that body
part contracts, the part straightens.
Frog Dissection (answer questions on separate page)
1.
2.
Put on safety goggles, gloves, and a lab apron.
Place a frog on a dissection tray. To determine the frog’s sex, look at the hand digits, or fingers, on its forelegs. A
male frog usually has thick pads on its "thumbs," which is one external difference between the sexes, as shown in
the diagram below. Male frogs are also usually smaller than female frogs. Observe several frogs to see the
difference between males and females.
Is your frog male or female? Answer here __________________________________
Female
3.
Male
Use the diagram below to locate and identify the external features of the head. Find the mouth, external nares,
tympani, eyes, and nictitating membranes. You can also use the dissection drawings. Be sure to label the diagram
handout.
4.
Turn the frog on its back and pin down the legs. Cut the hinges of the mouth and open it wide. Use the diagram
below to locate and identify the structures inside the mouth. Use a probe to help find each part: the vomerine teeth,
the maxillary teeth, the internal nares, the tongue, the openings to the Eustachian tubes, the esophagus, the
pharynx, and the slit-like glottis. Remove upper palate skin to reveal the muscle of the eyes.
5.
Look for the opening to the frog’s cloaca, located between the hind legs. Use forceps to lift the skin and use
scissors to cut along the center of the body from the cloaca to the lip. Turn back the skin, cut toward the side at
each leg, and pin the skin flat. The diagram above shows how to make these cuts.
Examine the lower side of the skin and note the pattern of the blood vessels. Study the muscle layers exposed by
the removal of the skin. Now, remove the muscle layers in the chest region in same manner in which you removed
the skin. In the region of the thorax, it will be necessary to cut through the bones of the arms and the shoulders.
Remove the muscle layers with your forceps.
6.
Lift and cut through the muscles and breast bone to open up the body cavity. If your specimen happens to be a
female, the body cavity will probably be nearly filled with eggs. In this case, it will be necessary to remove the
eggs with your forceps before proceeding further. Note that the eggs are loose in the body cavity. You will find
also, two long coiled , white oviducts leading from the anterior end of the body cavity to the posterior end. These
are the tubes through which the eggs pass and should not be confused with other tubular structures to be referred to
later.. If so, remove the eggs on one side so you can see the organs underlying them.
7.
Use the diagram above, locate and identify the organs of the digestive system: esophagus, stomach, small
intestine, large intestine, cloaca, liver, gallbladder, and pancreas.
Find the 3-lobed liver high in the body cavity. Spread the lobes of the liver apart with your probe and find the
bright, green gall bladder .Raise the liver on the left side and notice the position of the stomach. Follow the
intestine from the lower end of the stomach to the large intestine. Examine the mesentery and the manner in
which it holds the intestine in place. Find the spleen on the mesentery. The pancreas is attached to the lower part of
the stomach.
Next, remove the liver, using care not to damage other organs. Cut through the gullet at its upper end. Raise the
stomach with your forceps and carefully loosen the intestine as far as possible.The cloaca lies below the large
intestine between the hind legs. Lay the alimentary canal in your dissecting pan. Pin the stomach at the top and the
large intestine at the bottom. Find the muscular valve, the pylorus, at the lower end of the stomach, where it joins
the intestine.
8.
Again refer to the diagram to identify the parts of the circulatory and respiratory systems that are in the
chest cavity. Find the left atrium, right atrium, and ventricle of the heart. Find an artery attached to the heart and
another artery near the backbone. Find a vein near one of the shoulders. Find the two lungs.
Examine the heart ,which lies in a thin sac, the pericardium. Using your probe, find the great veins and arteries
leading to and from the heart. Examine the lungs and notice the pulmonary veins and arteries connecting the heart
and lungs. See if you can find the trachea leading from the mouth to the lungs. Remove the heart, severing the
necessary blood vessels. Examine the front side of the heart with our hand lens. The large vessel arising from the
ventricle, extending over the front surface of the heart, and forming a Y at the top of the heart is the conus
arteriosus. This great compound vessel sends one branch to the head, a second branch to the body, and a third
branch to the lungs and skin. Examine the dark, red, lobed kidneys lying along the back of either side of the spine.
Find a small, twisting tube, the ureter leading from each kidney to the cloaca for storage. Do not confuse the
ureters with the oviducts in a female .If your frog is an immature female, you will find two lobed, grayish ovaries
lying close to the kidneys. The testes of the male are in a corresponding position. Find the yellow, finger-like fat
bodies attached above the kidneys.
9.
Use a probe and scissors to lift and remove the intestines and liver. Use the diagram on the next page to
identify the parts of the urinary and reproductive systems. Remove the peritoneal membrane, which is connective
tissue that lies on top of the red kidneys. Observe the yellow fat bodies that are attached to the kidneys. Find the
ureters; the urinary bladder; the testes and sperm ducts in the male; and the ovaries, oviducts, and uteri in the
female.
SPINAL CORD AND NERVES: 15. During this work, refer to the accompanying chart of the nervous system in ventral
view. Study the spinal cord and note that it narrows down to a thread-like body, filum terminale at the posterior end. Now
turn the frog over and pin it out. Remove all of the viscera, taking care not to injure the nerves. There are ten spinal nerves
given off in pairs from the spinal cord.
THE MUSCULAR SYSTEM
16: Remove the skin from an uninjured hind leg. The flesh is now seen to be made up of a considerable number of muscles,
which may be readily separated from each other. These muscles fall into two categories: the flexors, which bend a joint;
and the extensors, which straighten it .Each muscle has a thickened middle portion and tapers toward the ends. Muscles are
attached to bones by tendons, which are continuous with the connective tissue sheath that surrounds and binds together the
numerous muscle scales making up each muscle.
Name: ____________________
Life Science – Mr. Raucci
Date: _______
Period: _____
Frog Lab Questions
The eustacian tubes connect the _______________ to the __________________.
In children, the eustacian tubes point downward from the mouth to the inner ear. How does this promote ear infections?
_____________________________________________________________________
_____________________________________________________________________
As the childs head grows the tubes change position so that they point upward from the mouth to the inner ear, therefore
adults have ___________________(more or less) ear infections than children.
The passage way that begins as the internal nares ends as the ____________________.
Name 3 parts/organs in the digestive system _______________________,__________________________,
___________________
Name 2 structures that help to clean the blood ________________, ________________
What does the nictitating membrane do?
___________________________________________________________________________________________________
_____________________________________________
What organs would be found in a female reproductive system?
1)
2)
What structures would be found in a male reproductive system?
1)
2)
How many lobes does a frog liver have? _______________________
Where is the gallbladder located? ____________________________________________
What kinds of things did you find when you opened the digestive tract> _____________
_______________________________________________________________________
What system includes the heart and the blood vessels? ____________________________
What system moves bones? _________________________________________________
Name 3 systems involved in waste removal? ___________________________________
Why would the small intestines have a lot of blood vessels around them? _____________
________________________________________________________________________
What color was the frog’s belly and back? Why would this be beneficial?
________________________________________________________________________
How are the front legs/toes different from the back legs/toes?
________________________________________________________________________
Why does the frog’s eyes bulge upward?
________________________________________________________________________
Why is the frog’s tongue so rough? _________________________________________________________
How did the frog’s chest size change when you forced air into the
glottis?________________________________________________________________________________
What are the 2 vomerine teeth
for?___________________________________________________________________________________
What is the eardrum connected
to?___________________________________________________________________________________