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Frog (Rana pipiens) Dissection Lab
Fill in the following information on the classification of your frog (use this website
http://www.ncbi.nlm.nih.gov/Taxonomy/taxonomyhome.html/ ):
Kingdom
Phylum
Sub-Phylum
Class
Order
Family
Genus
Species
The frog is a vertebrate, and as such, has many characteristics in common with other
vertebrates, including man. A study of the anatomy of the frog can give us some insight into
the structure and function of our own bodies.
Place your frog in a dissecting pan. (Do not pin it down yet, answer the following questions
first.)
External Anatomy
The body of the frog may be divided into two regions: the HEAD and the TRUNK. There is no
neck region or tail in the adult.
The anterior region of the head contains a broad mouth above which are the two external
nostrils which may be closed by nasal flaps during respiration.
1.
Make a lateral or side view drawing of your frog and then find and label the following
parts or body regions.
ANTERIOR
VENTRAL
EXTERNAL NOSTRILS
POSTERIOR
EYE
TYMPANIC MEMBRANE
DORSAL
MOUTH
2. Observe the coloration and markings on the dorsal and ventral surface of the frog.
Explain how this may be helpful to the frog in its natural environment.
3. Look closely at the frog’s eye. Find the semi-transparent NICTITATING MEMBRANE
that comes up from below the eye. What is the function of this covering?
2
Skeleton
The following is a diagram of the dorsal view of a frog’s skeleton. Using the diagram provided,
label the following bones clearly.
MAXILLA
SUPRASCAPULA
FEMUR
PHALANGES
VERTEBRAE
TIBIOFIBULA
RADIO-ULNA
ILIUM
TARSALS
HUMERUS
UROSTYLE
ISCHIUM
Mouth Cavity
Before opening the body cavity and directly studying the organs of digestion, you will examine
the mouth cavity and its structures.
Open the mouth by inserting the scalpel between the jaws and prying. Make a cut on each
corner of the mouth to open the mouth wide.
1.
Lift up the tongue. At which end is it fastened?
2. What is the shape of the free end of the tongue?
3. Rub your finger over the inner surface of the upper jaw. Are there any teeth?
4. Find the slit like opening in the back lower portion of the mouth. This is the GLOTTIS,
the opening of the tube leading down into the
.
The opening behind the glottis leads into the ESOPHAGUS, which is the passage to the
.
5. Insert a piece of wire into one of the frog’s nostrils. Where does it come out inside the
roof of the mouth?
3
6. On the drawing provided, label the following structures:
VOMERINE TEETH
MAXILLARY TEETH
INTERNAL NOSTRILS
ESOPHAGUS OPENING
GLOTTIS
TONGUE
OPENING OF EUSTACHIAN TUBE
OPENING OF VOCAL SACS
Muscles
There are essentially three different muscle types present in our bodies: The involuntary
(smooth) muscles of the gut, the cardiac or heart muscles, and the voluntary (skeletal or
striated) muscles.
Many skeletal muscles taper at the ends into tough white cords or tendons, which attach the
muscle to the bone. Such muscles have two points of attachment. The end that acts as the
point of anchorage and remains fixed during contraction of the muscle is the origin. The other
movable end or point of attachment is called the insertion.
Voluntary muscles of the skeleton always function in opposing pairs. Extensors are muscles that
straighten out a joint, while flexors are muscles that bend a joint.
Remove the skin from the ventral side of the body trunk as indicated by your teacher. Also
remove all the skin from one of the back legs.
Ventral Muscle Surface: Neatly draw the ventral view of your frog and label the following
muscles.
SUBMAXILLARY
DELTOID
PECTORALIS MAJOR
RECTUS ABDOMINOUS
EXTERNAL OBLIQUE
SARTORIUS
GRACILIS MAJOR
GRACILIS MINOR
GASTROCNEMIUS
TIBIALIS ANTERIOR
also show ACHILLES TENDON
Ventral view of muscles.
4
Dorsal Leg Surface: Draw the dorsal view of one leg and label the following muscles.
TRICEPS FEMORIS
GRACILIS MINOR
PERONEUS
SEMIMEMBRANOUS
GASTROCNEMIUS
ACHILLES TENDON
Dorsal view of leg.
Internal Anatomy
Now place your frog ventral side up in the dissecting pan. Follow the instructor’s directions for
cutting into the frog.
On the next page, draw and label each of the organs of the frog as you find them during the
rest of this lab.
1.
Examine the heart after opening the pericardium, the membranous
tissue surrounding the heart. Make a drawing of the frog’s heart and
label the two atria and one ventricle.
2. The liver is the largest reddish-brown organ posterior to the heart. The
liver is composed of parts called lobes. How many lobes of the liver are
there?
3. On the right side of the liver, beneath it or protruding from it, is the gall bladder, a
small greenish sac. What does the gall bladder do?
4. The lungs are sac-like organs on both sides of the thorax (chest cavity). Place one end
of a glass tube in the glottis. Try to blow up the lungs by blowing through the tube.
Next cut open one of the lungs. What do the lungs look like inside?
5. If the frog is female, the abdomen may be filled with small black and white eggs. Gently
remove the eggs and put them in a paper towel. Look for the oviducts, or egg laying
tubes, which will appear as small twisted white tubes. IF YOUR FROG IS MALE, BE
SURE YOU OBSERVE A FEMALE ALSO.
6. Locate the small intestine. Trace it upward to the stomach and downward to the large
intestine, rectum and cloaca. Locate the pancreas, a narrow band of tissue between the
stomach and the first loop of the intestine.
7. Locate the yellowish fat bodies. Find the round, reddish-brown body called the spleen.
The spleen stores red blood cells. The oblong, reddish kidneys lie near the backbone of
the frog. You will have to push aside other organs to see them. If the frog is a male,
the two bean-shaped testes will be found lying against the kidneys.
WHEN YOU HAVE FINISHED THE ENTIRE LAB AND HAVE HAD YOUR WORK CHECKED
BY YOUR’S TRULY, YOU MAY DISSECT YOUR FROG’S BRAIN OR EYE.
HEART
5
Draw and label the following structures you should have observed in your frog.
HEART
FAT BODIES
GONADS
LUNGS
PANCREAS
KIDNEYS
STOMACH
OVIDUCTS (♀)
GALL BLADDER
CLOACA
LIVER
SMALL INTESTINE
LARGE INTESTINE
URINARY BLADDER
SPLEEN
6
Internal Organ
Heart
Liver
Stomach
Small intestine
Large intestine
Lungs
Pancreas
Spleen
Kidneys
Fat bodies
Urinary bladder
Gonads (testes/ovaries)
Oviducts
Gall bladder
Cloaca
Body System
Function