Download Urogential System

Name:_____________________________________
Date:_________________________
FROG DISSECTION
LAB MANUAL
Prelab Discussion
The common grassfrog, Rana pipiens, belong to the class Amphibia. Amphibians have
adaptations for living in terrestrial as well as aquatic environments. Frogs are among the most
commonly studied organisms in biology. Although many differences exist between humans and
frogs, the basic body plans are similar. Humans and frogs both belong to the phylum Chordata.
By studying the anatomy of a frog, you will be better able to understand your own body.
In this investigation, you will examine the external features of a frog and identify parts of its
external anatomy. In addition, you will dissect a preserved frog to observe its internal structure.
Problem
How is a frog structured for survival?
Materials
Apron (if desired)
Dissecting pins
Dissecting tray
Forceps
Gloves
Hand lens
Medicine dropper
Paper towels
Plastic bag
Preserved frog
Probe
Scalpel
Scissors
Safety And Cleanup
Wear gloves at all times. If you are allergic to latex, notify me immediately, before putting on
gloves. Handle all instruments carefully. At end of lab, all instruments will be washed and dried thoroughly
and placed back into the dissecting kit. The dissecting kits will be inspected for cleanliness and completion
before and after each lab session. The lab bench will be washed and dried. If the frog will be used another
day, wrap it in a wet paper towel and place it in a plastic bag with a label. If not, the frog will be discarded.
Massachusetts State Frameworks:
4. Anatomy and Physiology
Central Concepts: There is a relationship between the organization of cells into tissues and the organization of
tissues into organs. The structures and functions of organs determine their relationships within body systems of an
organism. Homeostasis allows the body to perform its normal functions.
4.1
4.2
4.3
4.4
Explain generally how the digestive system (mouth, pharynx, esophagus, stomach, small and large
intestines, rectum) converts macromolecules from food into smaller molecules that can be used by cells for
energy and for repair and growth.
Explain how the circulatory system (heart, arteries, veins, capillaries, red blood cells) transports nutrients
and oxygen to cells and removes cell wastes. Describe how the kidneys and the liver are closely associated
with the circulatory system as they perform the excretory function of removing waste from the blood.
Recognize that kidneys remove nitrogenous wastes, and the liver removes many toxic compounds from
blood.
Explain how the respiratory system (nose, pharynx, larynx, trachea, lungs, alveoli) provides exchange of
oxygen and carbon dioxide.
Explain how the nervous system (brain, spinal cord, sensory neurons, motor neurons) mediates
communication among different parts of the body and mediates the body’s interactions with the
environment. Identify the basic unit of the nervous system, the neuron, and explain generally how it works.
4.5
4.6
Explain how the muscular/skeletal system (skeletal, smooth and cardiac muscles, bones, cartilage,
ligaments, tendons) works with other systems to support the body and allow for movement. Recognize that
bones produce blood cells.
Recognize that the sexual reproductive system allows organisms to produce offspring that receive half of
their genetic information from their mother and half from their father,
Procedure
Part A – External Anatomy
1. Put on gloves and apron, if desired.
2. Obtain a dissecting kit. Obtain a dissecting tray and frog. Wash frog gently but thoroughly under running water to remove
excess preservative. CAUTION: The preservative used on the frog can irritate your skin. Avoid touching your eyes while
working with the frog. Dry the frog with paper towels and place it in a dissecting tray.
3. Identify the dorsal and ventral surfaces and the anterior and posterior ends of the frog. When you are ready to show that
you have learned this section; call the teacher over to initial your demonstration of this.
________ dorsal
__________ ventral
__________ anterior
__________ posterior
4. Locate the forelegs and hindlegs. Each foreleg, or arm, is divided into four regions: upper arm, forearm, wrist, and hand.
Each hindleg also has four regions: thigh, lower leg, ankle, and foot. Identify the parts of the forelegs and hindlegs. Examine the
hands and feet of the frog. If the hands have enlarged thumbs, the frog is a male.
(check one) My frog is a _______________ male
_________________ female
5. Locate the large, protruding eyes. Lift the outer eyelid using a probe. Beneath the outer lid is an inner lid called the nictating
membrane.
6. Posterior to each eye is a circular region of tightly stretched skin. This region is the tympanic membrane, or eardrum.
Locate the tympanic membranes on both sides of the head.
__________ tympanic membrane
7. Anterior to the eyes, locate two openings called the external nares (singular, naris), or nostrils.
___________ external nares
8. Label the External Anatomy diagram.
9. Hold the frog firmly in the dissecting tray. Using scissors, make a small cut at each of the hinged points of the jaw, as shown
below. CAUTION: To avoid injury, cut in a direction away from your hands and body. Open the mouth as much as possible.
Under running water, rinse away any excess preservative if necessary.
10. The tongue is the most noticeable structure in the mouth. Observe where the tongue is attached and note the two
projections at the free end.
11. At the back of the mouth, locate the large horizontal opening, the gullet opening.
12. Examine the roof of the mouth. Near the front center, are two small bumps, the vomerine teeth, and on either side of these,
are the internal nares. The bulges behind the vomerine teeth are the eye sockets. Run your fingers along the top jaw. The
teeth you feel are the maxillary teeth. The openings of the Eustachian tubes are on either side near the back of the mouth.
Insert a probe into an opening of one Eustachian tube, and note where the probe stops.
________ internal nares __________ vomerine teeth __________ eustation tubes
Part B - Internal Anatomy
1. Place frog on tray with ventral surface up (belly up). Securely pin the frog’s hands and feet to the bottom of the dissecting
tray, as shown below.
2. With forceps, lift the loose skin of the abdomen. Carefully insert the tip of a pair of scissors beneath the skin. Cut away from
your body. Cut along line AB as shown above. Continue cutting lines CD and EF. Be sure not to cut deeper than the skin.
3. With your fingers and the probe, separate the skin from the underlying muscles. Open the flaps of skin as far back as
possible and pin them to the bottom of the dissecting tray. Note the muscles.
4. Carefully lift the abdominal muscles with the forceps. Cut a second AB incision. Keep the cut shallow so you don’t
damage the underlying organs. You will need to cut through the pectoral bone (the rib cage of the frog). Then make second
cuts of CD and EF. Open the abdomen as much as possible. You may need to re-pin.
5. Study the positions of the exposed organs. Most organs are held in place with a thin, tough membrane called mesentery.
6. If the frog is a mature female, the most obvious organs may be the ovaries, white sacs swollen with tiny black-and-white
eggs. Carefully lift the ovaries and cut at the base of them to remove them. If they burst, the eggs will spill out in a big mess.
________ ovaries/eggs
__________ no ovaries and eggs
7. The large reddish-brown organ in the upper part of the abdominal cavity is the liver.
8. With your fingers or a probe, lift and separate the lobes of a liver upward. Behind the middle lobe, look for a small greenish
gland, the gallbladder. Cut out the liver and gallbladder, place it in your tray. The rest of the organs will be much easier to see
with this cut out.
________ Liver __________ gallbladder
DIGESTIVE SYSTEM
9. Locate the esophagus, which is a white tube leading from the mouth and connecting to the upper part of the white, muscular
stomach. Notice the shape of the stomach. The stomach leads to the small intestine (long and coiled). Notice the mesentery
that holds the intestines in place. Inside the first loop of the small intestine near the stomach, locate a thin, white organ called
the pancreas (looks like a tongue with black spots on it – it makes insulin). Also in the intestinal mesentery, locate a brown
bean-shaped organ called the spleen (makes blood cells, so it looks blue).
10. The small intestine ends in a large bag-shaped organ, the large intestine. The last organ of the digestive system is the
cloaca, a saclike organ at the end of the large intestine. Undigested food leaves the frog’s body through an opening called the
anus.
Your teacher will, cut the esophagus near the stomach and then cut through the large intestine just above the cloaca. With
his/her fingers, he/she will carefully remove the digestive system from the body and stretch out the digestive system so that you
can measure it, and record this in the questions.
12. Open the stomach and examine its structure and contents. Dispose of the removed organs. Label the Digestive System
diagram.
________ espohagus
__________ stomach
__________ small intestines
__________ large intestines
__________pancreas
__________ spleen
__________ anus
Respiratory System
13. Locate the two lungs. They are small, spongy brown sacs that lie to the right and left of the heart. Look for the bronchial
tubes that extend from the anterior part of the lungs and join with the trachea or windpipe.
14. Insert a dropper into the glottis of the frog. Pump air into the lungs and observe what happens.
15. With scissors and forceps, carefully remove the lungs from the frog’s body. Dispose of the lungs according to your teacher’s
instructions.
Circulatory System
16. Locate the heart. The heart is encased in a membranous sac called the pericardium. With the tip o f the scissors, carefully
cut open the pericardium.
17. Note the vessel attached to the heart. The large artery on the ventral surface of the heart is the coronary artery. NOTE: If
the frog has been injected with red and blue latex paint, the veins and arteries will be obvious.
Urogential System
18. If your frog is a male, locate the testis; if your frog is a female; locate the ovaries.
LAB PRACTICAL: Know each of the following
EXTERNAL ANATOMY:
Directional terms
______ anterior, ______ posterior
______hindlimb ______ foo,
______external nares
______ dorsal
______ ventral
_______ hand
______ eye
______ tympanic membrane
______ nictating membrane.
MOUTH:
______ internal nares
______ maxillary teeth
______openings to Eustacian tubes ______ tongue
______vomerine teeth
______ gullet opening
DIGESTIVE:
______ esophagus ______ stomach ______ small intestine
______ liver
______ gallbladder______ pancreas
______ eye sockets
______ large intestine
______ anus
UROGENITAL SYSTEM:
(male): ______ kidney ______ fat body ______ urinary bladder ______ cloaca
______ trachea
REFERENCE GUIDE
______ cloaca
______ testes
(female): ______ kidney ______ fat body ______ urinary bladder ______ cloaca ______ ovary
RESPIRATORY:
______ Lungs
______ forelimb
______ mouth
QUESTIONS
1. Describe how the eyes of a frog close.
2. Describe how a frog jumps.
3. Are the hindlegs or forelegs more important in jumping?
4. Is the skin of the frog smooth or rough? Moist or dry?
5. Describe the color of the dorsal and ventral surfaces of the frog.
6. How many digits (fingers) are on each of the frog’s hands?
7. How many digits are on each of the frog’s feet?
8. Is your frog male or female? How can you tell?
9. Where is the nictating membrane attached?
10. Where is the tongue attached to the mouth?
11. How many lobes does the liver contain?
12. What is the shape of the stomach?
13. Describe the mesentery that holds the intestines.
14. Describe the general shape, or plan, of the frog’s digestive system.
15. How long (in centimeters) is the entire digestive system?
16. Describe the inside walls of the stomach.
17. Describe the contents of the frog’s stomach.
18. What happens when air is pumped into the lungs?
19. Describe the movement of the leg muscles as the leg is bent and straightened.
ANALYSIS AND CONLCUSIONS
1. How are the feet of a frog adapted for swimming?
2. How is the coloration of the frog an adaptation to its habitat?
3. How is the location of the nares an adaptation to living in water?
4. How is the location of the nares and adaptation to living in water?
5. The tip of the tongue in a live frog is sticky. What would be an advantage of this?
6. Frogs are insect eaters. How is the frog’s tongue designed for the type of food it eats?
7. How does the length of the small intestine relate to its function in absorbing digested food?
8. List three adaptations that permit the frog to live on land successfully.
a.
b.
c.
9. List three adaptations that permit the frog to live in water successfully.
a.
b.
c.