Name ______________________________
Per ____
Date_______
DISSECTION GUIDE FOR THE RAT – A BODY SYSTEMS ANALYSIS
INTRODUCTION:
Rats are mammals and belong to the genus Rattus. . The word “mamma” in Latin means these animals feed their young
through mammary glands within the breast. Mammals are also warm-blooded and covered with hair.
By studying the anatomy of the rat, you gain a better understanding not
only of human anatomy but also of other vertebrates as well.
LAB
Participation
Diagram
Clean up
Conclusion
CLEAN UP:
Each member of the dissection group will have a specific task for clean up
after the dissection. Multiple members of the group can participate in the
Total =
dissection, but it is not required.
Tasks include:
 Dissection
 Washing the table
 Returning the goggles & aprons
 Washing the tools & tray
MATERIALS:
 6- Pins
 Dissecting tray
- Forceps



Hand lens
Paper Towels
Probes



PTS
10
9
5
6
30
RECEIVED
Rat
Ruler
Scissors
PROCEDURE: PART A: External Anatomy
1. Rinse you rat with tap water to remove excess preservative. Place a label or tag with your name on it around a leg
of your rat.
2. The body is divided into a head and trunk, separated by the neck region.
3. There are two pairs of appendages attached to the trunk, the hindlimbs arising from the pelvic region and the
forelimbs arising from the shoulder region. On each of these feet, are the digits, digital pads, and the foot pads.
4. Use a ruler to measure your rat, measure from the tip of the head to the end of the rat's backbone
Your Rat (cm)
(do not include the tail in your measurement).
5. Note the hairy coat that covers the rat and the sensory hairs [whiskers] located on the rat’s face,
called vibrissae.
6. The mouth has a large cleft in the upper lip; the large front incisors. Rats are gnawing mammals and these incisors
will continue to grow for as long as the rat lives.
7. Locate the rat's eyes. The nictitating membrane is a clear membrane that attached to the inside corner of the eye
which helps to keep eyes moist in air and protected.
8. Examine the tail; the tails of rats do not have hair, although some rodents like gerbils have hair on their tails.
Adapted from John Sowash’s Rat Dissection ©2009
9. Locate the anus; it is ventral to the base of the tail.
10. Locate the teats on the ventral surface of the rat; these mammary papillae, which extend from the armpit region to
the groin region on either side of the midline. In rats there are usually 12 pairs which are most prominent in
pregnant or lactating females. Check a rat of another sex and determine whether both sexes have teats. YES or NO
11. Notice! Your rat is to be used to observe many systems in the investigations to
come. Therefore, it is important that directions for dissections be followed
exactly. Do not remove any organ or structure unless you are directed to do so.
12. Place the rat in the dissecting pan ventral (or belly) side up.
13. Like all tetrapods (four limbs or feet), your rat has two “cavities” in its body. The
abdominal cavity, containing the gut and its associated organs, and the thoracic
cavity (chest), containing the heart and lungs. The two cavities are separated by
the diaphragm, or breathing muscle.
14. Before you begin to open these cavities, remember one thing: Your goal is to
open both body cavities without spoiling or cutting the internal organs!
15. Use the forceps or scissors to lift the abdominal muscles away from the body
cavity.
16. Cut along the midline of the body from the pelvic to the mouth of the rat (see
picture).
17. Make lateral (horizontal) cuts near the arms and legs.
18. Lift the flaps of the body wall and pin back.
Image
Image
PART B: Internal Anatomy
19. Locate each of the organs below. Check the box to indicate
that you found the organs. If you have any questions, please
ask. You will be quizzed on the following as a group, so it is
important that everyone in your group can identify the parts
listed.
20. Esophagus – tube leading from the mouth to the stomach 
21. Trachea – tube leading from the mouth; the windpipe with
tough, cartilage rings 
22. Heart - at the top of the liver, the heart is a triangular
structure; mammalian hearts have four chambers 
23. Lungs - spongy organs on either side of the heart 
24. Diaphragm - a thin sheet of muscle beneath the lungs;
separates the chest and abdominal cavities 
25. Liver - a large, dark brown, multi-lobed liver, beneath to the
diaphragm 
26. Stomach - under the liver, the comma-like structure
underneath the liver is the stomach on the left side of the rat’s
body 
27. Spleen - the left side of the stomach is a long, slender, brown,
banana shaped organ [filters blood] 
28. Pancreas - light colored, located in the mesentery between
the stomach and the small intestine [produces digestive
29.
30.
31.
32.
enzymes] 
Small Intestine - after the stomach, tightly coiled 
Large Intestine – larger than the small intestine, it loops around the abdominal cavity and ends with the rectum 
Kidney – dark, bean shaped organs located at the lower back, near the spine; you may need to move the intestines
to the side to see 
Bladder – locate the ureter leaving the kidney and trace it down to the bladder 
Image
33. If female –
a. find the off white, almond-shaped ovaries beneath the kidneys 
b. oviducts or fallopian tubes, loop behind the ovaries 
c. oviducts lead into the wider tubes called the uterine horns [multiple births are common in rats] 
34. If male –
a. locate the scrotum on either side of the anus; it contains the testes 
b. the vas deferens is a tube that leads from the testes carrying seminal fluid; it joins the urethra to exit
through the penis 
35. Observe another lab group to see the opposite sex.
36. Review the major organs of the rat with your group; call your teacher over when you are ready for the oral quiz.
PART C: If time permits
37. Measuring the Small intestine: Carefully cut the mesentery (thin tissue surrounding the intestines) from intestinal
tube. Stretch the small intestine out and measure it.
Your Rat (cm) Intestines (cm)
38. Revisit number 4. Record the measurements below in centimeters.
a. Why is there such a difference in the length of your rat and the length
of the intestines?
POST LAB ANALYSIS:
Label the diagram using the
following:
–
Bladder
–
Diaphragm
–
Heart
–
Large intestine
–
Liver
–
Lungs
–
Small intestine
–
Stomach
–
Trachea
4. __________________________
7 & 9. _______________________
10. _________________________
11. _________________________
12. _________________________
13. _________________________
17. _________________________
19. _________________________
[after the small intestine]
20. _________________________
Image
Conclusion: What conclusions have you come to during the dissection about the way(s) that organ systems function in
the body and work together within an organism? What information was new and interesting? Explain.
Names
_____________________________________________________________
Per ____
Date_______
Names
_____________________________________________________________
Per ____
Date_______
DISSECTION GUIDE FOR THE RAT – A BODY SYSTEMS ANALYSIS
GROUP DISSECTION QUIZ
DISSECTION GUIDE FOR THE RAT – A BODY SYSTEMS ANALYSIS
GROUP DISSECTION QUIZ
Directions: Your teacher will quiz you on the major organs of the rat; each
group member is responsible for answering some of the questions
[individually] – some questions will be asked whole group.
Directions: Your teacher will quiz you on the major organs of the rat; each
group member is responsible for answering some of the questions
[individually] – some questions will be asked whole group.
1._______
1._______
2._______
2._______
3._______
3._______
4._______
4._______
5._______
5._______
6._______
6._______
7. _______
7. _______
8. _______
8. _______
9. _______
9. _______
10. ______
10. ______
Extra (If you missed one this could take its place if you get it right)________
Extra (If you missed one this could take its place if you get it right)________