Name: _________________________________
Rat Dissection
Introduction: The common rat originated in Southeast Asia and migrated west from China and India to
Europe. Scientists figure the rat traveled to Europe aboard ships in the 11 th and 12th centuries. The ships of
early European explorers brought the rat to the eastern North American coast by the mid 1500s.
External Anatomy
1. Label the following on the rat: dorsal, ventral, anterior, posterior (see page 700).
2. Mammals have two unique external characteristics which distinguish them from all other vertebrates:
3. Describe the outer covering of the rat.
4. How is the rat’s external anatomy similar to a human being? How is it different?
5. The external nares are situated on a more or less mobile nose which in some mammals may be
elongated and flexible. Why would it be important for the nose to “move”?
1
6. The ears possess a long, flexible external fold called the pinna. What is the function of the pinna?
7. The rat and many other mammals possess long sensory hairs on the face, chin and eyes called vibrissae.
What is the function of the vibrissae?
8. The tail of the rat has only a few scattered hairs. Why do you think the tail is so long?
9. The horny claws on the digits are derived from skin cells. Nails, horns and hooves are also derived from
skin cells. Name a mammal that has the following:
a. nails
b. horns
c. hooves
10. How does the rat walk? (Refer to the figure) The human foot structure allows us to walk on the soles
of our feet; this is called plantigrade. Horses, cattle and deer are considered unguligrade, allowing them
to walk on their flattened hooves (on their tiptoes). Rats, cats and other animals have digitigrade foot
structures, allowing them to walk on the digits with forefoot and hindfoot elevated.




Which of the letter choices in the figure above shows the rat’s form of locomotion? ______
Name of locomotion? _________________
Number of digits on one of the forelimbs: ___________
Number of digits on one of the hind legs: ____________
What might be an adaptive advantage for this type of foot arrangement?
2
11. The rat’s skin or integument is similar to that of other mammals. Under a microscope you can see that
the skin contains two distinct layers. There is a thin, top layer called the epidermis. This layer contains
non-living protein cells called keratin which function as the waterproofing layer. The dermis layer or
basement layer consists of a single layer of living cells that are in a state of continual growth. Hair,
nails, sweat glands, oil glands, blood vessels and nerve endings are embedded within the dermis region.
List three functions of the integumentary system for mammals. Use your textbook if necessary.
Skeletal System
Use the diagram of the human skeleton on pg 941 of your text book to label the corresponding bones on the rat.
Skull
Vertebra Radius
Carpals Femur
Clavicle
Ulna
Patella
Scapula
Pelvic Girdle
Tibia
Sternum
Metacarpals
Fibula
Humerus
Tarsals
Metatarsals
3
Muscular System
Use the diagram below to help you make incisions. Using the forceps to hold up the skin of the rat’s abdomen,
take the scissors and cut up towards the neck of the rat. Use pins to hold down the skin and examine the
muscles of the abdomen.
DO NOT CUT THE MUSCLES AND EXPOSE THE
INTERNAL ORGANS YET!!!
1. Describe what the muscles look like. Be as detailed as possible.
2. Most muscles are attached to bone by thick bands of white _____________________ tissue.
4
Digestive, Respiratory and Circulatory Systems
Use the scissors to make a shallow cut in the abdominal muscles. Open up the abdominal cavity in the same
manner that you cut open the skin. Peel back the abdominal muscles and pin them to your dissecting tray the
same way that you did for the skin.
BE CAREFUL NOT TO CUT ANY OF THE ORGANS
BENEATH THE ABDOMINAL MUSCLES!!
The trunk of the rat is divided into the thoracic and abdominal cavities. The two cavities are separated by a
muscle called the diaphragm. The thoracic cavity contains the esophagus, lungs and heart. The abdominal
cavity contains the stomach, intestines, liver, pancreas, spleen, kidney and reproductive organs.
1. Use the page numbers given in the table to identify the function of each of the organs listed. Be specific
in your description.
Organ
Esophagus
(1021)
Function
Lungs
(1001)
Heart
(994)
Stomach
(1021)
Intestines
(1022-1024)
Liver
(1022)
Pancreas
(1022)
Kidney
(1006)
5
2. Using the diagram below, identify and pin the following parts of your rat:
a. The esophagus pierces the diaphragm. Color the esophagus red.
b. It is distinguished from the trachea (windpipe) by its lack of cartilage rings. Color the trachea orange.
c. The lungs rest on either side of the heart. The left lung has only one lobe, but the right lung has four
parts. Color the lungs yellow.
d. The heart sits in the middle of the thoracic cavity. There are major blood vessels that enter and leave
the heart. Color the heart blue.
The heart has 4 chambers. The top chambers are called ___________________ and the bottom
chambers are called _____________________.
e. Locate the stomach on the left side just under the diaphragm. Color the stomach purple.
f. The small intestine is a slender coiled tube coming from the bottom of the stomach. Color the
intestines green.
g. Locate the colon, which is the large greenish tube that extends from the small intestine and leads to the
anus. The colon is also known as the large intestine. Color the intestines green.
h. Locate the liver, which is a dark colored organ suspended just under the diaphragm. Color the liver
black.
i. The pancreas is a brownish, flattened gland (looks like a feather) found in the tissue between the
stomach and small intestine. Color the pancreas brown.
intestines
Call the teacher over to examine your pins. Teacher’s initials ________
6
Urinary and Reproductive Systems
Using the diagrams below, identify and pin the following parts of your rat:
Color the following organs: kidneys = red, ureters = yellow, bladder = blue
**Be sure to check other tables to see what the opposite gender looks like.**
Call the teacher over to examine your pins. Teacher’s initials ________
**You must write a reflection (5-6 sentences) about your experience dissecting the rat. Use the space
provided below and on the back of this page. What was challenging? What did you enjoy? What didn’t
you enjoy? How do you think you did overall? Does the dissection give you a better understanding of
your internal organs and how you function as a human? Will this dissection give you nightmares? Be
specific in your answer.
7