Download Rat Dissection - Abbreviated ng

Names: _________________, _________________, _______________, ______________, ________________
Rat Dissection
Per: ___
Characteristics present in an organism determine how it is organized into taxonomic groups (Kingdom,
Phylum, Class, etc.). Relationships between organisms as well as evolutionary development of a species can
be better understood when their anatomy is carefully observed and compared. In this laboratory exercise, the
anatomy of the rat will be examined in some detail.
Objective: To investigate the internal anatomy of a rat to observe characteristics that make it unique as a
mammal and rodent.
The classification of the Rat (Rattus norvegicus): Classification of the Squid (
(Write the characteristics that place the rat in each group on the right.)
Rat
Characteristics
Squid
Domain
Eukarya
Eukarya
Kingdom
Animalia
Animalia
Phylum
Chordata
Mollusca
Subphylum
Vertebrata
XXXXXXXXXXX
Class
Mammalia
Cephalopoda
Characteristic
XXXXXXXXXXXXXXXXXXXX
Materials:
Rat, Dissecting tray, Dissecting tools (scissors, forceps, blunt probe), Rat dissection reference books and charts
Pre-Lab:
In this lab you will have to find and identify the structures from the following systems in a rat. Write a brief
description of the structure and the function that it has.
Digestive System:
Liver:
Stomach:
Small Intestine:
Large Intestine/Colon:
Esophagus:
Pancreas:
Cecum: (may require research)
Circulatory Respiratory:
Diaphragm:
Heart:
Lungs:
Trachea:
General Terminology:
Anterior:
Posterior:
Ventral:
Dorsal:
Procedure:
External Anatomy
1. Obtain your rat.
2. Rinse it off with water and place it in your dissecting pan to observe the general characteristics.
The rat's body is divided into six anatomical regions. Place a check mark in the space once you have
correctly identified each structure.
____ 1. Cranial region - head
____ 2. Cervical region - neck
____ 3. Pectoral region - area where front legs attach
____ 4. Thoracic region - chest area
____ 5. Abdomen - belly
____ 6. Pelvic region - area where the back legs attach
Read through the following information observing each characteristic and making note of highlighted
words.
____ 1. Note the hairy coat that covers the rat and the sensory hairs (whiskers) located on the rat's face, called
vibrissae.
____ 2. The mouth has a large cleft in the upper lip which exposes large front incisors. Rats are gnawing
mammals, and these incisors will continue to grow for as long as the rat lives.
____ 3. Note the eyes with the large pupil and the nictitating membrane found at the inside corner of the eye.
This membrane can be drawn across the eye for protection. The eyelids are similar to those found in humans.
____ 4. The ears are composed of the external part, called the pinna, and the auditory meatus, the ear canal.
____ 5. Locate the teats on the ventral surface of the rat. Check a rat of another sex and determine whether
both sexes have teats. What is the gender of your rat? ________________________
____ 6. Examine the tail, the tails of rats do not have hair. Though some rodents, like gerbils, have hair on
their tails.
____ 7. Locate the anus, which is ventral to the base of the tale.
____ 8. On female rats, just posterior to the last pair of teats, you will find the urinary aperture and behind
that the vaginal orifice which is in a small depression called the vulva.
____ 9. On males, you will find a large pair of of scrotal sacs which contain testes. Just anterior to the scrotal
sacs is the prepuce, which is a bulge of skin surrounding the penis. The end of the penis has a urogenital
orifice, where both urine and sperm exit.
Internal Anatomy
A.) Opening and Pinning Rat
1. Obtain a set of dissecting tools, a rat, as well as a dissecting pan.
2. Using scissors, make the incisions in the rat, following the guided numbers. Make sure to not cut too
deeply and keep the point of the scissors facing upward. Once the body cavity is opened, pin down the
flaps to the dissecting tray.
B. Thoracic Cavity Investigation
(place a check mark in the space once you have correctly identified each structure)
____ 1. Locate the diaphragm. This is the thin layer of muscle that separates the thoracic from the abdominal
cavity.
____ 2. Locate the heart. This is located in the center of the cavity. Note the four chambers: 2 atria and 2
ventricles.
____ 3. Locate the thymus gland. This is located directly above the heart. The thymus gland is involved in the
development of T cells in the immune system.
____ 4. Locate the trachea, bronchi, and lungs. The trachea is a hard ridged structure descending from the
pharynx. The trachea will branch off in two tubes called bronchi, then lead to the large soft tissue of
the left and right lungs.
C. Abdominal Cavity and Organ Investigation
(place a check mark in the space once you have correctly identified each structure)
____ 1. Locate the liver. The liver is the large dark purple/brown structure just underneath the diaphragm
used for producing bile as well as storing glycogen and detoxifying the blood. You will not see a gall
bladder in the rat as they do not have them!
____ 2. Locate the esophagus. The esophagus moves down from the pharynx through the thoracic cavity and
into the abdominal cavity ending at the stomach. It is next to the trachea and lacks the rings of
cartilage that the trachea has.
____ 3. Locate the stomach. The stomach is located underneath the diaghram in the left side of the abdominal
cavity.
____ 4. Locate the spleen. This a small dark purple/brown structure attached to the stomach. Although we did
not discuss the spleen in much detail in class it functions in the destruction of blood cells as well as
blood storage.
____ 5. Locate the pancreas. The pancreas is located in the tissue between the stomach and small intestine. It
is brown and flat. Look for a thin, membranous structure to find the pancreas.
____ 6. Locate the small intestine. The small intestine is thin and coiled as well as descends from the stomach.
____ 7. Locate the large intestine/colon. This is the large green colored tube that extends from the small
intestine to the anus.
____ 8. Locate the cecum. This is the large sac most often confused with the large intestine. It is actually the
point at which the small intestine becomes the large intestine.
D. Clean up
1. Wrap your rat with wet paper towels and place in plastic bag. Give this to your teacher.
2. Rinse and disinfect trays and tools.
3. Wipe down and disinfect lab table.
E. Drawing
In the space below, draw a rat showing the characteristics that make it a “rat.” Be sure to make reference to
the classification information from the beginning of the lab.
F. COMPARATIVE ANATOMY Discussion questions:
1. What structures make a rat better adapted to life on land than a squid?
2. What structures make a squid better adapted to life in the water than a rat?
3. Compare the mouth parts of the squid and the rat.
4. What adaptations do squid and rats have to avoid predators?
5. What adaptations do squid and rats have to locate food?