Download Rat Dissection Guide

RAT DISSECTION
Name(s):____________
Date:______
Period:____
Dissection Kit #______
Tray#_____
Standard(s):

BI9. a. Students know how the complementary activity of major body systems provides
cells with oxygen and nutrients and removes toxic waste products such as carbon
dioxide.
Learning Objective (s):
SWBAT…
 Understand the how the human body is organized starting from the smallest (cells) to the
largest (organism) level.
 Explain how different organ systems work together to maintain homeostasis.
 Understand the importance of maintaining a stable internal environment in the human
body.
Resources:
 http://www.richardtontaylor.k12.nd.us/science/Dissection%20Guide%20to%20the%20Rat.ppt#257
,2,Anatomical Terms
 http://www.biologymad.com/ratphotos/ratdissection_files/frame.htm
 http://kingdomcms.com/dissected-rat
INTRODUCTION
In this lab we will examine the anatomy of a rat. By dissecting the rat, we may look at the internal organs
that we have studied in close 3D detail! The internal anatomy of a rat is very similar in construction to a
humans’. Please remember that your rat was once a living organism and should be treated with respect and
care.
PURPOSE
 To investigate the internal anatomy of a rat to gain knowledge of human anatomy.
MATERIALS
 Rats
 Dissecting tray
 Dissecting pin
 Dissecting tools (scissors, scalpel, blunt probe)
Pre-Lab
Open the link below and review the rat dissection visual aides before beginning the lab.
Then answer the following questions.
 http://www.biologymad.com/ratphotos/ratdissection_files/frame.htm
Pre-Lab Questions:
1. Where do you make the first incisions at on the rat?
2. Describe the structure and function of each of the following terms.
Organs:
Liver:
Diaphragm:
Heart:
Lungs:
Trachea:
Small Intestine:
General Terminology(definitions):
Anterior:
Posterior:
Ventral:
Dorsal:
3. Describe the function of each of the tools listed below (hint check your
PPT-Introduction to Dissection:
Tools:
Forceps:
Dissecting Scissors:
Scalpel:
Dissecting Probe:
PROCEDURE
A.)External AnatomyDissection Keyshttp://www.biologymad.com/ratphotos/ratdissection_files/frame.htm
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb7pg3_files/ima
ge002.jpg
 Place a check mark in the space once you have correctly identified
each structure.
 Show your teacher each organ/tissue once you have located them all
1. ____Eyes
2. ____Ears
3. ____Vibrissae
4. ____External Nares
5. ____Tails
6. ____Incisors
7. ____Forearm
8. ____Scrotal Sacs (male only)
9. ____Urogenital Opening
10. ____Anus
Questions:
1. What is the function of the vibrissae?
2. What is the function of the external nares?
B.) Opening and Pinning Rat
1. Obtain a set of dissecting tools, a rat, as well as a dissecting pan..
2. Secure your specimen ventral side up, with the legs spread laterally.
3.Beginning at the opened skin of the throat, and cutting very shallowly (scissors
work better than scalpels for this), make a medial ventral incision the length of
the body, then lateral incisions at the collar bones, the posterior margin of the rib
cage, and at the hips, cutting deep enough to reach the body cavities but not so
deep as to damage the organs inside
C.) Thoracic Cavity Investigation:
 Read through the information below and follow any additional
directions.
 Place a check mark in the space once you have correctly identified
each structure.
 Show your teacher each organ/tissue once you have located them all.
The organs of the chest, or thoracic cavity, are also covered by various membranes: the
lungs on each side are encased in pleural membranes, while the heart, located in the
middle, is covered by the pericardium. These lubricated surfaces allow the two sets of
organs to move vigorously without wearing each other away. The posterior wall of the
cavity is the diaphragm. When its muscle contracts, the dome-shape flattens and moves
downward, increasing the space of the chest cavity; the lungs will with air to fill that
extra space. Ventral and somewhat anterior to the heart is the thymus gland. In this
organ, some white blood cells from the bone marrow mature, becoming T Cells (it is one
type of T Cell that is attacked by the AIDS virus). Activity in the thymus gland begins
during the first dew months of life, peaks around puberty, then drops off
steadily; our increased susceptibility to disease in old age is probably due at least partly
to the shrinkage of our thymus glands. Behind the heart is a stiff tube, whitish with rings
around it, which splits into tubes that run to the lobes of the lungs. The main tube is the
trachea, and the branches are bronchi. The rings around the tube are cartilage, and
reinforce the tubes in a way similar to the way that vacuum cleaner
hoses are reinforced. Working up the trachea to the larynx (voice box) in the throat area,
the thyroid gland should be a small structure on the surface. This organ produces
hormones that control metabolic rates, the general level of chemical activity in the cells.
On each side, somewhat anteriorly, of the larynx are salivary glands (there are others up
by the tongue and cheeks). Saliva from these glands sticks chewed-up food into a slick,
swallowable ball. Saliva also contains an amylase, an enzyme that can break down
starches to sugars. Cut through the heart, producing a front and back half.
____ 1. Locate the diaphragm. This is the thin layer of muscle that separates the thoracic from the
abdominal cavity.
____ 2. Locate the heart and pericardium. 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.
Questions:
1. What is the function of the thymus?
2. Which organ is typically known as the windpipe?
3. Describe the flow of blood through the heart.
D.) Abdominal Cavity Investigation:
 Read through the information below and follow any additional
directions.
 Place a check mark in the space once you have correctly identified
each structure.
 Show your teacher each organ/tissue once you have located them all.
Look in the abdominal cavity. The abdominal organs may still be covered with a
membrane, the peritoneum, but this usually comes off with the overlying layers.
Another membrane, the mesentery, surrounds and supports most of the digestive
system and its related circulation. Carefully remove the small intestines by pulling
apart the mesentery. Measure the small intestine using the ruler and record the
length here._____
____ 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 detoxifing 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 caecum. 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.
Questions:
1. What is the function of the caecum?
2. What is the function of the esophagus?
3. Describe the movement of food through the digestive system.
E. The Urogenital System
 Read through the information below and follow any additional
directions.
 Place a check mark in the space once you have correctly identified
each structure.
 Show your teacher each organ/tissue once you have located them all.
In females, the ovaries, which produce egg cells and female hormones, are small
and somewhat peanut-shaped, located just posterior to the kidneys, inside the
peritoneal membrane. These organs produce egg cells (ova) in the middle of
blister-like follicles, and female hormones in the follicle lining cells. To find an
intact ovary, you may need to look at the side opposite to where you removed the
kidney. The oviducts lead from the ovaries to the medial, Y-shaped uterus, which
connects by way of the vagina to the urogenital opening. In males, testes, which produce
sperm and male hormones, start out up inside the body cavity during fetal development,
then migrate out through two canals into the scrotum, passing through two slits in the
abdominal wall. Attached to each testis is an epididymis, which stores sperm and leads to
the sperm duct. The duct, and some semen glands, attach to the urethra , which carries
sperm out of the body through the penis. Remove a gonad from your specimen and
dissect it.
1.)___ Locate the scrotum (males)
2.)___Locate the kidneys.
3.)___ Locate the urinary bladder
4.)___Locate the ovaries or testes.
Questions:
1. Was your rat a male or female? How did you know?
2. What is the scientific name of “eggs”?
3. What is the function of the epididymis?
F. The Anterior Region
 Read through the information below and follow any additional
directions.
 Place a check mark in the space once you have correctly identified
each structure.
 Show your teacher each organ/tissue once you have located them all.
The top, somewhat rounded part of the head is the cranium ; it protects the brain.
Carefullyremove the skin and underlying tissue from this area, exposing the skull. You
need to remove the top of the skull - the best way is to use a scissor tip to get just inside,
then snip along the seam where the skull bone knit together. Be careful not to dig into the
brain beneath. Don't try to take the entire bone off at once - cut it into small pieces as you
go. The part of the brain that you're exposing is the cerebrum , the main information
processor. You may see some thin covering membranes: these meninges surround the
brain and spinal cord. The larger anterior, upper brain, the cerebrum, is the area that
processes "higher" thinking, including complex memory analysis and decision-making.
The cerebellum, posterior and slightly underneath, coordinates muscles and controls
balance. Posterior still is the medulla, which runs such "automatic" functions as
heartbeat, breathing, and digestion. Very carefully remove the brain, noting that major
cranial nerves are connected underneath in addition to the spinal cord that
runs out the posterior of the skull and down runs down a canal in the vertebral column.
1. ___Locate the cranium.
2. ___Locate the cerebrum.
3. ___Locate the meninges.
4. ___Locate the cerebellum.
Questions:
1. Which structures protect the brain?
2. Describe how the brain looks.
3. List the function of one part of the brain.
Clean-up:
Upon completion of your observations, discard the carcass of the rat in the
designated plastic bag. Clean with soap and water and dry all dissecting
instruments. Wash your table top with soap and rinse.
Wash your hands
Additional Organ Information:
1. Liver: The liver does many more things than making bile. It collects almost all of the
blood circulated through the intestines and processes many of the chemicals picked up
there (such as alcohol, which your liver detoxifies). Waste products from protein
metabolism are processed into the less-toxic form of urea, which will be removed in the
kidneys. Old red blood cells are broken down, with important things like the iron
recycled; the liver is also a major staging site for white blood cells of the immune system.
Temporary storage of sugar occurs in the liver: in response to insulin hormone from the
pancreas, sugar in the blood is absorbed and stored as the simple starch glycogen;
another pancreas hormone, glucagon, causes conversion of glycogen back to sugar and
its release into the blood as needed.
2. Gall Bladder: Tucked into a recess underneath is the gall bladder, where a secretion
called bile, also produced in the liver, is stored. Bile is a salty fluid (if too concentrated,
crystals can form - gallstones) used in the small intestine to emulsify fat, physically
making tiny, digestible blobs out of big, separated-out globs of fatty materials (dish
detergents do the same thing to grease).
3. Spleen: The spleen is not a digestive organ, but rather a major storage site for oxygen
carrying red blood cells, and immune-system white blood cells, as well as a processor. In
areas of the world with many disease organisms, the stress on the body's immune system
can cause both spleen and liver to expand, giving a "pot belly" appearance that is
sometimes wrongly attributed to malnutrition.
4. Stomach: This organ has an incoming tube, the esophagus, and an outgoing tube, the
small intestine. The stomach serves two major functions: it churns up the balls of food
sent down the esophagus from the mouth reseparating the pieces, and it begins the
chemical breakdown of the food with strong acids and with a powerful protein-digesting
enzyme. The stomach (and much of the intestines) is lined with a mucus layer to protect
the linings from the digestive secretions.
5. Intestines: The intestines (small and large) are held together by the mesentery
membrane, which also supports the pancreas. As mentioned before, the pancreas
controls blood sugar levels with hormone commands mostly to the liver, but it also makes
many digestive chemicals. Enzymes, specifically targeted at particular molecules, are
made in the pancreas, as is sodium bicarbonate, which neutralizes the acids in the
"soup" that comes out of the stomach. Most large molecules are broken down to
absorbable size as they travel along the small intestine; an exception is cellulose, "fiber,"
which is undigestible to most mammals except those few with bacterial "buddies" to do
the job for them. Separate out the small intestine, clipping gently through the mesentery
holding it together, until you have separated out a long single tube (you're going to
measure them for question 10). At a certain, clearly recognizable point, the small
intestine joins the large intestine, or colon, at the caecum. In the colon, water is drawn
out of the food, and a few vitamins and minerals, are processed by specialized bacteria
that live there. The cecum is a sac for fermentation of fibrous plant materials, also
processed by symbiotic bacteria.
6. Kidneys: With the intestines removed, the cavity is pretty much empty; however,
beyond the peritoneal membrane dorsally are the two kidneys. On the body wall are the
two main blood vessels: the abdominal aorta, a artery, and the inferior vena cava, a
vein; both send branches, to the kidneys. Expose the kidneys and the tubes connected to
them, which will include ureters, which connect to the bladder. On the kidneys' anterior
edge, or slightly separate from them but often difficult to see are the adrenal glands,
which produce a wide variety of hormones (including adrenaline). In the kidneys, blood
passes through physical filters that remove all molecules below a certain size (proteins
are too big to be lost); then, in a series of tubes, small molecules the body needs back
(sugar, water, some salts, etc...) are reabsorbed by the blood and larger molecules
the body does not need are pumped out - the resulting, waste-filled fluid is urine, which
leaves through the ureters and is stored in the urinary bladder .From there, urine leaves
the body through a single urethra.