Name: _________________________
Date: ___________________ PD:____
Structural Organization of the Body
Dissection of a Rat
Purpose:
1. View different sizes, shapes, locations, and relationships of organs within an organism
2. Apply anatomical terminology and dissection cuts to preserved specimen
3. You will be responsible for finding EVERY STRUCTURE IN BOLD LETTERS and
UNDERLINED. Points will be given for dissection class work.
Procedure:
1. Draw a small sketch in the box below labeling the anterior, posterior, medial, lateral, dorsal, and
ventral of a rat. Also sketch and label the 9 abdominopelvic regions. This diagram will help orient
you throughout the lab as you encounter terminology.
2. Place the rat in anatomical position (ventral side face up). Using the dissecting pins, anchor the
4 extremities to the dissecting tray.
3. Determine if you have a male or a female by noting if there are scrotal sacs lateral to the anal
opening (male) or a vaginal opening ventral to the anal opening (female).
4. Make a midsagittal superficial cut through the rat’s integument (skin) from the pubis to the
sternum. You should cut deep enough to penetrate through the internal layer of the
abdominal wall being careful not to cut into any of the underlying organs.
5. At a similar depth to cut in step 2, make a transverse cut across the pubis just anterior to the
external genitals and another transverse cut just posterior to the rib cage.
6. Fold back the abdominal walls just dissected to expose the viscera shown in figure 1-5.
Name: _________________________
Date: ___________________ PD:____
7. Observe and identify the following:
 Smooth, shiny, serous lining of the abdominal cavity called the parietal peritoneum (most
likely attached to the resected abdominal walls).
 Smooth, shiny, serous lining adherent to the abdominal organs called the visceral
peritoneum.
 Smooth, shiny lining adherent to the intestines that bind them together called the
mesentery.
 Abdominopelvic Organs:
i. Alimentary canal: stomach (with cardiac sphincter-opening between esophagus
and stomach; and pyloric sphincter-opening between stomach and duodenum),
small intestines specifically (in order) duodenum and ileum, jejunum, large
intestines (colon) including all the following sections transverse colon, sigmoid
colon, cecum (appendix is attached here), splenic flexure, descending colon,
ascending colon, hepatic flexure and rectum.
ii. Accessory organs: liver (right hypochondriac region), spleen (left hypochondriac
region-attached to top of stomach), pancreas (in curve of duodenum posterior and
slightly dorsal to stomach)
iii. Urinary System: kidneys (dorsal lateral wall of abdomen), ureters, bladder
(pelvic region), urethra
iv. Reproductive System (pelvic region):
1. male: seminal vesicles (vesicular glands), vas deferens, testis with
epididymis, scrotal sac, and penis
2. female: ovary, oviduct (fallopian tube), uterine horns (if smooth tube then
not pregnant or if multiple swells in tube then pregnant with fetuses), uterus
8. Open the thoracic cavity by extending the midsagittal cut from step #2 anteriorly to the neck
deep enough to penetrate the sternum. Again also make transverse cuts just anterior to diaphragm
and just posterior to neck. Then pin back the walls of the thoracic cavity.
9. Observe and identify the following:
 Serous membrane lining of the lungs called the parietal pleura.
 Sac surrounding heart in the mediastinum called the parietal pericardial sac
 Dome-like muscle separating the thoracic and abdominal cavities called the diaphragm
 Thoracic organs: heart, lungs, aorta (branches anteriorly off the heart and arches
downward toward posterior end), superior and inferior vena cava (blue veins from right
atrium of heart), trachea, esophagus (dorsal to trachea), larynx (anterior bulging end of
trachea)
Name: _________________________
Date: ___________________ PD:____
QUESTIONS (48 pts)
1. Identify the organ that anatomically divides the thoracic cavity from the abdominal cavity.
_______________________ (1 pt)
2. Label all structures on the diagrams attached to this lab. Label only the numbers written in the text
boxes next to the pictures. For help, go to
http://www.utm.edu/staff/rirwin/public_html/RatAnat.htm (18 pts)
3. Sketch and label the small intestines stretching from the stomach with correct valve labeled that
controls entry into the small intestines to the start of the large intestines highlighting the 3 portions
of the small intestines in order. (4 points)
4. Sketch and label the major portions of the large intestines starting from the correctly labeled final
portion of the small intestines and ending at the anus. Your diagram should include transverse
colon, sigmoid colon, cecum, splenic flexure, descending colon, ascending colon, hepatic flexure,
appendix, rectum. (9 pts)
Name: _________________________
Date: ___________________ PD:____
5. Sketch and label the anterior, posterior, dorsal, ventral, medial, and lateral areas of a rat. For
practice, also label superior and inferior ends of the rat being sure to justify your answer for your
choice. (6 pts)
6. List the 9 regions of the abdominopelvic cavity and name one organ that is clearly at least partially
contained within each region. (9 pts)
a. Try to pick different organs for each area
b. Challenge yourself to pick the most obvious organ in that region so you get acquainted
with orientation of the organs as well as the anatomical terminology. For example, the
organ I associate with the right hypochondriac region is the liver.
c. You must use specific portions of organs such as the cecum or hepatic flexure instead of
simply saying large intestines.
d. Don’t be worried that the organ may overlay more than one region as long as it definitely
overlays the region you associate it with.
REGION
ORGAN
Name: _________________________
Date: ___________________ PD:____
ABDOMINAL ORGANS
1.
2.
3.
4.
5.
6.
THORACIC CAVITY
1.
2.
3.
4.
Name: _________________________
Date: ___________________ PD:____
FEMALE
REPRODUCTIVE AND
URINARY
3,
5.
7.
FEMALE
REPRODUCTIVE AND
URINARY
1.
2.
3.
4.
9.
Name: _________________________
Date: ___________________ PD:____