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Fetal Pig Dissection Lab Exam Introduction · 2019-05-24 · Biology 12 Fetal Pig Dissection Name:...
Transcript of Fetal Pig Dissection Lab Exam Introduction · 2019-05-24 · Biology 12 Fetal Pig Dissection Name:...
Biology 12 Fetal Pig Dissection Name: ___________________
Fetal Pig Dissection Lab Exam
Introduction – Studying the internal and external features of the pig will provide an opportunity to observe
several structures that are homologous (similar) to the ones in humans. It will also allow for an opportunity to
see all these different organs organized in context with each other.
This lab will take place over two classes. The first class and a half will be spent opening the pig, removing
various parts, and identifying the structures. The last half of the second class will be the “exam” portion
wherein each lab member will be asked to identify various parts of the pig on their own.
Purpose – To observe and study the external and internal features of a fetal pig.
Materials and Equipment
Fetal Pig
Scissors
Disposable gloves
String/cord
Hand lens
Paper towels
Freezer bags
Scalpel
Forceps
Probe
Pins
Dissecting tray
Alcohol squirt bottle
Procedure
Prior to the lab
- In your groups, please collect 15 standard pins that are one inch or longer. These pins will require
colour coding to produce a set of 5 red pins, 5 blue pins, and 5 white pins. These pins will be used in
the exam portion of the lab. Each pin must be numbered – Red 1 – 5, Blue 6 – 10, White 11 – 15.
- Make a name card with all 3 group member names and your block on it. This will be left with the
dissected pig as identification for marking purposes.
- You may want to bring some latex gloves otherwise there will be some available for purchase on the
lab day.
- Also be sure to review the following terms – anterior, posterior, dorsal, and ventral.
Day 1
To Do: Identifying external features, determine the sex of the pig, exposing the thoracic and abdominal
cavities, and removal of the heart and digestive system.
Day 2
To Do: Removal of the heart and digestive system, removal of kidneys (if time is available), review the various
parts of the pig, 15-20 minutes for the exam portion of the lab.
Biology 12 Fetal Pig Dissection Name: ___________________
External features
Obtain a fetal pig and place it in a dissecting tray lined with paper towels.
Use Figure 1 to help identify the head, neck trunk, and tail. From the diagram provided, find and observe the
following structures:
Head – mouth, tongue, external nostrils, eyebrows, eyelid, pinna (ears) and chin hair.
Trunk – two pairs of legs, wrists, elbow, ankle, knee, toes, hooves, umbilical cord, anus, and genitals.
Determine the sex of the pig
In a female pig, the common orifice (opening) of the vagina and urinary tract is located ventral to the anus.
Note that the folds (labia) surrounding the orifices come together, forming a ventral spike.
In the male pig, the urogenital (relating to both urine and reproduction) is located posterior to the umbilical
cord. The penis may be felt through the belly skin. The scrotum, which will contains the testes in a mature
male, is located posterior to the hind legs.
Exposing the thoracic and abdominal cavities
Place the pig, dorsal side down, in a paper-lined dissecting tray. Tie string/cord to one foreleg and pass the
string under the tray to be tied to the other foreleg. Spread the forelegs as much as possible before tying the
second foreleg. Repeat this procedure for the hind legs so that the pig’s abdomen is now fully exposed.
Biology 12 Fetal Pig Dissection Name: ___________________
Using forceps, gather a fold of skin and muscle at the midline of the pig’s throat, towards the apex (point) of
the jaw. Cut through this fold with scissors (see Figure 2, incision 1). Insert
the scissors into this opening and cut down the ventral midline to the
umbilical cord. CAREFUL - While making this cut, lift the points of the
scissors upward so that the underlying organs are not damaged.
At the umbilical cord, shift the line of the cut to one side of the midline and
continue the incision posteriorly to the groin. When this is completed, make
a second incision that begins slightly anterior to the umbilical cord and
extends to the groin (see Figure 2, incision 2). This second incision should
parallel the first cut. This will result in the umbilical cord and, if the pig is
male, the urogenital tract to form a strip between the two incisions.
Using a probe, lift this abdomainl flap and locate the diaphragm. The
diaphragm divides the thoracic and abdominal cavities. Using scissors, make
incisions that follow the abdominal side of the diaphragm. Using a probe
and scalpel, cut the diaphragm away from the thoracic wall. Again, see
Figure 2, incision 3 for reference.
Biology 12 Fetal Pig Dissection Name: ___________________
Organs of the digestive system
Open the abdominal flaps and secure them with pins. Note the shiny membrane, the parietal peritoneum,
lining the inner surface of the abdomen. Gently cut this away. Note that the internal organs are joined by
membranes called omenta and that the organs are connected to the body wall by mesenteries.
From the diagram provided (Figure 3), find and observe the following structures in the fetal pig specimen:
Liver
Gall bladder (often colourless,
embedded on the ventral
surface of the liver)
Bile duct
Esophagus (move the liver
away from the left centre if it
the esophagus is hard to see)
Stomach
Pancreas
Small intestine
Caecum
Large intestine (colon)
Removing the digestive tract
Using scissors, cut through the esophagus as it passes through the diaphragm into the abdomen. Remove the
gastrointestinal tract from the specimen by cutting the bile and pancreatic ducts, mesentery tissue from the
tract, and by finally cutting the colon at the rectum.
Biology 12 Fetal Pig Dissection Name: ___________________
Lay the gastrointestinal tract next to the pig or on some paper towel next to the dissecting tray. Be sure
everyone in the group is familiar with the different parts of the system and their functions. While doing this,
place your fingers at the junction of the stomach and small intestine (duodenum). Roll this section back and
forth between your fingers. Move down the intestine and repeat this. Compare the feelings and consider why
this may be.
Identify the pyloric spinchter and the cardiac sphincter. The cardiac one may be felt from the inside where the
esophagus leads into the stomach.
Circulatory system
Open the thoracic cavity completely. This may require further cutting. Secure these flaps. A clear view of the
heart is likely blocked by the thymus gland. Note the location of the thymus and remove it completely. Note
the pericardial sac around the heart. Carefully remove it.
From the diagram provided (Figure 4), find and observe the structures listed below on the fetal pig specimen:
Right atrium
Left atrium
Right ventricle
Left ventricle
Pulmonary artery
Aorta
Superior vena cava
Inferior vena cava
Note the position of the heart and remove it completely from the body cavity. Cut the vessels about 1cm from
the heart. Place the heart in the dissecting tray in a position similar to the one it had in the thoracic cavity.
Using a scalpel, dissect the heart into a frontal and hind section. This is accomplished by starting the incision
high on the right atrium, approximately 5mm back from the ventral surface. Continue this incision downward
Biology 12 Fetal Pig Dissection Name: ___________________
to the apex (bottom point) of the heart. Open the heart to check that your incision exposes both the right
atrium and right ventricle. Repeat this procedure from the left atrium to the apex. Remove the front of the
heart by making an incision through the septum that divides the right and left chambers.
From the diagram provided (Figure 5), find and observe the structures listed below in the fetal heart:
Right atrium
Left atrium
Chordate tendinae
Bicuspid valve
Tricuspid valve
Right ventricle
Left ventricle
Pulmonary semilunar
valve
Aortic semilunar
valve
Biology 12 Fetal Pig Dissection Name: ___________________
Respiratory system
Extend the thoracic incision anteriorly to the base of the fetal pig jaw. Spread this incision to expose the
underlying tissue.
From the diagram provided (Figure 6), find and observe the structures listed below in the fetal pig specimen:
Larynx Trachea Bronchi Diaphragm Lungs
Biology 12 Fetal Pig Dissection Name: ___________________
Excretory system
Open the abdominal flaps of the fetal pig and secure these to expose the abdominal cavity. Fold the midflap
of tissue downward. This tissue contains the umbilical cord, bladder, and, if the pig is male, the penis. Locate
the kidneys, one on either side of the spine, high on the dorsal wall. Note that the kidneys are behind (or
outside) the peritoneum.
Using a scalpel and forceps, carefully remove the peritoneum.
From the diagram provided (Figure 7), find and observe the structures listed below on the fetal pig specimen:
Kidney Adrenal gland Renal artery Renal vein
Ureter
Biology 12 Fetal Pig Dissection Name: ___________________
If there is time – Using scissors, remove one kidney. Dissect the kidney into frontal and hind sections. To
accomplish, this make the first incision ventral to the point where the ureter leaves the kidney. Observe the
following structures:
Renal cortex
Renal medulla
Renal pyramids
Renal pelvis
Renal artery
Renal vein
Ureter
Reproductive organs
Male
Locate the urogenital orifice posterior to the umbilical cord. Using scissors, carefully cut the mid-ventral strip
from the orifice posteriorly. Fold this tissue to expose the penis.
From the diagram (Figure 8), find and observe the structures listed below on the fetal pig:
Penis Urethra Seminal vesicles
If there is time – using a probe, trace the ductus deferens to the scrotum. Using a scalpel, make an incision in
the scrotum to expose the testes. Locate a testis and the epididymis.
Biology 12 Fetal Pig Dissection Name: ___________________
Female
Locate the Y-shaped uterus. Using a scalpel and scissors, open the pelvic girdle to expose the urethra and
vagina.
From the diagram provided (Figure 9), find and observe the structures listed below on the fetal pig:
Vagina
Ovaries
Body of the uterus
Horns of the uterus
Cervix
Storage & Clean up
To store the pig, any organs that were removed should be placed back into the pig for convenience. Untie the
string/cord from the legs of the pig. Close the abdominal incisions as best as possible and tie the string/cord
around the abdomen to hold the pig together. Place the fetal pig in the plastic bag and tie the ends. Tape
some masking tape on it and write your group members’ names on the tape. Place the pig in the area
designated by the teacher.
Clean the dissecting trays, equipment, and bench thoroughly with soap and water, then dry them with paper
towel.
If it is the last day of the lab, leave the pins and a group name card to be marked. Be sure to return at the end
of the day to help clean up your dissection please.