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.


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.


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.


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.


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


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


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


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


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.


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.

fetal pig dissection lab exam introduction · 2019-05-24 · biology 12 fetal pig dissection name:...

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