1. Dissecting the Fetal Pig

2. Introduction to Mammals
Of all the classes of animal life, mammals are considered to be the most advanced.
Examples: dogs, cats, squirrels, pigs, whales, horses, sheep, and HUMANS!
Vary greatly in size…from 2 inches (the shrew) to 100 feet long (the blue whale)

3. Mammalian Characteristics
Vertebrates (have backbones)
Presence of lungs (breathe air)
Warm-blooded (endothermic)
This means that the body temperature of a mammal stays the same, no matter what the outside temperature is
4 chambered heart

4. Mammalian Characteristics, cont’d
Give birth to live young
Monotremes – mammals that lay eggs
EX: the platypus and the echidna (spiny anteater)
Body Hair
Produce milk (have mammary glands)
Platypus
Echidna

5. Mammalian Characteristics, con’t
Less Obvious Characteristics
The diaphragm separates the heart and lungs from the stomach
Lower jaw has one bone on each side
Different types of teeth adapted to different uses (tearing, chewing)
Brains are much more highly developed than any other animal

6. Comparative Anatomy
Study of similarities and differences in the anatomy (structure) of organisms
Many aspects of structure and function are identical between different species of mammals
Homologous Structures – same structure (embryologically speaking), different function (have a common evolutionary descent)
EX: wings of bats and arms of humans
Analogous Structures – different structure, same function (evolved in a similar environment)
EX: wings of bats and wings of insects

7. Comparative Anatomy Fetal Pigs Humans Kingdom Animalia Phylum Chordata
Class
Mammalia
Order
Artiodactyla
Primates
Family
Suidae
Hominidae
Genus
Sus
Homo
Species
Scrofa
sapiens

8. Why Fetal Pigs?
The fetal pig is a mammal, like humans. Nearly all the structures are the same or very similar in anatomy.
Fetal pigs are NOT bred for the purpose of dissection. They are a by-product of the pork food industry.
Fetal pigs are NOT killed for the purpose of dissection. Those that are not dissected are used for fertilizer or discarded.
Fetal pigs are relatively inexpensive. Even in the extra large size, when the structures are well-developed, they can be obtained for about 1/3 the cost of a similarly sized cat.
Most people do not think of pigs as “pets.”

9. Advantages to Dissection
Dissection is a hands-on, investigatory kind of activity for students. Dissection allows students to "test the truthfulness" of what they see in books.
Dissection impresses on students the normal variation that is present in the natural world. No two fetal pigs, even though they are perfectly normal, will look exactly the same.
In fact, to do well on practicals, students MUST looks at several examples of each structure in different animals. Occasionally, quite significant anatomical variations (anomalies) will be noticed.

10. Safety and Handling Sharps
All Dissecting tools should be considered dangerous.
Notify your teacher IMMEDIATELY if you are cut.
Handle probes, dissection scissors, razor blades, etc. with extreme caution.
Always cut away from you, never toward yourself or another person.
Dissection specimens should be properly mounted in the dissection pan before cutting.

11. Safety and Handling, cont’d
Do not place your hands near your mouth or eyes while handling preserved specimens.  Most of the preservatives in use today are non-toxic to the skin, but they may cause minor skin irritations.  If the preservative gets on your skin, wash with soap and warm water.
If the preservative gets in your eyes, rinse them thoroughly with the safety eyewash.
Wear lab gloves and goggles at all times!
Lab gloves and paper towels go in
the regular trash.  Skin and pieces
of pig go into the separate plastic
bag at the front of the room
(NOT down the sink).

12. Dissection Helpful Points
Actual cutting should be kept to a MINIMUM
Tissue are picked and teased apart with needle probes, forceps, and blunt probes in order to trace the pathways of blood vessels, nerves, muscles, and other structures.
NEVER CUT OR MOVE MORE THAN IS NECESSARY TO EXPOSE A GIVEN PART.
Compare dissections with other students, especially students whose pig is of a different sex. You will be responsible for both sexes on the lab practical (test).

13. Determine the Sex of your Pig
Female:  Look for a single urogenital opening just ventral to the anus.  A prominent genital papilla projects from the urogenital opening. 
Male:  Look for the scrotum, a sac-like swelling containing the testes and located ventral to the anus.  The male urogenital opening is faintly visible just posterior to the umbilicus.  Note that males as well as females have multiple nipples = teats = mammary papillae.

14. Female Male