Download UB Fetal Pig Day 1 - CGW-Life-Science

Upward Bound Fetal Pig Dissection Day 1
Background:
Mammals are vertebrates having hair on their body and mammary glands to nourish their
young. The majority are placental mammals in which the developing young, or fetus, grows
inside the female's uterus while attached to a membrane called the placenta. The placenta is the
source of food and oxygen for the fetus, and it also serves to get rid of fetal wastes.
Objectives:
1.Identify important external structures of the fetal pig.
2.Identify major structures associated with a fetal pig's digestive, respiratory, circulatory, and
urogenital systems.
3.Compare the functions of certain organs in a fetal mammal with those of an adult mammal.
Materials:
preserved fetal pig
dissecting tools
Directional Planes
Ventral: Stomach side (ventre)
Dorsal: Back side (think dorsal fin)
Medial: Towards the middle
Anterior: Toward the head (leading side)
Posterior: Toward the rear (trailing side)
Lateral: Towards the sides
Day 1 Procedures: External Anatomy
1. Lay the pig on its side and locate dorsal, ventral, and lateral surfaces. Also locate the
anterior and posterior ends.
Check In: Label these four directional planes on Figure 1.
2. Examine the pig's head. Locate the eyelids and the external ears or pinnae. Find the external
nostrils (nares). Label these parts on Figure 1. Examine the exterior of the fetal pig for hair.
Check In: Describe any hair that is found:
3. Study the pig's appendages and examine the pig's toes. Label the toes and hooves on Figure 1.
Check In: How many toes does your pig have on each hoof?
split or fused?
Are your pig’s hooves
4. Use a string and meter stick to measure your pig from the nose to the anus.
Check In: How long is your pig (cm)?
How old is your pig:
4. Locate the umbilical cord. With scissors, cut across the cord about 1 cm from the body.
Examine the 3 openings in the umbilical cord. The largest is the umbilical vein, which carries
blood from the placenta to the fetus. The two smaller openings are the umbilical arteries which
carry blood from the fetus to the placenta. Label the umbilical cord on Figure 1.
5. Lift the pig's tail to find the anus. Anterior from the anus along the ventral surface of the pig
study and note the tiny bumps called mammary papillae. These are present in both sexes. In the
female these structures connect to the mammary glands. Label both these structures on Figure 1
Check In: How many mammary papillae does your pig have?.
Figure 1: External Anatomy
A
B
C
E
F
G
D
6. Determine the sex of your pig by locating the urogenital opening through which liquid wastes
and reproductive cells pass. Females are identified by the urogenital papilla. This is a small,
fleshy, cone-shaped projection ventral to the anus. Locate the female's external genital opening at
the base of the urogenital papilla.
The male's testes (singular=testis) lie in the scrotum, a pouch ventral to the tail. In older
specimens, this area is enlarged and readily visible. In younger animals, a loose pouch may be
visible but the testes may still be in the abdominal cavity, having not yet descended.
Check In: Is your pig male or female? _________________ List 2 reasons why you’re sure.
Reason 1
Reason 2
7. With scissors, make a 3-cm incision in each corner of the pig's mouth. Your incision should
extend posteriorly through the jaw. Follow the curve of the jaw instead of cutting straiht back
into the neck. Spread the jaw open and examine the tongue.
8. Observe the palate on the roof of the mouth. The anterior part of the palate is the hard palate,
while the posterior part is the soft palate.
9. Locate the epiglottis, a cone-shaped structure at the back of the mouth.
Check In: What is the function of the epiglottis?
10: Above the epiglottis, find the round opening of the nasopharynx. This cavity carries air
from the nostrils to the trachea, a tube in the thoracic cavity which supplies air to the lungs.
11. Dorsal to the glottis, find the opening to the esophagus. Examine the tongue and note tiny
projections called sensory papillae.
Check In: Contrast the functions of the trachea and the esophagus.
12. Examine the teeth of the pig. Canine teeth are longer for tearing food, while incisor are
shorter and used for biting. Pigs are omnivores, eating plants and animals. Draw and label a
picture of the canines and incisors showing their contrasting shapes.
13 Observe the eyes of the pig. Use the scissors to carefully remove the eyelid so that you can
view the eye underneath.
Check In: Does the pig’s eye seem well developed?
Explain why you think pigs are born with their eyes open or shut.
14. Carefully lay the pig on one side in your dissecting pan and cut away the skin from the side
of the face and upper neck to expose the masseter muscle that works the jaw, lymph nodes, and
salivary glands. The salivary glands kind of look like chewing gum, and are often lost if you cut
too deeply.
CLEAN UP PROCEDURES:
Inventory and wipe all your tools down
□ 2 teasing probes
□ 2 scissors
□ 1 scalpel
□ 1 eyedropper
□ 1 forceps
□ 1ruler
Put all your tools in the plastic case.
Label your kit, pan and fetal pig bag with tape and your initials.
Wipe down your table and make sure everything is put away.
ANALYSIS QUESTIONS
1. List three questions that you now have after your first day of observations and dissection
of the fetal pig.
2. Name the two external characteristics that distinguish mammals from other animals.
3. Describe the major differences between a male and female pig's urogenital opening(s).
4. Explain three characteristics of living things that are demonstrated by the fetal pig.
5. What are four organ systems that you observed today with the pig? Give both the system
and the main structures that you observed.
Organ System
Main Structures Observed