Pigs, one of the most similar animals to humans, have been used to inform and teach students about the circulatory, respiratory, and digestive system through a procedure called a dissection for many years.
Pigs are similar to humans through the fact that they have skin, not fur or feathers, they are omnivores, and when they are a fetus they receive nutrients from an umbilical cord connected to the mother, so it is natural to pick such an animal to compare to the human organ systems.
Although the size of the fetus pig is smaller than that of the human body the organization of the major organs and the functions of such organs are still the same. This pig dissection is designed to visually show students the different systems inside a pig and, indirectly, their own bodies.
Upon dissection they see the heart, the major organ in the circulatory system that pumps the oxygenated blood around the body; the lungs, the major organ in the respiratory system that provides oxygen to the deoxygenated blood coming from the heart and the small intestines, the major organ in the digestive system that digests the food and absorbs the nutrients from the food. These organ system control basic functions of life and without one, all cannot perform.
- Safety Googles
- Latex Gloves
- Pig preserved in Formaldehyde (a colourless, toxic water soluble gas that is used to preserve the pig and its organs)
- Dissecting Pins
- Dissecting Tray
- Small Scissors
- Medium Scissors
- Measuring Tape
Pigs are complex organisms with an internal structure similar to that of the human body. The pig dissection was a learning experience that allowed students to distinguish the many organs and organ systems in the pig’s body and, ultimately, the organs and organ systems of the human body.
Although the pig fetus was larger than what was expected, the procedure went well and all the necessary parts of the pig were visible. However the discolouration of the organs was quite unusual. The entire pig was one beige colour. This could be due to the amount of time the pig was preserved for. Also, the heart was found to be smaller than previous expectation.
It was surrounded by the lungs protectively and was very muscular due to the constant pumping of blood. Some experimental errors that occurred during the experiment dealt mainly with the pig’s skin and the incisions. Due to the large size of the pig it was more difficult to create accurate incisions on the ventral side of the pig.
The skin and muscle was far thicker and harder to cut through than all the other pigs and resulted in the scalpel not cutting properly. In future experiments it would be better to have a smaller pig so that the incisions are much cleaner and easier to perform. This experiment allowed biology students to learn, in a hands-on way, about the many systems of the body.
It showed the organization of the pig’s internal organs and the significance of the position of each organ. For instance, the heart and the lungs are very close together because the heart needs oxygen for the blood very quickly.
If the heart doesn’t get this oxygenated blood quickly then it cannot deliver fast enough to the various parts of the body. The body tissue cells will run out of oxygen for ATP and thus the entire body will slow down.
What is the function of the umbilical cord?
The umbilical cord is the fetus’ way of getting oxygen, nourishment and nutrients in order to grow. It is attached to the mother’s placenta
which receives nourished oxygenated blood from the heart and the small intestines and delivers it to the fetus. The fetus also uses the umbilical cord to dispose of any wastes left in his/her body.
State the function of the following organs:
Stomach: The stomach stores about 1 – 2 L of food for about 4 hours. This J-shaped organ secretes gastric juices that prepare the food for digestion. Gastric juice is called pepsin (pepsin is created from pepsinogen in the presence of HCl) and it, along with HCl, is responsible for breaking down proteins.
The stomach lining produces rennin, an enzyme that coagulates milk proteins, and is made of mucous secreting cells, cells that protect the stomach from its acidic contents.
Gastrin, a hormone that is released into the blood as a signal to produce more HCl and pepsinogen, is also produced in the stomach and stimulate the stomach to contract.
Liver: The liver is the largest organ in the body and produces many enzymes and bile, which is stored in the gall bladder and contains bile salts that break down fat globules. Some of the livers other functions include detoxifying poisonous chemical substances such as caffeine and alcohol, and stores glycogen, vitamin A, B12, D and fats.
Small Intestine: The site where most of the digestion and absorption of nutrients take place, it is made of the duodenum, the jejunum and the ileum.
Digestion occurs in the duodenum and involves many different enzymes that break down the nutrients even more. The jejunum and the ileum both are the sites of absorption and are lined with villi and microvilli, which increase the surface area in and can absorb the nutrients digested by the duodenum.
Gall Bladder: The gall bladder is a small sac behind the liver that stores the bile made in the liver. The hormone cholecystokinin from the small intestine signals the gall bladder to release the bile into the duodenum to digest fats.
Pancreas: The pancreas produces both hormones and enzymes that aid digestion. It secretes bicarbonate ions (HCO3-) into the small intestine to neutralize the chymes low pH from the stomach so digestion can occur. Also the pancreas produces the hormone insulin and glycogen which reduces and increases the glucose in the blood stream.
Large Intestine: It is 1.5m long and 8 cm wide. It is made up of three arms: ascending, transverse, and descending colon. Its main function is to absorb water, minerals and salts that were missed in the small intestine. It also decomposes left over material through micro-organisms and bacteria.
Spleen: The spleen creates lymphocytes for the destruction and recycling of old red-blood cells. Also it is a blood reservoir that supplies the body with blood in emergencies like a large cut; it is the place where white blood cells trap and capture foreign organisms.
What is the function of the Mesentery?
The mesentery is a thin, connective tissue that holds the small intestine together in place. It holds mainly the jejunum and the ilieum.
Why does the left ventricle contain more muscle than the right ventricle?
The reason as to why the left ventricle contains more muscle than the right ventricle is because the left ventricle must be strong enough to pump the blood throughout the body while the right ventricle only needs to pump the blood to the nearby lungs.
Why do the lungs feel spongy?
The lungs feel spongy because there are millions of alveoli in the lungs. These alveoli are made so that the maximum surface area can take in oxygen for deoxygenated blood. Because there are little spaces between the alveoli, they do not make a solid feeling organ, they make a spongy feeling one.
What function do the cartilaginous rings of the trachea serve?
The cartilaginous rings of the trachea keep the trachea open for air to enter the lungs with oxygen and leave with carbon dioxide. It also maximizes the amount of air that is breathed in and out and prevents the accidental closing of the trachea which would result in suffocation.
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