The Nervous System

To conclude our journey, we worked on the pig's nervous system. in order to do so, not only did the spine have to be revealed, but the brain itself, the powerhouse of the nervous system, needed to be extracted. Unable to attend the dissection on this day, I was able to retrieve pictures from gabby and Kaylyn. The finds were stunning. 

Prior to its extraction, the brain was protected by the powerful skull, as well as membranous layers of matter that offer protection from head injury and prevent the brain from jostling around within the head. It's clear by observing these images here, that blood flow is extremely prevalent in the brain. Because of all the activity required by it, and the amazing capabilities of this organ, high blood and oxygen supply are required at all times. Look at all those veins! Once extracted, the size of the brain was revealed. It ended up being about the size of a small apple, and had various folds in its shape. The bottom part, protruding downward, is known as the cerebellum. This is the reception point for neurons that determines what they're trying to make the pig feel. It truly is a wonder of nature that we have such fascinating machinery in our own heads!

 

 

A better view of teh extracted brain.

The pigs spine, which acts as a track for neurons to speed to the brain most efficiently, is visible in this photograph. It's a flexible but fragile skeletal system that allows the pig to bend and move freely, but must be kept in tact or major nervous system problems could occur and the results could be fatal.

Another image of the extracted brain.

The Reproductive and Excretory System

On the fourth day of our dissection, we looked into the reproductive system of our pig. Our finds were intriguing, and we were able to determine without a doubt that we were dealing with a female. The excretory system, which encourages the removal of digestive wastes and excess water was also examined on this day. 

In this photo, the bladder is being displayed. The bladder functions in storage of urine, which is actually produced in the kidneys (Pictured further down). It runs beside the rectum, the dark hole located below it in the photograph.

This shows the bladder from a different angle, looking straight down into it. From this perspective, you can see the opening that runs through the bladder and out the pig's body, named the urethra. 

Pictured here are the kidneys, the producers of urine. There's a left one and right one, and they have a distinct shape. They're small in comparison to other organs, but were larger than I expected. Running in between them is the rectum, completely in tact before we snipped it out.

Pictured here is the pig's vagina, located below the rectum (but in this picture, above, because it's photographed upside down). The vagina is the reproductive organ of the pig, while the rectum is the last step in digestion, and functions in the elimination of waste. 

The small like-like folds that my finger are holding in place are the ovaries of the pig. These are reproductive glands that house eggs and encourage pregnancy in the pigs. They lie just behind the bladder and were small and extremely difficult to spot. 

The Circulatory System

Day three brought about an exploration of the pig's gas and blood circulation systems (including the heart and lungs). This brought about some fascinating discoveries, such as the four chambers of the heart, as well as some unappetizing finds, like the thyroid and the esophagus hidden behind it. 

The organ nearest to the incision we made was the heart, shown here between my thumb and forefinger. The heart, as we know, pumps oxygenated and deoxygenated blood throughout the body. 

Removal of the heart revealed large amounts of cardiac muscle, as well as the different sections of the organ. This image is great at showing the four sections of the heart. The top left and top right small sections, along with the bottom left and bottom right large sections are each visible. Scientifically named, the right chambers are named the right atrium (top) and right ventricle. The left chambers are named the left atrium (top) and left ventricle. As shown by the colored dyes in the blood, the right chambers contain the blood that lacks oxygen. 

A clearer image of the chambers of the heart, from within.

With the heart removed, the lungs are visible, The wing-like protrusions shown here are the lungs. They, as we know, aide in respiration and spread take in oxygen that they then transport to the bloodstream and circulate through the body. 

Above the heart and lungs, closer to the neck area, lies a gland named the thyroid gland.This gland is responsible for regulating metabolic processes as well as hormone levels in the bloodstream. Just behind it, where the scissors are poking, is the lower part of the esophagus, which as we mentioned extends all the way to the lungs to transport air. 

A full overview of the heart and lungs (My fingers are separating the rib cage, and the heart is in the center, surrounded by the lungs)

External Anatomy

On the first day of dissection, our focus was on the pig's exterior parts. Each student retrieved a fetal pig from a bucket of harmless fluid that helps keep them preserved after their death. We then determined the sex of our pig by observing the external reproductive organs. Our pig on the first day was a boy (noticeable by his scrotum), but was smaller and less developed than many of the other groups' pigs, and hadn't developed his testicles fully yet. When we observed the skin, we were surprised to find how stiff and cold it was. This made working with the tools a little bit more difficult than I anticipated, but I quickly got the hang of things. Particularly remarkable was the pigs expressionless face, as he bit down on his rough, hard tongue. Seeing the pig lying before us on the desk, some students began to feel uncomfortable with the assignment, but everyone quickly reorganized themselves and continued on in the name of science!

Our pig was primarily colorless. This photo shows the eerie facial expression of the pig when we first retrieved him, as well as the slit on his neck that many students were curious about. This slit was made prior to the dissection and was used to inject red dye into arteries and blue dye into veins to help us better distinguish between the two. 

Remember that the pigs were fetal at their time of death. Here, we get a good view of the pig's umbilical chord. 

The manual pictured here was used as a guide on the first day to give us a basic understanding of the fetal pig's external anatomy.

From this angle, many of the male pigs in the class had testicles that were easily visible. Ours however, had underdeveloped sex organs and was harder to determine. After some prodding and poking, we were lucky enough to find the scrotum, however, and safely concluded that we were dealing with a male. 

A tiny incision on the surface of the skin allowed us to see connective tissue, such as fascia, and capillaries (shown in red).Pictured here, however, is mostly fat (the clear-whitish substance), which can be used for insulation by the pig.

The Digestive System

On our second day of work, we took a detailed look at the pig's digestive system. Due to some complications, we were forced to take a pig different than the one we had observed the day before. Our new pig was determined to be a female, and was slightly larger than our old one. Along with observations of the digestive tract came the need for some heavy duty cutting. I took a deep breath and got right to work, snapping the pig's jaw in order to peek in, and later slicing the pig open straight down the abdomen.

                                                         

The inside of the pig's mouth revealed sharp teeth on both the top and bottom for chewing, as well as an air and food passage at the back of the throat called the esophagus. 

Bits of food and liquid that never got the chance to leave the pig's digestive system in its life spilled out onto the table when I made the first long slice, straight from the base of the neck, down and around the umbilical chord, all the way to the top of the pig's thigh.

The umbilical vein stretches from the liver where it attaches, to the entire length of the umbilical chord and supplies the fetal pig with nutrients as it grows within its mother's womb. We snapped the vein in half, but were sure to keep track of it because it's a vital part of the pig's digestive system. 

The lower abdomen. Shown here are the liver (The large brown organ). The top left coiled organ is the large intestine, responsible for water absorption in the digestive process, and the top right coiled organ next to it is the small intestine, responsible for nutrient absorption. 

An image of the small intestine when it's strung out.

The micro villi of the small intestine as seen through a microscope The small protrusions in the tract of the small intestine are able to aide in absorption and are vital to the successful digestion of the pig's food.

A larger image of the liver, which functions as a storage for chemicals that aide in the chemical processes of digestion. In our pig, the liver was soft and in terrible condition, but some groups had stiff, well-rounded livers. After a short time, we removed the liver. Also note that the thumb and forefinger of my left hand in this picture are clutching the umbilical vein, which I mentioned earlier, attaches to the liver. 

The mechanical breakdown of food through churning action, as well as the chemical breakdown of food by use of stomach acid is done in the stomach, pictured here. 

When all contents are removed, the stomach fell flat...

The Assignment

After a long, tedious unit of Anatomy and Physiology in AP Biology, dissection was the perfect way to see up close and personal all of the body systems and parts that we'd been discussing in class. By using a fetal pig, with anatomy similar to that of a human, the class was able to learn about the process of dissection hands-on, while at the same time getting a greater idea of what actual organs and various cells look like.

Shown here, the fetal pig lying on the dissection table before any incision had been made.