On Thursday and Friday of last week, my class and I began the dissection of a living (well, technically dead) animal. I'd been anticipating something like this from the beginning of the semester, and was quite ecstatic when I finally learned we would actually be dissecting an animal. This required not as many tools as previous dissections, which was pretty good, although this one was a bit more messy. The only tools we had to use were our hands, a small scalpel, pins and a few various other items. Gloves were also required, and made the task a lot more easier! When I first saw the rat, I expected a horrid stnech of kinds, but that wasn't the case, for the rat had been drained of all bodily fluids, and had been preserved, which essentially helped it lose it's smell. With that said, the rat felt squishy, yet kind of hard considering all of its organs were inside. The purpose of this dissection was to gain a better understanding of an animals anatomy by viewing it's external organs, as well, after careful incisions, viewing the inside of the rats anatomy. For the past 2 weeks, my classes focus has been on vertebrates, and that relates to why we dissected a rat instead of any other animal in the animal kingdom. The reason we dissect things is to gain a better understanding of how the body works through physical actions, rather than sitting down half asleep in a drowsy classroom. People tend to retain information better when they experience something before their eyes, rather than reading about it. For example, someone would probably learn more about the esophagus and where it's located by actually dissecting and seeing it rather than simply learning about it.
To start off, we observed the external anatomy of the rat. My group and I looked at things like the eyes, the number of fingers on each hand, the tail etc. Then we got to do some real dissecting! We were given a handout + guideline to follow, so our first incision started in the middle, for there was more space to work with there, and then it branched out ward, both up and down the body. I was half expecting some blood to spew out, or the wrong cut to be made (considering I had no idea it'd been drained of all fluids), but that didn't happen. Instead, everything went normally, and we cut the rat open without a problem. After all the major cutting was done, our next objective was to look for certain bod structures and organs, like the esophagus, and take down what they look like (and maybe even how they feel!). The internal body was pretty messy, and very clumped together, probably because the body has to fit a long digestive tract + several other organs all into one tiny space. Unlike the previous dissections of the Annelid and Squid, this one was really, really messy for me. Mostly because the scalpel was so small, so I used the tweezers to rip off the flesh that was in my way/ jutting out, which caused a lot of fur and guts to go everywhere. Unfortunately, this is most likely the last dissection we will probably do in Biology, until Bio 12 next year. I'm glad I joined this class because doing things like dissections to learn is always great fun!
Set 1
1.) Why are your hands the best tools for dissection?
Your hands are the best tools for dissection because you're already so used to using them that doing almost any task shouldn't be a problem (unless you're queasy around dead things!). This also gives you a literal hands on feel of what you're learning about.
2.) What is the purpose of having all the different labels and titles for the dissection?
The purpose behind this is to give you a better understanding through diagram and drawing, as well as to get you to think. If you're trying to come up with a title, you're subconciously using the information you've learned to do so. Also, labels help with memorization of facts and knowledge.
3.) In what way does the tail differ from the rest of the body?
The tail differs from the rest of the body because it doesn't have any specific use or function, and is more or less just an addition to the body of the animal. It probably does some sensory things, but isn't a primary sense organ. (Picture Down Below)
4.) What purpose is served by the vibrissae?
The purpose of the vibrissae is navigation and sensing. They feel vibrations (most mammals with these tend to put their face close to the ground), and also feel air speeds/ current. It helps them avoid any danger, most of the time at least.
5.) Your specimen is Bilaterally Symmetrical. What does this mean?
This means that if the specimen is cut in half, both sides will have the same features, just in opposite directions.
Set 2
1.) The sphincter is descrbed as a circular muscle. Why is it this shape and what does it do?
The sphincter helps mediate the release and entrance of liquids trhoughout the body of the rat, and is shaped like a circle to help give out maximum efficiency.
2.) Why is there a difference in size between the small and large intestine?
Small intestine helps in digestion and absorption of food, while the large intestine helps in reabsorption of food and elimination of wastes.
3.) The liver is the largest organ in the body. What are its function?
The liver helps clear the blood of drugs and other poisonous substances, it creates bile, and deoxifies & purifies oxygen.
4.) How did the duodenum get it's name?
The duodenum was given its name in latin because it is usually 12 fingerbreadths long, about 25 cm, which is what duodenum means.
5.) What is the purpose of the appendix in animals who retained this as a functional organ?
The appendix has a lot of digestive enzymes in it, and helps with the breaking down of tough-to-digest foods that animals eat. Considering how far humans have evolved, we no longer need use of this.
Set 3
1.) In each of the cavities, there is a membrane that cover both the wall of the cavity and the organ it contains. What is the function of the membrane?
It helps to keep all the fluids inside, working efficiently, and makes sure that the fluids don't accidenlty leave the cavity somehow.
2.) What us the function of the spleen?
It removes old red blood cells from the blood, and supplies and stores white blood cells, which in turn produce anitbodies, and so on and so forth
3.) What is the function of the diaphragm?
The diaphragm controls the flow of air into the lungs of this mammal, helping the respiration system tremendously. Without it we can't breath because it contracts and moves down to make us inhale and goes upward and expands to make us exhale.
4.) What distinguishes the atria from the ventricles?
There are a number of differences between the atria and the ventricles. For one,
the atria are smaller than the ventricles. Atria also consists of thinner muscle
tissue than the lower positioned ventricles. Atria also pump blood to the
ventricles, while the ventricles distribute blood around the entire body.
Because of the more complex job of the ventricles, they are larger than the
atria
5.) Why is the wall of the left ventricle thicker than that of the right?
The left ventricle needs to be thicker than the right because it needs to pump blood through the entire body. The right ventricle only pumps to the lungs to oxygenate the blood. Hence why the left is thicker, due to needed more muscle to do so.
6.) What similarities exist between the male and female reproductive system?
Many reproductive organs of males and females are derived from the same
embryologic structures. In addition, some hormones are the same
in males and females, even though they act in very different ways. The anatomy of the vulva is related to the anatomy of the male genitalia by a shared developmental biology. The clitoral glans are also homologous to the glans penis in males.
7.) What do the kidneys do?
They function by filtering out wastes to be excreted in the urine, but their main purpose is to separate mineral salts, toxins, and other waste products from the blood. In addition, the kidneys also conserve water, salts, and electrolytes.
8.) In the dissection, you located the thyroid, the thymus, and the adrenal glands. To which system do they belong, and what do they do ?
The thyroid,thymus and adrenal glands are a part of the lymphatic and endocrine organ system. The role of the thyroid is to stimulate metabolism, and control the body’s circulating calcium levels. The Thymus gland is where leukocytes aquire means to chemically identify specific foreign invaders and where Immature T cells from bone marrow move to thymus gland and mature. The Adrenal Glands are responsible for producing cortisol and aldosterone. These hormones regulate our heart rate, as well as, sexual desire and other bodily functions
