Rat Dissection

The Tragedy Of Stuart Little

       On one faithful day, StuartLittle was captured, killed, and preserved for the Biology studentsof Ms. Iannone to dissect and examine. This was the first big dissection thatmany of us done so we were all a little bit squimish and hesitant at first.When Ms. I placed the rat on our dissecting tray, my eyes lit up in wondermentand shock to see how big these animal were. Then I realized that now I getto open him up and take a look inside. The first cut was very nerve rackingbecause I did not want to cut open any organs that we needed to look at furtherthrough the dissection. However, after a few more cuts, I became moreconfident. When we opened the rat to expose the internal structures, we sawmany of the same internal structures that humans have except theenlarged livers and cecum. The knowledge of the human structure helped mygroup greatly to figure out the internals of the rat. By knowing this phylum'sinternal structure on paper, seeing it for our own personal viewing help usidentify and learn better.

Discussion Questions:

1. Why are your hands the best tools in dissection?

Hands in dissection can be the best tool to use in dissections because not only do you get to examine the feel of the part you are touching, but also it can be more accurate and easier to use when moving structures, in this case a rat, around.

2. What is the purpose of having all the different labels and titles for their dissection?

The different arrangement of labels and titles help in organizing and identifying structures and also it keeps the information accurate.

3. In what way did the tail differ from the rest of the body?

The tail of the rat appears to have scales and a bit of hair. It also felt hard and solid.

4. What purpose is served by the vibrissae?

Also known as whiskers, the vibrissae are used for tactile sensation; however, they contain no nerves inside. 

5. Your specimen is bilaterally symmetrical. What does this mean?

It means that if the animal was to be cut in half, the animal would mirror the other side of the body.

6. The Sphincter is described as a circular muscle. Why is it this shape and what does it do?

The sphincter is a circular muscles and it closes and open to regulate the passing of food and this circular shape fits the tube better because the tube is a circular shape as well.

7.Why is there a difference in size between the small and large intestine?

There is a size difference because the food in the large intestine is broken down more so the food is able to be processed and passed into the small intestine where other nutrients are extracted.

8. The liver is the largest organ in the body (after the integument.) What is it's function?

It produces essential enzymes for taking in nutrients. The liver of the rat is essential for filtering contaminants from the blood and converting wastes into a disposable form. The liver converts toxic ammonia from the blood to the urine.

9. How did the duodenum acquire its name?

The duodenum (L. duodeni, twelve) was acquired this name because it literally means 12 fingerbreadths long which means 25 cm. 

10. What purpose is served by the appendix in those animals that retain it as a functional organ?

It is a kind of "safe place" for certain benefical bacteria that help digest vegetables and other plant like food. Certain diseases can wipe out these bacteria. The appendix is a place where an extra supply of them are stored.

11. In each of the cavities, there is a membrane that covers both the wall of the cavity and the organ it contains. What is the function of the membrane?

The membrane is vital because it separates layers, lubricates the surface, for tension and protection. 

12. What is the function of the spleen? 

The spleen is a blood cleaner that contains white blood cells that destroy used up, old red blood cells.

13. What is the function of the diaphragm?

The Diaphragm has many functions but the main function is that is helps in respiration and breathing but contracting and expanding. The diaphragm helps air to exit and enter the lungs.

14. What distinguishes the atria from the ventricles?

The atria are smaller than the ventricles and consists of thinner muscle tissues than lower positioned ventricles. The atria also pumps blood to the ventricles while the ventricles distribute oxygenated blood around the body. The ventricles are also larger in size due to their complex job.

15. Why is the wall of the left ventricle thicker than that of the right?

The left ventricle is more muscular because it has to pump blood at a higher pressure to further distances.

16. What are the similarities exist between male and female reproductive systems?

Both female and male reproductive systems appear very different; however, one attribute that they both share is a pituitary gland.

17. What do the kidneys do? 

Kidneys in rats help to make waste OK to excrete along with regulating the balance of water in the body.

18. In the dissection, you located the thyroid, the thymus, and the adrenal glands. To which system do they belong to?

This structures are apart of the respiratory system.

Here is a little overview:

http://www.youtube.com/watch?v=spsnpit5AT8

http://www.youtube.com/watch?v=0hBl0UosmU8

Time to Open Up Squidward

Squid Dissection

In this class, we performed another dissection. Instead of dissecting a small earthworm, we got to dissect a squid! This time around, it was much easier to perform a dissection on this mollusk because it was much bigger. The purpose of this dissection was to again incorporate that visual aspect to our learning in Biology 11. A goal was to open this squid up and answer the questions on the lab to further extend our knowledge of a Cephalopod, also known as "head" "foot". With this dissection, we got to discover the flow of the water through the funnel and how it moves by jet propulsion. Also, using a microscope, we got to see the little pods of colour on the squid's skin that enables it to camouflage to it's surroundings. These were some of the many findings we discovered during this dissection. These help us understand not only how squid work, but also how we can save them. I enjoy dissecting animals because I love hands on work. It helps me learn about the animal we are discussing in class.

Questions: 

External Anatomy Questions

How many arms does your squid have? How many tentacles?

Squids have eight flexible tentacles and two long slender arms  with suckers on the end.

Based on the structure of the arms and the tentacles, describe how their purposes differ. What do the arms do and what do the tentacles do?

The purposes for the arms is to grab prey. The function for the tentacles are for pulling the prey to the beak for consumption. The two differ because the arms acts as more of a tool to attack and tentacles are used for help in feeding.

Draw arrows on the squid below to indicate the direction that water comes out of the funnel and the direction that the squid moves.

The water flows as shown on this picture. Also, the movement of the squid due to jet propulsion is shown.

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Name two external features that are adaptations for the squid's predatory life. How do these adaptations help the squid?

1. The suckers on the tentacles and the tentacles 

and arms themselves are used to grab prey and making

 it almost impossible to escape.

http://www.youtube.com/watch?v=X2aa6aHEyUI












2. The beak also serves as a serves as a tool for the squid's predatory life. The sharp talon looking beak is great for ripping apart the food for digestion.

Do you remember the general traits of mollusks we discussed in a lecture? Name two traits that the squid shares with other mollusks.

1. They both have a mantle. 

2. They also both have a visceral mass. 

As well, they all share bilateral symmetry and a soft body cavity. (coelom) 

Internal Anatomy Questions

How many pairs pf gills does the squid have?

The squid has two gills therefore the squid has one pair located near the stomach.

Magnified

Where does the ink sac empty into and what is it's function?

The ink sac empties into the water jet and it is used for defense by distracting the predators.

http://www.youtube.com/watch?v=O0iqRah3N0I

What is the function of the pen? What would happen if the squid didn't have a pen?

It provides stability for the squid so it could swim. Without it, the squid wouldn't have any structure and have many difficulties swimming. 

How do you think wastes exit the squid?

Waste exits the squid through the anus then the water jet where the waste is finally expelled into the water.

Worm Dissection

Have You Ever Dissected an Earthworm? 

    You see them in the dirt, or composes. They are the stars in the movie, "How to Eat Fried Worms?" Some are found under the sea , others have been seen on "Fear Factor" or in murky ponds. If you guessed Annelids, you are correct. In this phyla there are three major classes called: Class Oligoshaeta, better known as earthworms, Class Hirudinea, the leeches, and Class Polycheata, the Marine worms.in the dissection, we chose to dissect an earthworm. We got to use tools such as a scalpel  tongs and pins to open up the earthworm to expose the innards. The purpose of this dissection was to help us further learn the parts of an annelid. Using this hands on technique, I find it easier to understand and further learn the different parts of an annelid. This dissection help us understand the biological world because with the visual aspect, we saw what a real earthworm looks like, what it's food looks like, and an up close look at the parts in the annelid. We also got to exercise our dissection skills which will be useful for further dissections. All in all, I had a great time with dissection and look forward to others in the future.

Discussion Questions: 

The pumping organs of the circulatory system are called the five aortic arches. The circulatory fluid, also known as hemoglobin,travels through the arches of the ventral blood vessel to the capillary beds in the body. Then, the hemoglobin runs back through the dorsal blood vessels and back to the arches.

Magnified 

It was quite tough to uncover the digestive tract of the worm; however, food travels through the mouth, into the pharynx, to the esophagus where it travels into this sac like structure called the crop, then a bigger sac like structure called the gizzard. Then, the food travels down the intestinal tube and out the anus.

Magnifed

Little more of a clear picture of an Earthworm digestive track

The nervous system are made up of a ventral nerve cord. It travels the length of the worm on the ventral side. Ganglia also are included in the nervous system. They are masses of tissues containing many nerve cells. Also, there is a nerve collar that surrounds the pharynx along with ganglia. This ganglia is found both above and below the pharynx. Even though the earthworm's nervous system isn't as advance, the earthworm still responds to stimuli and are responsible for movement.

Magnified 

Some parts found in the dissection that are apart of the excretory system include the nephridia. They are found in pairs in each body segment. The anus is the last step of the excretory system where the waste it excreted. 

Magnified 

We can find out if a earthworm eats soil by dissecting it. In the dissection, we found dirt in the digestive tracks...

Magnified Soil in digestive track

YUM YUM SOIL

Each segment or section contain muscles and bristles called setae. Setae help anchor and control the worm when moving around it's environment  The setae hold a section of the worm firmly into the ground while the other part of the body moves forward.

Once the soil passes through the esophagus, calciferous glands release calcium carbonate to get rid of the excess calcium in the earthworm's body. The food moves into the crop where it is stored and then eventually moves into the gizzard. The gizzard uses stones that the earthworm eats to grind the food completely. That's how big parts of soil become little digestible particles.

Better shot of a Gizzard

We continued to dissect the rest of the worm and when we did, we found the rest of the digestive tract, soil and the anus. 

In the reproductive system, the ovaries, clitellum, testes and sperm all make up this system. In our dissection, we figured out how earthworms mated. We also found the ovaries and where this "egg cocoon" constructs itself during and after mating. During mating, two worms line up from each other so sperm can be exchanged. The earthworms each have two male openings. These take in the sperm from another mate. The earthworms have a pair of ovaries that produce eggs. The clitellum will form a slime tube around itself and fill with an albuminous fluid. As the earthworm passes through the slime tube, it will pass over the female opening and pick up the eggs. The tube will continue to move down the earthworm and go over the male opening which has sperm. The eggs will fertilize and the slime tube will close off as the worm moves completely out of the tube. Then, baby worms are formed in time. 

Craving for more knowledge?

http://www.youtube.com/watch?v=u9HHS1uPFSo

http://www.youtube.com/watch?v=9a0F82VJTsE