Dissection Of Small Animals

Introduction

Dissection of small animals in a classroom setting is a common activity. The purpose of the dissection exercise is to teach anatomy in Anatomy and Psychological courses. The dissected animal will enable students learn more on the anatomy of the animal that has been dissected. This enables them to relate the anatomy of the animal to the human anatomy. Cats are commonly chosen as animals to be dissected in the classroom. There are several reasons for this; first, the anatomy of the cat is almost similar to that of humans. Therefore, a lot of anatomical relationships can be illustrated using the cat. Second, the cat is a fairly large animal; it is large enough for students to distinguish its features clearly. Other animals like fetal pigs used are too small for this purpose to be achieved. Third, physically dissecting a cat is more effective as a learning tool as compared to virtual dissections available in computer programs. Fourth, cats are very many and relatively inexpensive thus a team of two students has a personal hand -on experience when it comes to the actual dissection process (Harrison, pg 6)

The goal for dissecting a cat is to be able to learn the human anatomy through the cat since the two anatomies are related. There have been issues of ethics raised against dissecting a cat for the purpose of studying anatomy. The ethical argument against the use of cats would be stronger if cats were bred only to be killed for dissection. However, most of the cats used are products of uncontrolled reproduction of pets. The excess cats end up in animal shelters where they undergo euthenization in hypobaric chambers. This leads to death of cats from being starved off oxygen. In most cases the carcasses are cremated or buried. Using the euthanized cats in classrooms yields a positive outcome of their deaths, which is the teaching medical science.

Procedure

Materials

Scrapple blades

Forceps

Dissecting scissors

Dissecting needles

Dissecting tray

Gloves

Apron

Preparation

One is supposed to wear an apron, disposable gloves and goggles

cat are placed in a plastic bag containing excess embalming fluid

the bag is cut from one end and fluid preserved in the bag

The bag should be safely stored and formalin solution used to prevent cat from drying

Skin removal

Cat is placed on dissection tray

skinning begins from ventral neck region where skin is cut to facilitate injection of latex into vessels

a lifting motion is used to separate skin from underling muscles

scissors are used to cut through the tail base

circular incisions made around tail, genitals and anus

continued incision made down each appendage to ankle

incisions extended laterally around the neck and continued to the other side for incision to meet up with initial midventral cut

the skin is carefully removed(Harrison,pg 32)

Actual dissection

After successful removal of skin a deeper cut is made so that the organs can be revealed

The fascia is trimmed ,connective tissue and fat that might be covering the muscles

Excess juices are poured off and the cat is washed twice

Using the forceps the visible skeletal, digestive and cardiovascular systems are separated

Extreme care should be taken so that none of these parts are damaged

Clean up

The dissected cat is sprayed with preservative if it needs to be used later

The cat is placed back into the bag and sealed

The dissecting tools should be washed thoroughly and dried

Fur, fat or stray pieces are cleaned from the desk

The table is cleaned using spray cleaners and dried(Harrison,pg 42)

Cat dissection organs

During dissection various organs can be seen; some organs must be removed to make other organs visible. The thoraxic cavity organs viewed it includes diaphragm which separates thoraxic and abdominal cavities. Within the thoraxic cavity the heart and lungs are seen. The thorax appears as a ringed tube in the throat. Behind it is the esophagus which is slightly to the side. Spongy lungs are visible, pushing the heart and lungs aside one can trace the path of the esophagus to where it meets the diaphragm and connects to the stomach. Below the diaphragm is the liver can be seen. It appears as the largest organ in the cat with four lobes. The gal bladder is seen embedded within the liver (Harrison, pg 68)

Abdominal; cavity

The liver is used as a reference point and the stomach lies under it posterior to the diaphragm. The stomach too has an entry point for the esophagus .Opposite side of the stomach is pyloric sphincter a point of connection between stomach, duodenum and small intestine. The next section of small intestine comprises of jejunum, followed by ileum connecting it to large intestine. Kidneys are visible far back on the abdominal cavity. They are bean shaped and the ureters appear attached on them. A bladder is visible next to the large intestine. The rectum is also seen and it is the part of the large intestine (Harrison, pg 72)

Reproductive system

The dissected cat was female hence its reproductive organs were exposed. Two uterine horns were visible with an ovary on top of them.

Comparison between human anatomy and cat anatomy

There are several similarities in the human and cat anatomies. All organs in the thoraxic, abdominal and reproductive systems in the cat are same. These organs are located in the same areas and in similar positions. However there are some slight differences between the anatomies of cats and humans. For instance, in the cat there are two uterine horns present as opposed to one uterus horn in humans. Uterine horns. In humans there is a fallopian tube which lacks in the cat but the uterine horns are analogous to it (Harrison, pg 96)

Conclusion

The use of animals in classrooms for the study of the human anatomy has become very common. This is because it is easy to dissect these animals in a lab setting compared to humans. It therefore becomes very easy to study the human anatomy using these animals.

The animals are very relevant as a tool for acquiring knowledge as their dissection allows visualization of these organs. It makes it very easy for students to relate what they see from the dissections from the theory they have learned about the human anatomy. This enhances easy and fast understanding of the human anatomy.

Works cited

Harrison, Bruce M. Dissection of the cat (and comparisons with man); a laboratory manual on Felis domestica. 6th ed. St. Louis: Mosby, 2007.Print.