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CAT DISSECTION A LABORATORY GUIDE

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CAT DISSECTION A LABORATORY GUIDE

CONNIE ALLEN VALERIE HARPER

Edison Community College

John Wiley & Sons, Inc.

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Allen and Harper Cat Dissection A Laboratory Guide

ISBN 0-471-26457-1

Printed in the United States of America.

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CAT DISSECTION A LABORATORY GUIDE

OUTLINE

Preface, p. 2 A. Preparing the Cat, p. 2 B. Removing the Skin, p. 3 C. Opening Ventral Body Cavities, p. 3

Dissection 1: Skeletal Muscles, p. 4 A. Dissecting Skeletal Muscles, p. 4 B. Muscles of the Head and Neck, p. 4 C. Muscles of the Chest, p. 6 D. Muscles of the Abdomen, p. 8 E. Muscles of the Back and Shoulder, p. 10 F. Muscles of the Arm and Forearm, p. 12 G. Muscles of the Thigh, p. 15 H. Muscles of the Leg, p. 18

Dissection 2: Brachial and Lumbosacral Plexuses and Major Nerves, p. 20 A. Brachial Plexus, p. 20 B. Lumbosacral Plexus, p. 22

Dissection 3: Endocrine Organs, p. 24

Dissection 4: Blood Vessels, p. 26 A. Arteries, p. 26 B. Veins, p. 29

Dissection 5: Lymphatic System, p. 30

Dissection 6: Respiratory System, p. 32

Dissection 7: Digestive System, p. 34 A. Mouth, Oropharynx, and Salivary Glands, p. 34 B. Esophagus and Abdominal Organs, p. 35

Dissection 8: Urinary and Reproductive Systems, p. 38 A. Urinary System, p. 38 B. Male Reproductive System, p. 40 C. Female Reproductive System, p. 41

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2

Cat Dissection

PREFACE

A. Preparing the Cat

1. With gloves on, remove the cat from its bag and lay the cat on a dissecting tray. Keep any liquid preserving solution that remains in the bag.

2. Review the directional terms for the cat in Figure CP.1. Note the differences between four-legged animals and humans. ? Anterior is toward the cephalic (head) end of the cat ? Posterior is toward the caudal (tail) end of the cat ? Superior is toward the dorsal (back) surface ? Inferior is toward the ventral (belly) surface

Superior (dorsal)

Posterior (caudal)

Anterior (cephalad)

(a) Incisions for skinning

Inferior (ventral)

F I G U R E C P. 1 Directional terminology for the cat.

3. Place your cat ventral surface up on the dissecting tray.

4. Identify the gender of your cat. Males have a scrotum and a prepuce, a small mound anterior to the scrotum in which the penis is located. Females have a urogenital aperture, an opening located anterior to the anus that is a common passageway for the urinary and reproductive systems. Four or five teats (nipples) are present on both male and female cats. Be able to identify both sexes externally.

5. Prepare a label for your cat with the names of your group members and the gender of your cat.

6. Follow the instructions for skinning the cat if you are dissecting skeletal muscles, or the instructions for opening the ventral body cavities if you are dissecting an organ system.

Diaphragm

(b) Opening ventral body cavities Incision line F I G U R E C P. 2 Cat incisions.

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Cat Dissection

3

B. Removing the Skin

1. Referring to Figure CP.2a, pinch the skin on the ventral surface of the neck. Using scissors, carefully make a small, longitudinal incision at the midline through the skin only. Use care not to cut into the underlying muscle layer.

2. Continue cutting longitudinally along the midline toward the lower lip and then posteriorly, stopping anterior to the genital area.

3. Cut the skin around the neck.

4. Make a horizontal cut across the chest and continue cutting down the midline of the extremities as indicated in Figure CP.2a. Make diagonal cuts in the groin and continue midline down the extremities. Cut the skin around all paws.

5. Use your fingers to carefully peel the skin from the underlying muscles. Cutaneous muscles, such as the platysma, are attached to the undersurface of the skin and will be removed as you peel away the skin.

6. Continue peeling the skin until it is only attached at the face and the tail. Cut around the base of the tail, leaving the skin on the tail. Cut the skin around the face of the cat, leaving the skin on the face, ears, and forehead. Peel the skin from the head and save it.

7. Carefully remove as much fat and superficial fascia as possible with your fingers or forceps.

8. Wrap the skin around the cat and follow your instructors directions for storing your cat in the plastic bag. The skin will prevent the tissues from drying out and

prevent the growth of bacteria and mold. Dispose of fascia and fat as indicated by your instructor. Do not forget to attach the label identifying your cat before storing it.

C. Opening Ventral Body Cavities

1. At the midline, just above the pubic bone, carefully make a longitudinal incision through the abdominal muscles. Refer to Figure CP.2b. Continue the incision to the ribs.

2. Cut either to the right or left of the sternum, cutting through the costal cartilages. Continue cutting midline through the neck.

3. Cut horizontal incisions at the top and at the base of the neck.

4. Cut horizontal incisions anterior and posterior to the diaphragm as indicated in Figure CP.2b, and cut the diaphragm away from the ventral body wall. Open the flaps to expose the thoracic and abdominal cavities, leaving the diaphragm intact.

5. Use a scalpel to make a longitudinal cut down each inner wall of the rib cage. Bend the walls outward to break the ribs, allowing the flaps of the thoracic wall to stay open.

6. Dispose of fascia and fat as indicated by your instructor. Do not forget to attach the label identifying your cat before storing it.

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Cat Dissection

DISSECTION 1: SKELETAL MUSCLES

Many skeletal muscles of the cat are similar to human muscles. This dissection will reinforce your knowledge of human skeletal muscles and allow you to observe the fascia that surrounds, protects, and compartmentalizes these muscles. Assemble your dissection equipment and safety glasses, put on your gloves, and obtain your cat. Position your cat within the dissection tray, including the tail. Keep any remaining preserving fluid in the bag to keep your cat moist and inhibit bacterial and mold growth.

Procedure

A. Dissecting Skeletal Muscles

It is important to carefully remove the fascia to observe the individual muscles. However, using scissors or scalpels

may result in cutting muscles or other structures. Blunt dissection is a technique that uses blunt probes and forceps to remove fascia and separate muscles. To observe a deep muscle, you will have to cut the superficial muscle at the midline and reflect (pull back) the edges toward the origin and insertion.

B. Muscles of the Head and Neck

1. Refer to Figure C1.1 to locate the following superficial muscles on the cat. Cats have a platysma, but this muscle was most probably removed during the skinning process. ? Masseter ? Digastric ? Mylohyoid ? Sternohyoid ? Sternothyroid ? Sternomastoid (sternocleidomastoid in humans)

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