Mink Dissection – Laboratory Guidelines



Mink Dissection – Laboratory Guidelines

1. BE PRESENT AND ON TIME!!

a. The only good reason for missing lab is DEATH (your own).

b. You may be given notes or special instructions during the first few minutes of lab. Make special note of any changes in materials to be used or procedures to be followed.

2. BRING MATERIALS/SUPPLIES.

a. Bring your laboratory manual and notebook to class everyday.

b. Be sure to put your name on everything (including boxes of gloves, if you brought them).

3. COME PREPARED TO WORK.

a. Prepare yourself BEFORE lab by reading the assigned exercise. It is important to have some understanding of what you are to do since the class periods are not very long, and some classes are large.

b. Be prepared for a poptest on the material covered the day before or material to be covered each day.

4. CHECK IN.

a. Use only equipment that is assigned to you.

b. Each day you will assemble the following dissection material: dissection tray and specimen, blunt probe, sharp probe, forceps (tweezers), scissors, and a scalpel.

c. BEFORE YOU BEGIN EACH DAY, check to see that all dissection equipment is clean and in place. Report any dirty or misplaced equipment to the instructor immediately. Dirty or misplace equipment will result in a daily grade of zero for the prior users.

5. BE SAFE.

a. NEVER eat, drink, or chew gum while dissecting in the laboratory.

b. Report any injuries to yourself or damage to equipment IMMEDIATELY.

c. Follow instructions precisely and proceed only when you understand them clearly. Do not skip any sections.

6. RECORD EVERYTHING.

a. Although it will be necessary for you to work within a group, try to remain independent when making observations and drawing conclusions. Remember that lab practicals will be taken without the aid of other group members.

b. Each day, record what you did and what structures you observed. These observations will be your daily log and will be placed at the end of your Mink Lab Report.

c. Daily instructions will be given concerning homework and lab report assignments.

7. MINK LAB REPORT MUST INCLUDE:

a. Log of what you did each day and what features you found. This log will be placed at the end of the report.

b. Drawings as indicated by daily handouts.

c. Written assignments as indicated by daily handouts.

d. Guide sheets.

8. CLEAN UP.

a. At the end of the period, clean your table with 409 or Clorox wipes and wash the instruments you have used. After drying your instruments, return them to the proper places and dispose of wastes as instructed.

b. WASH your hands thoroughly before leaving the classroom.

9. GRADING.

a. Your grades on the dissection of the mink will be composed of:

i. Mink Lab Report (1 test grade)

ii. Muscle Lab Practical (1 test grade)

iii. Internal Anatomy Lab Practical (1 test grade)

iv. Daily Participation

I have read the above instructions and regulations and understand them.

______________________________________(student signature) ____________________(date)

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 1

INTRODUCTION

Your first task, before actually beginning the mink dissection, will be to review material covered earlier in the year, focusing on directional terms and anatomical terminology. You must also become familiar with the classification and characteristics of your mink. Please complete the following assignments.

1. In your laboratory manual (Laboratory Anatomy of the Mink) read pages viii, 1 and 3.

2. Prepare a TITLE PAGE to be placed in your Mink Lab Report. Do not number the title page.

3. Insert the Laboratory Guidelines directly after the title page and number it as PAGE 1.

4. Insert this instruction sheet (Guide 1) next and number it as PAGE 2.

5. Next, write a brief narrative (1/2 to 1 page) describing the classification, characteristics, and habitat of the mink. Number this as PAGE 3.

6. Review the directional and anatomical terms on page 5-6 of the lab manual.

7. The first drawing you are to make is one similar to that found on page 5 (fig. 1) in the lab manual. DRAW and LABEL the directional terms and planes of reference. This should be a WHOLE-PAGE DRAWING on unlined paper and should be entitled PLATE 1: DIRECTIONAL TERMS AND PLANES OF SECTION. It should be numbered PAGE 4. Remember that all drawings will be graded on neatness and accuracy, not artistic ability.

8. Next, handwritten on lined paper or typed, define the following terms:

a. anterior (cranial)

b. posterior (caudal)

c. ventral

d. dorsal

e. medial

f. lateral

g. frontal plane

h. sagittal plane

i. transverse plane

j. pectoral limb

k. pelvic limb

*Number this PAGE 5 and insert it into your Mink Lab Report.

9. The SKELETAL SYSTEM of the mink is very similar to that of man in many ways. Read pages 7-14 in the lab manual for a complete discussion of the mink’s skeletal system. We do not have disarticulated skeletons, so we will not compete this section of the lab.

10. Review your notes describing the human skeletal system. Write a BRIEF SUMMARY (no more than 1 page) describing the likenesses and differences between the human and mink skeletal systems. This should be numbered PAGE 6 of your Mink Lab Report.

REMEMBER THAT ALL DRAWINGS ARE TO BE MADE ON UNLINED PAPER.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 2

THE MUSCULAR SYSTEM

Your mink has been skinned for you. Your task now is to clean the fat and fascia off so that muscle fiber directions can be seen and to separate each muscle from adjacent ones. Fingernails and the blunt probe are most useful. When cutting a muscle, first separate it completely from adjacent structures and pass the probe beneath the belly. Then cut downward to the probe with a scalpel from the outside. When cutting a number of muscles that run alongside one another in the same direction (such as muscles of the thigh), cut across the bellies of different muscles at different levels and reflect (fold back) the muscle halves.

Dissect the musculature on the LEFT SIDE OF THE ANIMAL ONLY, leaving the right side intact for the study of the nervous and circulatory systems. Where two depths of dissection are shown on one animal in the lab manual, the deeper is always on the animal’s left side.

Complete the following tasks:

1. Read pages 16-19 in your lab manual and review your class notes on the muscular system PRIOR TO LAB. Insert this guide as PAGE 7 in your Mink Lab Report.

2. As you did with the skeletal system, write a BRIEF SUMMARY describing the likenesses and differences between the muscular system of man and that of the mink. Please limit your discussion to one (1) page. (NOTE: It will be much easier to complete this assignment once you have completed the muscle dissection, but you need to watch closely for likenesses and differences as you dissect.) This summary should be numbered PAGE 8 of your Mink Lab Report.

3. Begin your dissection by carefully removing dermal muscle, fat, and fascia (connective tissue) from the neck, back, shoulder, and upper arm of the LEFT SIDE. This is best done using forceps and fingers, NOT A SCALPEL!!!

4. Following the instructions in your lab manual and the drawing at the top of page 17, identify the following muscles of the head and back, separating them as you go, but NOT CUTTING THEM:

a. TEMPORALIS

b. CLAVOTRAPEZIUS

c. ACROMIOTRAPEZIUS

d. SPINOTRAPEZIUS

e. LATISSIMUS DORSI

5. Once all members of your group are confident that they can identify the above muscles, proceed to identify the underlying muscles. Using a scalpel, cut THROUGH the belly of the SPINOTRAPEZIUS, ACROMIOTRAPEZIUS, and CLAVOTRAPEZIUS. Do not remove these muscles. Simply cut through the belly and pull back to either end in order to expose the underlying muscle layer. (This way you’ll be able to put them back into position when you get ready to review the muscle in step #4.)

6. Follow your manual and the middle drawing on page 17 to identify the following muscles of the underlying layer:

a. RHOMBOIDEUS

b. ATLANTOSCAPULARIS

c. SPLENIUS

d. OCCIPITOSCAPULARIS

e. OMOCERVICALIS

7. Make a full page lateral view DRAWING with the following muscles being labeled (use top drawing on page 17 as a guide, but make your drawing a full page):

a. TEMPORALIS

b. CLAVOTRAPEZIUS

c. ACROMIOTRAPEZIUS

d. SPINOTRAPEZIUS

e. LATISSIMUS DORSI

Label this drawing PLATE 2: SUPERFICIAL MUSCLE OF PECTORAL LIMB. Insert it into your mink lab report as PAGE 9.

8. Now make a full page lateral view DRAWING after step #6 has been completed. Label the following muscles (use the center drawing on page 17 as a guide):

a. OCCIPITOSCAPULARIS

b. SPLENIUS

c. ATLANTOSCAPULARIS

d. RHOMBOIDEUS

e. OMOCERVICALIS

Label this drawing PLATE 3: UNDERLYING MUSCLE OF THE PECTORAL LIMB. Insert it into your mink log as PAGE 10.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 3

THE MUSCULAR SYSTEM (cont.)

Now that you have completed the muscles of the head and shoulder, you are ready to begin identifying the muscles of the left anterior limb (pectoral limb) and the chest.

1. Begin by using figure 13 on page 17 (top drawing) to locate the following muscles on the lateral surface of the pectoral limb:

a. TRICEPS (lateral head)

b. TRICEPS (long head)

c. DORSOEPITROCHLEARIS

d. SPINODELTOID

2. Now identify each of the above muscles on your mink. DO NOT CUT THEM, as we will go no deeper than this surface layer of muscles.

3. Go back to your drawing labeled PLATE 2 and add the 4 muscles that you just identified in step #2.

Musculature of the forearm is complex, and only the larger, more superficial muscles will be described. These muscles are divided into a DORSAL EXTENSOR group and a VENTRAL EXTENSOR group. Bellies of these muscles are covered by very heavy fascia.

4. Of the extensor muscles, the BRACHIORADIALIS is the only one we will identify by name. Locate it now. (See figure 15, page 19.)

5. The remaining extensor muscles will simply be called the EXTENSOR CARPI. Locate them.

6. The muscles located on the ventral surface of the forearm we will collectively call the FLEXOR CARPI. Locate them.

7. These muscles will be labeled on a later drawing of the mink’s entire ventral surface. Do go back now to PLATE 2 and add the BRACHIORADIALIS and EXTENSOR CARPI.

8. Now place the mink on its back. Using figure 17 on page 21 as a guide, separate and identify the following muscles:

a. PECTORALIS MAJOR

b. PECTORALIS MINOR

These muscles will be labeled later after you have identified the muscles of the neck and head.

9. Insert this instruction sheet into your Mink Lab Report as PAGE 11.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 4

THE MUSCULAR SYSTEM (cont.)

Muscles of the head, neck, and abdomen.

Read pages 20-23 in the lab manual.

Place your mink on its back and begin removing as much connective tissue as possible from the neck region. Begin at the pectoralis muscles and clean anteriorly to the chin ON THE LEFT SIDE. This fascia will be EXTREMELY TOUGH! Use care not to tear the muscle tissue.

1. Place this instruction sheet into your mink lab report as PAGE 12. Then, using figure 17 on page 21 as a guide, identify the following muscles:

a. MASSETER

b. DIGASTRIC

c. MYLOHYOID

d. STERNOMASTOID

2. Also identify the hard MANDIBULAR GLANDS. These secrete saliva.

3. Cut and reflect the LEFT STERNOMASTOID. This will expose the STERNOHYOID, LARYNX, and TRACHEA. Locate each.

4. The THYROID GLANDS may be found alongside the larynx buried in fat. Attempt to locate them, but don’t be disappointed if you do not find them.

5. Concentrate now on the abdominal muscles. The lateral abdominal muscles of mammals consist of three superimposed sheets whose fibers run in different directions. The outermost layer is the EXTERNAL ABDOMINAL OBLIQUE. Locate it on your mink.

6. Slit and peel off a small section of the EXTERNAL ABDOMINAL OBLIQUE on the middle of the LEFT abdomen, about halfway up the body. BE CAREFUL – this muscle is about as thick as tissue paper. Under it you should see the INTERNAL ABDOMINAL OBLIQUE.

7. Slit the INTERNAL ABDOMINAL OBLIQUE (carefully) and see if you can find the TRANSVERSUS ABDOMINIS. Under this is the peritoneum and the abdominal cavity.

8. The abdominal muscles (external and internal oblique and transverses abdominis) attach with a fascia as they approach the ventral midline. Under this fascia, we find the RECTUS ABDOMINIS MUSCLE. Can you also find the LINEA ALBA?

9. Now make a FULL-PAGE drawing of the ventral surface of the upper body and label the following muscles (see figure 17):

a. PECTORALIS MAJOR e. MYLOHYOID i. EXTERNAL OBLIQUE

b. PECTORALIS MINOR f. STERNOMASTOID j. RECTUS ABDOMINIS

c. MASSETER g. MANDIBULAR GLAND

d. DIGASTRIC h. STERNOHYOID

This drawing should be PLATE 4. Insert it into your mink lab report as PAGE 13.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 5

THE MUSCULAR SYSTEM (cont.)

ASSIGNMENT: Read pages 23-26 in the lab manual carefully. Number this guide as PAGE 14 and

insert it into your mink lab report.

You have already identified the LATISSIMUS DORSI of the back. Locate it again. The musculature of the back consists of numerous bundles of fibers attaching on the ilium, processes of vertebrae, ribs, and the occipital region of the skull. Note that much of the muscle along the spine is covered by a think, glossy fascia.

Now we are ready to identify muscles of the pelvic limb. Remove fat and fascia from the pelvic limb and posterior part of the body ON THE LEFT SIDE. If your specimen is male, leave the fat in the inguinal region; the testicles may be buried in it. Be PARTICLULARLY careful when working between the legs and under the tail because the SCENT GLANDS may not have been removed when the animal was skinned. YOU AND EVERYONE ELSE IN THE ENTIRE BUILDING WILL KNOW IF YOU PUNCTURE ONE!!!

1. Observe the lateral surface of the hind leg and identify the following muscles (see top drawing on page 24, figure 20):

a. GLUTEUS MAXIMUS

b. TENSOR FASCIA LATA

c. FEMOROCOCCYGEUS

d. SEMITENDINOSUS

e. BICEPS FEMORIS

f. SARTORIUS

2. Now cut and reflect the BICEPS FEMORIS near the middle. (See middle drawing, figure 20.) Be very careful as you cut the biceps femoris because the TENUISSIMUS often adheres to the under surface of it and may be accidentally cut.

3. Identify the following muscles you have exposed:

a. VASTUS LATERALIS

b. TENUISSIMUS

4. Turn your mink over and observe the medial surface of the thigh. Using figure 21 on page 25 as a guide, separate and identify the following:

a. SARTORIUS

b. GRACILIS

5. Now carefully cut and reflect the SARTORIUS and GRACILIS to expose the following muscles:

a. SEMIMEMBRANOSUS

b. SEMITENDINOSIS

c. RECTUS FEMORIS

6. On the lower leg, identify the following muscles of the lateral surface using figure 22 on page 26 as a guide:

a. GASTROCNEMIUS

b. TIBIALIS CRANIALIS

7. You will make two DRAWINGS of the lower extremity. The first should be a FULL PAGE drawing of the lower extremity, lateral view (similar to the top drawing on page 24). The following muscles should be labeled:

a. GLUTEUS MAXIMUS

b. SARTORIUS

c. TENSOR FASCIA LATA

d. FEMOROCOCCYGEUS

e. SEMITENDINOSUS

f. BICEPS FEMORIS

g. GASTROCNEMIUS

h. TIBIALIS CRANIALIS

This drawing should be entitled PLATE 5 and inserted into your mink lab report as PAGE 15.

8. The next drawing should be of the medial surface of the pelvic limb (similar to figure 21) with the following muscles labeled:

a. SARTORIUS

b. GRACILIS

c. SEMITENDINOSUS

d. SEMIMEMBRANOSUS

e. RECTUS FEMORIS

This drawing should be PLATE 6 and should be inserted into your mink lab report as PAGE 16.

This completes the muscular system. Review in preparation for your laboratory practical.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 6

RESPIRATORY AND DIGESTIVE GLANDS

It is no longer necessary to take care in preserving the mink’s muscles. The remaining studies will be devoted to internal structures.

Please number this guide as PAGE 17 and insert it into your mink lab report.

1. Before opening the thoracic and abdominal cavities of the mink, review your text and notes on the contents of the human thoracic and abdominal cavities.

2. Write a BRIEF SUMMARY describing the contents of the human thoracic and abdominal cavities (please limit your discussion to one page). In your discussion, be sure to note any differences between the mink and human organization. Number this PAGE 18 and insert it into your mink lab report.

3. Read carefully pages 31-34 of the lab manual.

4. In the neck, located the ESOPHAGUS and TRACHEA. Note that the esophagus is normally collapsed. The trachea, on the other hand, is held open by a series of cartilaginous rings in its wall.

5. Make a transverse cut JUST ABOVE the larynx, cutting through the pharynx. CAUTION: DO NOT CUT THROUGH THE LARYNX – CUT ABOVE IT! Carefully detach the larynx and trachea from the body cavity until you can lift it out towards you. (NOTE: It will still be attached at the inferior end.)

6. Now cut the LARYNX midventrally and spread the two halves apart. Note the VOCAL CORDS that you have exposed.

7. Open the THORACIC CAVITY by cutting through the muscles and rib cartilages on the LEFT SIDE of and parallel to the sternum. Use your scissors to make this incision. Keep the scissors pointed ventrally as much as possible to avoid damaging structure in the cavity. After making an opening, insert your finger posteriorly to locate the DIAPHRAGM. Extend your opening just to, but not through, the diaphragm.

8. Spread the cavity open, breaking the ribs if necessary. You may make cuts laterally on either side if you wish to expand your opening. IMPORTANT: DO NOT REMOVE SECTIONS OF MUSCLE BECAUSE YOU WILL NEED TO CLOSE YOUR MINK BACK UP AT THE END OF THE PERIOD.

9. Note the PERICARDIAL CAVITY containing the HEART, and the PLEURAL CAVITIES, each containing a LUNG.

10. Locate the THYMUS GLAND (see figure 25) anterior to the heart.

11. Next identify the HEART. The heart lies in the PERICARDIAL CAVITY, surrounded by a tough PERICARDIAL SAC. Do not remove this sac.

12. The LUNGS lie in the PLEURAL CAVITIES, the other subdivisions of the thoracic cavity. The right lung has three major lobes, the APICAL, CARDIAC, and DIAPHRAGMATIC, and a fourth smaller lobe, the INTERMEDIATE. The left lung has two lobes, the APICAL and DIAPHRAGMATIC. (How does this compare with man – be sure to include this in your summary.)

13. Open the ABDOMINAL CAVITY by making a single incision through the ventral body wall from the DIAPHRAGM to the PUBIS. You may have to cut through the diaphragm in order to open the cavity for easy viewing. USE YOUR SCISSORS for this entire cutting.

14. Locate the LIVER just inferior to the diaphragm. It is divided into right and left sides by the FALCIFORM LIGAMENT.

15. Carefully separate the liver lobes to locate the dark green GALLBLADDER. Do you recall what it stores?

16. Note that fatty membrane covering the intestine. This is the GREATER OMENTUM. Carefully remove it.

17. Identify the STOMACH (figure 27). Its size will depend on how recently and well the individual ate. Cut the stomach open and not the RUGAE. What is their function?

18. Identify the SPLEEN to the left of and inferior to the stomach. It is a part of the circulatory system. Don’t confuse it with a liver lobe.

19. Find the PYLORIC REGION of the stomach and follow it to the SMALL INTESTINE. Remember that the small intestine is composed of DUODENUM, JEJUNUM, and ILEUM. See if you can find where the COMMON BILE DUCT enters the duodenum. (It should extend from the gallbladder to the duodenum. What does it carry?)

20. Look in the mesentery between the intestines for the PANCREAS. It is pinkish and rather loose in structure. The left limb of the pancreas lies near the stomach and extends to the spleen. The right limb lies in the mesentery between the intestines. What is its function?

21. The ileum opens into the LARGE INTESTINE, or COLON. In the mink, the organ is a short descending tube that ends in the rectum. It can be distinguished from the small intestine by looking at its internal structure.

22. To locate the ILEOCOLIC JUNCTION, slit the last few inches of intestine open and observe the lining. The small intestine is lined with VILLI, which give it a velvety appearance. The colon lacks villi and its inner surface bears longitudinal ridges instead.

23. Make a FULL PAGE drawing showing the organs of the thoracic and abdominal cavities and label the parts you have located. This is PLATE 7 and should be numbered PAGE 19.

Anatomy & Physiology

N. Roberson

Mink Dissection

Guide 7

THE UROGENITAL SYSTEM

Please number this guide as PAGE 20 and insert it into your mink lab report.

1. Read pages 42-45 in the lab manual carefully. You will be responsible for both male and female anatomy, so be sure to look at specimens of both sexes.

2. Carefully remove the fat surrounding the kidneys and genital organs. Use forceps and a blunt probe. Save all the ducts and blood vessels. Expose the KIDNEYS.

3. The ADRENAL GLANDS are small dark brown bodies lying in the fat medial to each kidney. Some years they are well preserved and easy to find, but usually they are not so conspicuous. See if you can locate them, but don’t worry if you do not see them.

4. Find and clean the URETERS and trace them to their connections to the URINARY BLADDER. Urine passes from the kidneys to the bladder via the ureters and is stored here. The urine eventually passes from the bladder to the outside of the body through the URETHRA.

5. The kidney of the mink is bean-shaped, having an indentation, the HILUM, medially (figure 34). The URETER, RENAL ARTERY, and RENAL VEIN enter the kidney at the hilum. Locate these now.

6. Remove one KIDNEY and slice it longitudinally with your scalpel. Locate the outer granular CORTEX, the striated MEDULLA, and the RENAL PELVIS.

7. On the female specimen, expose the OVARIES, OVIDUCTS, and the UTERUS (figure 35). Size and morphology of these structures vary with the reproductive state of the animal. The uterus of the mink is BICORNUATE, having two HORNS that meet dorsal to the bladder to form the BODY of the uterus. The oviducts are very tiny, coiled tubes directly associated with each ovary.

8. On a male specimen, find the TESTICLES and clean them of fat (figure 35). In the intact animal they are enclosed in the SCROTUM, which is removed with the pelt. Identify the PENIS, EPIDIDYMIS, and VAS DEFERENS. Sperm are produced in the testis, are stored in the epididymis, and eventually pass into the vas deferens and out the penis.

9. Make drawings of both the female and male urogenital systems and label the parts you have located. These will be PLATE 8 (PAGE 21) and PLATE 9 (PAGE 22).

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