Dissection of the Cat I: Skinning

Dissection of the Cat I: Skinning

At the University of Cincinnati Clermont College, the cat is used as the dissection animal to teach anatomy in our Anatomy and Physiology courses. There are several reasons why this choice of dissection animal has been made. First, the cat’s anatomy is similar enough to human anatomy that the majority of anatomical relationships can illustrated using this animal. Second, the cat is large enough for its features to be clearly distinguishable to the student. Fetal pigs, which some institutions use, are small for this purpose. Third, the physical act of dissection is an extremely effective learning tool in contrast with “virtual dissections” available in computer programs. Fourth, cats are plentiful and inexpensive enough so that each team of two students has the personal hands-on experience of the dissection. The question of the ethics of using cats for this purpose can and should be raised. See the bottom of this page for a discussion of this ethical question .

The following are the steps to the proper and orderly preparation and skinning of the cat to optimize its use for dissection throughout the rest of the year. At the conclusion of this and each dissection, thorough cleansing of instruments, desks, sinks and floors is extremely important. Please be rigorous in your cleanliness. Use a sponge for all steps of cleansing except the very last. Use a single paper towel to finish drying the cleansed desk.

Bag labeled with table number
Bag labeled with table number

1. LABEL BAG WITH YOUR TABLE NUMBER: Place bag on a clean table with the end you will open to the left (the end with the larger margin of plastic beyong the heat seal.) Attach a large label at the lower right of the bag with your table number and class hour written in large black marker letters. Fold it over so that the number is visible on both sides of the bag.

Emptying liquid from bag
Emptying liquid from bag

2. DRAIN THE FLUID: At the sink, with rubber gloves, carefully cut open plastic bag close to the heat seal (so that it can be securely closed when finished). Remove cat tail first into the sink so that excess preservative fluid drains away. Squeeze out excess fluid from the cat’s fur by milking down from head to tail. Set aside the bag, keep its outside clean and free of embalming fluid and cat parts…
lines to cut

3. LIE CAT ON ITS BACK on your desk. These cats have been injected with color coded latex: red for arteries, blue for veins, and yellow for the hepatic portal system. Note the three latex injection sites: 1) at the neck, 2) in the inner R thigh, and 3) in the right lumbar region of the abdomen. Try to include these cuts in the lines where you make your incisions. Before you cut, make an illustration of the ventral view of your cat in your notebook with dotted lines showing where you are going to cut. (Again, what do the three colors of latex indicate?)


4. CUT ALONG THE VENTRAL MIDLINE, THEN ALONG VENTRAL SURFACE OF THE LIMBS: Lift the skin just below the xiphoid process, snip a shallow cut with scissors. . Insert the rounded tip of the large scissors under the skin at the cut, lift the skin and extend the cut up to the neck, and down to the pubic bone, stopping just above the . Continue the cuts down the medial surface of each thigh to the anterior-surface of the leg, and out along the anterior surface of the forelimbs all the way to the dew claws . Extend the ventral cut anteriorly through the neck incision to the right corner of the mouth.

5. CAREFULLY TEASE THE SKIN AWAY from the underlying muscle (or bone) with a blunt instrument (fingers and thumbs work well). The cottony material which ties the skin down to the body is called superficial fascia. Watch the skin so that you leave all tissue on the body. If you come to a difficult area, work around and behind it for a better approach. Here are the problem areas to which muscle may adhere to the skin: 1) the flanks, 2) the neck, 3) the shins, and especially 4) the head . Do not tear or remove underlying muscle, but note that force is occasionally needed.

6. CUT AROUND EITHER SIDE OF THE PERINEUM TOWARD THE TAIL. Cut along either side of the genetalia past the anus. Then cut the skin between the tail and the anus to leave a ring of fur around the perineum (genitalia and anus). Make a cut along the ventral surface of the tail and peel back the skin down the tail. Continue skinning on the legs until the skin has been freed to the paws, cut the circumference of the skin around each limb. Take care not to cut the tendons of insertion in the wrists or ankles.


7 . SKIN THE HEAD carefully. After you cut to the R corner of the mouth, Peel the skin away from the base of the ears.
Feel for the base of the ears and cut through the auditory canal just above the base on upper side of the head. Leave muscles on the skull.

Peel the skin off the scalp until you feel the rims of the orbits . Pull on the pelt to show white cottony fascia over the eyes. Carefully and slowly release the fascia with light scalpal cuts. Leave the eyelids on the pelt.

Cut close to the bone to separate lips from upper and lower jaws.

Leave the entire nose on the pelt by cutting deeply into the flesh of the nose after the skin has been peeled away everywhere except the nose.


8. PUTTING IT AWAY: Wring out the pelt once more. To store your cat, pull the skin over the nose, wrap in proper position, place wrapped cat in the plastic bag, fold the bag longways and press out the air. Then twist the end, fold it over, and secure with 2 or 3 turns of a heavy rubber band. If you do not fold it, the juice will leak out into the box of cats… Place in the storage box so the numbers are in the right front corner so that it is easy to locate your cat for the next dissection.

9. CLEAN UP!! Wash dissecting tools thoroughly, dry them with a single paper towel, replace in the kits, and return to their proper location in the storage box. Clean up all fur, fat, and stray pieces from your desk, floor, sink and surrounding counter. Wash all surfaces and edges thoroughly with a sponge dipped in soapy water, picking up all hairs, and removing grease. Finally wipe to near dryness with a well-rinsed, wrung-out sponge. (Please do not waste paper towels for this step.)

THE ETHICS OF USING CATS FOR MEDICAL SCIENCE DISSECTIONS

The question of the ethics of using cats for medical science dissection and learning can and should be raised. The ethical argument against the use of cats would be stronger if cats were bred specifically to be killed for dissection. However, the cats we use are the product of uncontrolled reproduction of pets. The surplus wind up at the animal shelter. At the animal shelter, the majority of cats are “euthenized” in a hypobaric chamber. In this chamber, the air is pumped out until the animal first passes out, and eventually dies of oxygen starvation. In the great majority of cases, the carcasses are then either cremated or buried. It is clear that using these animals which have already been euthenized yields at least one positive outcome of their sad deaths, one of advancing the teaching of medical science. Until the pet population explosion is under control and there is no surplus of euthenized cats, it would seem that a constructive use of a social tragedy is to be encouraged.

Cranial Nerves in the Cat

Cranial Nerves in the Cat

In the previous lab, you dissected out the brain from your dissection cat. We are hopeful that the cranial nerves will not have been obliterated during the extraction. In this exercise, you will be guided through identification of some of the cranial nerves (in bold) on this specimen. See Gilbert, p 83 for an illustration of the ventral view of a sheep brain. Here is an images: cranial nerves 1

I_olfactory_P1211796

I Olfactory bulbs project out of anterior-most cerebra (often truncated during dissection)
Functions: Pure sensory: smell

II_optic_P1211792
II Optic form chiasma (if you preserved it) just anterior to hypothalamic infundibulum. During dissection, the chiasma may be torn off leaving only the stumps of the optic tracts.
Functions: Pure sensory: vision

III_oculomotor_P1211791

III Oculomotor Emerge from under medial side of cerebral peduncles just outside of Circle of Willis. Functions: Extrinsic eye muscles except for lat. Rectus & sup. oblique

IV_trochlear_P1211802md
tiny Trochlear Nerve Cranial Nerve IV

IV Trochlear tiny, most easily located by looking just below the corpora quadrigemmina on the backside of the brain. It is a thin thread that circles around to the ventral side of the brain.
Functions: superior oblique extrinsic eye muscle

V_trigeminal_P1211794
V Trigeminal largest cranial nerve, most anterior of the three large clustered cranial nerves, V, VII and VIII. Lateral to pons, points forward.
Functions: branches to form ophthalmic, maxillary & mandibular nerves.

VI_abducens_P1220193
VI Abducens tiny thread-like nerve, emerges somewhat near midline just below the pons.
Functions: lateral rectus extrinsic muscle of the eye

VII_facial_P1211793
VII Facial emerges laterally between pons and medulla , in front of the vestibulocochlear (VIII)
Functions: taste in ant. tongue, glands of nose & salivation, not parotid

VIII_auditory_P1211795
VIII Vestibulocochlear emerges laterally between pons and medulla, behind and larger than the facial (VII). (Also know as the auditory nerve.)
Functions: Pure sensory: hearing and balance

IX Glossopharangeal CRANIAL NERVES IX-XII ARE DIFFICULT TO DISTINGUISH IN THE CAT (for me…). emerges adjacent to and in front of the larger vagus (X)
Functions: taste in post. tongue, glands of pharynx, parotid gland

X Vagus emerges from upper side of medulla, larger than others in this area (Easily seen outside the cranium, attached to the carotid arteries.)
Functions: major parasympathetic nerve. Also detects taste at tongue base, and ennervates muscles of pharynx and larynx

XI Spinal Accessory originates below foramen magnum, collected just below X.
Functions: trapezius, sternocleidomastoid

XII Hypoglossal emerges from upper side of medulla just behind pyramids
Functions: extrinsic and intrinsic muscles of tongue

II_optic_pituitary_P1211797

Notice on this dissected brain that the pituitary is still intact just below the optic chiasma (indicated by the probe), a rarity because it is usually torn off by the circle of dura mater which surrounds the infundibulum.

Dissection of to Show Circulatory Features

Dissection of to Show Circulatory Features

The following directions should assist you in locating the major arteries and veins in the cat. You should also consult Gilbert’s Pictorial Anatomy of the Cat during the dissections. For the page numbers, see the protocol A

natomy of the Circulatory System in the Cat.

HEART AND CHEST:

heart_cat_P4113363med

With the chest cavity open, split the parietal pericardium by snipping upward from the apex toward the base. Peel it back to reveal the heart. Note the superior vena cava is prominent in the mediastinal space above the heart and the inferior vena cava is below and behind the heart in a direct line with the superior vena cava.

heart_cat_P4113363crop

Note the atria (R & L) the ventricles and the anterior interventricular artery. Note the pulmonary trunk emerging diagonally up to your right from the R ventricle.
Here is a labeled view of the cat heart.

heart_transverse_P4083877
You may wish to make a transverse section through the upper portions of the ventricles of the heart. Illustrate this transverse section to show the R ventricle, interventricular septum and the L ventricle . Comment on the differences observed. If you do not do this procedure, observe and illustrate one on which it has been performed.

Veins_thorax_P4083871

Use the blunt probe to trace the branching of the superior vena cava to produce in succession the R & L innominate veins. These branch to form the jugular and the subclavian. The subclavian branches to form the subscapular and the axillary veins.
Here is a labeled picture of the veins of the thorax.

aortic_arch_P4083878
Behind the pulmonary artery, use the probe to find the aortic arch and its two branches (three in the human): the innominant artery (or brachiocephalic) and the left subclavian. Follow the innominant to its branches: L & R common carotids, and the R subclavian. Trace this latter to the R axillary, and then the R brachial artery.
Here is a labeled view of the aortic arch and the “Great Vessels.”

Circle_Willis_P4083870
The circle of Willis is formed from the two vertebral arteries below, which join to form the basilar artery. The basilar splits into the R & L posterior cerebral arteries. The internal carotids enter the cranium on either side of the sella turcica, and split to form the middle and anterior cerebral arteries. Posterior communicating arteries join the posterior and middle cerebral arteries, and the anterior communication artery joins the two anterior cerebral arteries. Here is a labeled version of the circle of Willis .

intercostal_P4083879

Roll the L lung medially and follow the descending aorta down along the rear wall of the thorax. Note the intercostal arteries running between the ribs under the parietal pleura.

ABDOMEN:

Celiac_Art_P4083866

Move the abdominal contents to the right, and find the rear border of the diaphragm. (It is lower in the rear than the front.) using the blunt probe, remove the peritoneum and adventitia to reveal the celiac and superior mesenteric arteries immediately below the diaphragm over the vertebral column. Find the three branches of the celiac artery: the hepatic to the cat’s R, the splenic (the large central vessel), and to the L, the left gastric
Here is a labeled version of the upper abdominal arteries.

abdominal_low_arts_P4083876
R & L Renal arteries and veins should be easily located. Note that the L gonadal vein drains into the L renal vein, while the R gonadal vein empties directly into the inferior vena cava . The R & L gonadal arteries branch off the descending aorta below the level of the kidneys. The last major branch from the abdominal aorta is the inferior mesenteric.

LOWER GROIN AND LEGS:

vessels_leg_P4083874

The descending aorta ends where it splits into the R & L common iliac arteries [“external” iliac in the cat]. These branch to form the deep femoral arteries (plunge deep just before abdominal wall) and the femoral arteries at the exit point from the abdomen. The saphenous vein, the major superficial vein of the leg, runs down the medial surface of the of the leg.

FEATURES TO IDENTIFY AND ILLUSTRATE IN THE CAT:
III. CIRCLE OF WILLIS
(underside of well-excised brain) (p. 82)
basilar artery
R&L posterior cerebral arteries
R&L posterior communicating arteries
R&L internal carotid arteries
R&L middle cerebral arteries
R&L anterior cerebral arteries
anterior communicating artery (difficult)

IV. THORAX, NECK AND ARMS
External features of the heart
(p. 62-63, 68-69)
pericardium
right atrium
right ventricle
left atrium (toward the rear)
pulmonary trunk
aorta

Vessels of the thorax, neck and arms (p. 62-63)
Veins:
superior vena cava (precava)
R&L innominate veins
R&L subclavian veins
axillary vein
brachial vein
R&L external jugular veins (p. 20)

Arteries: (p. 65, 69) (as in cat)
innominate artery
R&L common carotid
R subclavian artery
R axillary artery
R brachial artery
L subclavian artery
[esophagus]
descending aorta
intercostal arteries

V. ABDOMEN, GROIN AND LEG (p. 49-55)
Vessels of the abdomen:
(often under fat, close to vertebral column)
inferior vena cava
descending aorta
celiac artery (move abdominal contents to cat’s R)
L gastric artery
splenic artery
(common) hepatic artery
superior mesenteric artery
renal vein and artery
L gonadal vein:
empties into L renal vein
R gonadal vein:
empties into inferior vena cava
R&L gonadal arteries
inferior mesenteric artery

Lower groin and leg (p. 71)
external [common] iliac artery & vein
deep femoral artery (plunges just before abdml wall)
femoral artery & vein
saphenous vein

Dissection of the Eye and its Orbit in the Cat

Dissection of  the Eye and its Orbit in the Cat

Follow protocol Notebook Illustrations

The brain should have previously been removed from your cat (see Removal and Study of the Cat Brain). You should identify the upper and lower eyelids, and the nictitating membrane which comes up from below the eye. Note the conjunctival surfaces, and the inferior fornix.

REMOVAL OF THE EYE

lines_to_cut_P2112028lbd

Locate the optic nerves where they enter the cranium through the optic foramina.
Draw lines from each optic nerve to the medial and lateral limits of the orbits.
The accompanying image shows the location of the cut to make.
cuts_in_cranial_floor_P2112029

Cut on these lines with the end of a hack saw. Be certain to cut laterally enough to prevent part of the frontal from overhanging, and all the way to the optic foramina.

lift_cut_triangle_P2112030

lift the triangle Lift off the triangular section of the roof of the orbit, cutting it free from any underlying tissue which may adhere to it, preserving features attached to the eye. Mark the superior-most muscle with an indelible “X” to keep track of it later in the dissection. (Can you find the superior oblique and its trochlea, on the medial superior border of the orbit? This is a challenge.)

05_nictitating_mem_P2112014

Cut the anterior portion of the eye loose from the socket by cutting closely along the bone to free up the eye itself. Lift up the entire structure, cutting any peripheral tissues which may hold it down. After you have lifted it in the front, slide the scalpel under the rear-most portion to free it from the skull. Note that the nictitating membrane marks the inferior portion of the dissected portion.
Note the membrane which surrounds the entire orbit (periorbita). The lacrimal gland is under it on the lateral superior side. Work the periorbita open with a blunt probe, remove the adipose tissue which served as padding. The most superficial superior muscle will be the levator palpebrae superioris, which raises the eyelid. It does not insert into the bulb.

DISSECTION OF THE EYE

The fat has been removed from the excised eye to reveal the muscles (upper picture).
Find the four rectus muscles:
lateral, superior, medial and inferior rectus
Use a blunt probe to free them from the optic nerve. The inferior obliquecrosses over the inferior rectus. The superior oblique should be present, but this dissection may not retain the trochlear loop. Its tendon of insertion is medial to the insertion of the superior rectus. Here is a labeled version of the right hand image. (Do not confuse the deeper four retractor bulbi muscles which are under the rectus muscles.)

Deep to the four rectus muscles (peeled back in this image) are four portions of the retractor bulbi. Note the optic nerve which exits the eye at the center of these four parts. The four retractor bulbi have been reflected to show the rear of the eye ball. The sclera is opalescent bluish white, the optic nerve at the center.

06_cut_P2112015
With the fine scissors, make a small vertical snip through the rear wall of the bulb just medial to the optic nerve (do not squeeze the bulb during this cut…).

07_extend_P2112017

Hold the eye over a petri dish lid, extend the cut (keep it shallow) sagittally through the center of the cornea. Note that aqueous humor drains out as the cornea is being cut.

14_portions_of_eye_P2112026
dissected cross section

As you lift the cut anterior piece, note that the lens is attached to it by suspensory ligaments. Cut through the iris, and lift off the cut portion, cutting its ligaments.

Note that the lens is opaque-white, an artifact of preservation. The posterior cavity is filled with clear jelly-like vitreous humor. Note the three tunics of the wall of the eye:
fibrous tunic (sclera plus cornea)
vascular tunic (iris, ciliary body and choroid)
nervous (retina)
Here is a labeled image of the components of the eye (upper image in left frame).


The retina will appear pearly yellow. Note the optic disk identifiable by the vessels may be seen to emerge from it, and pass under the retina. The fovea centralis will be towards the center and seen as a yellowish depression. (Here is a labeled image.) The retina peels away easily from the underlying choroid. This, a detached retina is a serious condition requiring immediate attention in patients to prevent death of the retina and blindness in the patient.

13_ciliary_processes_P2112025md

In the anterior portion of the eye, note that the lens is supported by suspensory ligaments. Posterior to it is the ruffled surface of the black pigmented ciliary processes which produce the aqueous humor. The ora serrata is the anterior boundary of the retina. The iris is golden on the exterior surface, black on the posterior. The cornea is tough and relatively thick.

Make three illustrations:
1) Cuts made to remove eye
2) muscles teased out
3) cross section of the eye

Peripheral Nerves to Locate in the Cat

Peripheral Nerves to Locate in the Cat

This dissection should be done in three phases. Make a full page illustration for each phase showing each region: the cuts made, the locations of the italicized features, and the nerves listed.

OPENING THE ABDOMEN: Pinch the ventral abdominal wall to produce a transverse fold. Snip with heavy scissors along the linea alba so that you nick the wall longitudinally. (Alternatively, use the cut made during latex injection.) Carefully insert the blunt end of the scissors into the nick and lift thesuperficial layer of abdominal muscles away from the underlying organs. Snip down to the pubis. Extend the cut up to the sternum, again taking care not to damage the underlying organs. Make two transverse cuts in the abdominal wall on each side 1) just inferior to the ribs, and 2) at the pubis (don’t cut vas deferens). Reflect the two abdominal flaps exposing the underlying organs.

OPENING THE THORAX: Slip the blunt end of the heavy scissors under the xiphoid process, lift and cut through the sternum all the way to the jugular notch. Keep the angle of the blunt tip shallow to avoid underlying organs. Insert the finger into the thorax just above the diaphragm, feel for the point of attachment just inferior to the ribs. Make lateral cuts to free it from the lower rib cage. Spread the thoracic walls. You need to crack some ribs at the vertebral column to get a good view. Note the mediastinum (the space between the lungs) contains the heart, its pericardium, the great vessels, the trachea and the thymus. Preserve connections of the vessels of the thorax for the cardiovascular lab studied next quarter.

NECK: Extend the cut up to the chin. Neck muscles adhere tightly to underlying organs. Cut and reflect the superficial muscles to expose the larynx. Along the sides, push (with some force) the outer wall of the neck to separate the superficial from the deep neck muscles (probe deeply) but do not sever the nerves. Cut the muscles just below the mandible so that you can turn out the flaps.

I. NERVES OF THE NECK AND THORAX AND THE CERVICAL PLEXUS

vagus_nerves_P1281875

vagus: Find the common carotid arteries on either side of the trachea. (Here we have lifted both the R and L common carotids). The vagus nerves are attached to the carotid arteries. (See Gilbert, p 62 & 65)

cervical_nerve_P1281876

cervical nerves: Find the longus capitis muscle deep behind the common carotid. It is just lateral to the cervical vertebral column. Emerging from under the longus capitis, you should see several cervical nerves emerging laterally.They form the delicate cervical plexus. (Gilbert, p. 67 & 95)
Here is a labeled view of the nerves ant features of the neck.


phrenic: There are R & L phrenic nerves, easily seen at diaphragm, attached to vena cava on R, in pleural folds on L. (p 69) They emerge from the fifth and sixth cervical nerves.
The right phrenic is attached to the inferior vena cava (upper image)
The left phrenic nerve is enfolded in the pleural folds which are attached to the diaphragm

chain_ganglia_P1281884
chain ganglia: Gently push thoracic contents to R side so that you can see the descending aorta along the center of the rear abdominal wall. Note the intercostal arteries which branch off it. The thin sympathetic chain ganglia lie on top of the intercostal arteries but under the parietal pleura on either side of the vertebral column. (Gilbert, p. 69)
Here is a labeled version of the thoracic cavity with chain ganglia.

II. NERVES OF THE ARM AND THE BRACHIAL PLEXUS (Gilbert, p. 62 & 95)

If not already dissected, cut and reflect the pectoralis major, pectoralis minor, the epitrochlearis and the deltoid complex. (Do not cut underlying features.)

brachial_plexus_P1281871

brachial plexus:Lies outside the rib cage below where the subclavian vein branches into the axillary and subscapular veins. (Pectoral muscles must be cut and reflected to see the brachial plexus) The brachial plexus produces the following major nerves of the arm (p. 95):

brachial_plexus_P1281871

If the epitrochlearis is not already cut and reflected, do so now to see the following nerves of the arm:
radial: This is the largest nerve emerging from brachial plexus, soon plunges below biceps brachii about half way down the arm.
Here is a labeled image showing radial, ulnar and median nerves.

ulnar_nerve_P1281872
ulnar: This is the medial-most of the three nerves, plunges below the surface near the olecranon. You know of this nerve because when you hit it on your elbow, you call it your “funny bone.”

median_nerve_P1281873

median: This is the smallest of the three nerves, lies between ulnar and radial nerves, follows the brachial artery into the forearm.

III. NERVES OF THE LEG AND THE SACRAL PLEXUS (Gilbert, p.98 & 99)

If not already dissected, cut and reflect the biceps femoris to reveal:

sciatic_nerve_P1281882
sciatic nerve branches to form the tibial and peroneal nerves

sciatic: The largest nerve in the body, it descends the latero-posterior thigh under the biceps femoris, branches to form several nerves of the leg. Note the muscular branch of the sciatic coming off at the L of the view.
Here is a labeled view of the sciatic nerve, sacral plexus, tibial and peroneal nerves.

tibial_peroneal_P1281882
Tibial: The larger of the branches of the sciatic, plunges between the heads of the gastrocnemius, supplies lower leg.
peroneal: The smaller branch of the sciatic, branches laterally to supply the “side of the shin.”


sacral plexus: Follow the sciatic nerve upward with a probe. Lift the muscles above it and cut the muscles which overlie it (the gluteal muscles and the piriformis). Note several component nerves. (p. 99)
The second illustration is labeled.

CLOSING UP: As always, when you have finished for the day, replace the internal organs in their proper locations, close the cat, wrap in its skin, place in the plastic bag, press out the air, seal with three turns of a large rubber band and return to the box with number to right. Wash your desk top with warm soapy water. Wash your instruments well, dry them, replace the kit in the storage box. Check the sinks and the floor around your desk to be sure they are thoroughly clean.

NERVE ENDINGS ON THE PERIPHERAL NERVOUS SYSTEM

Of the nerve endings in the perpheral nervous system, the most highly developed are those which detect pressure and vibration in an organ, the Pacinian corpuscles. We will be looking a sections of pancreas which display these features.

Pacinian_corpuscles_PC271521

Slide 10: Vater-Pacini corpuscles, pancreas, H-eosin (H 1688)
Pacinian Corpuscles (MF 9 th: page 229 and 147) at 100x:
Pacinian corpuscle:
connective tissue capsule
central cavity with numerous lamellae (with flattened nuclei)
naked dendrite
pancreatic acini
Here is a labeled view of Pacinian corpuscles.

Removal and Study of the Cat Brain

Removal and Study of the Cat Brain

Here are labeled images of other brains as well as the cat for study and cross reference:

Our impression is that it is rare for college anatomy and physiology courses to remove the brain from their preserved study animals (usually cats). While it is a challenge, and takes considerable time, we have found that the process teaches not only the structures of the brain, but the protective function of the cranium, the relationship of the meninges, the branching of the cranial nerves into the floor of the cranium, etc. If your class uses the following protocol, we would be interested to hear, and welcome any suggestions you might have to improve it.

Supplies: Skinned preserved cat, injected

Tools: Spot lighting, hacksaw blade, fine pointed scalpel, wide bladed screw driver, flat jawed pliers

02_lines_to_cut_P1141724md

1. Clean the surface of the skull of a skinned cat of all muscle. (Give it a “muscle shave”!) Pay special attention to the temporalis and muscles at the rear of the skull. Clean the occipital bone well below the occipital protuberance. Here are class notes on preparation, cuts, and extraction of the cat brain.

05_cut_rear_occipital_P1141728md

2. Make the following seven cuts with a sharp hack saw blade. Take care not to saw too deeply or you will damage the brain.
a: FIRST, cut across the rear of the occipital bone, well below the occipital protuberance as low on the skull as muscle allows.

06_cut_lat_occipital_P1141729md

b: NEXT, extend the first cut through the widest portion of the cranium, on either side of the anterior portions of the occipital and parietal bones (cutting the R and L side) .

c: EXTEND the previous cuts (keep them shallow) laterally through the temporal bones. Keep the cuts at the widest part of the skull to ease removal of the brain.

OLYMPUS DIGITAL CAMERA

d: LAST: Make the last two cuts, one each above the R and L superciliary ridges, so that the cuts form an X between the eyes. These cuts should meet the cuts through the temporal bone. Due to the large frontal sinuses, one must cut through two layers of frontal bone. Therefore, the cuts between the eyes must be much deeper than the other cuts.

3. Gently pry at the cuts using a wide-bladed screw driver, exploring where the cuts need to be made deeper. Start at the rear occipital cut and work forward. The frontal bone is difficult because of the large frontal sinuses. You must cut through both the exterior and interior layers of bone to free up the front of the unit. Do not push the screw driver too deep or you will damage the underlying brain. Repeat the sawing and testing with the screw driver until the calvarium becomes loose. Do not remove yet.


4. Remove the brain-calvarium unit: Lift the front of the calvarium, reach in and cut close to the bone cranial nerves and latex/vessels so that the unit lifts from the front. Lift as much as you can and cut the spinal cord as deeply as you can to leave it attached to the brain. Lift off the brain/calvarium as a unit.

 

12_brain_in_calvarium_P1141734md

5. Explore the edges of the cut bone around the brain. Often pieces of the frontal bone forming the orbital surfaces need to be flaked off, and overhanging pieces of bone around the cerebellum and the sides of the cerebrum prevent removal of the brain. Use flat nosed pliers to break away these pieces. You may need to saw off the anterior tip of the calvarium to remove the remaining frontal sinus pieces.
It is easier to remove the brain from the calvarium if the dura mater is snipped along the ventral surface. Press and pry the cerebrum out of the calvarium, leaving the dura mater attached to the calvarium. Because the tentorium cerebelli is ossified in the cat, you must pull the brain forward to avoid breaking brain apart at the midbrain.

13_pull_brain_fwd_P1141736md
6. Take great care in lifting out the brain, so that as many features remain attached to the brain as possible, including the cranial nerves, and as much of the spinal cord as possible. The pituitary is usuallyretained in the sella turcica by a constriction of dura mater and becomes detached from the brain.

ventral_brain_P1141755md

7. ILLUSTRATE THREE VIEWS OF THE ISOLATED BRAIN, label listed features:
a) ventral: cerebral hemispheres, the infundibulum, mammillary bodies, cerebral peduncles, pons, medulla oblongata
Here is a labeled version of the ventral brain.
Here is a version of the ventral brain with cranial nerves labeled
Here is a rough hand drawn illustration of the ventral brain.

14_brain_rear_view_P1141737

b) posterior: R&L cerebral hemispheres, longitudinal fissure, R&L cerebellar hemispheres, vermis, dorsal medulla oblongata
Here is a labeled version of the posterior brain.
Here is a hand drawn illustration of the posterior and deep posterior on the same page.
15_corpora_quad_P1141738md
c) posterior deep view by spreading R&L hemispheres: superior and inferior colliculi (= corpora quadrigemina), pineal gland, corpus callosum.
Here is a labeled version of the posterior deep brain.

NOTE: We will study the brain’s cranial nerves I, II, III, IV, V, VII and VIII next week.
Alternative means of removing calvarium (no longer used in 2001)
Remove the calvarium by sliding it backwards, leaving the brain in the skull. In the cat, the tentorium cerebelli is ossified, and is thus a challenge to remove the calvarium without damaging the connection between the cerebrum and the cerebellum. One strategy is to cut through the calvarium and attempt to slide the calvarium to the rear, between the cerebrum and cerebellum. Alternatively, two saw cuts may be made, one above and one below the tentorium, so that the calvarium is removed in two pieces.

Cat Muscles of the Lower Appendages

Cat Muscles of the Lower Appendages

See also Martini’s Fundamentals of Anatomy and Physiology, 5th, pp 246-355.

Be sure to remove all fascia from surface of muscles to see the muscle edges clearly. Page numbers refer to the page number of appropriate illustrations in Gilbert’s Pictorial Anatomy of the Cat. See previous handouts for techniques and preparation of the cat to this point.

Here is a directory of pictures of a model of muscles of the thigh, leg and foot.
Some are labeled: anterior thigh , anterior thigh deep, medial thigh, posterior thigh, posterior thigh deep, anterior leg, lateral posterior leg, (more to come)

This dissection is divided into muscles of the
MEDIAL THIGH Here is a labeled view of the muscles of the medial thigh.
LATERAL THIGH Here is a labeled view of the muscles of the lateral thigh.
LATERAL LEG Here is a labeled view of the anterior muscles of the leg and foot
MEDIAL LEG
Here is a directory of images taken 2009. Here is a selection which have been labeled:
gracilis and sartorious
tensor fascia lata
medial leg, deep
biceps femoris, cutting and reflecting
gluteal muscles

MEDIAL THIGH: Gilbert, pages 32, 34 and 35

01_sartorius_Pb292412mdsartorius
origin: anterior superior iliac spine
insertion: tibial medial epicondyle
cut and reflect

02_gracilis_Pb292413mdgracilis
origin: pubis
insertion: medial surface of tibia (by an aponeurosis)
It is wide and thin, runs down inside of thigh.
cut and reflect

06_tensor_fascia_lata_Pb292417md
tensor fascia lata
fascia lata (iliotibial tract)
origin: iliac crest
insertion: into the fascia lata
Locate where thigh joins abdomen, follow to connective tissue band: fascia lata (an aponeurosis on lateral side of thigh)
cut and reflect

03_semitendinosus_Pb292414md
semitendinosus
origin: ischial tuberosity
insertion: medial side of the tibia, below the epicondyle
It is a round, thin muscle whose tendon inserts in medial side of tibia below the semimembranosus.

04_semimembranosus_Pb292415md
semimembranosus
origin: ischium
insertion: medial epicondyle of tibia
It is a thick muscle, much larger and more anterior than the semitendinosus in the cat.

adductor_femoris_P1011340
Adductors
adductor femoris (adductor magnus)
adductor longus
both adductor femoris and adductor longus:
origin: pubis
insertions: medial femur
Adductor femoris is large, adjacent to semimembranosus (called adductor magnus in humans)
Adductor longus is small, adjacent to and above adductor femoris
Here are the adductor muscles (etc) labeled.

05_iliopsoas_Pb292416mdiliopsoas
origin: lumbar vertebrae and medial ilium
insertion: lesser trochanter.
It is superior and lateral to femoral vessels (which emerge thru the abdominal wall) (Look in rear of abdomen of previously dissected cat for best view.)
Here is a labeled view of the muscles of the medial thigh.

LATERAL THIGH: Gilbert, pages 31 and 33

08_biceps_femoris_reflected_Pb292419mdbiceps femoris (already cut and reflected)
sciatic nerve (white cord in picture)
origin: ischial tuberosity
insertion: lateral tibia (and patella and leg fascia)
It is the large lateral hamstring
cut and reflect (Don’t cut sciatic nerve)
09_gluteus_maximus_Pb292420mdgluteus maximus
origin: transverse processes of sacral & caudal vertebrae
insertion: greater trochanter
small in cat, inserts into femur and fascia lata
Here are the muscles of the lateral thigh labeled.

10_gluteus_medius_Pb292421md

gluteus medius
origin: ilium near the crest
insertion: greater trochanter
larger than maximus in cat, superior to maximus

07_rectus_femorus_Pb292418md
quadriceps femoris , including: vastus lateralis, vastus medialis, rectus femoris vastus intermedius
origin: all originate on femur except rectus femoris
rectus femoris origin: ilium
rectus femoris is a round, “hotdog in bun” common insertion: patella

patella_&_ligament_PC031350palettal and palettal ligament feel it by wiggling side to side directly over the knee below patella, connects to tibial tuberosity

LATERAL LEG: Gilbert, pages 31 and 33

11_calf_muscles_Pb292422md

Gastrocnemius soleus Achilles tendon
origin: lateral and medial heads of tibia
insertion: calcaneous via the achilles tendon
calf muscle, superficial to next muscle
directly under the gastrocnemius
tendon of insertion for next two muscles into calcaneus

12_tibialis_anterior_Pb292423mdtibialis anterior
origin: proximal ends of tibia and fibula
insertion: first metatarsal
anterior-most muscle of the lateral compartment, lies along tibia. Its tendon of insertion passes in front of the tibia to the medial side of the foot.

extensor digitorum longus
origin: lateral epicondyle of tibia
insertion: middle and distal phalanges 2-5
four-part insertions cross top of foot
extends four toes simultaneously lies under the tibialis anterior next to the tibia.
Tendon of insertion passes under the transverse ligament, splits into four parts.
(Do not confuse its tendon with that of tibialis anterior which angles down in the lower picture)
Here is a labeled view of the anterior muscles of the leg and foot

13_peroneus_longus_Pb292424mdperoneus longus tendon origin: proximal fibula
insertion: bases of metatarsals
passes lateral to lateral malleolus, passes under foot to 1st metatrsl

15_retinaculum_Pb292426md

transverse ligaments retinacula which hold down tendons of insertion

MEDIAL LEG: Gilbert, pages 32, 34 and 35

12_tibialis_anterior_Pb292423md

tibialis anterior tendon
origin: proximal tibia and fibula
insertion: first metatarsal
inserts medial side of first metatarsal (inverts foot)


flexor digitorum longus
origin: behind tibia, below semitendinosus.
insertion: bases of terminal phalanges 2-5
Its tendon lies just behind the tibial malleolus (pull tendon, all toes flex)

Muscles of the Head, Trunk and Arms

Muscles of the Head, Trunk and Arms


(Page numbers refer to Pictorial Anatomy of the Cat, rvsd, by Gilbert.)

We will be studying head and trunk muscles of the cat, most of which are analogous to those in the human. Working with a skinned cat ( see previous protocol ) remove cutaneous muscle layer (allows cat to twitch its skin) and a white layer of superficial fascia to better see muscle fiber directions and make the muscles more apparent. Carefully outline, separate and lift the muscles by use of a blunt probe. If the structure in question has multiple fibers in it, it is muscle. Look for intersections between fiber directions, this often indicates two muscles. Fingers are the best blunt probes…

When you need to cut separated superficial muscles to see deep muscles, the superficial muscle to be reflected should be snipped midway between insertion and origin, and laid back to its origin and insertion, noting where they are located. Make four illustrations:

1) ventral thorax, upper appendage and abdomen, superficial
2) Ventral thorax and upper appendage, deep
3) Dorsal (back) deep and dorsal superficial
4) Second illustration of the deep dorsal muscles.

VENTRAL NECK, CHEST AND ABDOMEN:

(See Gilbert, p. 18)

chest_undissected_PB261324md

Undissected chest. Remove as much adipose tissue and fascia as you can so that the fibers of the muscles can be seen.
Can you find the pectoantebracialis, pectoralis major, latissimus dorsi and triceps brachii?

Here is the same image with the chest muscles labeled.

OLYMPUS DIGITAL CAMERA
The pectoantebrachialis has been separated from the underlying pectoralis major, and is being lifted in the image. Origin: manubrium, insertion: proximal fascia of forearm.
deltoid_PB261325md
The deltoid (called clavobrachialis in the cat) has been freed from unterlying tissues. Origin: clavicle. Insertion: lateral humerus.

Lift deltoid and pectoantebrachialis as a unit and cut and reflect.

pectoralis_major_PB261328
pectoralis major and pectoralis minor pectoralis major: Origin: upper sternum. Insertion: proximal 2/3 of humerus between the biceps and brachialis pectoralis minor: Origin: lower sternum. Insertion: proximal 1/2 of humerus in the cat. (Gilbert, p. 24) (Human insertion: coracoid process
pectoralis_minor_PB200064
The pectoralis major has been pushed aside and pectoralis minor is being lifted by the probe. In humans, pectoralis originates from ribs and inserts in the coracoid process of scapula.
epitrochlearis_PB200065
The superficial-most muscle of the anterior surface of the arm is the epitrochlearis. It has no homolog in humans. It must be cut and reflected to see the underlying triceps brachii and biceps brachii.
biceps_brachii_PC031343
biceps brachii Origin: 1) long head: superior border of glenoid fossa. 2) humerus Insertion: radial tuberosity
triceps_brachii_PC031342
triceps brachii: Origin: 1) axillary border of scapula below glenoid fossa, 2) & 3) humerus Insertion: olecranon process

Here is a labeled view of the ventral surface of the upper appendage.

retinaculum_PB200056
retinaculum transverse carpal ligament on cat, holds down tendons of insertion

Separate pectoralis major from pectoralis minor, cut both, reflect to see: (Gilbert p. 24)

serratus_anterior_PB261323md
With the pectoralis major and minor cut and reflected, the scapula will fall away from the chest to reveal the subscapularis on its underside. subscapularis Origin: subscapular fossa. Insertion: lesser tuberosity of humerus.

Here is a labeled version of the deep muscles of the chest and scapula.

teres_major_PC031345
closest to axillary border of scapula teres major Origin: axillary border of scapula Insertion: proximal humerus (same as latissimus dorsi)
serratus_anterior_PB261334md
(serratus ventralis in the cat) serratus anterior Origin: first nine or ten ribs Insertion: vertebral border of scapula

Identify the external muscles of the abdomen (p. 24)

external_oblique_PC031349
external oblique superficial most muscle of the abdomenal wall
rectus_abdominis_PB261330
rectus abdominis anterior most muscle of abdomen

BACK: (p. 22)

Caution: the trapezius is very thin and easily torn when outlining it with the probe. Remove cutaneous muscle layer, note the boundary between trapezoid and the latissimus dorsi which plunges below it.

1. Lift trapezius from underlying latissimus dorsi.

trapezius_PB261317md
trapezius called acromio- and spinotrapezius in the cat
latissimus_dorsi_PB261319md
latissimus dorsi fr. spine of lower back to medial humerus

2. Cut and reflect trapezius to see muscles related to or on the scapula: (p. 25). Here is a labeled view of the deep muscles of the back and scapula.

trapezius_PB261317md
trapezius called acromio- and spinotrapezius in the cat
infraspinatus_PB200057
infraspinatus muscle of the glenohumoral joint, lies below spine of scapula
supraspinatus_PC031344
supraspinatus muscle of the glenohumoral joint, lies above spine of scapula
teres_major_PC031345
closest to axillary border of scapula teres major Origin: axillary border of scapula Insertion: proximal humerus (same as latissimus dorsi)
teres_minor_PB200059
teres minor muscle of the glenohumoral joint, inserts post. surf. humerus
levator_scapulae_PB200061
levator scapulae superior to rhomboideus muscles
rhomboideus_PC031347
rhomboideus & r. capitis from spine and skull to vertebral border of scapula

rhomboideus_PC031347

splenius capitis (to the left and below the tip of the probe)
Seen below the rhomboideus muscles.
The “bandage” muscle in the posterior neck.
Origin: upper thoracic spinous processes.
Insertion: mastoid process. process
Here again is a labeled view of the deep muscles of the back and scapula.


Muscles of the shoulders and arms

Brachial plexus: To be studied Winter Quarter:

deltoid and cutting the latissimus dorsi so that it can be reflected:

Cutting the pectoralis. The trapezius has been cut and reflected to show the scapula and rhomboideuses