Vesterby’s Cat Dissection 2015 Introduction (read this first) Welcome to cat dissection 2015! Each day will begin with logging on to your computer, putting.
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Transcript
Slide 1
Slide 2
Vesterbys Cat Dissection 2015
Slide 3
Introduction (read this first) Welcome to cat dissection 2015!
Each day will begin with logging on to your computer, putting on
required protective gear, and removing your cat from the bag.
Attendance is taken immediately, so be here on time! Make this
class a priority and do not come in late from your previous class
or schedule lessons during this time. You are responsible for
letting Mrs. V know if you are missing a teammate, so attendance
can be recorded. Each day will end with the cat going back into
storage, all unneeded/loose tissue going into the garbage, careful
cleaning and drying of the tools, sink, and table surface, thorough
washing of hands, and return of all tools and protective gear to
correct areas. You are to maintain a tidy work area. Personal items
(books, notebooks, beverages, etc.) are to be left at your desk.
Work diligently to get as much done each day as possible. Good
luck!
Slide 4
Step 1: Get dressed. Use the following check list to judge your
attire: shoes that cover your entire feet goggles covering eyes
gloves apron long hair tied back
Slide 5
Muscles of the Lower Leg: 1. Show time!! Expect to be busier
than a three-legged cat in a sandbox. Place your cat in the
pronated position (on its belly). Locate the cats foot and heel.
Make sure the skin is removed down to the heel. Attached to the
calcaneus find a white, shiny, round band of dense connective
tissue (c.t.) the Achilles tendon(39 ). 2. With a dull probe
separate the Achilles tendon from the surrounding tissue. 3. Two
muscles are attached to the Achilles tendon. Gastrocnemius(31) is
the larger, superficial muscle on the posterior surface of the
lower leg. The second calf muscle we will study is named the
soleus(32). It can be identified by the following clues: a) it is
attached to the Achilles tendon; b) it lies beneath gastrocnemius
on the lateral surface of the leg. (Warning: gastrocnemius
separates into right and left heads, near the knee. Dont mistake
one of them for the soleus.) 4. Trace gastrocnemius up the leg. At
the back of the knee, between the heads of the gastrocnemius and
between two of the upper thigh muscles you will find a fat-filled
pit at the back of the knee called the popliteal fossa. Clean the
fat out of the fossa so that you can follow the heads of the
gastrocnemius to the femur. 5. Place the cat into the supinated
position. Locate the tibia at the anterior surface of the lower
hind leg. Tibialis anterior(35) is a good sized, torpedo-shaped
muscle lying just lateral to the tibia. A c.t. sheath (called a
fascia) covers the muscle. Remove enough of the fascia to clearly
see tibialis anterior and free its borders. Follow its tendon
across the ankle to the medial side of the foot.
Slide 6
Slide 7
Superficial Muscles of the Medial Thigh: 1. With the cat in the
supinated position, two superficial muscles can be viewed on the
medial surface of the thigh. Sartorius (1) is a thin, flat muscle
covering the anterior, medial surface of the thigh. It goes from
the hip to the patella. Free its sides, lift it up and cut it in
half, to allow viewing of the deeper muscles. 2. The other
superficial muscle is named gracilis (8). It is similar to
sartorius in shape, but covers the posterior medial surface of the
thigh. It originates near the pubic symphysis and inserts on the
lower leg below the patella. Free its border near the patella, so
that the muscle can be folded back like a flap to expose the deeper
muscles.
Slide 8
Deep Muscles of the Medial Thigh: 1. Semimembranosus is one of
the three hamstring muscles. It is a large, thick, blocky muscle
lying under gracilis. There is a natural deep split between it and
the adjacent adductor femoris. On an average-sized cat,
semimembranosus is about an inch wide from its anterior to its
posterior border. Warning: A false split can often be made in the
middle of semimembranosus or in the middle of adductor femoris. 2.
Next find two adductor muscles located on the medial thigh. The
fibers of these muscles run from the pubic symphysis to the femur.
Adductor magnus (femoris) is the wide muscle lying in front of
semimembranosus. Adductor longus lies in front of adductor femoris.
It is a narrow band of fibers, which can be traced to the anterior
(and superior) tip of the pubic symphysis.
Slide 9
Muscles of the Anterior Thigh: The four deep muscles of the
anterior thigh make up a group called the quadriceps femoris muscle
group. The key to identifying the members of this group is to
locate rectus femoris. This muscle runs from the hip to the
patella, down the anterior surface of the thigh beneath sartorius.
It is round and more or less cylinder-shaped. Once rectus femoris
is located, vastus lateralis and vastus medialis are easy to find.
They are bulky muscles lying lateral and medial to rectus femoris.
They wrap around it, much like a bun wraps around a hotdog (rectus
femoris being the hotdog). Vastus intermedius is tricky to locate
because rectus femoris covers it up. Cut rectus femoris in half and
pull back the ends. Vastus intermedius is just underneath rectus
femoris. Vastus lateralis and vastus medialis are in contact with
vastus intermedius on its medial and lateral borders. (The medial
border separates poorly.) Push a probe through vastus intermedius.
You should hit the femur underneath. 1.Sartorius 2.Tensor fascia
latae 3.Rectus femoris 4.Vastus medialis 5.Pectineus 6.Adductor
longus 7.Adductor femoris 8.Gracilis 9.Semimembranosus 10.
-------------------- 11.Vastus lateralis 12. Iliopsoas 13.Vastus
intermedius
Slide 10
Muscles of the Posterior Thigh: 1. Return your cat to the
pronated position. The three muscles at the back of the thigh are
called the hamstring muscle group. The lateral hamstring muscle is
called biceps femoris. This large, thick, flat muscle covers the
lateral surface of the popliteal fossa. It overlaps the lateral
head of the gastrocnemius muscle. Clean enough c.t. and fat off its
surface to find the anterior and posterior borders. 2. At its
posterior border, biceps femoris touches a second hamstring muscle,
semitendinosus. This muscle is a long narrow muscle which passes
from the hip region, along the medial surface of the popliteal
fossa to the medial side of the lower leg. Separate out
semitendinosus. 3. The third hamstring muscle, semimembranosus,
lies anterior and medial to semitendinosus. This muscle lies under
gracilis and was already identified along with the muscles of the
deep medial thigh. 1. sartorius 2. tensor fascia latae (probe under
IT tract) 3. vastus lateralis 4. biceps femoris 5. semitendinosus
6. caudofemoralis (not in humans) 7. gluteus maximus 8. gluteus
medius 9. semimembranosus 10. gracilis
Slide 11
Muscles of the Hip and Butt: Locate the position of the greater
trochanter (large protrusion from the proximal end of the femur) by
moving the leg and pressing on the muscles. You should be able to
feel it as a prominent bony bump. Superior to the greater
trochanter find the iliac crest. Also locate the base of the cats
tail. The gluteal (butt) muscles lie superior to biceps femoris
between the tail, iliac crest and greater trochanter. Now that you
know the general location of the muscles, you must remove the c.t.
that obscures them. First, remove the c.t. and fat down to the
shiny dense c.t. fascia that tightly covers all the muscles in this
area. In order to really find the muscles, the fascia must now be
removed. Do this by lifting up on the fascia and carefully cutting
the fibers away from the backside of it. When you are done, you
should be down to bare muscle fibers. If you removed the fascia
completely, the muscles are fairly easy to locate. Gluteus medius
is a large triangular muscle whose fibers run from the iliac crest
to the greater trochanter. It lies lateral to the base of the cats
tail and sacrum. Gluteus maximus lies along the inferior border of
gluteus medius. It is a smaller muscle running from the base of the
tail to near the greater trochanter. The final muscle found in this
area is named tensor fascia latae. This thin muscle covers the
lateral surface of the hip and blends into a sheet of c.t. called
the iliotibial (IT) tract. 1. sartorius 2. tensor fascia latae with
IT tract 3. vastus lateralis 4. biceps femoris 5. semitendinosus 6.
caudofemoralis (not in humans) 7. gluteus maximus 8. gluteus medius
9. semimembranosus 10. gracilis
Slide 12
1. sartorius 2. tensor fascia latae with IT tract 3. vastus
lateralis 4. biceps femoris 5. semitendinosus 6. caudofemoralis
(not in humans) 7. gluteus maximus 8. gluteus medius 9.
semimembranosus 10. gracilis
Slide 13
The Deep Muscles of the Back: From the hip to the neck, the
vertebrae and ribs are covered with a thick braided muscle called
erector spinae. This is actually a group of muscles, but we will
not learn them individually. This muscle group is deep to the
shoulder muscles. It approaches the surface in the middle back
where it is covered by a tough white sheath of c.t. called the
lumbodorsal fascia. Remove a small strip of this fascia to get a
peek at the erector spinae. The fascia is actually composed of two
layers, so you will need to remove them both.
Slide 14
Muscles of the Abdominal Wall: Place the cat in the supinated
position. Four flat, very thin muscles make up the abdominal wall.
They are hard to identify unless you carefully observe the
direction that the muscle fibers run. Down the middle of the
abdominal wall from the sternum to the pubic symphysis locate a
narrow band of c.t. which makes a white line called the linea alba.
On either side of the linea alba lies a band-like muscle about one
inch wide. This muscle is named rectus abdominis. It is attached to
the lower ribs and sternum on one end and pubic bones at the other.
The fibers in this muscle run lengthwise on the cat (from head to
tail). To see the muscle fibers, remove a piece of the fascia
covering the surface. Dont waste your time cleaning the whole
muscle. The second abdominal muscle we will find is called external
oblique. It is the superficial muscle of the lateral abdominal
wall. It can be found by cleaning c.t. and fat off the abdominal
wall lateral to rectus abdominis. You can be sure you have it by
the direction its fibers run. Starting from the lower ribs and
upper back, the fibers wrap around the cat and pass down toward the
pelvis at about a 45-degree angle. Look through all of the photos
on the following slides, before proceeding. Also check out the
demo-cat!
Slide 15
Begin by loosening the connective tissue with a dull probe, as
shown. External oblique Connective tissue and fat Be careful up
here! Dont remove chest muscles! Stay below the ribs.
Slide 16
In this picture, the triangle of loosened c.t. that the probe
was under has been removed. The c.t. over rectus is hard to remove,
so just do it in a small area, External oblique Transverse
abdominis Rectus abdominis
Slide 17
External oblique is loosened and flipped back to show internal
oblique. You do not need to expose as much of the muscles, as shown
here, unless your c.t. happens to come off easily. Ribs-you dont
need to go up this far.
Slide 18
The muscle just deep to external oblique is cleverly called
internal oblique. The easiest way to see it is to free the medial
edge of the external oblique next to the rectus abdominis and peel
external oblique back. The fibers of internal oblique run
perpendicular to those of external oblique. The fibers of this
muscle do not extend as far around the cat toward rectus abdominis
as do those of external oblique. The last abdominal wall muscle
lies underneath the internal oblique muscle even further off to the
side. This paper-thin muscle, called transversus abdominis, can be
found by carefully peeling back internal oblique. Its fibers run
more or less across the abdomen perpendicular to those of rectus
abdominis. If you cant find it, look further off to the side.
Slide 19
Superficial Muscles of the Back Latissimus dorsi is fairly easy
to find. It is a wide thin muscle that originates on the
lumbodorsal fascia. Trace the muscle across the ribs and under the
arm to where it is attached to the humerus. Warning: It often
merges with the pectoralis muscles, a skin muscle, c.t. and fat,
just behind the armpit. You will have to do a bit of careful
scraping and cutting to expose this muscle. The cat has three
trapezius muscles called clavotrapezius, acromiotrapezius and
spinotrapezius. They are named from superior to inferior. All three
originate along the midline on the spinous processes of the
vertebrae. Clavotrapezius is a triangular-shaped thin muscle that
originates at the back of the head and neck. It is said to insert
on the clavicle. However, at the clavicle, the same triangular
muscle mass simply changes names and becomes the clavodeltoid
muscle. The border between the clavotrapezius and acromiotrapezius
muscles consists of a fairly wide, clear c.t. partition. You should
be able to find it if you carefully clean c.t. in the right area.
1. External oblique 2. Latissimus dorsi 3. Spinotrapezius 4.
Acromiotrapezius 5. Clavotrapezius 6. Levator scapulae ventralis 7.
Spinodeltoid 8. Acromiodeltoid 9. Clavodeltoid 10. Triceps brachii
(lateral head 11. Triceps brachii (long head)
Slide 20
Before finding the other trapezius muscles, you should locate
some important landmarks on the scapula. By moving the arm, you
should be able to locate the borders of the scapula under the
muscles. Near the shoulder joint, you should be able to find feel a
prominent, hard bump by pressing with your fingers. This bump is
the acromion process. Running more or less inferiorly from the
acromion process is a bony ridge on the scapula, the spine of the
scapula. This ridge can also be located by pressing your fingers
into the muscle. The acromiotrapezius muscle originates between the
scapulae in a thin strong sheet-like tendon called an aponeurosis.
(you may have already removed it). It inserts on the acromion
process and the spine of the scapula. The spinotrapezius muscle is
situated inferior to acromiotrapezius. It inserts on the inferior
part of the spine of the scapula. It overlaps a part of latissimus
dorsi. The border between spinotrapezius and acromiotrapezius is
another indistinct c.t. partition. 1. External oblique 2.
Latissimus dorsi 3. Spinotrapezius 4. Acromiotrapezius 5.
Clavotrapezius 6. Levator scapulae ventralis 7. Spinodeltoid 8.
Acromiodeltoid 9. Clavodeltoid 10. Triceps brachii (lateral head
11. Triceps brachii (long head)
Slide 21
Superficial Muscles of the Shoulder: When you first look at
your cats shoulder, you wont see the muscles as they appear in the
picture, because they are obscured by thick, close-fitting c.t.
Clean away this c.t. down to the muscle fibers. Locate the spine of
the scapula, acromion process, and clavicle, as they will serve as
landmarks. Clavodeltoid has probably already been located, but find
it again. This muscle is continuous with clavotrapezius.
Clavodeltoid starts at the point where clavotrapezius leaves off,
on the clavicle. Clavodeltoid passes over the shoulder joint out to
the forearm. It shares a border with pectoralis major on the
anterior surface of the cats arm. NOTE: This muscle is also
referred to as clavobrachialis. Locate the acromion process. The
acromiodeltoid muscle is a narrow triangular muscle that lies
behind clavodeltoid. It has a narrow base near the acromion process
and an insertion about halfway down the upper arm. The third
deltoid muscle, spinodeltoid, is rather difficult to find unless
you did a good job cleaning c.t. from the region of the spine of
the scapula. The origin of this muscle is along the spine of the
scapula. From there, it runs forward to contact the rear edge of
the acromiodeltoid. 1.Latissimus 2.teres major 3. infraspinatus 4.
5.spinodeltoid 6. Triceps long head 7. triceps lateral head
8.acromiodeltoid 9. Clavodeltoid (clavobrachialis) 10.supraspinatus
11. levator scapulae (ventralis) 12.clavotrapezius 13.sternomastoid
14. acromiotrapezius 15.spinotrapezius
Slide 22
Muscles of the Arm Triceps brachii has three divisions or
heads. The long head is the large, thick muscle along the posterior
surface of the arm. The lateral head is equally easy to find. It is
a large thick muscle mass on the lateral surface of the arm
anterior to the long head and inferior to spinotrapezius. The
third, medial head, can best be found by cutting the lateral head
and looking for a relatively narrow muscle wedged in between the
lateral head, the long head and the humerus. Warning: the medial
surface of the brachium is covered by a thin superficial muscle,
epitrochlearis, so the medial head cant be seen there. Remove and
disregard epitrochlearis. Brachialis is a torpedo-shaped muscle
closely associated with acromiodeltoid. It lies on the anterior
lateral surface of the upper arm near the lateral head of triceps
brachii. Clean c.t. and probe to find it. Biceps brachii lies on
the anterior medial surface of the upper arm. To find it, flop your
cat over on its back and move the pectoralis muscles toward the
head. Look for another torpedo-shaped muscle, but one larger than
brachialis. 1. Triceps brachii (lateral head) 2. Triceps brachii
(medial head) 3. Triceps brachii (long head) 4. Acromiodeltoid 5.
Spinodeltoid 6. Clavodeltoid 7. Brachioradialis (omit)
Slide 23
Deep Muscles of the Scapula: Before you go on, cut the
trapezius muscles, latissimus dorsi and the pectoralis muscles on
the side so that you can explore the deep muscles of the scapula.
It is suggested that you save the side you have already dissected
and cut the other side. Three powerful deep shoulder muscles have
the flat surfaces of the scapula as their origin. Locate the entire
spine of the scapula. Move aside the cut trapezius muscles. Deep to
acromiotrapezius, above the spine of the scapula, is a large muscle
supraspinatus (3). It fills the supraspinous fossa. If you probe
through supraspinatus, you will hit the scapula beneath it. Pull
down the cut edge of latissimus dorsi to expose the region below
the spine of the scapula and find another thick muscle attached to
the scapula. It is infraspinatus (4). It passes anteriorly to the
humerus and deep to spinodeltoid. It fills the infraspinous fossa.
Grab the scapula and rotate it out so the shoulder goes toward the
chest. At the same time, bring the vertebral border of the scapula
away from the spine. The purpose of this operation is to stretch
out the rhomboid (11 & 12) muscles, which lie deep to acromio-
and spino- trapezius. Their fibers run from the spinous processes
of the vertebrae to the vertebral border of the scapula. (Hint: The
vertebral border is perpendicular to the spine of the
scapula.)
Slide 24
Deep Scapula Locate the axillary border of the scapula. Teres
major (6) is a chunky round, little muscle that runs along this
border up to the humerus. If you look closely, you should be able
to find the clear-cut separation between teres major and
subscapularis. A probe pushed through supraspinatus, infraspinatus
or subscapularis will hit the scapula. One passed through teres
major will not, since it lies along the edge of the scapula, not on
its surface. While the cat is on its back, find serratus ventralis
(4). This muscle has several finger-like divisions that attach to
several of the lower ribs. Its superior end is attached to the
inferior point of the scapula. Fat often obscures the fingers of
this muscle and must be removed to see them. Now, flip the cat over
on its back and flop its arm and scapula out. The under surface of
the scapula, that is normally next to the ribs, is covered by
subscapularis (5), which fills the subscapular fossa.
Slide 25
1.Pectoantebrachialis 2.Pectoralis Major 3.Pectoralis Minor
4.Xiphihumeralis (not in humans) 5.Linea alba 6.Epitrochlearis
7.Triceps Brachii (long head) 8.Teres Major 9.Subscapularis
10.Serratus Ventralis (anterior in humans) 11.Latissimus Dorsi
Slide 26
Superficial Chest Muscles: These muscles are hard to dissect
because they are thin, overlapping and are joined tightly together
by connective tissue. First, find the sternum from the manubrium to
the xiphoid process. The chest muscles originate on the sternum.
Second, move the cats arm around to locate its elbow, shoulder, and
humerus. The chest muscles insert along the front of humerus. Now,
on one side only, clean off the c.t. right down to the muscle
fibers. Next, its time for a little feline massage. Give the cat a
good rubdown with a paper towel to dry the chest. If you do this
thoroughly, you should be able to locate the faint white cleavage
lines where the muscles come together. The superior border of the
pectoralis major (3) is in contact with clavodeltoid. The border
begins at the tip of the manubrium and runs out the arm. Locate the
cleavage line and separate these two muscles with careful pulling
and cutting. You will also loosen a cat muscle called
pectoantebrachialis (4), that lies over this area. Now we will look
for the hard-to-find cleavage line between pectoralis major and
pectoralis minor. Look for it along the sternum about three inches
below the superior border. At this cleavage line, pectoralis minor
dives under pectoralis major so the separation you make will go
down and forward under pectoralis major. A warning: inferior to the
true pectoralis major/pectoralis minor cleavage line, there is
often a false cleavage plane that will split pectoralis minor in
two. You will know you have the wrong cleavage plane if it goes in
and back instead of in and forward. Pectoralis minor lies deep to
pectoralis major. Trace it forward to the humerus. Its inferior
border is a fairly distinct line where it makes contact with a
muscle we will not dissect, xiphihumeralis (1). The superior border
of pectoralis minor lies beneath the body of pectoralis major,
about halfway toward the head. This edge can be found by probing
under pectoralis major.
Slide 27
Slide 28
Muscles of the Anterior Neck Region These muscles should be
dissected on the side of the cat from which you removed the ear.
The landmarks we will use to find these muscles are the external
auditory meatus, the mastoid process behind it, the sternum, and
the clavicle. The cats clavicle is a tiny bone about the size of a
paper match. It lies between the shoulder and sternum buried in
muscle. Pinch the muscle in this area to locate the clavicle. The
sternomastoid muscle is a strap-like muscle that runs on the
surface of the neck from the mastoid process to the superior top of
the sternum. Unfortunately, this muscle is obscured from view. At
the upper end, a salivary gland and blood vessels get in the way.
The middle part is crossed by a large vein. The entire neck region
is covered by an especially thick layer of c.t. Remove the c.t.
from the surface of the muscle and from between the muscle and the
blood vessel and salivary gland. Once the anterior border of the
muscle is free, start to work your way underneath with a dull
probe. Also, work beneath the muscle from the posterior border
until you have freed the muscle from mastoid process to sternum.
(Warning: Just above the sternum there is often a confusing set of
cross fibers which run from the right to the left across the
sternomastoid muscle. You can safely remove these fibers.) The
cleidomastoid muscle lies deep to the sternomastoid muscle. Trace
it from the clavicle to the mastoid process. Separate the
sternomastoid and cleidomastoid using a dull probe.