DISSECTION INFORMATION GUIDE
*Please read this guide. The material on pages 1, 2, and 6 are included on the Muscular System Exam.*
Cats will be distributed on Tuesday, February 16th. One student from each dissection group should report to Mr. Specks
during their off period. I will provide a specific location. Your group will be assigned a cat/dissection kit and you will be
briefed on general dissection instructions. Please know your Group # so that you will be assigned the correct materials.
Cat dissection will officially begin Thursday, February 18th. Your cat needs to be skinned by the start of class on the
18th. If done correctly and instructions have been read beforehand, skinning should take approximately one hour. You
are welcome to do this in your off period, lunch period, before, or after school once the cats have been assigned. Mr.
Specks will instruct you to the rooms you may use. NO LIVE ANIMALS ARE TO BE PRESENT. DO NOT ENTER THE
SURGICAL AREA UNDER ANY CIRCUMSTANCES.
Please use the information in this guide, the dissection powerpoint, as well as your notes from class and the book to aid
you in your studies and dissection of the cat. The labs will take place in the basement, during your regularly scheduled
A&P class time. Your group will be assigned to a specific basement classroom. The instructions for each day are listed in
this guide. If all of the day’s tasks have been completed, continue on to the instructions for the following day. Arriving
late/leaving early is not allowed. An absence will result in a 5 point deduction from your Dissection Exam grade. USE
YOUR TIME WISELY! STUDY HARD! HAVE FUN!
We will dissect for 4 days: Thursday, February 18th to Tuesday, February 23rd. The Dissection Exam will take place on
Wednesday, February 24th. You will be tested on the following about the muscles and structures listed in this guide:
location, origin, insertion, and function.
*THESE CATS HAVE BEEN PREPARED FOR YOUR EDUCATIONAL PURPOSES. YOU MUST TREAT THEM WITH RESPECT AND
CONDUCT YOURSELVES PROFESSIONALLY IN THE LAB. ANY STUDENT BEHAVING INAPPROPRIATELY WILL BE ASKED TO
LEAVE AND HAVE PROFESSIONALISM POINTS DEDUCTED.*
EVERY DAY GUIDELINES:
1. Pull your hair back from your face and remove any jewelry that will tear your gloves or dangle into the dissection
field.
2. Wear your face mask! Don’t lose it. It will be used during the entire dissection week.
3. Each group should have one dissection tray, one dissection kit with a blade, and one dissection guide book. You
must use the materials assigned to your group.
4. Glove up! You will have one pair of gloves for each day so be careful. Notify instructor if your gloves tear.
5. Remove your cat from the bag and place it on the dissection tray. PLEASE KEEP THE PRESERVATIVE FLUIDS THAT
COME WITH THE CAT IN THE BAG! THESE WILL HELP KEEP THE CAT MOIST FOR THE NEXT WEEK.
6. You must clean up your work station and supplies daily. Do not allow any tissue to enter the sink/tub when
rinsing your tray. Be sure to store your cat so that the fluids do not leak out of the bag.
7. You are welcome to bring pins to identify and label the cat as you dissect it. Paper/tape directly on the cat does
not stay on.
8. You are welcome to take pictures/videos to help in your learning as long as they are not misused or placed on
the internet.
REMOVING THE SKIN
1. This must be completed before the start of dissection. Read the instructions beforehand to lessen the time
spent on skinning.
2. Carefully place the scalpel blade on the handle if there is not an attached blade in your kit.
3. Use the scalpel or a pair of scissors to start a longitudinal incision on the ventral midline at the neck. Be careful
not to cut into the muscle or body cavities. There should already be a precut area in the neck. Begin there.
4. Extend the incision caudally to the inguinal region between the legs. Avoid cutting the genitals.
5. Make horizontal incisions along both thoracic and pelvic limbs as shown and cut skin around all 4 paws.
6. Cut around the base of the tail, leaving the skin on the tail. Cut the skin around the face of the cat, leaving the
skin on the ears, eyes, and forehead. Remove the skin over the cheeks.
7. Peel the skin away from the underlying musculature using your fingers. The skin should only be left around the
face, ears, forehead, and tail and should be removed in one piece.
8. Remove as much of the subcutaneous fat and as possible. This will save time when you start the actual
dissection. You should be able to see muscles after the skin is removed. The cutaneous trunci muscle will
probably be removed with the skin due to its location. You do not need to separate it from the skin.
9. Wrap the skin around the cat and store your cat in its plastic bag with the preservative fluids. The skin will
prevent the tissues from drying out and prevent the growth of bacteria and mold. Dispose of any removed fascia
and fat in a trash can, NEVER in the sink.
10. Do not begin dissecting the muscles until we start class dissection.
11. Do not open the body cavities of the cat. We will do this at the end of the week if time permits.
12. Identify the gender of your cat.
DAY 1 ACTIVITIES
IDENTIFY THE FOLLOWING MUSCLE OF THE SKIN
Cutaneous trunci – thin, broad muscle in the fascia just under the skin; FUNCTION: twitch the skin
IDENTIFY THE FOLLOWING MUSCLES OF THE HEAD AND NECK
Masseter- large, most powerful muscle of mastication; FUNCTION: close the jaw
Sternomastoid –straplike muscle on the ventrolateral surface of the neck; FUNCTION: turn the head
Sternohyoid-straplike muscle on the ventral surface of the neck; FUNCTION: pull the hyoid dorsally
IDENTIFY THE MUSCLES OF THE CHEST
Pectorals- these chest muscles include the pectoantebrachialis, pectoralis major, pectoralis minor, and xiphihumeralis.
Identify all 4 muscles of the pectorals. FUNCTION: adduct the front leg.
IDENTIFY THE FOLLOWING MUSCLES OF THE ABDOMEN
*FUNCTIONS: support the abdominal organs, flex (arch) the back, and participate in functions that involve
straining (urination, defecation, vomiting, parturition)*
External Abdominal Oblique – most superficial of the abdominal muscles; fibers run caudoventral
Internal Abdominal Oblique – these fibers run cranioventral
Rectus Abdominis – broad band of muscle on either side of the linea alba that forms the floor of the abdomen from the
sternum to the pubis. These fibers run in a craniocaudal direction.
Transversus Abdominis- deepest of the abdominal muscles; These fibers run in a transverse direction.
Linea Alba – white aponeuroses down midline of abdomen that serves as the attachment site for abdominal muscles
MUSCLE
ORIGIN
INSERTION
Masseter
External abdominal oblique
Internal abdominal oblique
Rectus abdominis
Zygomatic arch
Ribs and fascia
Ilium and fascia
First and second ribs
Mandible
Ventral midline
Ventral midline
Pubis
DAY 2 ACTIVITIES
IDENTIFY THE FOLLOWING SUPERFICIAL MUSCLES OF THE BACK & SHOULDER
Trapezius – lies on the dorsal aspect of the neck; FUNCTION: extend (raise) the head and neck. It actually consists of 3
separate muscles - the clavotrapezius, acromiotrapezius, and spinotrapezius. Identify all 3 parts of the trapezius.
Latissimus dorsi –broad triangular muscle that extends from the spinal column to the humerus; FUNCTION: Pulls front
leg backwards (caudo-dorsal direction)
Deltoids – These muscles of the shoulder consist of 3 separate muscles: the clavodeltoid, acromiodeltoid, and the
spinodeltoid); Identify all 3 muscles of the deltoids; FUNCTION: abduct and flex the shoulder joint.
NOTE: Some texts refer to the clavodeltoid as the clavobrachialis. This muscle extends from the clavicle to
the radius and ulna. In addition to the above functions, it assists the biceps by acting as a synergist, as it aids
in forearm flexion.
IDENTIFY THE FOLLOWING DEEP MUSCLES OF THE BACK & SHOULDER
Supraspinatus- fills the supraspinous fossa of the scapula; FUNCTION: extend the shoulder and stabilize the joint
Infraspinatus – fills the infraspinous fossa of the scapula; FUNCTION: flex the shoulder and stabilize the joint
*locate the spine of the scapula
IDENTIFY THE FOLLOWING MUSCLES OF THE BRACHIUM
Clavobrachialis- see note above
Brachialis – extends from the lateral surface of the humerus to the proximal end of the ulna; FUNCTION: flex the elbow
Biceps brachii – consists of 2 heads that extend from the scapula to the proximal radius; FUNCTION: flex the elbow
Triceps brachii – 3 heads (long head of the triceps, lateral head of the triceps, and medial head of the triceps) that
extend from the scapula and humerus to the olecranon process of the ulna; FUNCTION: extend (straighten) the elbow
joint. Identify all 3 parts of the triceps
MUSCLE
Latissimus dorsi
Pectorals
Deltoids (acromio/spino)
Brachialis
Biceps brachii
Triceps brachii
ORIGIN
lumbar vertebrae
Sternum
Scapula
Lateral humerus
Scapula
Scapula and Humerus
INSERTION
Humerus
Humerus
Humerus
Proximal ulna
Radius
Olecranon process of ulna
DAY 3 ACTIVITIES
IDENTIFY THE FOLLOWING MUSCLES OF THE PELVIC LIMB
MUSCLES OF THE THIGH
Gluteal muscles – this group consists of 2 separate muscles (the gluteus medius and gluteus maximus) that extend from
the pelvis down to the femur; FUNCTION: abduct thigh.
Hamstring muscles - this group consists of 3 separate muscles (the semimembranosus, semitendinosus, and biceps
femoris) on the caudal aspect of the thigh: FUNCTIONS: extend the hip joint; flexes the stifle joint
Biceps femoris-most lateral
Semimembranosus-most medial
Semitendinosus-most caudal
Quadriceps femoris – this group consists of 4 separate muscles (rectus femoris, vastus lateralis, vastus medialis, vastus
intermedius-not found in the cat) and is located on the cranial aspect of the thigh. The patella is located in the tendon of
this muscle. Identify all 4 muscles of the quadriceps. FUNCTION: extend the stifle joint.
MUSCLES OF THE LOWER LIMB
Gastrocnemius muscle- this is the calf muscle; FUNCTION: extend the hock
-Achilles tendon – large strong tendon of the gastrocnemius that runs down the back of the leg to attach on
the calcaneal tuberosity
IDENTIFY THE MUSLCES OF RESPIRATION
Diaphragm – this muscle separates the thoracic cavity from the abdominal cavity. FUNCTION: assist in inspiration
External intercostals – most superficial muscles between the ribs; FUNCTION: assist in inspiration
Internal intercostals- lies deep to the external intercostals; FUNCTION: assist in expiration.
MUSCLE
Gluteal muscles
Biceps femoris
Semimembranosus
Semitendinosus
Quadriceps femoris
Gastrocnemius
ORIGIN
Ilium and associated fascia
Ischium
Ischium
Ischium
Illium and femur
Condyles of the femur
INSERTION
Greater trochanter of femur
Tibia and patella
Tibia
Tibia
Tibial tuberosity
Calcaneal tuberosity of fibular
tarsal bone
DAY 4 ACTIVITIES
This is the final day to review each muscle on your cat. When you feel that you are confident with the information, you
may move forward and explore the thoracic and abdominal cavities, keeping the muscles of the chest and abdomen
intact. After class, the dissection practical set-up will begin. The classroom will be LOCKED until the start of the exam on
Wednesday, February 24th. For the exam, you will be expected to know the name, location, and function of ALL of the
muscles that we have studied during dissection. The muscles listed in the charts are the only ones that will be tested
on for origin and insertion. The exam will be worth 100 points. You will rotate to different stations around the room
during the exam. You will be allowed one minute per station. The exam will be administered twice during each A & P
class period. You will be assigned a testing time. NO SWITCHING OF TIMES WILL BE ALLOWED.