Day 2: MUSCULAR SYSTEM of the CAT

Skeletal muscles enable the body to move. Most are firmly anchored to bone at one end, the origin of the muscle, while the other end is attached to the bone to be moved, known as the insertion. The fleshy central portion is called the belly. The ends of the muscle are attached to bone most often by means of a narrow band of connective tissue called a tendon.

As you dissect, free the muscle from other muscles and from the nerves and blood vessels associated with it. The fine, transparent connective tissue which binds adjacent muscles is deep fascia, while tougher and more fibrous superficial fascia connects the skin to the muscles below.

The action of a muscle results from its contraction. Muscles are arranged in antagonistic pairs, meaning that while a muscle will cause a structure to move in one direction, the antagonist will cause it to move in the opposite direction.

ACTIONS OF MUSCLES:

Flexion – to bend at a joint decreasing the angle at that joint; examples: elbow or knee jointExtension – to straighten joint increasing the angle at that jointAdduction – to move appendage toward sagittal midline; example: lowering arms from shoulder level to

rest at the sides.Abduction – to move appendage away from sagittal midline; example: raising arms from rest at sides to

shoulder level.Supination – to turn palm of hand upward; foot turns outward.Pronation – to turn palm of hand downward; foot turns inward.Rotation – to move a structure about a point: example: turning head from side to side

HUMAN MUSCULAR SYSTEM

Muscles of the Chest (Thorax)

*The large triangular mass of chest muscles comprising the pectoral group: It originates in the sternum and inserts upon the humerus. It acts to pull the humerus toward the chest (adduction). In man, there are only 2; the cat has 4.

1. PECTOANTEBRANCHIALIS --- the most anterior of the 4; a narrow band across the top of the chest; this muscle is NOT found in man!

2. PECTORALIS MAJOR --- beneath the pectoantebranchialis; it is smaller than pectoralis minor (opposite of man!)3. PECTORALIS MINOR --- LARGEST of pectoral muscles of cat. It lies posterior to the pectoralis major.4. XIPHIHUMERALIS --- the most posterior of the pectoral muscles (this muscle is NOT found in man).

Pectoantebrachialis

Pectoralis Major

Pectoralis Minor

Xiphihumeralis

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Muscles of the Abdomen

The abdominal area is not protected by a bony structure as is the thorax. The abdominal organs are held in place by the pressure of the lateral abdominal muscles. They compress the abdominal wall and aid in flexion of the trunk.

1. EXTERNAL OBLIQUE--- thin broad sheet that covers the ventral & lateral surfaces.2. RECTUS ABDOMINUS --- a pair of parallel, innermost (medial) of the abdominal muscles that lie on

either side of the linea alba (mid-line area of the abdomen).

Rectus Abdominus

Caudal End Cranial

End

External

Obliques

HEAD & NECK MUSCLES

1. STERNOMASTOID --- large “V” shaped along ventral & lateral sides of neck.

2. DIGASTRIC --- below inner edge of mandible; along lateral sides of trachea. It extends from the occipital and temporal bones to the mandible and acts to lower the jaw.

3. MASSETER --- most prominent muscle on lateral surface of face. It is the primary muscle used for chewing. It extends from the zygomatic bone to the lateral surface of the mandible.

Digastric Masseter

Sternomastoid

Clavobrachialis Pectoantebrachialis

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SHOULDER & BACK MUSCLES

1. CLAVOBRACHIALIS --- the MOST anterior of the shoulder & arm muscles. It originates at the clavicle, crosses the shoulder & upper arm, & inserts upon the ulna near the elbow; extends humerus, turns head, flexes the elbow.

2. LATISSIMUS DORSI --- posterior (upper back); raise (adduct) humerus; prominent on the lateral ventral surface. It is a flat, broad muscle, triangular in shape. It gives to the humerus great power for pulling backward when the cat is running and climbing.

Clavobrachialis

Triceps brachii

Sternomastoid

Latissimus Dorsi

Clavobrachialis

ARM & FOREARM MUSCLES

1. Triceps Brachii --- this muscle has 3 heads in both man and in the cat that insert on the olecranonprocess of the ulna; it is visible on the lateral surface of the forelimb; acts to extend the forearm.

2. Brachioradialis--- most anterior of the forelimb muscles; rotates the radius; supinates & flexes the paw.3. Flexor Carpi Ulnaris --- located on medial surface; flexes wrist & digits.4. Extensor Carpi Ulnaris –located on lateral side; inserts on 5th metacarpal; extends lower forelimb, wrist.

Extensor Carpii UlnarisBrachioradialis

Triceps Brachii

Flexor Carpi Clavobrachialis Ulnaris

Pectoantebrachialis

Ventral view Dorsal view

----------------------------------------------------------------------------------------------------------------------------------------------Muscles of the Thigh/Leg

1. Sartorius --- anterior & lateral half of thigh; adducts thigh.2. Gracilis --- medial (inner) thigh; adducts thigh.3. Gastrocnemius --- major muscle of the calf; located on medial side; it originates on the femur and inserts

upon the heel bone (calcaneous) by the Achilles tendon; it acts as an extensor of the foot.4. Tibias Anterior --- anterior & lateral portion of the lower hind leg; lies over tibia.5. Biceps Femoris --- large, powerful muscle on lateral surface of thigh; acts to flex the shank

and abduct the thigh; it’s 2-2 ½ inches wide throughout most of its length.

Sartorius

GracilisBiceps

Tibialis Femoris Anterior

Gastrocnemius

Anterior view Anterior/Medial views Lateral view

LAB #2: Muscular System Name ________________________________SUMMARY SHEET Period ________________

Directions. LABEL the diagrams of the Cat with the correct name of the muscle; write ON the lines.

A B

3

1 4

2

5

C D

6 9

710

8

11

E 12 14

13

Anterior view Posterior view 15

Dorsal view of Arm