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.


(See Gilbert, p. 18)


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.

The pectoantebrachialis has been separated from the underlying pectoralis major, and is being lifted in the image. Origin: manubrium, insertion: proximal fascia of forearm.
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 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
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.
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 Origin: 1) long head: superior border of glenoid fossa. 2) humerus Insertion: radial tuberosity
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 transverse carpal ligament on cat, holds down tendons of insertion

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

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.

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


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