MUSCLES OF THE CAT

Your instructor will prepare a dissection of the muscle system in the cat. Because the cat is an adult and much larger than the fetal pig, the muscles are much easier to dissect. We will nevertheless study the largest and most conspicuous muscles only. Find and study as many of these muscles as you can.

EXTERNAL FEATURES:

If you have not previously had a chance, examine the cat’s external features. Notice that it is, like most mammals, covered with much more hair (fur) than the fetal pig. Above the nose, there are some especially long, sensitive hairs called vibrissae (“whiskers”). Cats walk in a digitigrade posture, typical of most carnivores, rodents, and other mammals.

HEAD AND NECK REGION:

Masseter This jaw muscle attaches to the angle of the lower jaw.

Temporalis This muscle runs from the temporal region of the skull to insert, beneath the

zygomatic arch, on the coronoid process of the mandible.

Occipitalis Visible on the read of the skull, this is an easily identified facial muscle.

Platysma This is the largest facial muscle, forming a sheet along the ventral surface.

Mylohyoid This muscle runs transversely across the floor of the mouth.

Digastricus This muscle pulls on the front end of the mandible to open the mouth.

Sternohyoid This muscle originates from the sternum and inserts onto the hyoid bone.

Sternothyroid, thyrohyoid The thyroid cartilage interrupts the sternohyoid to form these muscles.

Sternocleidomastoid This muscle runs diagonally toward the ear, inserting on the mastoid process.

Clavobrachialis This is a portion of the sternocleidomastoid combined with part of the deltoid.

TRUNK OF THE BODY:

Cutaneus maximus A very thin sheet, attached to the skin, overlying the other muscles of the trunk.

Trapezius Identify this by its position and its fiber directions (converging onto the scapula).

Rhomboideus These muscles lie deep to the trapezius and attach to the scapula’s dorsal border.

Splenius In the neck region, this is the most prominent portion of the erector spinae system.

Latissimus dorsi See under limb muscles.

Serratus anterior This muscle, deep to the latissimus dorsi, forms a sling that supports the rib cage.

External oblique Deep to the caudal border of the latissimus dorsi. Examine its fiber direction.

Internal oblique Deep to the external oblique, with a different fiber direction.

Transversus abdominis A very thin muscle, running transversely beneath the ext. and int. oblique.

Rectus abdominis Running longitudinally along the ventral midline, just beneath the ext. oblique.

Diaphragma The body’s major breathing muscle, separating the thoracic & abdominal cavities.

CONTINUED ON REVERSE SIDE

SHOULDER AND FORELIMB:

Deltoid A very strong extensor and abductor, located cranially in the shoulder region.

Latissimus dorsi A very broad muscle, originating from the lumbodorsal aponeurosis, and

converging onto a tendon that inserts on the humerus.

Pectoralis major, minor These muscles originate ventrally and converge onto the humerus.

Supraspinatus A strong lateral rotator, occupying the supraspinous fossa of the scapula.

Infraspinatus A strong lateral rotator, occupying the infraspinous fossa of the scapula.

Teres major, minor Lateral rotators located beneath the infraspinatus.

Triceps brachii The major extensor muscle on the caudal side of the arm.

Subscapularis A major medial rotator of the arm, located on the deep side of the scapula.

Biceps brachii The major flexor & supinator muscle on the cranial side of the arm.

Brachialis A pure flexor of the elbow, located alongside the biceps.

PELVIS AND HIND LIMB:

Tensor fasciae latae: A small muscle, in series with the gluteals, that tenses the fascia lata.

Gluteus medius, maximus, miinmus: Notice the position of these muscles, which are abductors

in most mammals. The gluteus maximus is small in cats; gluteus medius is the largest.

Sartorius Flexor muscle running diagonally across the thigh to flex both hip and knee.

Quadriceps femoris (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius):

These muscles lie beneath the fascia lata and more medially, on the anterior side of the thigh.

Semitendinosus, semimembranosus, biceps femoris:

Locate these “hamstring” muscles along the posterior half of the thigh.

Gracilis (meaning “graceful”): This broad but thin muscle accompanies the hamstrings.

Adductor longus, magnus: These muscles are on the inner (medial) side of the thigh.

Gastrocnemius: This is the principal extensor of the ankle joint. Note the strong Achilles tendon.

Tibialis anterior: Forceful dorsiflexor of the ankle joint.