Abdominal Muscles

Category Muscle Description

Abdominal External Oblique The outermost layer of the abdominal wall.

Muscles Its anterior part is concealed under a large fat
muscle, the latissimus dorsi. Its fibers pass
obliquely downward and backward.

Internal Oblique The second layer, underlying external

oblique. It is a short muscle lying beneath the
more dorsal portion of the external oblique.
Its fibers are directed obliquely downward
and forward.

Transverse Abdominis The third muscle layer and can be located on

cutting through the internal oblique. This is a
very thin muscle. Its fibers are directed
ventrally and slightly posteriorly.

Rectus Abdominis The long slender muscle on each side of the

linea alba extending from the pubic
symphysis to the anterior part of the thorax. It
is found inside of and between the
aponeuroses of the oblique muscles.

II. Thorax & Abdominal Muscles

Muscle Origin Insertion Action

External oblique lumbodorsal fascia linea alba and on constricts the abdomen
pubis

Internal oblique lumbodorsal fascia linea alba compresses the abdomen

Intercostals

- External caudal border of cranial border of raise ribs at inhalation

intercostals one rib next rib caudal

- Internal cranial border of caudal border of next draw adjacent ribs together
intercostals one rib rib cranial and lower ribs
Rectus pubic symphysis sternum and costal retracts ribs and sternum;
abdominis cartilages compresses abdomen

Transverse lumbodorsal fascia linea alba compresses the abdomen

abdominis

Epaxial Muscles
Epaxial Multifidus Spinae The slender, narrow median portion, just on
Muscles the sides of the vertebrae.

Sacrospinalis The very thick lateral portion, which are

divisible anteriorly into three divisible parts –
(1) semispinalis, (2) longissimus, and (3)
iliocostalis.

Chest (Pectoral) Muscles

Chest Pectoantibrachialis A long, thin, ribbonlike muscle. It is anterior
(Pectoral) and most superficial of the chest muscles. In
Muscles most cats, this is difficult to dissect because
the fascia is tough. Be certain that you see its
outlines before you begin, and do not dissect
too deeply or you will be including part of
another muscle. Separate between origin and
insertion.

Pectoralis Major Posterior to the preceding and extending

anteriorly dorsal to the preceding. To expose
this muscle, cut across the
pectoantibrachialis. This is also a thin
muscle, but much broader than the
pectoantibrachialis, which crosses it. With
your finger or a probe, loosen the pectoralis
major from the underlying muscle as far
anteriorly as possible.
 Pectoralis Minor Posterior to the preceding and covered in
large part by the pectoralis major. This
muscle is larger than the pectoralis major and
runs underneath it and the
pectoantibrachialis. This is the thickest
muscle of this group as well as the broadest.

Xiphihumeralis The last of the chest muscles. It is a thin, flat,

long muscle, passing from the xiphoid
process of the sternum, its anterior part
passing dorsal to the posterior part of the
pectoralis minor, and inserted on the
humerus. There are neither
pectoantibrachialis and xiphihumeralis
muscles in humans.

Neck and Throat Muscles

Neck and Sternomastoid The superficial muscle of the ventral side of
Throat the neck. It is the large V-shaped muscle
Muscles between the sternum and the head.

Sternohyoid The muscle in the middle of the neck

between the sternomastoids.

Sternothyroid The slender muscle lying on each side of the

trachea, dorsal to the sternohyoids. To see
this muscle, separate the two sternohyoids in
the median line and exposing the trachea or
windpipe.

Thyrohyoid Short, narrow muscles on each side of the

thyroid cartilage.

Cricothyroid A small muscle lying ventrally on the larynx.

Cleidomastoid A long muscle lateral to the sternomastoid

passing from the head to the upper arm.

Clavotrapezius A long muscle on the side of the neck that

extends from the skull to the clavicle.
 Clavobrachialis/Clavodeltoid The muscle which appears to be connected to
the preceding muscle that extends from the
clavicle to the forearm.

Masseter The great thick muscle covering the angle of

the jaws, situated in front of the submaxillary
and parotid glands. It is covered by a very
tough shining fascia.

Temporal The great mass of muscle covered by a strong

shining fascia occupying the temporal fossa
of the skull, dorsal to the ear.

Digastric The muscle lying along the medial surface of

each half of the mandible.

Mylohyoid The thin transverse sheet passing across

between the two digastrics from one half of
the mandible to the other.

Geniohyoid The slender muscle lying in the median line

under the mylohyoids. To expose this muscle,
cut through the median raphe of the
mylohyoid.

I. Head & Neck Muscles

Muscle Origin Insertion Action

Cricothyroid cricoid cartilage thyroid cartilage tenses vocal cords

Digastric jugular and mastoid mandible lowers the lower jaw

process

Geniohyoid medial surface of the body of hyoid bone pulls the hyoid forward
mandible near the
symphysis

Mylohyoid cricoid cartilage of hyoid bone raises floor of mouth;

larynx pulls hyoid forward

Sternohyoid sternum anterior horn of the pulls hyoid posteriorly;

hyoid bone raises ribs and sternum
Stylohyoid stylohyal bone of hyoid body of hyoid bone raises hyoid

Thyrohyoid thyroid cartilage posterior horn of the raises the larynx

hyoid bone

Muscles of the Upper Back, Shoulder, and Back of the Neck,

Muscle Group Muscle Name Description

Latissimus Dorsi Latissimus dorsi Large flat muscle extending obliquely forward
from the middle of the back to the upper arm.

Trapezius Muscles Spinotrapezius Posterior trapezius muscle.

Acromiotrapezius Middle trapezius muscle in front of

spinotrapezius.

Clavotrapezius Anterior trapezius muscle.

Levator Scapulae Levator scapulae Flat, bandlike muscle passing anteriorly,

ventralis diverging from the acromiotrapezius, and passing
internal to the clavotrapezius.

Rhomboideus Rhomboideus Thick muscle beneath the spinotrapezius and

Muscles acromiotrapezius, extending from the vertebral
border of the scapula to the mid-dorsal line.

Rhomboideus Most ventral portion of the rhomboideus, a

capitis practically separate muscle extending as a slender
band forward.

Splenius Splenius Large sheet of muscle covering the back of the

neck in front of the rhomboideus, internal to the
trapezius muscles, and crossed by the
rhomboideus capitis.

Rotator Cuff & Supraspinatus Stout muscle occupying the supraspinous fossa of
Shoulder Muscles the scapula.

Acromiodeltoid Short, thick muscle passing ventrally from the

acromion process, lying lateral to the
clavobrachialis.
 Spinodeltoid Muscle passing to the upper arm across the upper
ends of the muscles of the upper arm.

Infraspinatus Muscle that fills the infraspinous fossa of the

scapula.

Teres major Stout muscle immediately behind the

infraspinatus with fibers running in the same
direction.

Teres minor Small muscle somewhat covered by the

infraspinatus on the posterior border of the
scapula.

Subscapularis Muscle occupying the subscapular fossa.

Serratus Muscles Serratus ventralis Large, fan-shaped muscle extending from the
ventral border of the scapula to the sides of the
thorax and neck.

Serratus dorsalis Serrated muscle lateral to the latissimus dorsi,

originating by a thin, long aponeurosis.

Scalenes Scalenes Long muscles in the chest wall that help raise the
pectoralis muscles from the chest wall.

Intercostal External External layer with fibers running obliquely

Muscles intercostals backward and downward.

Internal intercostals Internal layer with fibers running obliquely

forward and downward.

Epaxial Muscles Semispinalis dorsi Dorsal part next to the median dorsal line.
of the Thorax

Longissimus dorsi Median part.

Iliocostalis Ventral part.

III. Back & Shoulder Muscles

Muscle Origin Insertion Action
Infraspinatus infraspinous fossa of greater tuberosity of rotates humerus
scapula humerus

Latissimus dorsi spines of thoracic intertubercular groove of pulls arm dorsally

and lumbar vertebrae humerus and caudally

Rhomboideus

- Major neural spines of vertebral border of the draws scapula

thoracic vertebrae scapula dorsally and
medially

- Minor neural spines of vertebral border of the draws scapula

thoracic vertebrae scapula dorsally and
medially

- Capitis lambdoidal ridge vertebral border of the draws the scapula

(superior nuchal scapula cranially and rotates
line) it

Serratus ventralis first ten ribs medial surface of scapula draws scapula
cranially and lowers
it

Splenius neural spines of lambdoidal ridge (superior turns and raises the
thoracic vertebrae nuchal line) head

Supraspinatus supraspinous fossa greater tuberosity of extends the

of scapula humerus humerus

Teres major axillary border of medial surface of the flexes, rotates, and
scapula humerus in common with lowers the humerus
latissimus dorsi

Teres minor axillary border of greater tuberosity of assists teres major

scapula humerus

Trapezius Group

- Spinotrapezius spines of thoracic spines of scapula pulls scapula

vertebrae dorsally and
caudally
- Acromiotrapezius spines of cervical spine and metacromion draws scapula
and thoracic process of scapula dorsally and hold
vertebrae scapulae together

- Clavotrapezius superior nuchal line clavicle draws the clavicle

dorsally and
cranially

Muscles of the Upper Arm

Muscle Description

Triceps brachii The great extensor muscle on the back of the upper arm;
usually has three heads:

- Long head The large mass of muscle on the back of the upper arm

- Lateral head Muscle on the lateral surface of the upper arm

- Medial head Deeper muscle in contact with the humerus; to expose, cut
through the lateral head

Epitrochlearis / Extensor Thin muscle on the medial surface of the long head of triceps
antibrachii brachii, attached to it via a fascia

Biceps brachii Spindle-shaped muscle on the anterior surface of the upper

arm; seen by removing the insertions of pectoral muscles

Brachialis Lateral to biceps, in contact with the lateral head of triceps

Anconeus Small triangular muscle at the elbow joint, covered by the

distal end of the lateral head

Muscles of the Forearm

Muscle Description

Extensor carpi ulnaris First muscle preaxial to the ulna

Extensor digitorum Next to preceding, going toward preaxial side

lateralis
Extensor digitorum Next to preceding
communis

Brachioradialis / Supinator Next to preceding, loose and standing away from underlying
longus extensor

Extensor carpi radialis Underlies brachioradialis and extends onto inner/medial

surface of forearm

Pronator teres Next to extensor carpi radialis, proceeding on medial surface

of forearm toward ulnar side

Flexor carpi radialis Next to, mostly under, preceding muscle

Palmaris longus Flat muscle forming outer surface of forearm, next to

preceding

Flexor profundus Complex muscle under preceding, projects to radial side

digitorum

Flexor carpi ulnaris Two nearly separate muscles forming ulnar border of
forearm from medial view

IV. Arm & Forearm Muscles

Muscle Origin Insertion Action

Biceps brachii coracoid process of the radius flexes and suplinates

scapula the forearm

Brachialis lateral surface of humerus proximal end of flexes forearm

ulna

Triceps brachii olecranon process of extensors of the

ulna forearm

- Long head axillary border of the

scapula

- Lateral head deltoid ridge of humerus

- Medial head dorsal surface of the shaft

of humerus
Extensor carpi humerus 2nd and 3rd extends hand
radialis metacarpals

Flexor carpi distal end of humerus pisiform bone of flexes digits

ulnaris wrist

Muscles of the Thigh

Muscle Description

Tensor fascia latae Thick triangular muscle on dorsal part of tough fascia covering
anterior thigh

Biceps femoris Large muscle on lateral surface of thigh, posterior to fascia lata,
covering more than half of thigh surface

Caudofemoralis Most posterior muscle between median dorsal line and thigh

Gluteus maximus Thin, flat muscle anterior to preceding, embedded in fascia,

continuous with tensor fascia latae

Gluteus medius Large triangular muscle immediately in front of preceding, partly

covered by it

Sartorius Forms anterior margin of lateral thigh view, covers anterior medial
surface of thigh

Vastus lateralis Large, stout muscle covered by fascia lata

Rectus femoris Stout muscle medial to vastus lateralis, covered externally by

sartorius

Vastus medialis Muscle on medial side of thigh, posterior to rectus femoris

Vastus intermedius Deep muscle next to femur shaft, seen by separating rectus femoris
from vastus lateralis

Gracilis Large, flat muscle forming posterior medial thigh

Adductor longus Small muscle positioned anteriorly on medial thigh after cutting
gracilis

Adductor femoris Large muscle lying next to preceding

Semimembranosus Large muscle posterior to adductor muscles, divisible into two parts

Semitendinosus Most posterior muscle of thigh, posterior to semimembranosus

Tenuissimus Narrow, long muscle beneath biceps femoris; cut through middle of
biceps femoris to expose

V. Hip & Thigh Muscles

Muscle Origin Insertion Action

Adductor femoris pubis femur abducts thigh

Adductor longus cranial border of pubis femur abducts thigh

Biceps femoris ischium patella and abducts thigh and

lateral border of flexes shank
tibia

Caudofemoralis transverse processes of the patella abducts thigh and

2nd and 3rd caudal vertebrae flexes shank

Gluteus maximus transverse processes of the greater abducts thigh

last sacral vertebra and the trochanter of
1st caudal vertebra femur

Gluteus medius adjacent fascia, crest of greater abducts thigh

ilium, and lateral surface of trochanter of
ilium femur

Gracilis border between ischium and proximal end of abducts thigh

pubis tibia

Quadriceps femoris patella and extends lower leg

adjacent
ligaments

- Rectus femoris ventral border of ilium near

acetabulum
- Vastus lateralis greater trochanter and
surface of femur

- Vastus medialis femur

- Vastus intermedius surface of femur

Sartorius ventral border of ilium patella and abducts and rotates

proximal end of thigh; extends tibia
tibia

Semimembranosus ischium medial surface extends thigh

and shaft of
femur

Semitendinosus ischial tuberosity proximal end of flexes shank

tibia

Tensor fascia lata ilium and neighboring fascia patella and extends thigh and
tendon by fascia aids in abduction
lata and rotation

Tenuissimus transverse process of the 2nd inserting fascia Abductor of thigh in

caudal vertebra of biceps common with biceps
femoris femoris

Muscles of the Shank

Muscle Description

Tibialis anterior Most ventral muscle, ventral border in contact with tibia

Extensor digitorum Next to preceding, on lateral surface of shank

longus

Peroneus Next to preceding, on posterior or caudal surface of shank

Gastrocnemius Large muscle forming surface of shank

Soleus Internal to gastrocnemius; found by separating lateral

gastrocnemius head
Plantaris Internal to gastrocnemius; found by separating medial
gastrocnemius head

Flexor digitorum longus Immediately dorsal to tibia on medial shank

Tibialis posterior Muscle internal to preceding

VI. Leg & Foot Muscles

Muscle Origin Insertion Action

Extensor digitorum distal end of femur tendons to all phalanges extends

longus toes/digits

Flexor digitorum tibia, fibula and tendons on all digits flexes digits
longus adjacent fascia

Gastrocnemius knee fascia and calcaneus by Achilles tendon extends foot

distal end of femur

Peroneus proximal of fibula bases of metatarsals extends toes

Plantaris patella and femur by a thick tendon into the flexes

ventral surface of calcaneus toes/digits

Soleus proximal end of calcaneus extends foot

fibula

Tibialis anterior proximal ends of tendon to 1st metacarpal flexes foot

tibia and fibula

Tibialis posterior tibia, fibula, and scaphoid and medial extends foot
fascia cuneiform of ankle