Muscle Origins, Insertions, and Functions

Splenius Origin

spines of the thoracic vertebrae

Splenius Insertion

superior nuchal line of skull

Splenius Function

to extend and rotate the head

Scalenus (Scalenes) Origin

anterior tubercle of transverse processes of cervical vertebrae

Scalenus (Scalenes) Insertion

anterior scalene tubercle of rib 1

Scalenus (Scalenes) Function

Neck flexion

Transversus thoracis (costarum) Origin

surface of the body of the sternum and the xiphoid process

Transversus thoracis (costarum) Insertion

internal surface of the costal cartilages of ribs 2-6

Transversus thoracis (costarum) Function

depresses ribs during forced expiration

External Intercostals Origin

lower border of ribs

External Intercostals Insertion

upper border of adjacent ribs

External Intercostals Function

protraction of ribs

Internal Intercostals Origin

upper border of ribs

Internal Intercostals Insertion

lower border of adjacent ribs

Internal Intercostals Function

retraction of ribs

External oblique Origin

posterior ribs and lumbdorsal fascia

External oblique Insertion

linea alba

External oblique Function

compresses abdomen

Internal oblique Origin

the pelvis and lumbdorsal fascia

Internal oblique Insertion

linea alba

Internal oblique Function

compresses abdomen

Transversus Origin

the posterior ribs, lumbar vertebrae, and illium

Transversus Insertion

linea alba

Transversus Function

compresses abdomen

Rectus abdomenis Origin

pubic symphasis

Rectus abdomenis Insertion

costal cartilage

Rectus abdomenis Function

compresses internal organs of abdomen

Trapezius Origin

spinous process of cervical and thoracic vertebrae, lambdoidal crest, and nuchal lines

Trapezius Insertion

scapular spine and clavicle

Trapezius Function

pulls and holds scapula in place, draws scapula cranially + dorsally

Levator scapulae Origin

occipital bone + atlas

Levator scapulae Insertion

vertebral (medial) border of scapula

Levator scapulae Function

pulls scapula towards the head (elevates the scapula)

Rhomboideus major Origin

spinous process and ligaments of posterior cervical and anterior thoracic vertebrae

Rhomboideus major Insertion

dorsal posterior angle of the scapula

Rhomboideus major Function

draws scapula forward and dorsally

Rhomboideus minor Origin

spines of posterior cervical and anterior thoracic vertebrae

Rhomboideus minor Insertion

vertebral border of scapula

Rhomboideus minor Function

draws scapula forward and dorsally

Serratus anterior Origin

first 9 ribs

Serratus anterior Insertion

medial surface of scapula

Serratus anterior Function

pulls scapula anterior and ventral

Pectoralis minor Origin

sternum

Pectoralis minor Insertion

humerus

Pectoralis minor Function

adducts the humerus

Deltoid Origin

acromion process, scapula, clavicle

Deltoid Insertion

proximal end of humerus, and on the ulna

Deltoid Function

flex humerus + rotate it laterally

Pectoralis major Origin

sternum + clavicle

Pectoralis major Insertion

lateral lip of the intertubercular sulcus (bicipital groove) of the humerus; radial tuberosity (in cat)

Pectoralis major Function

flexion, adduction, internal/medial rotation; flexor of forelimb

Subscapularis Origin

subscapular fossa

Subscapularis Insertion

lesser tuberosity of humerus

Subscapularis Function

pull humerus medially

Supraspinatus Origin

lateral surface of the scapula in the supraspinous fossa

Supraspinatus Insertion

on the humerus

Supraspinatus Function

extends humerus

Infraspinatus Origin

below the spine of the scapula (infraspinous fossa)

Infraspinatus Insertion

on the humerus

Infraspinatus Function

rotates humerus laterally

Teres minor Origin

dorsal lateral border of scapula

Teres minor Insertion

on the humerus

Teres minor Function

rotates humerus laterally

Teres major Origin

the axillary (medial) border of the scapula

Teres major Insertion

on the humerus

Teres major Function

flex + rotate humerus

Coracobrachialis Origin

axillary (lateral) border of the scapula/coracoid process

Coracobrachialis Insertion

proximal end of humerus

Coracobrachialis Function

rotates humerus and draws the bone posteriorly

Latissimus dorsi Origin

spines of the thoracic and lumbar vertebrae

Latissimus dorsi Insertion

medial humerus

Latissimus dorsi Function

pulls forelimb posteriorly and dorsally

Biceps brachii Origin

glenoid fossa, coracoid process

Biceps brachii Insertion

radius

Biceps brachii Function

flexes the forearm

Brachialis Origin

humerus

Brachialis Insertion

ulna

Brachialis Function

flexes the forearm

Brachioradialis Origin

distal humerus

Brachioradialis Insertion

radial styloid process

Brachioradialis Function

flexes the forearm

Triceps brachii- lateral head Origin

greater tuberosity of humerus

Triceps brachii- lateral head Insertion

olecranon process

Triceps brachii- lateral head Function

extends the forearm

Triceps brachii- long head Origin

axillary border of scapula

Triceps brachii- long head Insertion

olecranon process

Triceps brachii- long head Function

extends the forearm

Triceps brachii- medial head Origin

the humerus

Triceps brachii- medial head Insertion

olecranon process

Triceps brachii- medial head Function

extends the forearm

Gluteus maximus Origin

sacral and caudal vertebrae

Gluteus maximus Insertion

greater trochanter

Gluteus maximus Function

abducts the thigh

Gluteus medius Origin

sacral and caudal vertebrae

Gluteus medius Insertion

greater trochanter

Gluteus medius Function

abducts the thigh

Tensor fasciae latae Origin

illium

Tensor fasciae latae Insertion

fascia lata

Tensor fasciae latae Function

tighten (tense) the fascia lata

Adductor magnus Origin

pubis