Posterior Muscles

Question 1

Erector Spinae (A. Only)

Answer 1

A = prime mover of back extension (I.D. muscle and action only),

Question 2

Trapezius (O.I.A.N)

Answer 2

O = occipital bone
ligamentum nuchae
spinous processes of C7-T12

I = spine and acromion of scapula
lateral 1/3 of clavicle

A = stabilizes
      elevates
      retracts
      depresses
      rotates scapula forward

N = Accessory Nerve (CN XI)
Spinal Nerves C3-C4

Question 3

Levator scapulae (O.I.N)

Answer 3

O = transverse processes of C1-C4

I = superior vertebral border of scapula

N = Spinal Nerves C3-C5 (C5 via the dorsal scapular nerve)

Question 4

Rhomboideus major (O.I.A.N)

Answer 4

O = spinous processes of T2-T5

I = medial border of scapula from spine to inferior angle

A = adducts scapula and performs downward rotation of scapula

N = Spinal Nerve C5 (via dorsal scapular nerve)

Question 5

Rhomboideus minor (O.I.A.N)

Answer 5

O = spinous processes of C7-T1

I = medial border of scapula, superior to spine of scapula

A = adducts scapula and performs downward rotation of scapula

N = Spinal Nerve C5 (via dorsal scapular nerve)

Question 6

Teres major (O.I.A.N)

Answer 6

O = inferior angle of scapula

I = intertubercular groove of humerus

A = extension
medial rotation
adduction of arm

N = Subscapular Nerve

Question 7

Latissimus dorsi (“swimmer’s muscle”) (O.I.A.N)

Answer 7

O = spines of T7-T12 and L1-L5
ribs 8-12
iliac crest

I = intertubercular groove of humerus

A = prime arm extensor
adduction
medial rotation at the shoulder
depresses shoulder

N = Thoracodorsal Nerve (C6-C8)

Question 8

Supraspinatus (O.I.A.N)

Answer 8

O = supraspinous fossa of scapula

I = greater tubercle of humerus

A = stabilizes shoulder joint
abducts arm

N = Suprascapular Nerve

Question 9

Infraspinatus (O.I.A.N)

Answer 9

O = infraspinous fossa of scapula

I = greater tubercle of humerus

A = stabilizes shoulder joint
laterally rotates arm

N = Suprascapular Nerve

Question 10

Teres minor (O.I.A.N)

Answer 10

O = lateral scapular border

I = greater tubercle of humerus

A = stabilizes shoulder joint
laterally rotates arm

N = Axillary Nerve

Question 11

Subscapularis (O.I.A.N)

Answer 11

O = subscapular fossa of scapula

I = lesser tubercle of humerus

A = stabilizes shoulder joint
prime medial rotator of arm

N = Subscapular Nerve

Question 12

Triceps brachii (O.I.A.N)

Answer 12

O = long head–infraglenoid tubercle of scapula

lateral head–proximal end of lateral humeral margin

medial head–distal to radial groove on posterior humeral shaft

I = olecranon process of ulna

A = prime extensor of forearm; extends arm

N = Radial Nerve (CN VII)

Question 13

Anconeus (O.I.A.N)

Answer 13

O = lateral epicondyle of humerus

I = lateral aspect of olecranon process of ulna

A = abduction of ulna during forearm pronation; forearm extensor

N = Radial Nerve (CN VII)

Question 14

Gluteus maximus (“running muscle”) (O.I.A.N)

Answer 14

O = dorsal ilium
sacrum
coccyx
lumbodorsal fascia

I = gluteal tuberosity of femur and iliotibial tract

A = major thigh extensor; lateral rotation of thigh

N = Inferior Gluteal Nerve

Question 15

Gluteus medius (“walking muscle”) (O.I.A.N)

Answer 15

O = anterior iliac crest of ilium between posterior and anterior gluteal lines

I = greater trochanter of femur

A = abduction and medial rotation of thigh; steadies pelvis

N = Superior Gluteal Nerve

Question 16

Gluteus minimus (O.I.A.N)

Answer 16

O = lateral surface of ilium between inferior and anterior gluteal lines

I = greater trochanter of femur

A = abduction and medial rotation of thigh; steadies pelvis

N = Superior Gluteal Nerve

Question 17

Piriformis (O.I.A.N.)

Answer 17

O = anterolateral surface of sacrum

I = greater trochanter of femur

A = abduction (when thigh flexed) and lateral rotation of thigh

N = Spinal Nerves L5-S2

Question 18

Superior gemellus (O.I.A.N)

Answer 18

O = ischial spine

I = medial surface of greater trochanter of femur

A = lateral rotation of thigh; abduction (when thigh flexed)

N = Spinal Nerves L5-S1 (nerve to obturator internus)

Question 19

Obturator internus (O.I.A.)

Answer 19

O = obturator membrane and obturator foramen

I = greater trochanter of femur

A = lateral rotation of thigh

N = Spinal Nerves L5-S1

Question 20

Inferior gemellus (O.I.A.N.)

Answer 20

O = ischial tuberosity

I = medial surface of greater trochanter of femur

A = lateral rotation of thigh; abduction (when thigh flexed)

N = Spinal Nerves L5-S1 (nerve to quadratus femoris)

Question 21

Quadratus femoris (O.I.A.N)

Answer 21

O = ischial tuberosity

I = intertrochanteric crest of femur

A = lateral rotation of thigh

N = Spinal Nerves L5-S1

Question 22

Biceps femoris (O.I.A.N)

Answer 22

O = long head–ischial tuberosity
short head–linea aspera

I = head of fibula and lateral condyle of tibia

A = extension of thigh; flexion and lateral rotation of leg

N = Sciatic Nerve

Question 23

Semitendinosus (O.I.A.N)

Answer 23

O = ischial tuberosity

I = medial aspect of proximal tibial shaft

A = extension of thigh; flexion and medial rotation of leg

Question 24

Semimembranosus (O.I.A.N)

Answer 24

O = ischial tuberosity

I = medial condyle of the tibia

A = extension of thigh; flexion and medial rotation of leg

N = Sciatic Nerve