Anatomy Exam 5 - Muscles: Origin, Insertion, Fxn

Question 1

Trapezius

Answer 1

*Extrinsic back muscle (hypaxial/ventral rami)
Superficial layer

Origin: Nuchal ligament; Vertebrae

Insertion: Scapula; Acromion of scapula

Function: Elevates, depresses, rotates, and retracts the scapula

Innervation:
Motor: CNXI (Accessory nerve)
Sensory: Ventral rami of cervical plexus

Question 2

Latissimus dorsi

Answer 2

*Extrinsic back muscle (hypaxial/ventral rami)
Superficial layer

Origin: Vertebrae; Thoracolumbar fascia; Ribs; Inferior angle of scapular

Insertion: Intertubercular sulcus of the humerus

Function: Extends, adducts, medially rotates humerus; elevates torso when humerus is fixed

Innervation:
Motor: Thoracodorsal n.
Sensory: Ventral rami of cervical plexus

Question 3

Levator scapulae

Answer 3

*Extrinsic back muscle (hypaxial/ventral rami)
Middle layer

Origin: Transverse processes of C1-C4

Insertion: Medial border of scapula

Function: Elevates scapulae

Innervation:
Motor: Dorsal scapular n. and ventral rami of cervical plexus.
Sensory: Ventral rami of cervical plexus

Question 4

Rhomboid minor

Answer 4

*Extrinsic back muscle (hypaxial/ventral rami)
Middle layer

Origin: Nuchal ligament, spinous processes of C7-T1

Insertion: Medial border of scapula

Function: Elevates scapulae; retracts scapulae

Innervation:
Motor: Dorsal scapular nerve
Sensory: Ventral rami of cervical plexus

Question 5

Rhomboid major

Answer 5

*Extrinsic back muscle (hypaxial/ventral rami)
Middle layer

Origin: Spinous process of T2-T5

Insertion: Medial border of scapula

Function: Elevates scapulae; retracts scapulae

Innervation:
Motor: Dorsal scapular nerve
Sensory: Ventral rami of cervical plexus

Question 6

Serratus posterior superior

Answer 6

*Extrinsic back muscle (hypaxial/ventral rami)
Deep layer

Origin: Nuchal ligament, spinous processes of C7-T3

Insertion: Ribs 2-5

Function: Elevates ribs

Innervation:
Motor: Intercostal nerve branches
Sensory: none

Question 7

Serratus posterior inferior

Answer 7

*Extrinsic back muscle (hypaxial/ventral rami)
Deep layer

Origin: Spinous processes of T11-L2

Insertion: Ribs 9-12

Function: Depress ribs

Innervation:
Motor: Intercostal nerve branches
Sensory: none

Question 8

Iliocostalis

Answer 8

*Intrinsic back muscle (epaxial/dorsal rami)
Erector spinae group

Origin: Ribs 3-12; lateral crest of sacrum; thoracolumbar fascia

Insertion: Superior vertebrae and ribs (positioned most laterally)

Function: Extension of spine (bilateral use); lateral flexion (unilateral use- ipsilateral)

Innervation: Dorsal rami of spinal nerves

Question 9

Longissimus

Answer 9

*Intrinsic back muscle (epaxial/dorsal rami)
Erector spinae group

Origin: Vertebrae

Insertion: Superior vertebrae and ribs (positioned between iliocostalis and spinalis)

Function: Extension of spine (bilateral use); lateral flexion (unilateral use- ipsilateral)

Innervation: Dorsal rami of spinal nerves

Question 10

Spinalis

Answer 10

*Intrinsic back muscle (epaxial/dorsal rami)
Erector spinae group

Origin: Ribs 3-12; lateral crest of sacrum; thoracolumbar fascia

Insertion: Superior vertebrae (positioned most medially)

Function: Extension of spine (bilateral use); lateral flexion (unilateral use- ipsilateral)

Innervation: Dorsal rami of spinal nerves

Question 11

Semispinalis

Answer 11

*Intrinsic back muscle (epaxial/dorsal rami)
Transversospinalis group

Origin: Transverse processes of vertebrae
Primarily found in the thoracic region

Insertion: Spinous processes of vertebrae

Function: Assist in extension of spine (bilateral use); rotation (unilateral use- contralateral)

Innervation: Dorsal rami of spinal nerves

Question 12

Multifidus

Answer 12

*Intrinsic back muscle (epaxial/dorsal rami)
Transversospinalis group

Origin: Vertebrae - found in all spinal regions

Insertion: Vertebrae

Function: Assist in extension of spine (bilateral use); rotation (unilateral use- contralateral)

Innervation: Dorsal rami of spinal nerves

Question 13

Rotatores

Answer 13

*Intrinsic back muscle (epaxial/dorsal rami)
Transversospinalis group

Origin: Transverse processes of vertebrae
Primarily found in the thoracic region, smaller than semispinalis

Insertion: Spinous processes of vertebrae

Function: Proprioception and stabilization

Innervation: Dorsal rami of spinal nerves

Question 14

Pectoralis major

Answer 14

Origin: Clavicular head = clavicle
Sternocostal head = anterior sternum
Abdominal head = rectus sheath

Insertion: Greater tubercle of humerus

Function: Adduction, internal rotation; moves scapula anteriorly if humerus is fixed

Innervation: Medial and lateral pectoral nerves from brachial plexus

Question 15

Pectoralis minor

Answer 15

Origin: Ribs 3-5

Insertion: Medial border and the coracoid process of the scapula

Function: Pulls scapula anteriorly; stabilizes it on posterior thorax

Innervation: Medial pectoral nerve

Question 16

Serratus anterior

Answer 16

Origin: Ribs

Insertion: Scapula, from the superior angle, medial border, and inferior angle

Function: Protraction, superior rotation

Innervation: Long thoracic nerve

Question 17

Subclavius

Answer 17

Origin: Sternal end of rib 1

Insertion: Clavicle

Function: Anchors, depresses clavicle

Innervation: Nerve to subclavius

Question 18

Deltoid

Answer 18

**NOT a rotator cuff muscle!

Origin: Clavicle; Acromion; Spine of scapula

Insertion: Deltoid tuberosity of humerus

Function: Flex, extend, medially and laterally rotate, and abduct the humerus

Innervation: Axillary nerve

Question 19

Teres major

Answer 19

**NOT a rotator cuff muscle!

Origin: Inf. angle of scapula

Insertion: Lesser tubercle of humerus

Function: Adduct, medially rotate humerus

Innervation: Lower subscapular nerve

Question 20

Supraspinatus

Answer 20

Rotator cuff muscle!

Origin: Supraspinatus fossa of scapula

Insertion: Greater tubercle of humerus

Function: Abduction of humerus; stabilization of shoulder joint

Innervation: Lower subscapular nerve

Question 21

Teres minor

Answer 21

Rotator cuff muscle!

Origin: Lateral border of scapula

Insertion: Greater tubercle of humerus

Function: Lateral rotation of humerus, stabilization

Innervation: Axillary nerve

Question 22

Subscapularis

Answer 22

Rotator cuff muscle!

Origin: Subscapular fossa of scapula

Insertion: Greater tubercle of humerus

Function: Medial rotation of humerus

Innervation: Upper and lower subscapular nerves

Question 23

Infraspinatus

Answer 23

Rotator cuff muscle!

Origin: Infraspinous fossa of scapula

Insertion: Greater tubercle of humerus

Function: Lateral rotation of humerus, stabilization

Innervation: Suprascapular nerve (which is confusing)

Question 24

Biceps brachii

Answer 24

Anterior compartment
Origin:
Long head: Supraglenoid tubercle of the scapula
Short head: Coracoid process of the scapula

Insertion: Radial tuberosity of the radius

Function: Forearm flexion, pronation

Innervation: Musculocutaneous nerve

Question 25

Coracobrachialis

Answer 25

Anterior compartment Origin: Coracoid process of scapula Insertion: Shaft of humerus Function: Arm flexion, arm adduction Innervation: Musculocutaneous nerve

Question 26

Brachialis

Answer 26

Anterior compartment Origin: Distal humerus Insertion: Coranoid process of ulna Function: Strong flexion of forearm Innervation: Musculocutaneous nerve and radial nerve

Question 27

Triceps brachii

Answer 27

Posterior compartment Origin: Long head: Supraglenoid tubercle of scapula Short head: Coracoid process of scapula Insertion: Radial tuberosity of radius Function: Extension of forearm Innervation: Radial nerve

Question 28

Anconeous

Answer 28

Posterior compartment Origin: Lateral epicondyle of humerus Insertion: Olecranon Function: Abducts ulna during pronation; Stablizes elbow; Assists extension Innervation: Radial nerve